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1.  Change in N-terminal-pro-B-type-natriuretic-peptide and the risk of sudden death, stroke, myocardial infarction, and all-cause mortality in diabetic dialysis patients 
European Heart Journal  2008;29(17):2092-2099.
Aims
N-terminal-pro-B-type-natriuretic-peptide (NT-pro-BNP) concentrations are altered in renal failure. This study examined the effect of baseline and change from baseline NT-pro-BNP on cardiovascular outcome and mortality in haemodialysis patients.
Methods and results
On the basis of the German Diabetes and Dialysis Study, which evaluated atorvastatin in 1255 type 2 diabetes mellitus (T2DM) haemodialysis patients (median follow-up 4 years), the impact of NT-pro-BNP on pre-specified, adjudicated endpoints was investigated: sudden death (SD; n = 160), stroke (n = 99), myocardial infarction (MI; n = 200), cardiovascular events (CVEs: cardiac death, MI, stroke; n = 465), all-cause mortality (n = 612). Patients with baseline NT-pro-BNP ≥9252 pg/mL (fourth quartile) exhibited a more than four-fold risk of stroke [hazard ratio (HR) 4.1; 95% confidence interval (CI) 2.0–8.4] and a more than two-fold risk of SD (HR 2.0; 95% CI 1.2–3.3), CVE (HR 2.0; 95% CI 1.5–2.7), and mortality (HR 2.1; 95% CI 1.6–2.7) compared with patients with baseline NT-pro-BNP ≤ 1433 pg/mL (first quartile). Change in NT-pro-BNP was strongly associated with SD, CVE, and mortality. Doubling of NT-pro-BNP increased the risk of death by 46% (95% CI 1.1–2.0). Neither baseline nor change in NT-pro-BNP was significantly associated with MI.
Conclusion
Increasing NT-pro-BNP is a risk factor for SD, CVE, and mortality in haemodialysis patients with T2DM. Whether NT-pro-BNP-guided treatment improves outcome needs to be evaluated prospectively.
doi:10.1093/eurheartj/ehn278
PMCID: PMC2519248  PMID: 18617483
NT-pro-BNP; Serial measurement; Cardiovascular events; Mortality; Haemodialysis; Diabetes mellitus
2.  Homoarginine, heart failure, and sudden cardiac death in haemodialysis patients 
European Journal of Heart Failure  2011;13(8):852-859.
Aims
Sudden cardiac death (SCD) is a major contributor to the excess mortality of patients on maintenance dialysis. Homoarginine deficiency may lead to decreased nitric oxide availability and endothelial dysfunction. Based on this rationale we assessed whether homoarginine deficiency is a risk factor for SCD in dialysis patients.
Methods and results
This study examined the association of homoarginine with cardiovascular outcomes in 1255 diabetic haemodialysis patients from the German diabetes and dialysis study. During a median of 4 years of follow-up, hazard ratios (HR) (95% CI) for reaching the following pre-specified, adjudicated endpoints were determined: SCD, myocardial infarction, stroke, death due to heart failure, and combined cardiovascular events. There was a strong association of low homoarginine concentrations with the presence of congestive heart failure and left ventricular hypertrophy as well as increased levels of brain natriuretic peptide. Per unit decrease in homoarginine, the risk of SCD increased three-fold (HR 3.1, 95% CI 2.0–4.9), attenuating slightly in multivariate models (HR 2.4; 95% CI 1.5–3.9). Patients in the lowest homoarginine quintile experienced a more than two-fold increased risk of SCD, and more than three-fold increased risk of heart failure death than patients in the highest quintile, which accounted for the high incidence of combined cardiovascular events. Low homoarginine showed a trend towards increased risk of stroke, however, myocardial infarction was not meaningfully affected.
Conclusion
Low homoarginine is a strong risk factor for SCD and death due to heart failure in haemodialysis patients. Further studies are needed to elucidate the underlying mechanisms, offering the potential to develop new interventional strategies.
doi:10.1093/eurjhf/hfr056
PMCID: PMC3143829  PMID: 21791541
Homoarginine; Sudden cardiac death; Heart failure; Amino acids; Haemodialysis
3.  Antioxidative vitamines for prevention of cardiovascular disease for patients after renal transplantation and patients with chronic renal failure  
Introduction
The mortality from cardiovascular disease in patients with chronic renal failure is much higher than in the general population. In particular, patients with chronic renal failure with replacement therapies (dialysis patients and patients with renal transplantation) show both increased traditional risk factors and risk factors due to the dysfunction of the renal system. In combination with necessary medication for renal insufficiency oxidative stress is elevated. Progression of atherosclerosis is promoted due to increased oxidation of lipids and endothelium damage. This link between lipid oxidation and artherogenesis provides the rationale for the supposed beneficial effect of supplementation with antioxidative vitamins (vitamin A, C and E). Such an effect could not be demonstrated for patients with a history of cardiovascular disease and without kidney diseases. However, in high risk patients with chronic renal failure and renal replacement therapies this could be different.
Objectives
The objective of this systematic literature review was to assess the clinical effectiveness and cost-effectiveness of supplementation with antioxidative vitamins A, C or E to reduce cardiovascular events in patients with chronic kidney diseases, dialysis-requiring patients and patients after a renal transplantation with or without cardiovascular diseases.
Methods
A systematic literature review was conducted with documented search and selection of the literature, using a priori defined inclusion and exclusion criteria as well as a documented extraction and assessment of the literature according to the methods of evidence-based medicine.
Results
21 publications met the inclusion criteria for the evaluation of clinical effectiveness. No study could be identified for the economic evaluation. Two studies (four publications) analysed the effect of oral supplementation on the secondary prevention of clinical cardiovascular endpoints. Studies analysing the effect on patients without a history of cardiovascular disease could not be identified. 17 studies analysed the effect of oral supplementation or infusion with antioxidative vitamins or the supplementation with dialysis membranes coated with vitamin E on intermediate outcomes like oxidative stress or vessel parameters.
The two randomized clinical trials analysing the effect of orally supplemented vitamin E on clinical endpoints in patients with mild-to-moderate renal insufficiency and for haemodialysis patients respectively reported different results. After 4.5 years supplementation with a daily dose of 400 IU vitamin E renal insufficiency patients showed neither a beneficial nor a harmful effect on a combined event rate of myocardial infarction, stroke or death by cardiovascular causes. The second study reported a 50% risk reduction (RR=0.46, 95%-KI: 0.27-0.78, p=0.014) on the combined event rate of fatal myocardial infarction, nonfatal myocardial infarction, stroke, peripheral vascular disease or unstable angina pectoris in the study arm with vitamin E-Supplementation of 800 IU daily.
In 16 of 17 studies with intermediate endpoints the supplementation with vitamins was associated with a change of one or several of the examined endpoints in the expected direction. This means that the concentrations of the markers for oxidative stress decreased in the Vitamin E-group, the progression of aortic calcification (only one study) was reduced, the intima media thickness decreased and the lipid profile improved. No studies regarding costs or cost-effectiveness were identified.
Discussion
A possible explanation for the different results in the two studies with clinical endpoints may be due to the different study populations with different risk profiles, to different dosage during the intervention or to variation by chance. Due to the absence of clinically meaningful endpoints, the relevance of studies analysing the effect of antioxidative vitamins on intermediate endpoints like oxidative stress markers is basically limited to show single intermediate steps of the postulated biological effect mechanisms by which a potentially preventive effect could possibly be mediated. The mainly unsatisfactory planning and reporting quality of the 17 identified studies and a possible "publication bias" are further limitations.
Conclusion
The available evidence is not sufficient to support or to reject an effect of antioxidative vitamins on secondary prevention for cardiovascular disease for patients with chronic renal insufficiency or renal replacement therapy. There is a lack of randomized, placebo-controlled studies with a sufficient number of cases and clinical endpoints of cardiovascular disease, on the effect of antioxidative vitamins either orally applied or given by vitamin E-modified dialysers.
No data are available about supplementation with antioxidative vitamins for primary prevention of cardiovascular disease. Therefore the current evidence does not allow to draw conclusions concerning this subject either. As opposed to patients with a history of cardiovascular disease without kidney diseases where there is enough evidence to exclude a beneficial effect on secondary prevention of cardiovascular disease for patients with chronic renal insufficiency and renal replacement therapy this question remains unanswered. Conclusions about costs and cost-effectiveness also cannot be drawn.
PMCID: PMC3011345  PMID: 21289965
4.  Implantable Cardioverter Defibrillators. Prophylactic Use 
Executive Summary
Objective
The use of implantable cardiac defibrillators (ICDs) to prevent sudden cardiac death (SCD) in patients resuscitated from cardiac arrest or documented dangerous ventricular arrhythmias (secondary prevention of SCD) is an insured service. In 2003 (before the establishment of the Ontario Health Technology Advisory Committee), the Medical Advisory Secretariat conducted a health technology policy assessment on the prophylactic use (primary prevention of SCD) of ICDs for patients at high risk of SCD. The Medical Advisory Secretariat concluded that ICDs are effective for the primary prevention of SCD. Moreover, it found that a more clearly defined target population at risk for SCD that would be likely to benefit from ICDs is needed, given that the number needed to treat (NNT) from recent studies is 13 to 18, and given that the per-unit cost of ICDs is $32,000, which means that the projected cost to Ontario is $770 million (Cdn).
Accordingly, as part of an annual review and publication of more recent articles, the Medical Advisory Secretariat updated its health technology policy assessment of ICDs.
Clinical Need
Sudden cardiac death is caused by the sudden onset of fatal arrhythmias, or abnormal heart rhythms: ventricular tachycardia (VT), a rhythm abnormality in which the ventricles cause the heart to beat too fast, and ventricular fibrillation (VF), an abnormal, rapid and erratic heart rhythm. About 80% of fatal arrhythmias are associated with ischemic heart disease, which is caused by insufficient blood flow to the heart.
Management of VT and VF with antiarrhythmic drugs is not very effective; for this reason, nonpharmacological treatments have been explored. One such treatment is the ICD.
The Technology
An ICD is a battery-powered device that, once implanted, monitors heart rhythm and can deliver an electric shock to restore normal rhythm when potentially fatal arrhythmias are detected. The use of ICDs to prevent SCD in patients resuscitated from cardiac arrest or documented dangerous ventricular arrhythmias (secondary prevention) is an insured service in Ontario.
Primary prevention of SCD involves identification of and preventive therapy for patients who are at high risk for SCD. Most of the studies in the literature that have examined the prevention of fatal ventricular arrhythmias have focused on patients with ischemic heart disease, in particular, those with heart failure (HF), which has been shown to increase the risk of SCD. The risk of HF is determined by left ventricular ejection fraction (LVEF); most studies have focused on patients with an LVEF under 0.35 or 0.30. While most studies have found ICDs to reduce significantly the risk for SCD in patients with an LVEF less than 0.35, a more recent study (Sudden Cardiac Death in Heart Failure Trial [SCD-HeFT]) reported that patients with HF with nonischemic heart disease could also benefit from this technology. Based on the generalization of the SCD-HeFT study, the Centers for Medicare and Medicaid in the United States recently announced that it would allocate $10 billion (US) annually toward the primary prevention of SCD for patients with ischemic and nonischemic heart disease and an LVEF under 0.35.
Review Strategy
The aim of this literature review was to assess the effectiveness, safety, and cost effectiveness of ICDs for the primary prevention of SCD.
The standard search strategy used by the Medical Advisory Secretariat was used. This included a search of all international health technology assessments as well as a search of the medical literature from January 2003–May 2005.
A modification of the GRADE approach (1) was used to make judgments about the quality of evidence and strength of recommendations systematically and explicitly. GRADE provides a framework for structured reflection and can help to ensure that appropriate judgments are made. GRADE takes into account a study’s design, quality, consistency, and directness in judging the quality of evidence for each outcome. The balance between benefits and harms, quality of evidence, applicability, and the certainty of the baseline risks are considered in judgments about the strength of recommendations.
Summary of Findings
Overall, ICDs are effective for the primary prevention of SCD. Three studies – the Multicentre Automatic Defibrillator Implantation Trial I (MADIT I), the Multicentre Automatic Defibrillator Implantation Trial II (MADIT II), and SCD-HeFT – showed there was a statistically significant decrease in total mortality for patients who prophylactically received an ICD compared with those who received conventional therapy (Table 1).
Results of Key Studies on the Use of Implantable Cardioverter Defibrillators for the Primary Prevention of Sudden Cardiac Death – All-Cause Mortality
MADIT I: Multicentre Automatic Defibrillator Implantation Trial I; MADIT II: Multicentre Automatic Defibrillator Implantation Trial II; SCD-HeFT: Sudden Cardiac Death in Heart Failure Trial.
EP indicates electrophysiology; ICD, implantable cardioverter defibrillator; NNT, number needed to treat; NSVT, nonsustained ventricular tachycardia. The NNT will appear higher if follow-up is short. For ICDs, the absolute benefit increases over time for at least a 5-year period; the NNT declines, often substantially, in studies with a longer follow-up. When the NNT are equalized for a similar period as the SCD-HeFT duration (5 years), the NNT for MADIT-I is 2.2; for MADIT-II, it is 6.3.
GRADE Quality of the Evidence
Using the GRADE Working Group criteria, the quality of these 3 trials was examined (Table 2).
Quality refers to the criteria such as the adequacy of allocation concealment, blinding and follow-up.
Consistency refers to the similarity of estimates of effect across studies. If there is important unexplained inconsistency in the results, our confidence in the estimate of effect for that outcome decreases. Differences in the direction of effect, the size of the differences in effect, and the significance of the differences guide the decision about whether important inconsistency exists.
Directness refers to the extent to which the people interventions and outcome measures are similar to those of interest. For example, there may be uncertainty about the directness of the evidence if the people of interest are older, sicker or have more comorbidity than those in the studies.
As stated by the GRADE Working Group, the following definitions were used to grade the quality of the evidence:
High: Further research is very unlikely to change our confidence n the estimate of effect.
Moderate: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low: Any estimate of effect is very uncertain.
Quality of Evidence – MADIT I, MADIT II, and SCD-HeFT*
MADIT I: Multicentre Automatic Defibrillator Implantation Trial I; MADIT II: Multicentre Automatic Defibrillator Implantation Trial II; SCD-HeFT: Sudden Cardiac Death in Heart Failure Trial.
The 3 trials had 3 different sets of eligibility criteria for implantation of an ICD for primary prevention of SCD. Conclusions
Conclusions
Overall, there is evidence that ICDs are effective for the primary prevention of SCD. Three trials have found a statistically significant decrease in total mortality for patients who prophylactically received an ICD compared with those who received conventional therapy in their respective study populations.
As per the GRADE Working Group, recommendations consider 4 main factors:
The tradeoffs, taking into account the estimated size of the effect for the main outcome, the confidence limits around those estimates, and the relative value placed on the outcome;
The quality of the evidence (Table 2);
Translation of the evidence into practice in a specific setting, taking into consideration important factors that could be expected to modify the size of the expected effects, such as proximity to a hospital or availability of necessary expertise; and
Uncertainty about the baseline risk for the population of interest
The GRADE Working Group also recommends that incremental costs of health care alternatives should be considered explicitly with the expected health benefits and harms. Recommendations rely on judgments about the value of the incremental health benefits in relation to the incremental costs. The last column in Table 3 is the overall trade-off between benefits and harms and incorporates any risk or uncertainty.
For MADIT I, the overall GRADE and strength of the recommendation is “moderate” – the quality of the evidence is “moderate” (uncertainty due to methodological limitations in the study design), and risk/uncertainty in cost and budget impact was mitigated by the use of filters to help target the prevalent population at risk (Table 3).
For MADIT II, the overall GRADE and strength of the recommendation is “very weak” – the quality of the evidence is “weak” (uncertainty due to methodological limitations in the study design), but there is risk or uncertainty regarding the high prevalence, cost, and budget impact. It is not clear why screening for high-risk patients was dropped, given that in MADIT II the absolute reduction in mortality was small (5.6%) compared to MADIT I, which used electrophysiological screening (23%) (Table 3).
For SCD-HeFT, the overall GRADE and strength of the recommendation is “weak” – the study quality is “moderate,” but there is also risk/uncertainty due to a high NNT at 5 years (13 compared to the MADIT II NNT of 6 and MADIT I NNT of 2 at 5 years), high prevalent population (N = 23,700), and a high budget impact ($770 million). A filter (as demonstrated in MADIT 1) is required to help target the prevalent population at risk and mitigate the risk or uncertainty relating to the high NNT, prevalence, and budget impact (Table 3).
The results of the most recent ICD trial (SCD-HeFT) are not generalizable to the prevalent population in Ontario (Table 3). Given that the current funding rate of an ICD is $32,500 (Cdn), the estimated budget impact for Ontario would be as high as $770 million (Cdn). The uncertainty around the cost estimate of treating the prevalent population with LVEF < 0.30 in Ontario, the lack of human resources to implement such a strategy and the high number of patients required to prevent one SCD (NNT = 13) calls for an alternative strategy that allows the appropriate uptake and diffusion of ICDs for primary prevention for patients at maximum risk for SCD within the SCD-HeFT population.
The uptake and diffusion of ICDs for primary prevention of SCD should therefore be based on risk stratification through the use of appropriate screen(s) that would identify patients at highest risk who could derive the most benefit from this technology.
Overall GRADE and Strength of Recommendation for the Use of Implantable Cardioverter Defibrillators for the Primary Prevention of Sudden Cardiac Death
MADIT I: Multicentre Automatic Defibrillator Implantation Trial I; MADIT II: Multicentre Automatic Defibrillator Implantation Trial II; SCD-HeFT: Sudden Cardiac Death in Heart Failure Trial.
NNT indicates number needed to treat. The NNT will appear higher if follow-up is short. For ICDs, the absolute benefit increases over time for at least a 5-year period; the NNT declines, often substantially, in studies with a longer follow-up. When the NNT are equalized for a similar period as the SCD-HeFT duration (5 years), the NNT for MADIT-I is 2.2; for MADIT-II, it is 6.3.
NSVT indicates nonsustained ventricular tachycardia; VT, ventricular tachycardia.
PMCID: PMC3382404  PMID: 23074465
5.  The association between parathyroid hormone and mortality in dialysis patients is modified by wasting 
Nephrology Dialysis Transplantation  2009;24(10):3151-3157.
Background. The association between parathyroid hormone (PTH) level and mortality in dialysis patients is controversial. We hypothesized that wasting, a common condition potentially related to adynamic bone disease, modifies the association of PTH with mortality and cardiovascular events (CVE), respectively.
Methods. We analysed data from 1255 diabetic haemodialysis patients, participating in the German Diabetes and Dialysis Study between 1998 and 2004. The patients were stratified by the presence or absence of wasting (albumin ≤3.8 versus albumin >3.8 g/dL; BMI ≤23 versus BMI >23 kg/m2). Using Cox regression analyses, we calculated the risks of (1) all-cause mortality and (2) CVE according to baseline PTH levels. All analyses were adjusted for age, sex, atorvastatin treatment, duration of dialysis, comorbidity, HbA1c, phosphate, calcium, blood pressure, haemoglobin and C-reactive protein.
Results. Patients had a mean age of 66 ± 8 years, and 54% were male. Among patients without wasting (albumin >3.8 g/dL, n = 586), the risks of death and CVE during 4 years of follow-up significantly increased by 23% and 20% per unit increase in logPTH. Patients in the highest PTH tertile had a 74% higher risk of death (HRadj 1.74, 95% CI 1.27–2.40) and a 49% higher risk of CVE (HRadj 1.49, 95% CI 1.05–2.11) compared to patients in the lowest PTH tertile. In contrast, no effect was found in patients with wasting. Accordingly, additional analyses in strata of BMI showed that PTH significantly impacted on death and CVE [HR(logPTH)adj 1.15 and 1.14, respectively] only in patients without, but not in patients with, wasting.
Conclusions. Wasting modifies the association of PTH with adverse outcomes in diabetic dialysis patients. High PTH levels are of concern in the patients without wasting, while the effect of PTH on mortality is nullified in the patients with wasting.
doi:10.1093/ndt/gfp260
PMCID: PMC2747498  PMID: 19474272
cardiovascular events; haemodialysis; mortality; parathyroid hormone; wasting
6.  The Association of Visceral Adiposity with Cardiovascular Events in Patients with Peripheral Artery Disease 
PLoS ONE  2013;8(12):e82350.
Background
Previous studies have suggested that patients with peripheral artery disease (PAD) suffer from a high incidence of cardiovascular events (CVE). Visceral adiposity has been implicated in promoting CVEs. This study aimed to assess the association of relative visceral adipose volume with incident cardiovascular events in patients with peripheral artery disease.
Methods
This was a prospective cohort study including 260 patients with PAD who presented between 2003 and 2012. Cases were patients with diagnosed PAD including symptomatic lower limb athero-thrombosis and asymptomatic abdominal aortic aneurysm. All patients underwent computed tomography angiography (CTA). Abdominal visceral to total adipose volume ratio (relative visceral adipose volume) was estimated from CTAs using a previously validated workstation protocol. Cardiovascular risk factors were recorded at entry. The association of visceral adiposity with major CVEs (death, non-fatal myocardial infarction or stroke) was examined using Kaplan Meier and Cox proportional hazard analyses.
Results
A total of 92 major CVEs were recorded in 76 patients during a median follow-up of 2.8 (IQR 1.2 to 4.8) years, including myocardial infarction (n = 26), stroke (n = 10) and death (n = 56). At 3 years the incidence of major CVEs stratified by relative visceral adipose volume quartiles were 15% [Quartile (Q) 1], 17% (Q2), 11% (Q3) and 15% (Q4) (P = 0.517). Relative visceral adipose volume was not associated with major CVEs after adjustment for other risk factors.
Conclusion
This study suggests that visceral adiposity does not play a central role in the predisposition for major CVEs in patients with PAD.
doi:10.1371/journal.pone.0082350
PMCID: PMC3873921  PMID: 24386093
7.  Clinical Utility of Vitamin D Testing 
Executive Summary
This report from the Medical Advisory Secretariat (MAS) was intended to evaluate the clinical utility of vitamin D testing in average risk Canadians and in those with kidney disease. As a separate analysis, this report also includes a systematic literature review of the prevalence of vitamin D deficiency in these two subgroups.
This evaluation did not set out to determine the serum vitamin D thresholds that might apply to non-bone health outcomes. For bone health outcomes, no high or moderate quality evidence could be found to support a target serum level above 50 nmol/L. Similarly, no high or moderate quality evidence could be found to support vitamin D’s effects in non-bone health outcomes, other than falls.
Vitamin D
Vitamin D is a lipid soluble vitamin that acts as a hormone. It stimulates intestinal calcium absorption and is important in maintaining adequate phosphate levels for bone mineralization, bone growth, and remodelling. It’s also believed to be involved in the regulation of cell growth proliferation and apoptosis (programmed cell death), as well as modulation of the immune system and other functions. Alone or in combination with calcium, Vitamin D has also been shown to reduce the risk of fractures in elderly men (≥ 65 years), postmenopausal women, and the risk of falls in community-dwelling seniors. However, in a comprehensive systematic review, inconsistent results were found concerning the effects of vitamin D in conditions such as cancer, all-cause mortality, and cardiovascular disease. In fact, no high or moderate quality evidence could be found concerning the effects of vitamin D in such non-bone health outcomes. Given the uncertainties surrounding the effects of vitamin D in non-bone health related outcomes, it was decided that this evaluation should focus on falls and the effects of vitamin D in bone health and exclusively within average-risk individuals and patients with kidney disease.
Synthesis of vitamin D occurs naturally in the skin through exposure to ultraviolet B (UVB) radiation from sunlight, but it can also be obtained from dietary sources including fortified foods, and supplements. Foods rich in vitamin D include fatty fish, egg yolks, fish liver oil, and some types of mushrooms. Since it is usually difficult to obtain sufficient vitamin D from non-fortified foods, either due to low content or infrequent use, most vitamin D is obtained from fortified foods, exposure to sunlight, and supplements.
Clinical Need: Condition and Target Population
Vitamin D deficiency may lead to rickets in infants and osteomalacia in adults. Factors believed to be associated with vitamin D deficiency include:
darker skin pigmentation,
winter season,
living at higher latitudes,
skin coverage,
kidney disease,
malabsorption syndromes such as Crohn’s disease, cystic fibrosis, and
genetic factors.
Patients with chronic kidney disease (CKD) are at a higher risk of vitamin D deficiency due to either renal losses or decreased synthesis of 1,25-dihydroxyvitamin D.
Health Canada currently recommends that, until the daily recommended intakes (DRI) for vitamin D are updated, Canada’s Food Guide (Eating Well with Canada’s Food Guide) should be followed with respect to vitamin D intake. Issued in 2007, the Guide recommends that Canadians consume two cups (500 ml) of fortified milk or fortified soy beverages daily in order to obtain a daily intake of 200 IU. In addition, men and women over the age of 50 should take 400 IU of vitamin D supplements daily. Additional recommendations were made for breastfed infants.
A Canadian survey evaluated the median vitamin D intake derived from diet alone (excluding supplements) among 35,000 Canadians, 10,900 of which were from Ontario. Among Ontarian males ages 9 and up, the median daily dietary vitamin D intake ranged between 196 IU and 272 IU per day. Among females, it varied from 152 IU to 196 IU per day. In boys and girls ages 1 to 3, the median daily dietary vitamin D intake was 248 IU, while among those 4 to 8 years it was 224 IU.
Vitamin D Testing
Two laboratory tests for vitamin D are available, 25-hydroxy vitamin D, referred to as 25(OH)D, and 1,25-dihydroxyvitamin D. Vitamin D status is assessed by measuring the serum 25(OH)D levels, which can be assayed using radioimmunoassays, competitive protein-binding assays (CPBA), high pressure liquid chromatography (HPLC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). These may yield different results with inter-assay variation reaching up to 25% (at lower serum levels) and intra-assay variation reaching 10%.
The optimal serum concentration of vitamin D has not been established and it may change across different stages of life. Similarly, there is currently no consensus on target serum vitamin D levels. There does, however, appear to be a consensus on the definition of vitamin D deficiency at 25(OH)D < 25 nmol/l, which is based on the risk of diseases such as rickets and osteomalacia. Higher target serum levels have also been proposed based on subclinical endpoints such as parathyroid hormone (PTH). Therefore, in this report, two conservative target serum levels have been adopted, 25 nmol/L (based on the risk of rickets and osteomalacia), and 40 to 50 nmol/L (based on vitamin D’s interaction with PTH).
Ontario Context
Volume & Cost
The volume of vitamin D tests done in Ontario has been increasing over the past 5 years with a steep increase of 169,000 tests in 2007 to more than 393,400 tests in 2008. The number of tests continues to rise with the projected number of tests for 2009 exceeding 731,000. According to the Ontario Schedule of Benefits, the billing cost of each test is $51.7 for 25(OH)D (L606, 100 LMS units, $0.517/unit) and $77.6 for 1,25-dihydroxyvitamin D (L605, 150 LMS units, $0.517/unit). Province wide, the total annual cost of vitamin D testing has increased from approximately $1.7M in 2004 to over $21.0M in 2008. The projected annual cost for 2009 is approximately $38.8M.
Evidence-Based Analysis
The objective of this report is to evaluate the clinical utility of vitamin D testing in the average risk population and in those with kidney disease. As a separate analysis, the report also sought to evaluate the prevalence of vitamin D deficiency in Canada. The specific research questions addressed were thus:
What is the clinical utility of vitamin D testing in the average risk population and in subjects with kidney disease?
What is the prevalence of vitamin D deficiency in the average risk population in Canada?
What is the prevalence of vitamin D deficiency in patients with kidney disease in Canada?
Clinical utility was defined as the ability to improve bone health outcomes with the focus on the average risk population (excluding those with osteoporosis) and patients with kidney disease.
Literature Search
A literature search was performed on July 17th, 2009 using OVID MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL), the Cochrane Library, and the International Agency for Health Technology Assessment (INAHTA) for studies published from January 1, 1998 until July 17th, 2009. Abstracts were reviewed by a single reviewer and, for those studies meeting the eligibility criteria, full-text articles were obtained. Reference lists were also examined for any additional relevant studies not identified through the search. Articles with unknown eligibility were reviewed with a second clinical epidemiologist, then a group of epidemiologists until consensus was established. The quality of evidence was assessed as high, moderate, low or very low according to GRADE methodology.
Observational studies that evaluated the prevalence of vitamin D deficiency in Canada in the population of interest were included based on the inclusion and exclusion criteria listed below. The baseline values were used in this report in the case of interventional studies that evaluated the effect of vitamin D intake on serum levels. Studies published in grey literature were included if no studies published in the peer-reviewed literature were identified for specific outcomes or subgroups.
Considering that vitamin D status may be affected by factors such as latitude, sun exposure, food fortification, among others, the search focused on prevalence studies published in Canada. In cases where no Canadian prevalence studies were identified, the decision was made to include studies from the United States, given the similar policies in vitamin D food fortification and recommended daily intake.
Inclusion Criteria
Studies published in English
Publications that reported the prevalence of vitamin D deficiency in Canada
Studies that included subjects from the general population or with kidney disease
Studies in children or adults
Studies published between January 1998 and July 17th 2009
Exclusion Criteria
Studies that included subjects defined according to a specific disease other than kidney disease
Letters, comments, and editorials
Studies that measured the serum vitamin D levels but did not report the percentage of subjects with serum levels below a given threshold
Outcomes of Interest
Prevalence of serum vitamin D less than 25 nmol/L
Prevalence of serum vitamin D less than 40 to 50 nmol/L
Serum 25-hydroxyvitamin D was the metabolite used to assess vitamin D status. Results from adult and children studies were reported separately. Subgroup analyses according to factors that affect serum vitamin D levels (e.g., seasonal effects, skin pigmentation, and vitamin D intake) were reported if enough information was provided in the studies
Quality of Evidence
The quality of the prevalence studies was based on the method of subject recruitment and sampling, possibility of selection bias, and generalizability to the source population. The overall quality of the trials was examined according to the GRADE Working Group criteria.
Summary of Findings
Fourteen prevalence studies examining Canadian adults and children met the eligibility criteria. With the exception of one longitudinal study, the studies had a cross-sectional design. Two studies were conducted among Canadian adults with renal disease but none studied Canadian children with renal disease (though three such US studies were included). No systematic reviews or health technology assessments that evaluated the prevalence of vitamin D deficiency in Canada were identified. Two studies were published in grey literature, consisting of a Canadian survey designed to measure serum vitamin D levels and a study in infants presented as an abstract at a conference. Also included were the results of vitamin D tests performed in community laboratories in Ontario between October 2008 and September 2009 (provided by the Ontario Association of Medical Laboratories).
Different threshold levels were used in the studies, thus we reported the percentage of subjects with serum levels of between 25 and 30 nmol/L and between 37.5 and 50 nmol/L. Some studies stratified the results according to factors affecting vitamin D status and two used multivariate models to investigate the effects of these characteristics (including age, season, BMI, vitamin D intake, skin pigmentation, and season) on serum 25(OH)D levels. It’s unclear, however, if these studies were adequately powered for these subgroup analyses.
Study participants generally consisted of healthy, community-dwelling subjects and most excluded individuals with conditions or medications that alter vitamin D or bone metabolism, such as kidney or liver disease. Although the studies were conducted in different parts of Canada, fewer were performed in Northern latitudes, i.e. above 53°N, which is equivalent to the city of Edmonton.
Adults
Serum vitamin D levels of < 25 to 30 nmol/L were observed in 0% to 25.5% of the subjects included in five studies; the weighted average was 3.8% (95% CI: 3.0, 4.6). The preliminary results of the Canadian survey showed that approximately 5% of the subjects had serum levels below 29.5 nmol/L. The results of over 600,000 vitamin D tests performed in Ontarian community laboratories between October 2008 and September 2009 showed that 2.6% of adults (> 18 years) had serum levels < 25 nmol/L.
The prevalence of serum vitamin D levels below 37.5-50 nmol/L reported among studies varied widely, ranging from 8% to 73.6% with a weighted average of 22.5%. The preliminary results of the CHMS survey showed that between 10% and 25% of subjects had serum levels below 37 to 48 nmol/L. The results of the vitamin D tests performed in community laboratories showed that 10% to 25% of the individuals had serum levels between 39 and 50 nmol/L.
In an attempt to explain this inter-study variation, the study results were stratified according to factors affecting serum vitamin D levels, as summarized below. These results should be interpreted with caution as none were adjusted for other potential confounders. Adequately powered multivariate analyses would be necessary to determine the contribution of risk factors to lower serum 25(OH)D levels.
Seasonal variation
Three adult studies evaluating serum vitamin D levels in different seasons observed a trend towards a higher prevalence of serum levels < 37.5 to 50 nmol/L during the winter and spring months, specifically 21% to 39%, compared to 8% to 14% in the summer. The weighted average was 23.6% over the winter/spring months and 9.6% over summer. The difference between the seasons was not statistically significant in one study and not reported in the other two studies.
Skin Pigmentation
Four studies observed a trend toward a higher prevalence of serum vitamin D levels < 37.5 to 50 nmol/L in subjects with darker skin pigmentation compared to those with lighter skin pigmentation, with weighted averages of 46.8% among adults with darker skin colour and 15.9% among those with fairer skin.
Vitamin D intake and serum levels
Four adult studies evaluated serum vitamin D levels according to vitamin D intake and showed an overall trend toward a lower prevalence of serum levels < 37.5 to 50 nmol/L with higher levels of vitamin D intake. One study observed a dose-response relationship between higher vitamin D intake from supplements, diet (milk), and sun exposure (results not adjusted for other variables). It was observed that subjects taking 50 to 400 IU or > 400 IU of vitamin D per day had a 6% and 3% prevalence of serum vitamin D level < 40 nmol/L, respectively, versus 29% in subjects not on vitamin D supplementation. Similarly, among subjects drinking one or two glasses of milk per day, the prevalence of serum vitamin D levels < 40 nmol/L was found to be 15%, versus 6% in those who drink more than two glasses of milk per day and 21% among those who do not drink milk. On the other hand, one study observed little variation in serum vitamin D levels during winter according to milk intake, with the proportion of subjects exhibiting vitamin D levels of < 40 nmol/L being 21% among those drinking 0-2 glasses per day, 26% among those drinking > 2 glasses, and 20% among non-milk drinkers.
The overall quality of evidence for the studies conducted among adults was deemed to be low, although it was considered moderate for the subgroups of skin pigmentation and seasonal variation.
Newborn, Children and Adolescents
Five Canadian studies evaluated serum vitamin D levels in newborns, children, and adolescents. In four of these, it was found that between 0 and 36% of children exhibited deficiency across age groups with a weighted average of 6.4%. The results of over 28,000 vitamin D tests performed in children 0 to 18 years old in Ontario laboratories (Oct. 2008 to Sept. 2009) showed that 4.4% had serum levels of < 25 nmol/L.
According to two studies, 32% of infants 24 to 30 months old and 35.3% of newborns had serum vitamin D levels of < 50 nmol/L. Two studies of children 2 to 16 years old reported that 24.5% and 34% had serum vitamin D levels below 37.5 to 40 nmol/L. In both studies, older children exhibited a higher prevalence than younger children, with weighted averages 34.4% and 10.3%, respectively. The overall weighted average of the prevalence of serum vitamin D levels < 37.5 to 50 nmol/L among pediatric studies was 25.8%. The preliminary results of the Canadian survey showed that between 10% and 25% of subjects between 6 and 11 years (N= 435) had serum levels below 50 nmol/L, while for those 12 to 19 years, 25% to 50% exhibited serum vitamin D levels below 50 nmol/L.
The effects of season, skin pigmentation, and vitamin D intake were not explored in Canadian pediatric studies. A Canadian surveillance study did, however, report 104 confirmed cases1 (2.9 cases per 100,000 children) of vitamin D-deficient rickets among Canadian children age 1 to 18 between 2002 and 2004, 57 (55%) of which from Ontario. The highest incidence occurred among children living in the North, i.e., the Yukon, Northwest Territories, and Nunavut. In 92 (89%) cases, skin pigmentation was categorized as intermediate to dark, 98 (94%) had been breastfed, and 25 (24%) were offspring of immigrants to Canada. There were no cases of rickets in children receiving ≥ 400 IU VD supplementation/day.
Overall, the quality of evidence of the studies of children was considered very low.
Kidney Disease
Adults
Two studies evaluated serum vitamin D levels in Canadian adults with kidney disease. The first included 128 patients with chronic kidney disease stages 3 to 5, 38% of which had serum vitamin D levels of < 37.5 nmol/L (measured between April and July). This is higher than what was reported in Canadian studies of the general population during the summer months (i.e. between 8% and 14%). In the second, which examined 419 subjects who had received a renal transplantation (mean time since transplantation: 7.2 ± 6.4 years), the prevalence of serum vitamin D levels < 40 nmol/L was 27.3%. The authors concluded that the prevalence observed in the study population was similar to what is expected in the general population.
Children
No studies evaluating serum vitamin D levels in Canadian pediatric patients with kidney disease could be identified, although three such US studies among children with chronic kidney disease stages 1 to 5 were. The mean age varied between 10.7 and 12.5 years in two studies but was not reported in the third. Across all three studies, the prevalence of serum vitamin D levels below the range of 37.5 to 50 nmol/L varied between 21% and 39%, which is not considerably different from what was observed in studies of healthy Canadian children (24% to 35%).
Overall, the quality of evidence in adults and children with kidney disease was considered very low.
Clinical Utility of Vitamin D Testing
A high quality comprehensive systematic review published in August 2007 evaluated the association between serum vitamin D levels and different bone health outcomes in different age groups. A total of 72 studies were included. The authors observed that there was a trend towards improvement in some bone health outcomes with higher serum vitamin D levels. Nevertheless, precise thresholds for improved bone health outcomes could not be defined across age groups. Further, no new studies on the association were identified during an updated systematic review on vitamin D published in July 2009.
With regards to non-bone health outcomes, there is no high or even moderate quality evidence that supports the effectiveness of vitamin D in outcomes such as cancer, cardiovascular outcomes, and all-cause mortality. Even if there is any residual uncertainty, there is no evidence that testing vitamin D levels encourages adherence to Health Canada’s guidelines for vitamin D intake. A normal serum vitamin D threshold required to prevent non-bone health related conditions cannot be resolved until a causal effect or correlation has been demonstrated between vitamin D levels and these conditions. This is as an ongoing research issue around which there is currently too much uncertainty to base any conclusions that would support routine vitamin D testing.
For patients with chronic kidney disease (CKD), there is again no high or moderate quality evidence supporting improved outcomes through the use of calcitriol or vitamin D analogs. In the absence of such data, the authors of the guidelines for CKD patients consider it best practice to maintain serum calcium and phosphate at normal levels, while supplementation with active vitamin D should be considered if serum PTH levels are elevated. As previously stated, the authors of guidelines for CKD patients believe that there is not enough evidence to support routine vitamin D [25(OH)D] testing. According to what is stated in the guidelines, decisions regarding the commencement or discontinuation of treatment with calcitriol or vitamin D analogs should be based on serum PTH, calcium, and phosphate levels.
Limitations associated with the evidence of vitamin D testing include ambiguities in the definition of an ‘adequate threshold level’ and both inter- and intra- assay variability. The MAS considers both the lack of a consensus on the target serum vitamin D levels and assay limitations directly affect and undermine the clinical utility of testing. The evidence supporting the clinical utility of vitamin D testing is thus considered to be of very low quality.
Daily vitamin D intake, either through diet or supplementation, should follow Health Canada’s recommendations for healthy individuals of different age groups. For those with medical conditions such as renal disease, liver disease, and malabsorption syndromes, and for those taking medications that may affect vitamin D absorption/metabolism, physician guidance should be followed with respect to both vitamin D testing and supplementation.
Conclusions
Studies indicate that vitamin D, alone or in combination with calcium, may decrease the risk of fractures and falls among older adults.
There is no high or moderate quality evidence to support the effectiveness of vitamin D in other outcomes such as cancer, cardiovascular outcomes, and all-cause mortality.
Studies suggest that the prevalence of vitamin D deficiency in Canadian adults and children is relatively low (approximately 5%), and between 10% and 25% have serum levels below 40 to 50 nmol/L (based on very low to low grade evidence).
Given the limitations associated with serum vitamin D measurement, ambiguities in the definition of a ‘target serum level’, and the availability of clear guidelines on vitamin D supplementation from Health Canada, vitamin D testing is not warranted for the average risk population.
Health Canada has issued recommendations regarding the adequate daily intake of vitamin D, but current studies suggest that the mean dietary intake is below these recommendations. Accordingly, Health Canada’s guidelines and recommendations should be promoted.
Based on a moderate level of evidence, individuals with darker skin pigmentation appear to have a higher risk of low serum vitamin D levels than those with lighter skin pigmentation and therefore may need to be specially targeted with respect to optimum vitamin D intake. The cause-effect of this association is currently unclear.
Individuals with medical conditions such as renal and liver disease, osteoporosis, and malabsorption syndromes, as well as those taking medications that may affect vitamin D absorption/metabolism, should follow their physician’s guidance concerning both vitamin D testing and supplementation.
PMCID: PMC3377517  PMID: 23074397
8.  Internet-Based Device-Assisted Remote Monitoring of Cardiovascular Implantable Electronic Devices 
Executive Summary
Objective
The objective of this Medical Advisory Secretariat (MAS) report was to conduct a systematic review of the available published evidence on the safety, effectiveness, and cost-effectiveness of Internet-based device-assisted remote monitoring systems (RMSs) for therapeutic cardiac implantable electronic devices (CIEDs) such as pacemakers (PMs), implantable cardioverter-defibrillators (ICDs), and cardiac resynchronization therapy (CRT) devices. The MAS evidence-based review was performed to support public financing decisions.
Clinical Need: Condition and Target Population
Sudden cardiac death (SCD) is a major cause of fatalities in developed countries. In the United States almost half a million people die of SCD annually, resulting in more deaths than stroke, lung cancer, breast cancer, and AIDS combined. In Canada each year more than 40,000 people die from a cardiovascular related cause; approximately half of these deaths are attributable to SCD.
Most cases of SCD occur in the general population typically in those without a known history of heart disease. Most SCDs are caused by cardiac arrhythmia, an abnormal heart rhythm caused by malfunctions of the heart’s electrical system. Up to half of patients with significant heart failure (HF) also have advanced conduction abnormalities.
Cardiac arrhythmias are managed by a variety of drugs, ablative procedures, and therapeutic CIEDs. The range of CIEDs includes pacemakers (PMs), implantable cardioverter-defibrillators (ICDs), and cardiac resynchronization therapy (CRT) devices. Bradycardia is the main indication for PMs and individuals at high risk for SCD are often treated by ICDs.
Heart failure (HF) is also a significant health problem and is the most frequent cause of hospitalization in those over 65 years of age. Patients with moderate to severe HF may also have cardiac arrhythmias, although the cause may be related more to heart pump or haemodynamic failure. The presence of HF, however, increases the risk of SCD five-fold, regardless of aetiology. Patients with HF who remain highly symptomatic despite optimal drug therapy are sometimes also treated with CRT devices.
With an increasing prevalence of age-related conditions such as chronic HF and the expanding indications for ICD therapy, the rate of ICD placement has been dramatically increasing. The appropriate indications for ICD placement, as well as the rate of ICD placement, are increasingly an issue. In the United States, after the introduction of expanded coverage of ICDs, a national ICD registry was created in 2005 to track these devices. A recent survey based on this national ICD registry reported that 22.5% (25,145) of patients had received a non-evidence based ICD and that these patients experienced significantly higher in-hospital mortality and post-procedural complications.
In addition to the increased ICD device placement and the upfront device costs, there is the need for lifelong follow-up or surveillance, placing a significant burden on patients and device clinics. In 2007, over 1.6 million CIEDs were implanted in Europe and the United States, which translates to over 5.5 million patient encounters per year if the recommended follow-up practices are considered. A safe and effective RMS could potentially improve the efficiency of long-term follow-up of patients and their CIEDs.
Technology
In addition to being therapeutic devices, CIEDs have extensive diagnostic abilities. All CIEDs can be interrogated and reprogrammed during an in-clinic visit using an inductive programming wand. Remote monitoring would allow patients to transmit information recorded in their devices from the comfort of their own homes. Currently most ICD devices also have the potential to be remotely monitored. Remote monitoring (RM) can be used to check system integrity, to alert on arrhythmic episodes, and to potentially replace in-clinic follow-ups and manage disease remotely. They do not currently have the capability of being reprogrammed remotely, although this feature is being tested in pilot settings.
Every RMS is specifically designed by a manufacturer for their cardiac implant devices. For Internet-based device-assisted RMSs, this customization includes details such as web application, multiplatform sensors, custom algorithms, programming information, and types and methods of alerting patients and/or physicians. The addition of peripherals for monitoring weight and pressure or communicating with patients through the onsite communicators also varies by manufacturer. Internet-based device-assisted RMSs for CIEDs are intended to function as a surveillance system rather than an emergency system.
Health care providers therefore need to learn each application, and as more than one application may be used at one site, multiple applications may need to be reviewed for alarms. All RMSs deliver system integrity alerting; however, some systems seem to be better geared to fast arrhythmic alerting, whereas other systems appear to be more intended for remote follow-up or supplemental remote disease management. The different RMSs may therefore have different impacts on workflow organization because of their varying frequency of interrogation and methods of alerts. The integration of these proprietary RM web-based registry systems with hospital-based electronic health record systems has so far not been commonly implemented.
Currently there are 2 general types of RMSs: those that transmit device diagnostic information automatically and without patient assistance to secure Internet-based registry systems, and those that require patient assistance to transmit information. Both systems employ the use of preprogrammed alerts that are either transmitted automatically or at regular scheduled intervals to patients and/or physicians.
The current web applications, programming, and registry systems differ greatly between the manufacturers of transmitting cardiac devices. In Canada there are currently 4 manufacturers—Medtronic Inc., Biotronik, Boston Scientific Corp., and St Jude Medical Inc.—which have regulatory approval for remote transmitting CIEDs. Remote monitoring systems are proprietary to the manufacturer of the implant device. An RMS for one device will not work with another device, and the RMS may not work with all versions of the manufacturer’s devices.
All Internet-based device-assisted RMSs have common components. The implanted device is equipped with a micro-antenna that communicates with a small external device (at bedside or wearable) commonly known as the transmitter. Transmitters are able to interrogate programmed parameters and diagnostic data stored in the patients’ implant device. The information transfer to the communicator can occur at preset time intervals with the participation of the patient (waving a wand over the device) or it can be sent automatically (wirelessly) without their participation. The encrypted data are then uploaded to an Internet-based database on a secure central server. The data processing facilities at the central database, depending on the clinical urgency, can trigger an alert for the physician(s) that can be sent via email, fax, text message, or phone. The details are also posted on the secure website for viewing by the physician (or their delegate) at their convenience.
Research Questions
The research directions and specific research questions for this evidence review were as follows:
To identify the Internet-based device-assisted RMSs available for follow-up of patients with therapeutic CIEDs such as PMs, ICDs, and CRT devices.
To identify the potential risks, operational issues, or organizational issues related to Internet-based device-assisted RM for CIEDs.
To evaluate the safety, acceptability, and effectiveness of Internet-based device-assisted RMSs for CIEDs such as PMs, ICDs, and CRT devices.
To evaluate the safety, effectiveness, and cost-effectiveness of Internet-based device-assisted RMSs for CIEDs compared to usual outpatient in-office monitoring strategies.
To evaluate the resource implications or budget impact of RMSs for CIEDs in Ontario, Canada.
Research Methods
Literature Search
The review included a systematic review of published scientific literature and consultations with experts and manufacturers of all 4 approved RMSs for CIEDs in Canada. Information on CIED cardiac implant clinics was also obtained from Provincial Programs, a division within the Ministry of Health and Long-Term Care with a mandate for cardiac implant specialty care. Various administrative databases and registries were used to outline the current clinical follow-up burden of CIEDs in Ontario. The provincial population-based ICD database developed and maintained by the Institute for Clinical Evaluative Sciences (ICES) was used to review the current follow-up practices with Ontario patients implanted with ICD devices.
Search Strategy
A literature search was performed on September 21, 2010 using OVID MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL), the Cochrane Library, and the International Agency for Health Technology Assessment (INAHTA) for studies published from 1950 to September 2010. Search alerts were generated and reviewed for additional relevant literature until December 31, 2010. Abstracts were reviewed by a single reviewer and, for those studies meeting the eligibility criteria full-text articles were obtained. Reference lists were also examined for any additional relevant studies not identified through the search.
Inclusion Criteria
published between 1950 and September 2010;
English language full-reports and human studies;
original reports including clinical evaluations of Internet-based device-assisted RMSs for CIEDs in clinical settings;
reports including standardized measurements on outcome events such as technical success, safety, effectiveness, cost, measures of health care utilization, morbidity, mortality, quality of life or patient satisfaction;
randomized controlled trials (RCTs), systematic reviews and meta-analyses, cohort and controlled clinical studies.
Exclusion Criteria
non-systematic reviews, letters, comments and editorials;
reports not involving standardized outcome events;
clinical reports not involving Internet-based device assisted RM systems for CIEDs in clinical settings;
reports involving studies testing or validating algorithms without RM;
studies with small samples (<10 subjects).
Outcomes of Interest
The outcomes of interest included: technical outcomes, emergency department visits, complications, major adverse events, symptoms, hospital admissions, clinic visits (scheduled and/or unscheduled), survival, morbidity (disease progression, stroke, etc.), patient satisfaction, and quality of life.
Summary of Findings
The MAS evidence review was performed to review available evidence on Internet-based device-assisted RMSs for CIEDs published until September 2010. The search identified 6 systematic reviews, 7 randomized controlled trials, and 19 reports for 16 cohort studies—3 of these being registry-based and 4 being multi-centered. The evidence is summarized in the 3 sections that follow.
1. Effectiveness of Remote Monitoring Systems of CIEDs for Cardiac Arrhythmia and Device Functioning
In total, 15 reports on 13 cohort studies involving investigations with 4 different RMSs for CIEDs in cardiology implant clinic groups were identified in the review. The 4 RMSs were: Care Link Network® (Medtronic Inc,, Minneapolis, MN, USA); Home Monitoring® (Biotronic, Berlin, Germany); House Call 11® (St Jude Medical Inc., St Pauls, MN, USA); and a manufacturer-independent RMS. Eight of these reports were with the Home Monitoring® RMS (12,949 patients), 3 were with the Care Link® RMS (167 patients), 1 was with the House Call 11® RMS (124 patients), and 1 was with a manufacturer-independent RMS (44 patients). All of the studies, except for 2 in the United States, (1 with Home Monitoring® and 1 with House Call 11®), were performed in European countries.
The RMSs in the studies were evaluated with different cardiac implant device populations: ICDs only (6 studies), ICD and CRT devices (3 studies), PM and ICD and CRT devices (4 studies), and PMs only (2 studies). The patient populations were predominately male (range, 52%–87%) in all studies, with mean ages ranging from 58 to 76 years. One study population was unique in that RMSs were evaluated for ICDs implanted solely for primary prevention in young patients (mean age, 44 years) with Brugada syndrome, which carries an inherited increased genetic risk for sudden heart attack in young adults.
Most of the cohort studies reported on the feasibility of RMSs in clinical settings with limited follow-up. In the short follow-up periods of the studies, the majority of the events were related to detection of medical events rather than system configuration or device abnormalities. The results of the studies are summarized below:
The interrogation of devices on the web platform, both for continuous and scheduled transmissions, was significantly quicker with remote follow-up, both for nurses and physicians.
In a case-control study focusing on a Brugada population–based registry with patients followed-up remotely, there were significantly fewer outpatient visits and greater detection of inappropriate shocks. One death occurred in the control group not followed remotely and post-mortem analysis indicated early signs of lead failure prior to the event.
Two studies examined the role of RMSs in following ICD leads under regulatory advisory in a European clinical setting and noted:
– Fewer inappropriate shocks were administered in the RM group.
– Urgent in-office interrogations and surgical revisions were performed within 12 days of remote alerts.
– No signs of lead fracture were detected at in-office follow-up; all were detected at remote follow-up.
Only 1 study reported evaluating quality of life in patients followed up remotely at 3 and 6 months; no values were reported.
Patient satisfaction was evaluated in 5 cohort studies, all in short term follow-up: 1 for the Home Monitoring® RMS, 3 for the Care Link® RMS, and 1 for the House Call 11® RMS.
– Patients reported receiving a sense of security from the transmitter, a good relationship with nurses and physicians, positive implications for their health, and satisfaction with RM and organization of services.
– Although patients reported that the system was easy to implement and required less than 10 minutes to transmit information, a variable proportion of patients (range, 9% 39%) reported that they needed the assistance of a caregiver for their transmission.
– The majority of patients would recommend RM to other ICD patients.
– Patients with hearing or other physical or mental conditions hindering the use of the system were excluded from studies, but the frequency of this was not reported.
Physician satisfaction was evaluated in 3 studies, all with the Care Link® RMS:
– Physicians reported an ease of use and high satisfaction with a generally short-term use of the RMS.
– Physicians reported being able to address the problems in unscheduled patient transmissions or physician initiated transmissions remotely, and were able to handle the majority of the troubleshooting calls remotely.
– Both nurses and physicians reported a high level of satisfaction with the web registry system.
2. Effectiveness of Remote Monitoring Systems in Heart Failure Patients for Cardiac Arrhythmia and Heart Failure Episodes
Remote follow-up of HF patients implanted with ICD or CRT devices, generally managed in specialized HF clinics, was evaluated in 3 cohort studies: 1 involved the Home Monitoring® RMS and 2 involved the Care Link® RMS. In these RMSs, in addition to the standard diagnostic features, the cardiac devices continuously assess other variables such as patient activity, mean heart rate, and heart rate variability. Intra-thoracic impedance, a proxy measure for lung fluid overload, was also measured in the Care Link® studies. The overall diagnostic performance of these measures cannot be evaluated, as the information was not reported for patients who did not experience intra-thoracic impedance threshold crossings or did not undergo interventions. The trial results involved descriptive information on transmissions and alerts in patients experiencing high morbidity and hospitalization in the short study periods.
3. Comparative Effectiveness of Remote Monitoring Systems for CIEDs
Seven RCTs were identified evaluating RMSs for CIEDs: 2 were for PMs (1276 patients) and 5 were for ICD/CRT devices (3733 patients). Studies performed in the clinical setting in the United States involved both the Care Link® RMS and the Home Monitoring® RMS, whereas all studies performed in European countries involved only the Home Monitoring® RMS.
3A. Randomized Controlled Trials of Remote Monitoring Systems for Pacemakers
Two trials, both multicenter RCTs, were conducted in different countries with different RMSs and study objectives. The PREFER trial was a large trial (897 patients) performed in the United States examining the ability of Care Link®, an Internet-based remote PM interrogation system, to detect clinically actionable events (CAEs) sooner than the current in-office follow-up supplemented with transtelephonic monitoring transmissions, a limited form of remote device interrogation. The trial results are summarized below:
In the 375-day mean follow-up, 382 patients were identified with at least 1 CAE—111 patients in the control arm and 271 in the remote arm.
The event rate detected per patient for every type of CAE, except for loss of atrial capture, was higher in the remote arm than the control arm.
The median time to first detection of CAEs (4.9 vs. 6.3 months) was significantly shorter in the RMS group compared to the control group (P < 0.0001).
Additionally, only 2% (3/190) of the CAEs in the control arm were detected during a transtelephonic monitoring transmission (the rest were detected at in-office follow-ups), whereas 66% (446/676) of the CAEs were detected during remote interrogation.
The second study, the OEDIPE trial, was a smaller trial (379 patients) performed in France evaluating the ability of the Home Monitoring® RMS to shorten PM post-operative hospitalization while preserving the safety of conventional management of longer hospital stays.
Implementation and operationalization of the RMS was reported to be successful in 91% (346/379) of the patients and represented 8144 transmissions.
In the RM group 6.5% of patients failed to send messages (10 due to improper use of the transmitter, 2 with unmanageable stress). Of the 172 patients transmitting, 108 patients sent a total of 167 warnings during the trial, with a greater proportion of warnings being attributed to medical rather than technical causes.
Forty percent had no warning message transmission and among these, 6 patients experienced a major adverse event and 1 patient experienced a non-major adverse event. Of the 6 patients having a major adverse event, 5 contacted their physician.
The mean medical reaction time was faster in the RM group (6.5 ± 7.6 days vs. 11.4 ± 11.6 days).
The mean duration of hospitalization was significantly shorter (P < 0.001) for the RM group than the control group (3.2 ± 3.2 days vs. 4.8 ± 3.7 days).
Quality of life estimates by the SF-36 questionnaire were similar for the 2 groups at 1-month follow-up.
3B. Randomized Controlled Trials Evaluating Remote Monitoring Systems for ICD or CRT Devices
The 5 studies evaluating the impact of RMSs with ICD/CRT devices were conducted in the United States and in European countries and involved 2 RMSs—Care Link® and Home Monitoring ®. The objectives of the trials varied and 3 of the trials were smaller pilot investigations.
The first of the smaller studies (151 patients) evaluated patient satisfaction, achievement of patient outcomes, and the cost-effectiveness of the Care Link® RMS compared to quarterly in-office device interrogations with 1-year follow-up.
Individual outcomes such as hospitalizations, emergency department visits, and unscheduled clinic visits were not significantly different between the study groups.
Except for a significantly higher detection of atrial fibrillation in the RM group, data on ICD detection and therapy were similar in the study groups.
Health-related quality of life evaluated by the EuroQoL at 6-month or 12-month follow-up was not different between study groups.
Patients were more satisfied with their ICD care in the clinic follow-up group than in the remote follow-up group at 6-month follow-up, but were equally satisfied at 12- month follow-up.
The second small pilot trial (20 patients) examined the impact of RM follow-up with the House Call 11® system on work schedules and cost savings in patients randomized to 2 study arms varying in the degree of remote follow-up.
The total time including device interrogation, transmission time, data analysis, and physician time required was significantly shorter for the RM follow-up group.
The in-clinic waiting time was eliminated for patients in the RM follow-up group.
The physician talk time was significantly reduced in the RM follow-up group (P < 0.05).
The time for the actual device interrogation did not differ in the study groups.
The third small trial (115 patients) examined the impact of RM with the Home Monitoring® system compared to scheduled trimonthly in-clinic visits on the number of unplanned visits, total costs, health-related quality of life (SF-36), and overall mortality.
There was a 63.2% reduction in in-office visits in the RM group.
Hospitalizations or overall mortality (values not stated) were not significantly different between the study groups.
Patient-induced visits were higher in the RM group than the in-clinic follow-up group.
The TRUST Trial
The TRUST trial was a large multicenter RCT conducted at 102 centers in the United States involving the Home Monitoring® RMS for ICD devices for 1450 patients. The primary objectives of the trial were to determine if remote follow-up could be safely substituted for in-office clinic follow-up (3 in-office visits replaced) and still enable earlier physician detection of clinically actionable events.
Adherence to the protocol follow-up schedule was significantly higher in the RM group than the in-office follow-up group (93.5% vs. 88.7%, P < 0.001).
Actionability of trimonthly scheduled checks was low (6.6%) in both study groups. Overall, actionable causes were reprogramming (76.2%), medication changes (24.8%), and lead/system revisions (4%), and these were not different between the 2 study groups.
The overall mean number of in-clinic and hospital visits was significantly lower in the RM group than the in-office follow-up group (2.1 per patient-year vs. 3.8 per patient-year, P < 0.001), representing a 45% visit reduction at 12 months.
The median time from onset of first arrhythmia to physician evaluation was significantly shorter (P < 0.001) in the RM group than in the in-office follow-up group for all arrhythmias (1 day vs. 35.5 days).
The median time to detect clinically asymptomatic arrhythmia events—atrial fibrillation (AF), ventricular fibrillation (VF), ventricular tachycardia (VT), and supra-ventricular tachycardia (SVT)—was also significantly shorter (P < 0.001) in the RM group compared to the in-office follow-up group (1 day vs. 41.5 days) and was significantly quicker for each of the clinical arrhythmia events—AF (5.5 days vs. 40 days), VT (1 day vs. 28 days), VF (1 day vs. 36 days), and SVT (2 days vs. 39 days).
System-related problems occurred infrequently in both groups—in 1.5% of patients (14/908) in the RM group and in 0.7% of patients (3/432) in the in-office follow-up group.
The overall adverse event rate over 12 months was not significantly different between the 2 groups and individual adverse events were also not significantly different between the RM group and the in-office follow-up group: death (3.4% vs. 4.9%), stroke (0.3% vs. 1.2%), and surgical intervention (6.6% vs. 4.9%), respectively.
The 12-month cumulative survival was 96.4% (95% confidence interval [CI], 95.5%–97.6%) in the RM group and 94.2% (95% confidence interval [CI], 91.8%–96.6%) in the in-office follow-up group, and was not significantly different between the 2 groups (P = 0.174).
The CONNECT Trial
The CONNECT trial, another major multicenter RCT, involved the Care Link® RMS for ICD/CRT devices in a15-month follow-up study of 1,997 patients at 133 sites in the United States. The primary objective of the trial was to determine whether automatically transmitted physician alerts decreased the time from the occurrence of clinically relevant events to medical decisions. The trial results are summarized below:
Of the 575 clinical alerts sent in the study, 246 did not trigger an automatic physician alert. Transmission failures were related to technical issues such as the alert not being programmed or not being reset, and/or a variety of patient factors such as not being at home and the monitor not being plugged in or set up.
The overall mean time from the clinically relevant event to the clinical decision was significantly shorter (P < 0.001) by 17.4 days in the remote follow-up group (4.6 days for 172 patients) than the in-office follow-up group (22 days for 145 patients).
– The median time to a clinical decision was shorter in the remote follow-up group than in the in-office follow-up group for an AT/AF burden greater than or equal to 12 hours (3 days vs. 24 days) and a fast VF rate greater than or equal to 120 beats per minute (4 days vs. 23 days).
Although infrequent, similar low numbers of events involving low battery and VF detection/therapy turned off were noted in both groups. More alerts, however, were noted for out-of-range lead impedance in the RM group (18 vs. 6 patients), and the time to detect these critical events was significantly shorter in the RM group (same day vs. 17 days).
Total in-office clinic visits were reduced by 38% from 6.27 visits per patient-year in the in-office follow-up group to 3.29 visits per patient-year in the remote follow-up group.
Health care utilization visits (N = 6,227) that included cardiovascular-related hospitalization, emergency department visits, and unscheduled clinic visits were not significantly higher in the remote follow-up group.
The overall mean length of hospitalization was significantly shorter (P = 0.002) for those in the remote follow-up group (3.3 days vs. 4.0 days) and was shorter both for patients with ICD (3.0 days vs. 3.6 days) and CRT (3.8 days vs. 4.7 days) implants.
The mortality rate between the study arms was not significantly different between the follow-up groups for the ICDs (P = 0.31) or the CRT devices with defribillator (P = 0.46).
Conclusions
There is limited clinical trial information on the effectiveness of RMSs for PMs. However, for RMSs for ICD devices, multiple cohort studies and 2 large multicenter RCTs demonstrated feasibility and significant reductions in in-office clinic follow-ups with RMSs in the first year post implantation. The detection rates of clinically significant events (and asymptomatic events) were higher, and the time to a clinical decision for these events was significantly shorter, in the remote follow-up groups than in the in-office follow-up groups. The earlier detection of clinical events in the remote follow-up groups, however, was not associated with lower morbidity or mortality rates in the 1-year follow-up. The substitution of almost all the first year in-office clinic follow-ups with RM was also not associated with an increased health care utilization such as emergency department visits or hospitalizations.
The follow-up in the trials was generally short-term, up to 1 year, and was a more limited assessment of potential longer term device/lead integrity complications or issues. None of the studies compared the different RMSs, particularly the different RMSs involving patient-scheduled transmissions or automatic transmissions. Patients’ acceptance of and satisfaction with RM were reported to be high, but the impact of RM on patients’ health-related quality of life, particularly the psychological aspects, was not evaluated thoroughly. Patients who are not technologically competent, having hearing or other physical/mental impairments, were identified as potentially disadvantaged with remote surveillance. Cohort studies consistently identified subgroups of patients who preferred in-office follow-up. The evaluation of costs and workflow impact to the health care system were evaluated in European or American clinical settings, and only in a limited way.
Internet-based device-assisted RMSs involve a new approach to monitoring patients, their disease progression, and their CIEDs. Remote monitoring also has the potential to improve the current postmarket surveillance systems of evolving CIEDs and their ongoing hardware and software modifications. At this point, however, there is insufficient information to evaluate the overall impact to the health care system, although the time saving and convenience to patients and physicians associated with a substitution of in-office follow-up by RM is more certain. The broader issues surrounding infrastructure, impacts on existing clinical care systems, and regulatory concerns need to be considered for the implementation of Internet-based RMSs in jurisdictions involving different clinical practices.
PMCID: PMC3377571  PMID: 23074419
9.  Prognostic value of admission heart rate in patients with ST-segment elevation myocardial infarction: Role of Type 2 diabetes mellitus 
Background
It’s unknown whether the prognostic value of admission heart rate (HR) was different in patients with ST-segment elevation myocardial infarction (STEMI) with or without concomitant type 2 diabetes mellitus (T2DM).
Methods
Consecutive STEMI patients who presented within 12 hours of symptom onset were recruited from 274 hospitals in China. Participants were stratified into quartiles by admission HR. Baseline characteristics, current therapeutic recommenda- tions, laboratory biochemical tests, 30-day all-cause mortality and Cardiovascular Events (CVE, including all-cause death, reinfarction and stroke) were compared across admission HR quartiles.
Results
We evaluated 7294 STEMI patients, of these 820 (11.2%) had known T2DM. The admission HR quartile stratification was significantly associated with all-cause mortality and CVE regardless of T2DM status (P < 0.001 both for survival and CVE). After adjusted other risk factors, in patients without T2DM, comparing with HR <66 b.p.m., the increase of HR level was associated with worse prognosis (P < 0.05). In patients with T2DM, the hazard ratios for 30-day CVE were 1.75 (95%CI), 1.92 (95%CI), 3.00 (95%CI) in the HR of 66–76 b.p.m., 77–88 b.p.m., and >88 b.p.m., respectively. Results were similar for 30-day all-cause mortality, but the hazard ratios in Q2 (P = 0.139 and P =0.086 for survival and CVE, respectively) and Q3 groups were non-significant (P = 0.072 and P =0.033 for survival and CVE, respectively). There was a significant interaction effect of HR and T2DM on 30-day CVE mortality (P = 0.035), which was not found on all-cause mortality (P = 0.126).
Conclusion
Admission heart rate was an important risk factor of 30-day all-cause mortality and CVE in patients with STEMI with or without T2DM. However, the predictive effect was modified by T2DM.
doi:10.1186/1471-2261-12-104
PMCID: PMC3521170  PMID: 23153317
Heart rate; ST-segment elevation myocardial infarction; Type 2 Diabetes Mellitus; Prognosis
10.  Depression and Risk of Sudden Cardiac Death and Coronary Heart Disease in Women: Results from the Nurses’ Health Study 
Objectives
We assessed the association between depression and sudden cardiac death (SCD) and cardiac events among individuals without baseline coronary heart disease (CHD).
Background
Depression is a risk factor for cardiac events and mortality among those with CHD, possibly from arrhythmia.
Methods
We studied depressive symptoms, and a proxy variable for clinical depression consisting of severe symptoms and/or antidepressant medication use, and their relationship to cardiac events in the Nurses’ Health Study. Questionnaires in 1992, 1996, and 2000 assessed symptoms with the Mental Health Index (MHI-5), and antidepressant use was assessed in 1996 and 2000. Primary endpoints included SCD, fatal CHD, and non-fatal myocardial infarction (MI).
Results
Among 63,469 women without prior CHD/stroke in 1992, 7.9% had MHI-5 scores (<53) previously found to predict clinical depression. Depressive symptoms were associated with CHD events, and the relationship was strongest for fatal CHD, where the association remained significant even after controlling for CHD risk factors (HR=1.49; 95% CI 1.11–2.00 for MHI-5 score<53). In models from 1996 onward, our proxy variable for clinical depression was most associated with SCD in multivariable models (HR=2.33, 95% CI 1.47–3.70), and this risk was primarily due to a specific relationship between antidepressant use and SCD (HR=3.34, 95% CI 2.03–5.50).
Conclusions
In this cohort of women without baseline CHD, depressive symptoms were associated with fatal CHD, and a measure of clinical depression including antidepressant use was specifically associated with SCD. Although antidepressant use may be a marker of worse depression, its specific association with SCD merits further study.
CONDENSED ABSTRACT
We prospectively analyzed the association between depression and cardiac events in the Nurses’ Health Study. Symptoms of depression as measured by Mental Health Index (MHI-5) score were directly associated with risk of CHD events, and the relationship was strongest for fatal CHD. A proxy variable for clinical depression comprised of MHI-5 score<53 or antidepressant use was strongly associated with sudden cardiac death (SCD), primarily due to a specific relationship between antidepressant use and SCD. Although antidepressant use may be a marker of worse depression, its specific association with SCD merits further study.
doi:10.1016/j.jacc.2008.10.060
PMCID: PMC2664253  PMID: 19281925
sudden cardiac death; coronary disease; epidemiology; women
11.  Sudden Death after Myocardial Infarction 
Context
Sudden cardiac death (SCD) after myocardial infarction (MI) has not recently been assessed in the community. Post-MI risk stratification for SCD commonly relies on baseline characteristics and little is known about the relationship between recurrent ischemia or heart failure (HF) and SCD.
Objective
To evaluate the risk of SCD after MI and the impact of recurrent ischemia and HF on SCD.
Design, setting, and participants
2,997 Olmsted County residents experiencing an MI between 1979 and 2005.
Main outcome measures
SCD defined as out-of-hospital death due to coronary disease. Observed survival free of SCD compared to that expected in Olmsted County.
Results
During a median follow-up of 4.7 years (25th–75th percentile 1.6–7.1, date of last follow-up 02-29-2008), 1,160 deaths occurred, 282 (24%) SCD. The 30-day cumulative incidence of SCD was 1.2% (95% confidence interval [CI] 0.8–1.6%). Thereafter, the rate of SCD was constant at 1.2%/year yielding a 5-year cumulative incidence of 6.9% (95% CI 5.9% to 7.9%). The 30-day incidence of SCD was 4-fold higher than expected (standardized mortality ratio=4.2, 95% CI 2.9 to 5.8). In the year thereafter, the risk of SCD was lower than expected (standardized mortality ratio=0.66, 95% CI 0.50 to 0.85). The risk of SCD declined over time (hazard ratio=0.62, 95% CI 0.44 to 0.88 for MIs in 1997–2005 compared to 1979–1987; p =0.03). Recurrent events, ischemia (n=842) or HF (n=365), occurred in 2,080 patients. After adjustment for baseline characteristics, recurrent ischemia was not associated with SCD (hazard ratio=1.26, 95% CI 0.96 to 1.65; p=0.09), while HF markedly increased the risk of SCD (hazard ratio= 4.20, 95% CI 3.10 to 5.69; p<0.001)
Conclusions
The risk of SCD is highest during the first month after MI and declined over time. SCD is independently associated with HF but not with recurrent ischemia.
doi:10.1001/jama.2008.553
PMCID: PMC2731625  PMID: 18984889
12.  Associations of Plasma 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D Concentrations With Death and Progression to Maintenance Dialysis in Patients With Advanced Kidney Disease 
Background
Low vitamin D concentrations are prevalent in chronic kidney disease (CKD) patients. We investigated the relationship between plasma 25-hydroxyvitamin D (25(OH)D) or 1,25-dihydroxyvitamin D (1,25(OH)2D) concentrations with death, cardiovascular events (CVE) and dialysis initiation in patients with advanced CKD. Study Design: The Homocysteine Study was a randomized double-blind trial evaluating the effects of high doses of folic acid on death and chronic dialysis initiation in patients with advanced CKD (stage 4 and 5 not yet on dialysis). 25(OH)D and 1,25(OH)2D concentrations were measured in stored plasma samples obtained 3 months after trial initiation and evaluated at clinically defined cutoffs (<10, 10-30, and >30 ng/mL) and tertiles (< 15, 15-22, and >22 pg/mL), respectively. Cox-proportional hazard models were used to examine the association between vitamin D concentrations and clinical outcomes.
Setting & Participants
1,099 patients with advanced CKD from 36 Veteran Affairs Medical Centers
Predictors
25(OH)D and 1,25(OH)2D concentrations
Outcomes
Death, CVE and time to initiation of chronic dialysis.
Results
After a median follow-up period of 2.9 years, 41% (n=453) died, while 56% (n=615) initiated dialysis. Mean 25(OH)D and 1,25(OH)2D concentrations were 21±10 ng/mL and 20±11 pg/mL, respectively. After adjustment for potential confounders, the lowest tertile of 1,25(OH)2D was associated with death (HR, 1.33; 95% CI, 1.01-1.74) and initiation of chronic dialysis (HR, 1.78; 95% CI, 1.40-2.26), compared to the highest tertile. The association with death and initiation of dialysis was moderately attenuated after adjustment for plasma fibroblast growth factor-23 (FGF23) concentrations (HRs of lower tertiles of 1.20 [95% CI, 0.91-1.58] and 1.56 [95% CI, 1.23-1.99], respectively, compared to highest tertile). There was no association between 25(OH)D concentrations and outcomes.
Limitations
Participants were mostly male.
Conclusions
Low plasma 1,25(OH)2D concentrations are associated with death and initiation of chronic dialysis in advanced CKD. Fibroblast growth factor-23 may attentuate this relationship.
doi:10.1053/j.ajkd.2012.04.014
PMCID: PMC3439559  PMID: 22621970
13.  Impact of age and sex on sudden cardiovascular death following myocardial infarction 
Heart  2002;88(6):573-578.
Objective: To evaluate and compare the risk of sudden cardiovascular death (SCD) and non-SCD after myocardial infarction (MI) associated with age and sex.
Design: Cohort study of patients admitted with an enzyme verified acute MI and discharged alive. Patients were followed up for up to four years.
Patients: 5983 consecutive hospital survivors of acute MI were enrolled in the TRACE (trandolapril cardiac evaluation) registry from 1990–92. Four age groups were prespecified: < 56, 56–65, 66–75, and ≥ 76 years.
Main outcome measures: SCD was defined as cardiovascular death within one hour of onset of symptoms.
Results: There were 536 SCD and 725 non-SCD. SCD mortality was 4.8% in the youngest and 15.7% in the oldest age groups. Non-SCD mortality was 3.5% and 25%, respectively. The ratio of SCD to non-SCD mortality varied from 1.44 in the youngest (< 56 years) to 0.55 in the oldest patients (≥ 76 years). Age significantly increased both SCD and non-SCD risk (p < 0.0001), but the increase in non-SCD risk was 40% higher (p < 0.0001). Male sex was associated with increased risk of SCD independently of age (risk ratio 1.34, p < 0.005). However, the absolute three year probability of SCD among women older than 66 years exceeded 10%.
Conclusions: Compared with non-SCD the risk of SCD is relatively highest in the younger age groups, but the absolute risk of SCD is much higher among the upper age groups than the younger. The risk of SCD was slightly lower in women but not enough to warrant a different treatment strategy.
PMCID: PMC1767447  PMID: 12433881
sudden death; women; aging; myocardial infarction
14.  Incidence and Clinical Features of Cerebrovascular Disease Among HIV-Infected Adults in the Southeastern United States 
AIDS Research and Human Retroviruses  2013;29(7):1068-1074.
Abstract
With aging of the HIV-infected population, non-AIDS conditions such as cardiovascular disease (CVD) now account for substantial mortality and morbidity. While myocardial infarction is the major outcome of interest in the field of HIV and CVD, cerebrovascular disease remains understudied, especially in the Southeastern United States. We determined the incidence and clinical features of cerebrovascular events (CVE) in a large HIV clinical cohort in North Carolina (NC). A total of 2,515 HIV-infected adults contributed a median of 4.5 years (IQR: 2.0, 7.8) of follow-up. Fifty-three CVEs were adjudicated for an incidence rate of 3.87 per 1,000 person-years (95% CI: 2.90, 5.06). The ischemic stroke incidence was 2.26 per 1,000 person-years (95% CI: 1.53, 3.21), approximately 1.5 times the rate of a population-based cohort in NC. At the time of CVE, the median age was 48 years (IQR: 42, 55). Of ischemic strokes 76% resulted from large artery atherosclerosis or small vessel (lacunar) disease. In multivariable analyses, age, hypertension, dyslipidemia, recent CD4+ cell count ≤200 cells/mm3, and recent HIV RNA >400 copies/ml were associated with an increased risk of CVE. Antiretroviral therapy (ART) was not associated with the risk of CVE. We concluded that in the post-ART era, HIV-infected individuals appear to be at moderately increased risk of stroke. Prevention of CVEs in this population will require modification of traditional CVD risk factors and early, effective treatment of HIV infection.
doi:10.1089/aid.2012.0334
PMCID: PMC3685694  PMID: 23565888
15.  Sudden Cardiac Death in Patients with Human Immunodeficiency Virus Infection 
Objectives
We sought to determine the incidence and clinical characteristics of sudden cardiac death (SCD) in patients with HIV.
Background
As the HIV-infected population ages, cardiovascular disease prevalence and mortality are increasing; however, the incidence and features of SCD have not yet been described.
Methods
Records of 2860 consecutive patients in a public HIV clinic in San Francisco, CA between April 2000 and August 2009 were examined. Identification of deaths, causes of death, and clinical characteristics were obtained by search of the National Death Index and/or clinic records. SCDs were determined using published retrospective criteria: (1) ICD10 code for all cardiac causes of death and (2) circumstances of death meeting WHO criteria.
Results
Of 230 deaths over 3.7 median years’ follow-up, 30 (13%) met SCD criteria, 131 (57%) were due to AIDS, 25 (11%) other (natural) diseases, and 44 (19%) overdose/suicides/unknown. SCDs accounted for 86% (30/35) of all cardiac deaths. The mean SCD rate was 2.6 per 1,000 person-years (95%CI 1.8-3.8), 4.5-fold higher than expected. SCDs occurred in older patients than AIDS deaths (mean 49.0 vs. 44.9 years, p=0.02). Compared to AIDS and natural deaths combined, SCDs had higher prevalence of prior MI (17% vs. 1%, p<0.0005), cardiomyopathy (23% vs. 3%, p<0.0005), heart failure (30% vs. 9%, p=0.004), and arrhythmias (20% vs. 3%, p=0.003).
Conclusions
SCDs account for most cardiac and many non-AIDS natural deaths in HIV-infected patients. Further investigation is needed to ascertain underlying mechanisms, which may include inflammation, antiretroviral therapy interruption, and concomitant medications.
doi:10.1016/j.jacc.2012.02.024
PMCID: PMC3356565  PMID: 22595409
AIDS; death, sudden; arrhythmia
16.  Predictors of the first cardiovascular event in patients with systemic lupus erythematosus - a prospective cohort study 
Arthritis Research & Therapy  2009;11(6):R186.
Introduction
Cardiovascular disease (CVD) is a major cause of premature mortality among Systemic lupus erythematosus (SLE) patients. Many studies have measured and evaluated risk factors for premature subclinical atherosclerosis, but few studies are prospective and few have evaluated risk factors for hard endpoints, i.e. clinically important cardiovascular events (CVE). We investigated the impact of traditional and lupus associated risk factors for the first ever CVE in a longitudinal cohort of SLE patients.
Methods
A total of 182 SLE patients (mean age 43.9 years) selected to be free of CVE were included. Cardiovascular and autoimmune biomarkers were measured on samples collected after overnight fasting at baseline. Clinical information was collected at baseline and at follow up. End point was the first ever CVE (ischemic heart, cerebrovascular or peripheral vascular disease or death due to CVD). Impact of baseline characteristics/biomarkers on the risk of having a first CVE was evaluated with Cox regression.
Results
Follow up was 99.5% after a mean time of 8.3 years. Twenty-four patients (13%) had a first CVE. In age-adjusted Cox regression, any positive antiphospholipid antibody (aPL), elevated markers of endothelial activation (von Willebrand factor (vWf), soluble vascular cellular adhesion molecule-1 (sVCAM-1)) and fibrinogen predicted CVEs. Of SLE manifestations, arthritis, pleuritis and previous venous occlusion were positively associated with future CVEs while thrombocytopenia was negatively associated. Among traditional risk factors only age and smoking were significant predictors. In a multivariable Cox regression model age, any positive aPL, vWf and absence of thrombocytopenia were all predictors of the first CVE.
Conclusions
In addition to age, positive aPL, biomarkers indicating increased endothelial cell activity/damage, and absence of thrombocytopenia were independent predictors of CVEs in this prospective study. Our results indicate that activation of the endothelium and the coagulation system are important features in SLE related CVD. Furthermore, we observed that the risk of CVEs seems to differ between subgroups of SLE patients.
doi:10.1186/ar2878
PMCID: PMC3003532  PMID: 20003285
17.  Vitamin D Levels Predict All-Cause and Cardiovascular Disease Mortality in Subjects With the Metabolic Syndrome 
Diabetes Care  2012;35(5):1158-1164.
OBJECTIVE
Optimal vitamin D levels are associated with reduced cardiovascular and all-cause mortality. We investigated whether optimal 25-hydroxyvitamin D (25[OH]D) is protective in individuals with the metabolic syndrome.
RESEARCH DESIGN AND METHODS
The Ludwigshafen Risk and Cardiovascular Health (LURIC) study is a cohort study of subjects referred for coronary angiography between 1997 and 2000, from which 1,801 with the metabolic syndrome were investigated. Mortality was tracked for a median of 7.7 years. Multivariable survival analysis was used to estimate the association between 25(OH)D levels and mortality.
RESULTS
Most subjects (92%) had suboptimal levels of 25(OH)D (<75 nmol/L), with 22.2% being severely deficient (<25 nmol/L). During follow-up, 462 deaths were recorded, 267 (57.8%) of which were cardiovascular in origin. After full adjustment, including the metabolic syndrome components, those with optimal 25(OH)D levels showed a substantial reduction in all-cause (hazard ratio [HR] 0.25 [95% CI 0.13–0.46]) and cardiovascular disease mortality (0.33 [0.16–0.66]) compared with those with severe vitamin D deficiency. For specific cardiovascular disease mortality, there was a strong reduction for sudden death (0.15 [0.04–0.63]) and congestive heart failure (0.24 [0.06–1.04]), but not for myocardial infarction. The reduction in mortality was dose-dependent for each of these causes.
CONCLUSIONS
Optimal 25(OH)D levels substantially lowered all-cause and cardiovascular disease mortality in subjects with the metabolic syndrome. These observations call for interventional studies that test whether vitamin D supplementation provides a useful adjunct in reducing mortality in these subjects.
doi:10.2337/dc11-1714
PMCID: PMC3329808  PMID: 22399697
18.  Are Markers of Inflammation More Strongly Associated with Risk for Fatal Than for Nonfatal Vascular Events? 
PLoS Medicine  2009;6(6):e1000099.
In a secondary analysis of a randomized trial comparing pravastatin versus placebo for the prevention of coronary and cerebral events in an elderly at-risk population, Naveed Sattar and colleagues find that inflammatory markers may be more strongly associated with risk of fatal vascular events than nonfatal vascular events.
Background
Circulating inflammatory markers may more strongly relate to risk of fatal versus nonfatal cardiovascular disease (CVD) events, but robust prospective evidence is lacking. We tested whether interleukin (IL)-6, C-reactive protein (CRP), and fibrinogen more strongly associate with fatal compared to nonfatal myocardial infarction (MI) and stroke.
Methods and Findings
In the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER), baseline inflammatory markers in up to 5,680 men and women aged 70–82 y were related to risk for endpoints; nonfatal CVD (i.e., nonfatal MI and nonfatal stroke [n = 672]), fatal CVD (n = 190), death from other CV causes (n = 38), and non-CVD mortality (n = 300), over 3.2-y follow-up. Elevations in baseline IL-6 levels were significantly (p = 0.0009; competing risks model analysis) more strongly associated with fatal CVD (hazard ratio [HR] for 1 log unit increase in IL-6 1.75, 95% confidence interval [CI] 1.44–2.12) than with risk of nonfatal CVD (1.17, 95% CI 1.04–1.31), in analyses adjusted for treatment allocation. The findings were consistent in a fully adjusted model. These broad trends were similar for CRP and, to a lesser extent, for fibrinogen. The results were also similar in placebo and statin recipients (i.e., no interaction). The C-statistic for fatal CVD using traditional risk factors was significantly (+0.017; p<0.0001) improved by inclusion of IL-6 but not so for nonfatal CVD events (p = 0.20).
Conclusions
In PROSPER, inflammatory markers, in particular IL-6 and CRP, are more strongly associated with risk of fatal vascular events than nonfatal vascular events. These novel observations may have important implications for better understanding aetiology of CVD mortality, and have potential clinical relevance.
Please see later in the article for Editors' Summary
Editors' Summary
Background
Cardiovascular disease (CVD)—disease that affects the heart and/or the blood vessels—is a common cause of death in developed countries. In the USA, for example, the leading cause of death is coronary heart disease (CHD), a CVD in which narrowing of the heart's blood vessels by “atherosclerotic plaques” (fatty deposits that build up with age) slows the blood supply to the heart and may eventually cause a heart attack (myocardial infarction). Other types of CVD include stroke (in which atherosclerotic plaques interrupt the brain's blood supply) and heart failure (a condition in which the heart cannot pump enough blood to the rest of the body). Smoking, high blood pressure, high blood levels of cholesterol (a type of fat), having diabetes, and being overweight all increase a person's risk of developing CVD. Tools such as the “Framingham risk calculator” take these and other risk factors into account to assess an individual's overall risk of CVD, which can be reduced by taking drugs to reduce blood pressure or cholesterol levels (for example, pravastatin) and by making lifestyle changes.
Why Was This Study Done?
Inflammation (an immune response to injury) in the walls of blood vessels is thought to play a role in the development of atherosclerotic plaques. Consistent with this idea, several epidemiological studies (investigations of the causes and distribution of disease in populations) have shown that people with high circulating levels of markers of inflammation such as interleukin-6 (IL-6), C-reactive protein (CRP), and fibrinogen are more likely to have a stroke or a heart attack (a CVD event) than people with low levels of these markers. Although these studies have generally lumped together fatal and nonfatal CVD events, some evidence suggests that circulating inflammatory markers may be more strongly associated with fatal than with nonfatal CVD events. If this is the case, the mechanisms that lead to fatal and nonfatal CVD events may be subtly different and knowing about these differences could improve both the prevention and treatment of CVD. In this study, the researchers investigate this possibility using data collected in the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER; a trial that examined pravastatin's effect on CVD development among 70–82 year olds with pre-existing CVD or an increased risk of CVD because of smoking, high blood pressure, or diabetes).
What Did the Researchers Do and Find?
The researchers used several statistical models to examine the association between baseline levels of IL-6, CRP, and fibrinogen in the trial participants and nonfatal CVD events (nonfatal heart attacks and nonfatal strokes), fatal CVD events, death from other types of CVD, and deaths from other causes during 3.2 years of follow-up. Increased levels of all three inflammatory markers were more strongly associated with fatal CVD than with nonfatal CVD after adjustment for treatment allocation and for other established CVD risk factors but this pattern was strongest for IL-6. Thus, a unit increase in the log of IL-6 levels increased the risk of fatal CVD by half but increased the risk of nonfatal CVD by significantly less. The researchers also investigated whether including these inflammatory markers in tools designed to predict an individual's CVD risk could improve the tool's ability to distinguish between individuals with a high and low risk. The addition of IL-6 to established risk factors, they report, increased this discriminatory ability for fatal CVD but not for nonfatal CVD.
What Do These Findings Mean?
These findings indicate that, at least for the elderly at-risk patients who were included in PROSPER, inflammatory markers are more strongly associated with the risk of a fatal heart attack or stroke than with nonfatal CVD events. These findings need to be confirmed in younger populations and larger studies also need to be done to discover whether the same association holds when fatal heart attacks and fatal strokes are considered separately. Nevertheless, the present findings suggest that inflammation may specifically help to promote the development of serious, potentially fatal CVD and should stimulate improved research into the use of inflammation markers to predict risk of deaths from CVD.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000099.
The MedlinePlus Encyclopedia has pages on coronary heart disease, stroke, and atherosclerosis (in English and Spanish)
MedlinePlus provides links to many other sources of information on heart diseases, vascular diseases, and stroke (in English and Spanish)
Information for patients and caregivers is provided by the American Heart Association on all aspects of cardiovascular disease, including information on inflammation and heart disease
Information is available from the British Heart Foundation on heart disease and keeping the heart healthy
More information about PROSPER is available on the Web site of the Vascular Biochemistry Department of the University of Glasgow
doi:10.1371/journal.pmed.1000099
PMCID: PMC2694359  PMID: 19554082
19.  N-terminal pro-B-type Natriuretic Peptide is Associated with Sudden Cardiac Death Risk: the Cardiovascular Health Study 
Background
Sudden cardiac death (SCD), the cause of 250,000-450,000 deaths per year, is a major public health problem. The majority of those affected do not have a prior cardiovascular diagnosis. Elevated B-type natriuretic peptide levels have been associated with the risk of heart failure and mortality, as well as sudden death in women.
Objective
To examine the relationship between N-terminal pro-B-type natriuretic peptide (NT-proBNP) and SCD in the Cardiovascular Health Study population.
Methods
The risk of SCD associated with baseline NT-proBNP was examined in 5447 participants. Covariate-adjusted Cox model regressions were used to estimate the hazard ratios of developing SCD as a function of baseline NT-proBNP
Results
Over a median follow-up of 12.5 years (maximum of 16), there were 289 cases of SCD. Higher NT-proBNP levels were strongly associated with SCD, with an unadjusted hazard ratio of 4.2 (95% CI: 2.9, 6.1, p<0.001) in the highest quintile compared to the lowest. NT-proBNP remained associated with SCD even after adjustment for numerous clinical characteristics and risk-factors (age, sex, race, and other associated conditions), with an adjusted hazard ratio for the 5th versus the 1st quintile of 2.5 (95% CI: 1.6, 3.8, p<0.001).
Conclusion
NT-proBNP provides information regarding the risk of sudden cardiac death in a community based population of older adults, beyond other traditional risk factors. This biomarker may ultimately prove useful in targeting the population at risk with aggressive medical management of comorbid conditions.
doi:10.1016/j.hrthm.2010.10.038
PMCID: PMC3826546  PMID: 21044699
Sudden cardiac death; B-type natriuretic peptide; BNP; NT-proBNP
20.  Aldosterone and cortisol affect the risk of sudden cardiac death in haemodialysis patients 
European Heart Journal  2012;34(8):578-587.
Background
Sudden cardiac death is common and accounts largely for the excess mortality of patients on maintenance dialysis. It is unknown whether aldosterone and cortisol increase the incidence of sudden cardiac death in dialysis patients.
Methods and results
We analysed data from 1255 diabetic haemodialysis patients participating in the German Diabetes and Dialysis Study (4D Study). Categories of aldosterone and cortisol were determined at baseline and patients were followed for a median of 4 years. By Cox regression analyses, hazard ratios (HRs) were determined for the effect of aldosterone, cortisol, and their combination on sudden death and other adjudicated cardiovascular outcomes. The mean age of the patients was 66 ± 8 years (54% male). Median aldosterone was <15 pg/mL (detection limit) and cortisol 16.8 µg/dL. Patients with aldosterone levels >200 pg/mL had a significantly higher risk of sudden death (HR: 1.69; 95% CI: 1.06–2.69) compared with those with an aldosterone <15 pg/mL. The combined presence of high aldosterone (>200 pg/mL) and high cortisol (>21.1 µg/dL) levels increased the risk of sudden death in striking contrast to patients with low aldosterone (<15 pg/mL) and low cortisol (<13.2 µg/dL) levels (HR: 2.86, 95% CI: 1.32–6.21). Furthermore, all-cause mortality was significantly increased in the patients with high levels of both hormones (HR: 1.62, 95% CI: 1.01–2.62).
Conclusions
The joint presence of high aldosterone and high cortisol levels is strongly associated with sudden cardiac death as well as all-cause mortality in haemodialysed type 2 diabetic patients. Whether a blockade of the mineralocorticoid receptor decreases the risk of sudden death in these patients must be examined in future trials.
doi:10.1093/eurheartj/ehs361
PMCID: PMC3578266  PMID: 23211232
Aldosterone; Cortisol; Sudden cardiac death; Cardiovascular events; Mortality; Kidney disease
21.  Complement Activation and Prognosis in Patients With Type 2 Diabetes and Myocardial Infarction 
Diabetes Care  2012;35(4):911-917.
OBJECTIVE
The activation of the complement system may be involved in the pathology of myocardial infarction (MI) and type 2 diabetes. To explore their potential as prognostic markers, we characterized two factors in the complement cascade, the end product sC5b-9 and the mannose-binding lectin–associated Ser protease-2 (MASP-2), in type 2 diabetic patients with suspected MI.
RESEARCH DESIGN AND METHODS
Plasma sC5b-9 and MASP-2 were determined in patients with MI and type 2 diabetes (n = 397; median age 70; male 68%). The adjudicated end points were cardiovascular events (CVEs), including cardiovascular mortality and nonfatal MI or stroke.
RESULTS
The median sC5b-9 was 134 μg/L (interquartile range [IQR] 101–190 μg/L) and the median MASP-2 was 333 μg/L (IQR 235–463 μg/L), with no significant correlation between them. Women had higher sC5b-9 than men (median 152 vs. 130 μg/L; P = 0.02). Both sC5b-9 and MASP-2 were correlated to age and creatinine clearance, while MASP-2 was also correlated to BMI. During a median follow-up of 2.4 years, CVEs occurred in 141 patients (36%). Both sC5b-9 (hazard ratio 1.37 [95% CI 1.13–1.65]; P < 0.01) and MASP-2 (0.68 [0.51–0.92]; P = 0.01) predicted CVEs in unadjusted analyses. After multiple adjustments, the predictive capacity remained for sC5b-9 (1.30 [1.02–1.66]; P = 0.04) but not for MASP-2.
CONCLUSIONS
In type 2 diabetic patients with MI, high levels of sC5b-9 predict future CVE. This indicates that the complement system may play a significant role in the pathology of the subsequent myocardial damage and that the pathways leading to complement activation warrant further exploration as potential therapeutic targets to improve the prognosis for these patients.
doi:10.2337/dc11-1642
PMCID: PMC3308270  PMID: 22357179
22.  Cardiopulmonary Complications Leading to Premature Deaths in Adult Patients with Sickle Cell Disease 
American journal of hematology  2010;85(1):10.1002/ajh.21569.
Sickle cell disease (SCD) is associated with early mortality. We sought to determine the incidence, cause, and risk factors for death in an adult population of patients with SCD. All patients aged ≥18 years seen at the Adult Sickle Cell Center at Duke University Medical Center between January 2000 and April 2005 were enrolled. Forty-three patients (21 males and 22 females) died during the study period. Median age of survival was 39 years for females (95% CI 34–56), 40 years for males (95% CI 34–48), and 40 years overall (95% CI 35–48). Cardiac causes of death accounted for 25.6% (11/43 patients); pulmonary, 14.0% (6 patients); other SCD related, 32.6% (14 patients); unknown, 14.0% (6 patients); and others, 14.0% (6 patients). Pulseless electrical activity arrest, pulmonary emboli, multi-organ failure, and stroke were the most frequent causes of death. Among the deceased patients, the most common pre-morbid conditions were cardiopulmonary: ACS/pneumonia (58.1%), pHTN (41.9%), systemic hypertension (HTN) (25.6%), congestive heart failure (CHF) (25.6%), myocardial infarction (20.9%), and arrhythmias (14.0%). Tricuspid regurgitant jet velocity (TRv) was significantly higher (3.1 m/s vs. 2.6 m/s, p<0.001) and hemoglobin significantly lower (8.3 g/dL vs. 9.2 g/dL, p<0.05) in deceased patients as compared to patients who lived, respectively. With improved preventive and therapeutic advances, including hydroxyurea therapy, acute complications such as infection are no longer the leading cause of death; instead causes of death and pre-morbid conditions are shifting to chronic cardiopulmonary complications. Further, arrhythmia leading to premature death is under-recognized in SCD and warrants further investigation.
doi:10.1002/ajh.21569
PMCID: PMC3865703  PMID: 20029950
sickle cell disease; adult; mortality; risk factors; cardiopulmonary complications
23.  Atrial Fibrillation and the Risk of Sudden Cardiac Death: The Atherosclerosis Risk in Communities (ARIC) Study and Cardiovascular Health Study (CHS) 
JAMA internal medicine  2013;173(1):29-35.
Background
It is unknown whether atrial fibrillation (AF) is associated with an increased risk of sudden cardiac death (SCD) in the general population. This association was examined in 2 population-based cohorts.
Methods
In the Atherosclerosis Risk in Communities (ARIC) Study, we analyzed data from 15439 participants (baseline 45–64 years, 55% women, and 27% black) from baseline (1987–1989) through December 31, 2001. In the Cardiovascular Health Study (CHS), we analyzed data from 5479 participants (baseline ≥65 years, 58% women, and 15% black) from baseline (first cohort, 1989–1990; second cohort, 1992–1993) through December 31, 2006. The main outcome was physician-adjudicated SCD, defined as death from a sudden, pulseless condition presumed due to a ventricular tachyarrhythmia. The secondary outcome was non-SCD (NSCD): coronary heart disease death not meeting SCD criteria. We used Cox proportional hazards models to assess the association between AF and SCD/NSCD, adjusting for baseline demographic and cardiovascular risk factors.
Results
In ARIC, 894 AF, 269 SCD, and 233 NSCD events occurred during follow-up (median, 13.1 years). The crude incidence rates of SCD were 2.89/1000 person-years (with AF) and 1.30/1000 person-years (without AF). The multivariable hazard ratios (HRs) (95% CI) of AF for SCD and NSCD were 3.26 (2.17–4.91) and 2.43 (1.60–3.71), respectively. In CHS, 1458 AF, 292 SCD, and 581 NSCD events occurred during follow-up (median, 13.1 years). The crude incidence rates of SCD were 12.00/1000 person-years (with AF) and 3.82/1000 person-years (without AF). The multivariable HRs (95% CI) of AF for SCD and NSCD were 2.14 (1.60–2.87) and 3.10 (2.58–3.72), respectively. The meta-analyzed HRs (95% CI) of AF for SCD and NSCD were 2.47 (1.95–3.13) and 2.98 (2.52–3.53), respectively.
Conclusions
Incident AF is associated with an increased risk of SCD and NSCD in the general population. Additional research to identify predictors of SCD in AF patients is warranted.
doi:10.1001/2013.jamainternmed.744
PMCID: PMC3578214  PMID: 23404043
24.  Predictive Value of Beat-to-Beat QT Variability Index across the Continuum of Left Ventricular Dysfunction: Competing Risks of Non-cardiac or Cardiovascular Death, and Sudden or Non-Sudden Cardiac Death 
Background
The goal of this study was to determine the predictive value of beat-to-beat QT variability in heart failure (HF) patients across the continuum of left ventricular dysfunction.
Methods and Results
Beat-to-beat QT variability index (QTVI), heart rate variance (LogHRV), normalized QT variance (QTVN), and coherence between heart rate variability and QT variability have been measured at rest during sinus rhythm in 533 participants of the Muerte Subita en Insuficiencia Cardiaca (MUSIC) HF study (mean age 63.1±11.7; males 70.6%; LVEF >35% in 254 [48%]) and in 181 healthy participants from the Intercity Digital Electrocardiogram Alliance (IDEAL) database. During a median of 3.7 years of follow-up, 116 patients died, 52 from sudden cardiac death (SCD). In multivariate competing risk analyses, the highest QTVI quartile was associated with cardiovascular death [hazard ratio (HR) 1.67(95%CI 1.14-2.47), P=0.009] and in particular with non-sudden cardiac death [HR 2.91(1.69-5.01), P<0.001]. Elevated QTVI separated 97.5% of healthy individuals from subjects at risk for cardiovascular [HR 1.57(1.04-2.35), P=0.031], and non-sudden cardiac death in multivariate competing risk model [HR 2.58(1.13-3.78), P=0.001]. No interaction between QTVI and LVEF was found. QTVI predicted neither non-cardiac death (P=0.546) nor SCD (P=0.945). Decreased heart rate variability (HRV) rather than increased QT variability was the reason for increased QTVI in this study.
Conclusions
Increased QTVI due to depressed HRV predicts cardiovascular mortality and non-sudden cardiac death, but neither SCD nor excracardiac mortality in HF across the continuum of left ventricular dysfunction. Abnormally augmented QTVI separates 97.5% of healthy individuals from HF patients at risk.
doi:10.1161/CIRCEP.112.970541
PMCID: PMC3432262  PMID: 22730411
ECG; ejection fraction; heart failure; sudden death; QT variability
25.  Risk Factor and Prediction Modeling for Sudden Cardiac Death in Women with Coronary Artery Disease 
Archives of internal medicine  2011;171(19):1703-1709.
Background
The risk of sudden cardiac death and the assessment of risk factors in prediction models have not been assessed in women with coronary artery disease (CAD). We sought to evaluate sudden cardiac death (SCD) incidence, risk factors and their predictive accuracy among a population of women with CAD.
Methods
The Hormone and Estrogen Replacement Study (HERS) evaluated the effects of hormone replacement therapy on cardiovascular events among 2,763 postmenopausal women with CAD. SCD was defined as death from cardiac origin that occurred within 1 hour of symptom onset. The associations between candidate predictor variables and SCD were evaluated in a Cox proportional hazards model. The C-index was used to compare the predictive value of the clinical risk factors with left ventricular ejection fraction alone and in combination. The net reclassification improvement (NRI) was also computed.
Results
Over a mean follow-up of 6.8 years, SCD comprised 136 of the 254 cardiac deaths. The annual SCD event rate was 0.79% (95% CI, 0.67–0.94%). The following variables were independently associated with SCD in the multivariate model: myocardial infarction, heart failure, estimated glomerular filtration rate (eGFR) <40ml/min/1.73m2, atrial fibrillation, physical inactivity and diabetes. The incidences of SCD among women with 0 (n=683), 1 (n=1224), 2 (n=610), and 3 plus (n=246) risk factors at baseline were 0.3, 0.5, 1.2 and 2.9% per year, respectively. The combination of clinical risk factors and LVEF (C-index 0.681) were better predictors of SCD than LVEF alone (C-index 0.600) and resulted in a NRI of 0.20 (p<0.001).
Conclusions
SCD comprised the majority of cardiac deaths among postmenopausal women with CAD. Independent predictors of SCD including myocardial infarction, heart failure, eGFR <40ml/min/1.73m2, atrial fibrillation, physical inactivity and diabetes improved SCD prediction when used in addition to LVEF.
doi:10.1001/archinternmed.2011.328
PMCID: PMC3547327  PMID: 21788534

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