editorials; antiplatelet; aspirin; medical decision making; patient centered care; primary prevention
Background and Purpose
Patients discovered to have a patent foramen ovale in the setting of a cryptogenic stroke may be treated with percutaneous closure, antiplatelet therapy, or anticoagulants. A recent randomized trial (CLOSURE I) did not detect any benefit of closure over medical treatment alone; the optimal medical therapy is also unknown. We synthesized the available evidence on secondary stroke prevention in patients with patent foramen ovale and cryptogenic stroke.
A MEDLINE search was performed for finding longitudinal studies investigating medical treatment or closure, meta-analysis of incidence rates (IR), and IR ratios of recurrent cerebrovascular events.
Fifty-two single-arm studies and 7 comparative nonrandomized studies and the CLOSURE I trial were reviewed. The summary IR of recurrent stroke was 0.36 events (95% CI, 0.24–0.56) per 100 person-years with closure versus 2.53 events (95% CI, 1.91–3.35) per 100 person-years with medical therapy. In comparative observational studies, closure was superior to medical therapy (IR ratio=0.19; 95% CI, 0.07–0.54). The IR for the closure arm of the CLOSURE I trial was higher than the summary estimate from observational studies; there was no significant benefit of closure over medical treatment (P=0.002 comparing efficacy estimates between observational studies and the trial). Observational and randomized data (9 studies) comparing medical therapies were consistent and suggested that anticoagulants are superior to antiplatelets for preventing stroke recurrence (IR ratio=0.42; 95% CI, 0.18–0.98).
Although further randomized trial data are needed to precisely determine the effects of closure on stroke recurrence, the results of CLOSURE I challenge the credibility of a substantial body of observational evidence strongly favoring mechanical closure over medical therapy.
meta-analysis; observational; studies; patent; foramen; ovale; stroke
While the prevalence of patent foramena ovale (PFOs) in the general population is around 25%, it is approximately doubled among cryptogenic stroke (CS) patients. This has generally been attributed to paradoxical embolism and many physicians recommend PFO closure to prevent recurrence. However, the benefit of PFO closure in patients with stroke has not been demonstrated. Further, the epidemiology of stroke recurrence in patients with CS with PFO versus without PFO, and in those with large right-to-left shunts versus small right-to-left shunts, has yielded results that appear difficult to reconcile with the hypothesis that paradoxical embolism is an important cause of stroke recurrence. The purpose of this review is to critically examine the epidemiological evidence that PFO is a potentially modifiable risk factor for stroke recurrence in patients with cryptogenic stroke. The evidence suggests that many patients with CS and PFO have strokes that are PFO-attributable, but that many have strokes that are unrelated to their PFO.. We introduce the concept of “PFO-propensity”, defined as the patient-specific probability of finding a PFO in a patient with cryptogenic stroke based on their age and other risk factors. We show that this value is directly related to the probability that a CS is PFO-attributable. Because there is substantial heterogeneity both in PFO-propensity and in recurrence risk among patients with PFO and cryptogenic stroke, stratification for closure by these joint probabilities will likely prove crucial for appropriate patient selection.
Patent foramen ovale; Risk factors for stroke; Secondary stroke prevention; Cryptogenic Stroke
It has been suggested that the benefits of drug-eluting stents compared to bare metal stents (BMS) have been over-estimated in part because target lesion/vessel revascularization (TLR/TVR) rates in the BMS control group of these trials were spuriously high.
We used meta-analytic techniques to systematically compare clinical event rates among patients treated with BMS in trials where BMS were the experimental (BMSexperimental) rather than the control (BMScontrol) intervention. MEDLINE searches were performed to identify eligible randomized trials comparing either drug-eluting stents with BMScontrol, or BMSexperimental with balloon angioplasty in patients with non-acute coronary artery disease. Trial characteristics and 6 to 12 month rates for death, myocardial infarction, TLR/TVR and major adverse cardiac events (MACE) were extracted and assessed.
Eligible trials yielded 50 BMS cohorts: 19 in the BMScontrol group (4 046 patients) and 31 in the BMSexperimental group (5 068 patients). Summary death and infarction rates did not differ between groups. The summary TLR/TVR rates were 16.2% (95% confidence interval, CI: 13.5, 19.3) versus 13.8% (95% CI: 12.0, 15.7) in BMScontrol versus BMSexperimental groups, respectively (p=0.15). Among 39 BMS cohorts with ≤250 patients, TLR/TVR rates were significantly higher in BMScontrol versus BMSexperimental groups (18.9% [95% CI: 16.0, 22.2] versus 13.7% [95% CI: 11.5, 16.3], p=0.01). There were no between-group differences among larger BMS cohorts (p=0.98).
While overall clinical event rates did not differ in the BMScontrol and the BMSexperimental groups, a higher rate of TVR/TLR was seen in the BMScontrol group among smaller trials.
Patent foramen ovale (PFO) is significantly associated with cryptogenic stroke (CS). However, even in patients with CS, a PFO can be an incidental finding. We sought to estimate the probability that a PFO in a patient with CS is incidental.
A systematic search identified 23 case-control studies examining the prevalence of PFO in patients with CS versus controls with stroke of known-cause. Using simple assumptions and Bayes’ theorem we calculated the probability a PFO is incidental in patients with CS. Random effects meta-analyses estimated the odds ratio (OR) of a PFO in CS versus controls in different age populations, with or without atrial septal aneurysms (ASA), and were used to summarize across studies the probability that a PFO in CS is incidental.
The summary OR (95% confidence limits) for PFO in CS versus controls was 2.9 (CI 2.1, 4.0). The corresponding ORs for young and old patients (< or ≥ 55 years) were 5.1 (3.3, 7.8) and 2.0 (1.0, 3.7), respectively. The corresponding probabilities that a PFO in patients with CS is incidental were 33% (28%, 39%) in age-inclusive studies, 20% (16%, 25%) in younger patients, and 48% (34%, 66%) in older patients. These probabilities were much lower when an ASA was present.
In patients with otherwise CS, approximately a third of discovered PFOs are likely to be incidental, and hence not benefit from closure. This probability is sensitive to patient characteristics such as age and the presence of an ASA, suggesting the importance of patient-selection in therapeutic decision-making.
Patent foramen ovale; Risk factors for stroke; Secondary stroke prevention
The risk of death in dialysis patients remains high, but varies significantly among patients. No prediction tool is widely used in current clinical practice. We aimed to predict long-term mortality in incident dialysis patients with easily obtainable variables.
Prospective nationwide multicenter cohort study in the United Kingdom (UK Renal Registry); Models were developed using Cox proportional hazards.
Setting and Participants
Patients initiating hemodialysis or peritoneal dialysis between 2002 and 2004, who survived at least three months on dialysis treatment, were followed for three years. Analyses were restricted to subjects in whom information on comorbid conditions and laboratory measurements were available (n=5447). The dataset was divided into datasets for model development (n=3631, training) and validation (n=1816) by random selection.
Basic patient characteristics, comorbidity and laboratory variables.
All cause mortality censored for kidney transplant, recovery of kidney function, and loss to follow-up.
In the training dataset, 1078 patients (29.7%) died within the observation period. The final model of the training dataset included patient characteristics (age, race, primary kidney disease, treatment modality), comorbidities (diabetes, history of cardiovascular disease, smoking) and laboratory variables (hemoglobin, serum albumin, creatinine, calcium) and reached a C-statistic of 0.75 (95% CI, 0.73–0.77) and could accurately discriminate between patients with low (6%), intermediate (19%), high (33%) and very high (59%) mortality risk. The model was further applied to the validation dataset and achieved a C-statistic of 0.73 (95% CI, 0.71–0.76).
Number of missing comorbidity data and lack of an external validation dataset.
Basic patient characteristics, comorbidity and laboratory variables can predict three-year mortality in incident dialysis patients with sufficient accuracy. Identification of subgroups of patients according to mortality risk can guide future research and subsequently target treatment decisions in individual patients.
End stage renal disease; predictive model; mortality; hemodialysis; peritoneal dialysis
A 10-point Surgical Apgar Score, based on patients’ estimated blood loss, lowest heart rate, and lowest mean arterial pressure during surgery, was developed to rate patients’ outcomes in general and vascular surgery but has not been tested for patients having orthopaedic surgery.
For patients undergoing hip and knee arthroplasties, we asked (1) whether the score provides accurate risk stratification for major postoperative complications, and (2) whether it captures intraoperative variables contributing to postoperative risk based on the three parameters independent of preoperative risk.
Patients and Methods
We retrospectively reviewed the electronic records for all 3511 patients who underwent a hip or knee arthroplasty from March 2003 to August 2006 and extracted data to calculate a Surgical Apgar Score. We evaluated the relationship between scores and likelihood of major postoperative in-hospital complications and assessed its discrimination and calibration.
Complication rates increased monotonically as the score decreased. Even after controlling for preoperative risk, each 1-point decrease in the score was associated with a 34.0% increase (95% confidence interval, 0.66–0.84) in the odds of a complication. The overall discriminatory performance of the score was a c-statistic of 0.61. Seventy-six percent of all major complications occurred in patients classified as low risk with scores of 7 or greater.
For patients undergoing hip and knee arthroplasties, the score captures important intraoperative information regarding risk of complications and contributes additional information to preoperative risk, but on its own is insufficient to provide comprehensive postoperative risk stratification for arthroplasties.
Level of Evidence
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
Variability in phenotypic characterization of coronary artery disease (CAD) may contribute to the heterogeneity of genetic association studies, and more consistency in phenotype definitions might improve replication of genetic associations. We assessed the extent of phenotypic heterogeneity, and quantified its impact, in a large literature sample of association studies.
Methods and Results
We searched for large (≥15 studies) meta-analyses of genetic associations and reviewed all studies included therein. From each primary study, we extracted phenotypic definitions, demographics, study design characteristics and genotypic data. For each association, we assessed the magnitude and heterogeneity of genetic effects within and across CAD phenotypes using meta-analytic methodologies. 965 individual studies investigating 32 distinct variants in 22 genes were included, from which we grouped CAD phenotypes into 3 categories: acute coronary syndromes (ACS) (426 studies, 44%), angiographically-documented disease (323 studies, 34%) and “broad, not otherwise specified CAD” (216 studies, 22%). These clinical phenotypes were overlapping. Subgroup meta-analyses by phenotype showed discordant results but phenotypic classification generally explained small proportions of between-study heterogeneity. Differences between phenotypic groups were minimized for associations with robust statistical support. No CAD phenotype was consistently associated with larger or more homogeneous genetic effects in meta-analyses.
Substantial phenotypic heterogeneity exists in CAD genetic associations, but differences in phenotype definition have a small contribution to between-study heterogeneity. We did not find a consistent effect in terms of the magnitude or homogeneity of summary effects for a specific phenotype to support its preferential use in genetic studies or meta-analyses for CAD.
coronary artery disease; myocardial infarction; meta-analysis; genetic association study; phenotype; heterogeneity
In controlled clinical trials, random assignment of treatment is appropriate only when there is equipoise, i.e., no clear preference among treatment options. However, even when equipoise appears absent because prior trials show, on average, one treatment yields superior outcomes, random assignment still may be appropriate for some patients and circumstances. In such cases, enrollment into trials may be assisted by real-time patient-specific predictions of treatment outcomes, to determine whether there is equipoise to justify randomization.
The Percutaneous Coronary Intervention Thrombolytic Predictive Instrument (PCI-TPI) computes probabilities of 30-day mortality for patients having ST elevation myocardial infarction (STEMI), if treated with thrombolytic therapy, and if treated with PCI. We estimated uncertainty around differences in their respective predicted benefits using the estimated uncertainty of the model coefficients. Using the 2,781-patient PCI-TPI development dataset, we evaluated the distribution of predicted benefits for each patient. For three typical clinical situations, randomization was potentially warranted for 70%, 93%, and 80% of patients.
Predictive models may allow real-time patient-specific determination of whether there is equipoise that justifies trial enrollment for a given patient. This approach may have utility for comparative effectiveness trials and for application of trial results to clinical practice.
To determine association of anemia and RBC transfusions with NEC in preterm infants.
111 preterm infants with NEC ≥ Stage 2a were compared with 222 matched controls. 28 clinical variables, including hematocrit and RBC transfusions were recorded. Propensity scores and multivariate logistic regression models were created to examine effects on the risk of NEC.
Controlling for other factors, lower hematocrit was associated with increased odds of NEC [OR 1.10, p =0.01]. RBC transfusion has a temporal relationship with NEC onset. Transfusion within 24h (OR=7.60, p=0.001) and 48h (OR=5.55, p=0.001) has a higher odds of developing NEC but this association is not significant by 96h (OR= 2.13, p =0.07), post transfusion
Anemia may increase the risk of developing NEC in preterm infants. RBC transfusions are temporally related to NEC. Prospective studies are needed to better evaluate the potential influence of transfusions on the development of NEC.
transfusion related gut injury; hematocrit
Decisions to limit treatment in critically ill patients often rely on publications that make claims of futility based on outcome data. Our objective was to systematically review the criteria for futility and the strength of empirical evidence across clinical studies that purport to support or refute claims of futility.
The MEDLINE database was searched for relevant articles published between1980 and 2008. Selected studies reported original outcome data in critically ill or cardiac arrest patients and claimed that these data can support or refute decisions to limit treatment in comparable patients. Two authors independently abstracted data on patient characteristics, intervention, outcomes, cost, and design.
Forty seven studies supporting a claim of futility and 45 refuting it were reviewed. Median point estimate for adverse outcome in studies supporting claims of futility was 100% (range 75% to 100%); median lower 95% confidence limit was 91% (range 48% to 99%). Explicit thresholds for futility were missing in 88% of articles. The original criteria for quantitative futility were fulfilled by only 28% of data, and almost exclusively in studies of cardiopulmonary resuscitation (CPR) for cardiac arrest. Substantial statistical overlap was observed between data brought in support of futility claims and data brought to refute them.
Most studies that purport to guide determinations of futility are based on insufficient data to provide statistical confidence for clinical decision-making. They usually lack explicit a priori thresholds for determination of futility. Many studies draw disparate conclusions based on statistically similar data. In most circumstances these problems preclude confident determinations of futility.
critically ill; futility; empirical evidence; cardiac arrest
Paraoxonase 1 (PON1) polymorphisms have been implicated as risk factors for coronary artery disease, but the results of genetic association studies on the related phenotype of ischemic stroke are inconclusive. We performed a meta-analysis of published studies investigating the association between ischemic stroke and two non-synonymous PON1 polymorphisms, rs662 (p.Q192R) and rs854560 (p.L55M) in humans.
We searched multiple electronic databases through 06/30/2009 for eligible studies. In main analyses we calculated allele-based odds ratios (OR) with random effects models. In secondary analyses we examined dominant and recessive genetic models as well, and performed subgroup and sensitivity analyses.
Regarding rs662, we identified 22 eligible studies (total of 7384 cases/11,074 controls), yielding a summary OR of 1.10 per G allele (95% confidence interval, CI, 1.04–1.17) with no evidence of between-study heterogeneity. For rs854560, 16 eligible studies (total of 5518 cases/8951 controls) yielded a summary OR of 0.97 per T allele (95% CI, 0.90–1.04), again with no evidence of between-study heterogeneity. For both polymorphisms, analyses with dominant and recessive genetic models yielded the same inferences as allele-based comparisons. Subgroup and sensitivity analyses showed similar results.
In agreement with observations in coronary artery disease, PON1 rs662 appears to be associated with a small increase in the risk of ischemic stroke.
paraoxonase 1; PON1; rs662; rs854560; stroke; meta-analysis
Despite the diffusion into practice of percutaneous closure of a patent foramen ovale (PFO) in patients with cryptogenic stroke (CS), the benefits have not been demonstrated, and remain unclear. For any individual presenting with a PFO in the setting of CS, it is not clear whether the PFO is pathogenically-related to the index event or an incidental finding. Further, the overall rate of stroke recurrence is low in patients with CS and PFO. How patient-specific factors affect the likelihood that a discovered PFO is related to an index stroke or affect the risk of recurrence is not well understood. These probabilities are likely to be important determinants of the benefits of PFO closure in CS.
The goal of the Risk of Paradoxical Embolism (RoPE) Study is to develop and test a set of predictive models that can identify those patients most likely to benefit from preventive treatments for PFO-related stroke recurrence, such as PFO closure. To do this, we will construct a database of patients with CS, both with and without PFO, by combining existing cohort studies. We will use this pooled database to identify patient characteristics associated with the presence (versus the absence) of a PFO, and to use this "PFO propensity" to estimate the patient-specific probability that a PFO was pathogenically related to the index stroke (Model #1). We will also develop, among patients with both a CS and a PFO, a predictive model to estimate patient-specific stroke recurrence risk based on clinical, radiographic and echocardiographic characteristics. (Model #2). We will then combine Models #1 and #2 into a composite index that can rank patients with CS and PFO by their conditional probability that their PFO was pathogenically related to the index stroke and the risk of stroke recurrence. Finally, we will apply this composite index to completed clinical trials (currently on-going) testing endovascular PFO closure against medical therapy, to stratify patients from low-expected-benefit to high-expected-benefit.
Purpose of review
The etiology of stroke remains unknown in roughly one third of patients despite extensive investigation. The prevalence of PFOs in the general population is around 25% but the prevalence in cryptogenic stroke patients is doubled. This suggests a causal relationship between PFO and CS. This has generally been attributed to paradoxical embolism. Regardless of mechanism, ~30,000 young patients each year have a cryptogenic stroke and PFO. Optimal management is uncertain.
Many physicians recommend PFO closure, an intuitively attractive mechanical solution for stroke prevention. Unfortunately, the benefit of PFO closure in patients with stroke has not been demonstrated. There are ongoing clinical trials comparing the safety and efficacy of PFO closure to medical therapy. Interpreting these trials will be complicated by two issues: first, it is unclear whether a patient's PFO is causally related to the event (“pathogenic”) or not (“incidental”); and second, recurrent strokes may be due to paradoxical embolism or another stroke mechanism.
Substantial heterogeneity of patients within trials along these two dimensions of risk may make overall trial results difficult to interpret. With appropriate analyses, the trials may be more informative than the overall data may suggest.
Cryptogenic stroke; patent foramen ovale; risk heterogeneity; endovascular PFO closure; clinical trials
Although randomized controlled trials are the gold standard for establishing causation in clinical research, their aggregated results can be misleading when applied to individual patients. A treatment may be beneficial in some patients, but its harms may outweigh benefits in others. While conventional one-variable-at-a-time subgroup analyses have well-known limitations, multivariable risk-based analyses can help uncover clinically significant heterogeneity in treatment effects that may be otherwise obscured. Trials in kidney transplantation have yielded the finding that a reduction in acute rejection does not translate into a similar benefit in prolonging graft survival and improving graft function. This paradox might be explained by the variation in risk for acute rejection among included kidney transplant recipients varying the likelihood of benefit or harm from intense immunosuppressive regimens. Analyses that stratify patients by their immunological risk may resolve these otherwise puzzling results. Reliable risk models should be developed to investigate benefits and harms in rationally designed risk-based subgroups of patients in existing RCT datasets. These risk strata would need to be validated in future prospective clinical trials examining long term effects on patient and graft survival. This approach may allow better individualized treatment choices for kidney transplant recipients.
Over the last 20 years, percutaneous transluminal balloon coronary angioplasty (PTCA), bare metal stents (BMS) and drug eluting stents (DES) succeeded each other as catheter-based treatments for coronary artery disease (CAD). We present an overview of randomised trials comparing these interventions with each other and with medical therapy in patients with nonacute CAD.
We searched Medline for trials contrasting at least two of the aforementioned interventions. Outcomes of interest were death, myocardial infarction (MI), coronary artery bypass grafting (CABG), target lesion or vessel revascularisation (TLR/TVR), and any revascularisation. Random effects meta-analyses summarised head-to-head (direct) comparisons, and network meta-analyses integrated direct and indirect evidence.
61 eligible trials (25 388 patients) investigated 4 of 6 possible comparisons between the 4 interventions. No trials directly compared DES with medical therapy or PTCA. In all direct or indirect comparisons, succeeding advancements in PCI did not yield detectable improvements in deaths and MI. The risk ratio for indirect comparisons between DES and medical therapy was 0·96 (95% confidence interval: 0·60, 1·52) for death and 1·15 (0·73, 1·82) for MI. In contrast, there were sequential significant reductions in TLR/TVR with BMS compared to PTCA and with DES compared to BMS. The risk ratio for the indirect comparison between DES and PTCA for TLR/TVR was 0·30 (0·17, 0·51).
Sequential innovations in the catheter-based treatment of nonacute CAD showed no evidence of an impact on death or MI when compared with medical therapy.
Primary percutaneous coronary intervention (PCI) is more effective on average than fibrinolytic therapy (FT) in the treatment of ST-segment elevation myocardial infarction (STEMI). Yet most U.S. hospitals are not equipped for PCI and FT is still widely used. This study evaluated the comparative effectiveness of STEMI regionalization strategies to increase the use of PCI against standard emergency transport and care.
METHODS AND RESULTS
We estimated incremental treatment costs and quality-adjusted life expectancies of 2,000 patients with STEMI who received PCI or FT in simulations of emergency care in a regional hospital system. To increase access to PCI across the system, we compared a base case strategy to 12 hospital-based strategies of building new PCI labs or extending the hours of existing labs, and one emergency medical services (EMS)-based strategy of transporting all patients with STEMI to existing PCI-capable hospitals. The base case resulted in 609 (569, 647) patients getting PCI. Hospital-based strategies increased the number of patients receiving PCI, the costs of care, and quality-adjusted life years (QALYs) saved, and were cost effective under a variety of conditions. An EMS-based strategy of transporting every patient to an existing PCI facility was less costly and more effective than all hospital expansion options.
Our results suggest that new construction and staffing of PCI labs may not be warranted if an EMS strategy is both available and feasible.
cost-benefit analysis; fibrinolysis; Percutaneous coronary intervention; ST-segment elevation myocardial infarction; thrombolysis
Mounting evidence suggests that there is frequently considerable variation in the risk of the outcome of interest in clinical trial populations. These differences in risk will often cause clinically important heterogeneity in treatment effects (HTE) across the trial population, such that the balance between treatment risks and benefits may differ substantially between large identifiable patient subgroups; the "average" benefit observed in the summary result may even be non-representative of the treatment effect for a typical patient in the trial. Conventional subgroup analyses, which examine whether specific patient characteristics modify the effects of treatment, are usually unable to detect even large variations in treatment benefit (and harm) across risk groups because they do not account for the fact that patients have multiple characteristics simultaneously that affect the likelihood of treatment benefit. Based upon recent evidence on optimal statistical approaches to assessing HTE, we propose a framework that prioritizes the analysis and reporting of multivariate risk-based HTE and suggests that other subgroup analyses should be explicitly labeled either as primary subgroup analyses (well-motivated by prior evidence and intended to produce clinically actionable results) or secondary (exploratory) subgroup analyses (performed to inform future research). A standardized and transparent approach to HTE assessment and reporting could substantially improve clinical trial utility and interpretability.
In patients with a major cardiac event, the first priority is to minimize time to treatment. For many patients, first contact with the health system is through emergency medical services (EMS). We set out to identify patient and neighborhood-level factors that were associated with time in EMS.
A retrospective cohort study was conducted in ten municipalities in Dallas County, Texas from January 1 through December 31, 2004. The dataset included 5,887 calls with a primary complaint that was cardiac in nature. The region was served by 29 hospitals and 98 EMS depots. Multivariate models included measures of distance traveled, time of day, day of week, patient and neighborhood characteristics. The main outcomes were elapsed time in EMS (continuous; in minutes) and delay in EMS (dichotomous; > 15 minutes beyond median time).
We found positive associations between patient characteristics and both average time and serious delay in EMS care. Variation in average time was not large enough to be clinically meaningful. Approximately 11% (n = 647) of patients were delayed 15 minutes or more. Being non-white was associated with delays, but few patients were affected. Women were more likely to be seriously delayed (adjusted odds ratio 1.52; 95% confidence interval: 1.32, 1.74), and this association did not change after adjusting for other characteristics, including neighborhood socio-economic composition.
Compared to otherwise similar men, women have 50% greater odds of being delayed in the EMS setting. The determinants of serious delay should be a special focus of EMS studies where time to treatment is a priority.
Patients; population; women; emergency medical services; cardiac care