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1.  Stenting for Peripheral Artery Disease of the Lower Extremities 
Executive Summary
In January 2010, the Medical Advisory Secretariat received an application from University Health Network to provide an evidentiary platform on stenting as a treatment management for peripheral artery disease. The purpose of this health technology assessment is to examine the effectiveness of primary stenting as a treatment management for peripheral artery disease of the lower extremities.
Clinical Need: Condition and Target Population
Peripheral artery disease (PAD) is a progressive disease occurring as a result of plaque accumulation (atherosclerosis) in the arterial system that carries blood to the extremities (arms and legs) as well as vital organs. The vessels that are most affected by PAD are the arteries of the lower extremities, the aorta, the visceral arterial branches, the carotid arteries and the arteries of the upper limbs. In the lower extremities, PAD affects three major arterial segments i) aortic-iliac, ii) femoro-popliteal (FP) and iii) infra-popliteal (primarily tibial) arteries. The disease is commonly classified clinically as asymptomatic claudication, rest pain and critical ischemia.
Although the prevalence of PAD in Canada is not known, it is estimated that 800,000 Canadians have PAD. The 2007 Trans Atlantic Intersociety Consensus (TASC) II Working Group for the Management of Peripheral Disease estimated that the prevalence of PAD in Europe and North America to be 27 million, of whom 88,000 are hospitalizations involving lower extremities. A higher prevalence of PAD among elderly individuals has been reported to range from 12% to 29%. The National Health and Nutrition Examination Survey (NHANES) estimated that the prevalence of PAD is 14.5% among individuals 70 years of age and over.
Modifiable and non-modifiable risk factors associated with PAD include advanced age, male gender, family history, smoking, diabetes, hypertension and hyperlipidemia. PAD is a strong predictor of myocardial infarction (MI), stroke and cardiovascular death. Annually, approximately 10% of ischemic cardiovascular and cerebrovascular events can be attributed to the progression of PAD. Compared with patients without PAD, the 10-year risk of all-cause mortality is 3-fold higher in patients with PAD with 4-5 times greater risk of dying from cardiovascular event. The risk of coronary heart disease is 6 times greater and increases 15-fold in patients with advanced or severe PAD. Among subjects with diabetes, the risk of PAD is often severe and associated with extensive arterial calcification. In these patients the risk of PAD increases two to four fold. The results of the Canadian public survey of knowledge of PAD demonstrated that Canadians are unaware of the morbidity and mortality associated with PAD. Despite its prevalence and cardiovascular risk implications, only 25% of PAD patients are undergoing treatment.
The diagnosis of PAD is difficult as most patients remain asymptomatic for many years. Symptoms do not present until there is at least 50% narrowing of an artery. In the general population, only 10% of persons with PAD have classic symptoms of claudication, 40% do not complain of leg pain, while the remaining 50% have a variety of leg symptoms different from classic claudication. The severity of symptoms depends on the degree of stenosis. The need to intervene is more urgent in patients with limb threatening ischemia as manifested by night pain, rest pain, ischemic ulcers or gangrene. Without successful revascularization those with critical ischemia have a limb loss (amputation) rate of 80-90% in one year.
Diagnosis of PAD is generally non-invasive and can be performed in the physician offices or on an outpatient basis in a hospital. Most common diagnostic procedure include: 1) Ankle Brachial Index (ABI), a ratio of the blood pressure readings between the highest ankle pressure and the highest brachial (arm) pressure; and 2) Doppler ultrasonography, a diagnostic imaging procedure that uses a combination of ultrasound and wave form recordings to evaluate arterial flow in blood vessels. The value of the ABI can provide an assessment of the severity of the disease. Other non invasive imaging techniques include: Computed Tomography (CT) and Magnetic Resonance Angiography (MRA). Definitive diagnosis of PAD can be made by an invasive catheter based angiography procedure which shows the roadmap of the arteries, depicting the exact location and length of the stenosis / occlusion. Angiography is the standard method against which all other imaging procedures are compared for accuracy.
More than 70% of the patients diagnosed with PAD remain stable or improve with conservative management of pharmacologic agents and life style modifications. Significant PAD symptoms are well known to negatively influence an individual quality of life. For those who do not improve, revascularization methods either invasive or non-invasive can be used to restore peripheral circulation.
Technology Under Review
A Stent is a wire mesh “scaffold” that is permanently implanted in the artery to keep the artery open and can be combined with angioplasty to treat PAD. There are two types of stents: i) balloon-expandable and ii) self expandable stents and are available in varying length. The former uses an angioplasty balloon to expand and set the stent within the arterial segment. Recently, drug-eluting stents have been developed and these types of stents release small amounts of medication intended to reduce neointimal hyperplasia, which can cause re-stenosis at the stent site. Endovascular stenting avoids the problem of early elastic recoil, residual stenosis and flow limiting dissection after balloon angioplasty.
Research Questions
In individuals with PAD of the lower extremities (superficial femoral artery, infra-popliteal, crural and iliac artery stenosis or occlusion), is primary stenting more effective than percutaneous transluminal angioplasty (PTA) in improving patency?
In individuals with PAD of the lower extremities (superficial femoral artery, infra-popliteal, crural and iliac artery stenosis or occlusion), does primary stenting provide immediate success compared to PTA?
In individuals with PAD of the lower extremities (superficial femoral artery, infra-popliteal, crural and iliac artery stenosis or occlusion), is primary stenting associated with less complications compared to PTA?
In individuals with PAD of the lower extremities (superficial femoral artery, infra-popliteal, crural and iliac artery stenosis or occlusion), does primary stenting compared to PTA reduce the rate of re-intervention?
In individuals with PAD of the lower extremities (superficial femoral artery, infra-popliteal, crural and iliac artery stenosis or occlusion) is primary stenting more effective than PTA in improving clinical and hemodynamic success?
Are drug eluting stents more effective than bare stents in improving patency, reducing rates of re-interventions or complications?
Research Methods
Literature Search
A literature search was performed on February 2, 2010 using OVID MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, OVID EMBASE, the Cochrane Library, and the International Agency for Health Technology Assessment (INAHTA). 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. The quality of evidence was assessed as high, moderate, low or very low according to GRADE methodology.
Inclusion Criteria
English language full-reports from 1950 to January Week 3, 2010
Comparative randomized controlled trials (RCTs), systematic reviews and meta-analyses of RCTs
Proven diagnosis of PAD of the lower extremities in all patients.
Adult patients at least 18 years of age.
Stent as at least one treatment arm.
Patency, re-stenosis, re-intervention, technical success, hemodynamic (ABI) and clinical improvement and complications as at least an outcome.
Exclusion Criteria
Non-randomized studies
Observational studies (cohort or retrospective studies) and case report
Feasibility studies
Studies that have evaluated stent but not as a primary intervention
Outcomes of Interest
The primary outcome measure was patency. Secondary measures included technical success, re-intervention, complications, hemodynamic (ankle brachial pressure index, treadmill walking distance) and clinical success or improvement according to Rutherford scale. It was anticipated, a priori, that there would be substantial differences among trials regarding the method of examination and definitions of patency or re-stenosis. Where studies reported only re-stenosis rates, patency rates were calculated as 1 minus re-stenosis rates.
Statistical Analysis
Odds ratios (for binary outcomes) or mean difference (for continuous outcomes) with 95% confidence intervals (CI) were calculated for each endpoint. An intention to treat principle (ITT) was used, with the total number of patients randomized to each study arm as the denominator for each proportion. Sensitivity analysis was performed using per protocol approach. A pooled odds ratio (POR) or mean difference for each endpoint was then calculated for all trials reporting that endpoint using a fixed effects model. PORs were calculated for comparisons of primary stenting versus PTA or other alternative procedures. Level of significance was set at alpha=0.05. Homogeneity was assessed using the chi-square test, I2 and by visual inspection of forest plots. If heterogeneity was encountered within groups (P < 0.10), a random effects model was used. All statistical analyses were performed using RevMan 5. Where sufficient data were available, these analyses were repeated within subgroups of patients defined by time of outcome assessment to evaluate sustainability of treatment benefit. Results were pooled based on the diseased artery and stent type.
Summary of Findings
Balloon-expandable stents vs PTA in superficial femoral artery disease
Based on a moderate quality of evidence, there is no significant difference in patency between primary stenting using balloon-expandable bare metal stents and PTA at 6, 12 and 24 months in patients with superficial femoral artery disease. The pooled OR for patency and their corresponding 95% CI are: 6 months 1.26 (0.74, 2.13); 12 months 0.95 (0.66, 1.38); and 24 months 0.72 (0.34. 1.55).
There is no significant difference in clinical improvement, re-interventions, peri and post operative complications, mortality and amputations between primary stenting using balloon-expandable bare stents and PTA in patients with superficial femoral artery. The pooled OR and their corresponding 95% CI are clinical improvement 0.85 (0.50, 1.42); ankle brachial index 0.01 (-0.02, 0.04) re-intervention 0.83 (0.26, 2.65); complications 0.73 (0.43, 1.22); all cause mortality 1.08 (0.59, 1.97) and amputation rates 0.41 (0.14, 1.18).
Self-expandable stents vs PTA in superficial femoral artery disease
Based on a moderate quality of evidence, primary stenting using self-expandable bare metal stents is associated with significant improvement in patency at 6, 12 and 24 months in patients with superficial femoral artery disease. The pooled OR for patency and their corresponding 95% CI are: 6 months 2.35 (1.06, 5.23); 12 months 1.54 (1.01, 2.35); and 24 months 2.18 (1.00. 4.78). However, the benefit of primary stenting is not observed for clinical improvement, re-interventions, peri and post operative complications, mortality and amputation in patients with superficial femoral artery disease. The pooled OR and their corresponding 95% CI are clinical improvement 0.61 (0.37, 1.01); ankle brachial index 0.01 (-0.06, 0.08) re-intervention 0.60 (0.36, 1.02); complications 1.60 (0.53, 4.85); all cause mortality 3.84 (0.74, 19.22) and amputation rates 1.96 (0.20, 18.86).
Balloon expandable stents vs PTA in iliac artery occlusive disease
Based on moderate quality of evidence, despite immediate technical success, 12.23 (7.17, 20.88), primary stenting is not associated with significant improvement in patency, clinical status, treadmill walking distance and reduction in re-intervention, complications, cardiovascular events, all cause mortality, QoL and amputation rates in patients with intermittent claudication caused by iliac artery occlusive disease. The pooled OR and their corresponding 95% CI are: patency 1.03 (0.56, 1.87); clinical improvement 1.08 (0.60, 1.94); walking distance 3.00 (12.96, 18.96); re-intervention 1.16 (0.71, 1.90); complications 0.56 (0.20, 1.53); all cause mortality 0.89 (0.47, 1.71); QoL 0.40 (-4.42, 5.52); cardiovascular event 1.16 (0.56, 2.40) and amputation rates 0.37 (0.11, 1.23). To date no RCTs are available evaluating self-expandable stents in the common or external iliac artery stenosis or occlusion.
Drug-eluting stent vs balloon-expandable bare metal stents in crural arteries
Based on a very low quality of evidence, at 6 months of follow-up, sirolimus drug-eluting stents are associated with a reduction in target vessel revascularization and re-stenosis rates in patients with atherosclerotic lesions of crural (tibial) arteries compared with balloon-expandable bare metal stent. The OR and their corresponding 95% CI are: re-stenosis 0.09 (0.03, 0.28) and TVR 0.15 (0.05, 0.47) in patients with atherosclerotic lesions of the crural arteries at 6 months follow-up. Both types of stents offer similar immediate success. Limitations of this study include: short follow-up period, small sample and no assessment of mortality as an outcome. Further research is needed to confirm its effect and safety.
PMCID: PMC3377569  PMID: 23074395
2.  The Relevance of Different Methods of Calculating the Ankle-Brachial Index 
American Journal of Epidemiology  2009;171(3):368-376.
The authors aimed to determine differences in the prevalence of peripheral arterial disease (PAD) and its associations with cardiovascular disease (CVD) risk factors, using different methods of calculating the ankle-brachial index (ABI). Using measurements taken in the bilateral brachial, dorsalis pedis, and posterior tibial arteries, the authors calculated ABI in 3 ways: 1) with the lowest ankle pressure (dorsalis pedis artery or posterior tibial artery) (“ABI-LO”), 2) with the highest ankle pressure (“ABI-HI”), and 3) with the mean of the ankle pressures (“ABI-MN”). For all 3 methods, the index ABI was the lower of the ABIs calculated from the left and right legs. PAD was defined as an ABI less than 0.90. Among 6,590 subjects from a multiethnic cohort (baseline examination: 2000–2002), in comparison with ABI-HI, the relative prevalence of PAD was 3.95 times higher in women and 2.74 times higher in men when ABI-LO was used. The relative magnitudes of the associations were largest between PAD and both subclinical atherosclerosis and CVD risk factors when ABI-HI was used, except when risk estimates for PAD were less than 1.0, where the largest relative magnitudes of association were found using ABI-LO. PAD prevalence and its associations with CVD risk factors and subclinical atherosclerosis measures depend on the ankle pressure used to compute the ABI.
PMCID: PMC2842203  PMID: 20042436
ankle brachial index; cardiovascular diseases; continental population groups; ethnic groups; peripheral vascular diseases
3.  Alternative ankle-brachial index method identifies additional at-risk individuals 
To determine whether utilization of an alternative ankle-brachial index (ABI) calculation method improves mortality risk prediction compared to traditional methods.
The ABI is used to diagnose peripheral arterial disease (PAD), and to identify those at risk for cardiovascular events. Traditionally, the ABI is calculated using the higher of the dorsalis pedis and posterior tibial ankle arteries. Studies directly comparing calculation methods are limited.
The ABI was calculated at baseline in 1,413 study participants undergoing non-emergent coronary angiography subsequently followed for all-cause and cardiovascular mortality. There were 224 individuals assigned to the traditional-PAD group (ABI < 0.90) using the traditional ABI method. Of those remaining, an alternative ABI method utilizing the lower of the two ankle pressures assigned 282 patients to the alternative-PAD group. The 862 individuals not assigned to PAD by either method were the no-PAD group.
There were 163 mortalities during a median follow-up of 5.0 years. Adjusted Cox regression models showed that the alternative-PAD group had an increased risk for all-cause (HR=1.49; 95% CI, 1.01-2.19) and cardiovascular mortality (HR=3.21; 95% CI, 1.53-6.37) versus the no-PAD group. Additionally, in the no-PAD group, there was an 11% (HR=1.11; 95% CI, 1.05-1.17) increased risk of all-cause mortality per 1mm Hg increased difference between the left and right brachial systolic pressures.
The implementation of an alternative ABI method and use of the brachial difference identifies individuals at an increased risk for mortality who are currently missed using traditional ABI methods. Current ABI protocols may need to be evaluated.
PMCID: PMC3732795  PMID: 23707317
peripheral artery disease; mortality; diagnosis
4.  To screen or not to screen for peripheral arterial disease in subjects aged 80 and over in primary health care: a cross-sectional analysis from the BELFRAIL study 
BMC Family Practice  2011;12:39.
Peripheral arterial disease (PAD) is common in older people. An ankle-brachial index (ABI) < 0.9 can be used as an indicator of PAD. Patients with low ABI have increased mortality and a higher risk of serious cardiovascular morbidity. However, because 80% of the patients are asymptomatic, PAD remains unrecognised in a large group of patients. The aims of this study were 1) to examine the prevalence of reduced ABI in subjects aged 80 and over, 2) to determine the diagnostic accuracy of the medical history and clinical examination for reduced ABI and 3) to investigate the difference in functioning and physical activity between patients with and without reduced ABI.
A cross-sectional study embedded within the BELFRAIL study. A general practitioner (GP) centre, located in Hoeilaart, Belgium, recruited 239 patients aged 80 or older. Only three criteria for exclusion were used: urgent medical need, palliative situation and known serious dementia. The GP recorded the medical history and performed a clinical examination. The clinical research assistant performed an extensive examination including Mini-Mental State Examination (MMSE), Geriatric Depression Scale (GDS-15), Activities of Daily Living (ADL), Tinetti test and the LASA Physical Activity Questionnaire (LAPAQ). ABI was measured using an automatic oscillometric appliance.
In 40% of patients, a reduced ABI was found. Cardiovascular risk factors were unable to identify patients with low ABI. A negative correlation was found between the number of cardiovascular morbidities and ABI. Cardiovascular morbidity had a sensitivity of 65.7% (95% CI 53.4-76.7) and a specificity of 48.6% (95% CI 38.7-58.5). Palpation of the peripheral arteries showed the highest negative predictive value (77.7% (95% CI 71.8-82.9)). The LAPAQ score was significantly lower in the group with reduced ABI.
The prevalence of PAD is very high in patients aged 80 and over in general practice. The clinical examination, cardiovascular risk factors and the presence of cardiovascular morbidity were not able to identify patients with a low ABI. A screening strategy for PAD by determining ABI could be considered if effective interventions for those aged 80 and over with a low ABI become available through future research.
PMCID: PMC3121584  PMID: 21605447
5.  Effects of age, sex and smoking on ankle-brachial index in a Finnish population at risk for cardiovascular disease 
Smoking is a well-known risk factor for peripheral arterial disease (PAD). Data regarding differences in the prevalence of PAD between sexes are somewhat controversial. In addition, most studies indicate that the prevalence of PAD increases with age in both sexes. In the present study, the effects of sex, age and smoking on the ankle-brachial index (ABI) in a Finnish cardiovascular risk population were investigated.
To investigate the relationship between the ankle-brachial index, and age, sex and smoking in a Finnish population at risk for cardiovascular disease.
All men and women between 45 and 70 years of age living in a rural town (Harjavalta, Finland; total population 7700) were invited to participate in a population survey (Harmonica study). Patients with previously diagnosed diabetes or vascular disease were excluded. In total, 2856 patients were invited to participate in the study. From these subjects, a cardiovascular risk population was screened. Complete data were available from 1028 persons. ABI (the ratio between the posterior tibial or dorsalis pedis artery and brachial artery pressures) was measured, and questionnaires were used to detect smoking status and relevant medical history. Only current smoking status was taken into account.
The mean ABI for the entire study population was 1.10 (range 0.56 to 1.64). Current smokers had a lower mean ABI (1.06; P<0.001). There was no statistically significant difference in ABI values among age groups, although the majority of patients with ABI values below 0.9 were older than 60 years of age. There was no statistically significant difference in ABI between sexes.
As previously reported, the present study shows the significant effect of smoking in the development of PAD. No statistically significant difference was found among age groups, but the tendency was toward lower ABIs in the oldest age groups. Sex had a minimal effect on the ABI.
PMCID: PMC2733029  PMID: 22477327
Age; Ankle-brachial index; Cardiovascular risk; Epidemiology; Sex; Smoking
6.  Surrogates of Large Artery versus Small Artery Stiffness and Ankle-Brachial Index 
Peripheral artery tonometry (PAT) is a novel method for assessing arterial stiffness of small digital arteries. Pulse pressure can be regarded as a surrogate of large artery stiffness. When ankle-brachial index (ABI) is calculated using the higher of the two ankle systolic pressures as denominator (ABI-higher), leg perfusion can be reliably estimated. However, using the lower of the ankle pressures to calculate ABI (ABI-lower) identifies more patients with isolated peripheral arterial disease (PAD) in ankle arteries. We aimed to compare the ability of PAT, pulse pressure, and different calculations of ABI to detect atherosclerotic disease in lower extremities. We examined PAT, pulse pressure, and ABI in 66 cardiovascular risk subjects in whom borderline PAD (ABI 0.91 to 1.00) was diagnosed 4 years earlier. Using ABI-lower to diagnose PAD yielded 2-fold higher prevalence of PAD than using ABI-higher. Endothelial dysfunction was diagnosed in 15/66 subjects (23%). In a bivariate correlation analysis, pulse pressure was negatively correlated with ABI-higher (r = −0.347, p = 0.004) and with ABI-lower (r = −0.424, p < 0.001). PAT hyperemic response was not significantly correlated with either ABI-higher (r = −0.148, p = 0.24) or with ABI-lower (r = −0.208, p = 0.095). Measurement of ABI using the lower of the two ankle pressures is an efficient method to identify patients with clinical or subclinical atherosclerosis and worth performing on subjects with pulse pressure above 65 mm Hg. The usefulness of PAT measurement in detecting PAD is vague.
PMCID: PMC3331653  PMID: 22942632
Ankle-brachial index; peripheral arterial disease; hypertension
7.  Peripheral artery disease assessed by ankle-brachial index in patients with established cardiovascular disease or at least one risk factor for atherothrombosis - CAREFUL Study: A national, multi-center, cross-sectional observational study 
To investigate the presence of peripheral artery disease (PAD) via the ankle brachial index (ABI) in patients with known cardiovascular and/or cerebrovascular diseases or with at least one risk factor for atherothrombosis.
Patients with a history of atherothrombotic events, or aged 50-69 years with at least one cardiovascular risk factor, or > = 70 years of age were included in this multicenter, cross-sectional, non-interventional study (DIREGL04074). Demographics, medical history, physical examination findings, and physician awareness of PAD were analyzed. The number of patients with low ABI (< = 0.90) was analyzed.
A total of 530 patients (mean age, 63.4 ± 8.7 years; 50.2% female) were enrolled. Hypertension and dyslipidemia were present in 88.7% and 65.5% of patients, respectively. PAD-related symptoms were evident in about one-third of the patients, and at least one of the pedal pulses was negative in 6.5% of patients. The frequency of low ABI was 20.0% in the whole study population and 30% for patients older than 70 years. Older age, greater number of total risk factors, and presence of PAD-related physical findings were associated with increased likelihood of low ABI (p < 0.001). There was no gender difference in the prevalence of low ABI, PAD symptoms, or total number of risk factors. Exercise (33.6%) was the most common non-pharmacological option recommended by physicians, and acetylsalicylic acid (ASA) (45.4%) was the most frequently prescribed medication for PAD.
Our results indicate that advanced age, greater number of total risk factors and presence of PAD-related physical findings were associated with increased likelihood of low ABI. These findings are similar to those reported in similar studies of different populations, and document a fairly high prevalence of PAD in a Mediterranean country.
PMCID: PMC3033857  PMID: 21247449
8.  Dorsalis pedis arterial pulse: palpation using a bony landmark 
Postgraduate Medical Journal  2002;78(926):746-747.
Introduction: The unreliability of the pulse examination of the foot has primarily been due to variability of technique between examiners. Whereas the groove between the medial malleolus and the Achilles tendon more readily defines the location of the posterior tibial pulse, the location of the dorsalis pedis pulse remains vague. In this paper a novel method of locating the dorsalis pedis pulse by physical examination is described.
Methods: Forty one consecutive patients admitted to a general surgery service of a tertiary medical centre within a two month period were examined. Using the dorsal most prominence of the navicular bone as a landmark, the distance to the dorsalis pedis pulse in bilateral lower extremities was measured by palpation and compared to Doppler ultrasound. Measurements were confirmed by two separate examiners blinded to each others' results.
Results: The dorsalis pedis artery was palpable in 78% of extremities and present by Doppler ultrasound in 95%. The location of the left dorsalis pedis artery was a mean (SD) 9.8 (1.4) mm by palpation and 11.1 (2.1) mm by Doppler ultrasound from the dorsal most prominence of the navicular bone. The right dorsalis pedis artery was 10.4 (3.4) mm by palpation and 11.5 (0.7) mm from the dorsal most prominence of the navicular bone. No significant differences in location of the dorsalis pedis artery were observed bilaterally between Doppler ultrasound and palpation; No significant differences were observed comparing contralateral dorsalis pedis arteries nor any differences between the examiners' results.
Conclusion: The dorsal most prominence of the navicular bone provides a bony landmark to readily locate the dorsalis pedis artery. Reliability of the examination may be increased as to the patency of the dorsalis pedis artery by using this dependable anatomic landmark.
PMCID: PMC1757948  PMID: 12509693
We studied associations of borderline and low-normal ankle brachial index (ABI) values with functional decline over five-year follow-up.
Associations of borderline and low-normal ABI with functional decline are unknown.
The 666 participants included 412 with peripheral arterial disease (PAD). Participants were categorized as follows: Severe PAD (ABI < 0.50), moderate PAD (ABI 0.50-0.69), mild PAD (ABI 0.70 to 0.89), borderline ABI (0.90 to 0.99), low normal ABI (1.00 to 1.09), and normal ABI (ABI 1.10-1.30). Outcomes were assessed annually for five years. Mobility loss was defined as loss of the ability to walk ¼ mile or walk up and down one flight of stairs without assistance among those without baseline mobility impairment. Becoming unable to walk for six minutes continuously was defined as stopping during the six minute walk at follow-up among those who walked for six minutes continuously at baseline. Results adjust for age, sex, race, comorbidities, and other confounders.
Hazard ratios (HR) for mobility loss according to ABI category were as follows. Severe PAD: HR=4.16 (95% Confidence Interval (CI)=1.58-10.92), moderate PAD: HR=3.82 (95% CI=1.66-8.81), mild PAD: HR=3.22 (95% CI=1.43-7.21), borderline ABI: HR=3.07 (95% CI=1.21-7.84), low normal ABI: HR=2.61 (95% CI=1.08-6.32) (p trend=0.0018). Similar associations were observed for becoming unable to walk six-minutes continuously (p trend<0.0001).
At five-year follow-up, persons with borderline ABI values have a higher incidence of mobility loss and becoming unable to walk for six minutes continuously compared to persons with a normal baseline ABI. A low normal ABI is associated with an increased incidence of mobility loss compared to persons with a normal ABI.
We studied associations of borderline and low-normal ABI values with functional decline over five-year follow-up among 666 participants, including 412 with lower extremity peripheral arterial disease (PAD). At five year follow-up, participants with borderline ABI values at baseline (ABI 0.90 to 0.99) had significantly greater mobility loss and were more likely to become unable to walk for six-minutes continuously compared to those with a normal baseline ABI. Participants with low normal ABI values (ABI 1.00 to 1.09) had significantly greater mobility loss compared to those with a normal baseline ABI.
PMCID: PMC3215766  PMID: 19298919
ankle brachial index; physical functioning; peripheral arterial disease; intermittent claudication
10.  Peripheral arterial disease and osteoporosis in older adults: the Rancho Bernardo Study 
Osteoporosis International  2009;20(12):2071-2078.
We examined the association between peripheral arterial disease (PAD) and bone health in 1,332 adults. We found a weak association between PAD and osteoporosis and bone loss only in women, but the association was not independent of age. PAD was not associated with fractures in this community-based population.
Increased rates of osteoporosis have been reported in patients with cardiovascular disease, suggesting a link between osteoporosis and atherosclerosis.
We examined the association between PAD and bone health in 1,332 adults who attended a research visit in 1992–1996, when the ankle–brachial index (ABI), bone mineral density (BMD), and spine X-rays were obtained. A total of 837 participants attended a follow-up visit in 1997–2000.
PAD defined by an ABI ≤ 0.90 was present in 15.4% of the women and 13.3% of the men. Prevalence of osteoporosis was significantly higher in women with PAD compared to women without PAD (p < 0.05). During an average 4-year follow-up, women with PAD had a significantly higher rate of bone loss than women without PAD (p = 0.05). The associations were no longer significant after age adjustment. In men, PAD was not associated with osteoporosis, but men with PAD had lower BMD at the femoral neck than men without PAD (p = 0.03). PAD was not associated with osteoporotic fractures in either sex.
We found a weak and age-dependent association between PAD and osteoporosis in women but not men. PAD was not associated with fractures in this community-based population.
PMCID: PMC2777212  PMID: 19308300
Osteoporosis; Peripheral artery disease
11.  Ankle Brachial Index Values, Leg Symptoms, and Functional Performance Among Community‐Dwelling Older Men and Women in the Lifestyle Interventions and Independence for Elders Study 
The prevalence and significance of low normal and abnormal ankle brachial index (ABI) values in a community‐dwelling population of sedentary, older individuals is unknown. We describe the prevalence of categories of definite peripheral artery disease (PAD), borderline ABI, low normal ABI, and no PAD and their association with lower‐extremity functional performance in the LIFE Study population.
Methods and Results
Participants age 70 to 89 in the LIFE Study underwent baseline measurement of the ABI, 400‐m walk, and 4‐m walking velocity. Participants were classified as follows: definite PAD (ABI <0.90), borderline PAD (ABI 0.90 to 0.99), low normal ABI (ABI 1.00 to 1.09), and no PAD (ABI 1.10 to 1.40). Of 1566 participants, 220 (14%) had definite PAD, 250 (16%) had borderline PAD, 509 (33%) had low normal ABI, and 587 (37%) had no PAD. Among those with definite PAD, 65% were asymptomatic. Adjusting for age, sex, race, body mass index, smoking, and comorbidities, lower ABI was associated with longer mean 400‐m walk time: (definite PAD=533 seconds; borderline PAD=514 seconds; low normal ABI=503 seconds; and no PAD=498 seconds [P<0.001]). Among asymptomatic participants with and without PAD, lower ABI values were also associated with longer 400‐m walk time (P<0.001) and slower walking velocity (P=0.042).
Among older community‐dwelling men and women, 14% had PAD and 49% had borderline or low normal ABI values. Lower ABI values were associated with greater functional impairment, suggesting that lower extremity atherosclerosis may be a common preventable cause of functional limitations in older people.
Clinical Trial Registration
URL: Unique identifier: NCT01072500.
PMCID: PMC3886743  PMID: 24222666
aging; exercise; peripheral vascular disease
12.  Superficial Femoral Artery Plaque, the Ankle Brachial Index, and Leg Symptoms in Peripheral Arterial Disease: The Walking and Leg Circulation Study (WALCS) III 
The clinical significance of magnetic resonance imaged (MRI) plaque characteristics in the superficial femoral artery (SFA) is not well established. We studied associations of the ankle brachial index (ABI) and leg symptoms with MRI-measured plaque area and percent lumen area in the SFA in participants with and without lower extremity peripheral arterial disease (PAD).
Methods and Results
Four hundred twenty-seven participants (393 with PAD) underwent plaque imaging of the first 30 millimeters of the SFA. Twelve 2.5 millimeter cross-sectional images of the SFA were obtained. Outcomes were normalized plaque area, adjusted for artery size (0–1 scale, 1=greatest plaque), and lumen area, expressed as a percent of the total artery area. Adjusting for age, sex, race, smoking, statins, cholesterol, and other covariates, lower ABI values were associated with higher normalized mean plaque area (ABI < 0.50:0.79; ABI 0.50 to 0.69:0.73; ABI 0.70 to 0.89:0.65; ABI 0.90 to 0.99:0.62; ABI 1.00 to 1.09:0.48; ABI 1.10–1.30:0.47 (P trend <0.001)) and smaller mean percent lumen area (P trend<0.001). Compared to PAD participants with intermittent claudication, asymptomatic PAD participants had lower normalized mean plaque area (0.72 vs. 0.65, p=0.005) and larger mean percent lumen area (0.30 vs. 0.36, p=0.01), adjusting for the ABI and other confounders.
Lower ABI values are associated with greater MRI-measured plaque burden and smaller lumen area in the first 30 millimeters of the SFA. Compared to PAD participants with claudication, asymptomatic PAD participants have smaller plaque area and larger lumen area in the SFA.
PMCID: PMC3229716  PMID: 21436300
atherosclerosis; magnetic resonance imaging; peripheral vascular disease; plaque
13.  Facilitators and Barriers to Implementation of the Ankle Brachial Index in Outpatient Physical Therapy Practice: A Qualitative Study 
The ankle brachial index (ABI) is a valid and reliable measurement of lower extremity circulation and can be used as a screening tool for peripheral arterial disease (PAD), but the usage pattern in physical therapy practice is virtually unknown.
This study was performed to describe the phenomenon of using the ABI in outpatient physical therapy practice.
Nine participants from 3 different outpatient physical therapy clinics were provided with a hand held Doppler and education on how to accurately perform an ABI. Over a 3-month period, participants performed the ABI on any patient presenting with age > 50 with at least two risk factors for PAD. Immediately following the 3-month data collection period, two focus group interviews were performed to examine the therapist's experience using the ABI. Transcripts were analyzed to identify facilitators and barriers to implementation.
Facilitators identified include familiarity, ease of use, accuracy, and confidence with results. Barriers included flow and routine disruption, patient did not want/refused, and issues related to direct access.
Although some barriers to use of the ABI in an outpatient clinical setting need to be considered, most participants found the experience of using the ABI positive and feasible.
PMCID: PMC3677180  PMID: 23754934
ankle brachial index; peripheral arterial disease; physical therapy
14.  Aortic Augmentation Index is Associated with the Ankle Brachial Index; A Community Based Study 
Atherosclerosis  2007;195(2):248-253.
Increased arterial stiffness has been associated with greater risk of cardiovascular events. We investigated whether aortic augmentation index (AIx), a measure of arterial stiffness and wave reflection, was associated with the ankle-brachial index (ABI), a measure of peripheral arterial disease (PAD).
AIx and ABI were measured in a community-based sample of 475 adults without prior history of heart attack or stroke (mean age 59.3 years, 46.5% men). Radial artery pulse waveforms were obtained by applanation tonometry and an ascending aortic pressure waveform derived by a transfer function. AIx is the difference between the first and second systolic peak of the ascending aortic pressure waveform indexed to the central pulse pressure. ABI was measured using a standard protocol, and subjects with non-compressible vessels (ABI >1.5) were excluded from the analyses. Multivariable linear and logistic generalized estimating equations (GEE) analyses were used to assess whether AIx was associated with ABI and ABI <1.00 respectively, independent of conventional risk factors.
Mean (± SD) values were: AIx, 29.3±11.6 %; ABI, 1.12±0.13; 59 (12.4%) participants had an ABI <1.00. Variables associated with a lower ABI (and ABI <1.00) included older age, shorter height, female sex, higher total cholesterol, hypertension medication use, history of smoking, and higher AIx. After adjustment for mean arterial pressure and the above variables, higher AIx remained associated with a lower ABI (P=0.015) and ABI <1.00 (P=0.002). A significant interaction (P=0.007) was present between AIx and age in the prediction of ABI; the (inverse) association of AIx with ABI was stronger in older subjects (>65 years).
AIx, a measure of arterial stiffness and wave reflection, was independently associated with a lower ABI in asymptomatic subjects from the community, and this association was modified by age.
PMCID: PMC3249443  PMID: 17254587
arterial stiffness; ankle-brachial index; arteries
15.  Lower Extremity Ischemia, Calf Skeletal Muscle Characteristics, and Functional Impairment in Peripheral Arterial Disease 
To determine whether lower ankle brachial index (ABI) levels are associated with lower calf skeletal muscle area and higher calf muscle percentage fat in persons with and without lower extremity peripheral arterial disease (PAD).
Three Chicago-area medical centers.
Four hundred thirty-nine persons with PAD (ABI<0.90) and 265 without PAD (ABI 0.90–1.30).
Calf muscle cross-sectional area and the percentage of fat in calf muscle were measured using computed tomography at 66.7% of the distance between the distal and proximal tibia. Physical activity was measured using an accelerometer. Functional measures included the 6-minute walk, 4-meter walking speed, and the Short Physical Performance Battery (SPPB).
Adjusting for age, sex, race, comorbidities, and other potential confounders, lower ABI values were associated with lower calf muscle area (ABI<0.50, 5,193 mm2; ABI 0.50–0.90, 5,536 mm2; ABI 0.91–1.30, 5,941 mm2; P for trend <.001). These significant associations remained after additional adjustment for physical activity. In participants with PAD, lower calf muscle area in the leg with higher ABI was associated with significantly poorer performance in usual- and fast-paced 4-meter walking speed and on the SPPB, adjusting for ABI, physical activity, percentage fat in calf muscle, muscle area in the leg with lower ABI, and other confounders (P<.05 for all comparisons).
These data support the hypothesis that lower extremity ischemia has a direct adverse effect on calf skeletal muscle area. This association may mediate previously established relationships between PAD and functional impairment.
PMCID: PMC2645649  PMID: 17341243
physical functioning; peripheral vascular disease; intermittent claudication; sarcopenia
16.  Low Lifetime Recreational Activity is a Risk Factor for Peripheral Arterial Disease 
The relationship between lifetime physical activity and the risk of developing peripheral arterial disease (PAD) is not known.
We studied 1381 patients referred for elective coronary angiography in a point prevalence analysis. PAD was defined as ankle-brachial index (ABI) < 0.9 at the time or a history of revascularization of the lower extremities regardless of ABI measure. We used a validated physical activity questionnaire to retrospectively measure each patient's lifetime recreational activity (LRA). Multivariate and logistic regression analyses were used to assess the independent association of LRA to ABI and the presence of PAD.
PAD was present in 19% (n=258) of all subjects. Subjects reporting no regular LRA had greater diastolic BP and were more likely to be female. They had lower average ABI, and a higher proportion had PAD (25.6%). In a regression model including traditional risk factors and LRA, multivariate analysis showed that age (p <0.001), female gender (p <0.001), systolic blood pressure (p =0.014), fasting glucose (p <0.001), serum triglycerides (p =0.02) and cumulative pack years (p <0.001) were independent negative predictors of ABI, and LRA was a positive predictor of ABI (p <0.001). History of sedentary lifestyle independently increased the odds ratio for PAD (OR =1.46; 95% CI, 1.0112.103) when assessed by logistic regression. Intriguingly, there is a correlation between physical activity and gender, such that women with low lifetime recreational activity are at greatest risk.
Recalled lifetime recreational activity is positively correlated to ABI and associated with PAD. Whereas the mechanism for this effect is not clear, LRA may be a useful clinical screening tool for PAD risk and strategies to increase adult recreational activity may reduce the burden of PAD later in life.
PMCID: PMC3152670  PMID: 21664093
Intermittent claudication; exercise; vascular disease; atherosclerosis
17.  Profound influence of different methods for determination of the ankle brachial index on the prevalence estimate of peripheral arterial disease 
BMC Public Health  2007;7:147.
The ankle brachial index (ABI) is an efficient tool for objectively documenting the presence of lower extremity peripheral arterial disease (PAD). However, different methods exist for ABI calculation, which might result in varying PAD prevalence estimates. To address this question, we compared five different methods of ABI calculation using Doppler ultrasound in 6,880 consecutive, unselected primary care patients ≥65 years in the observational getABI study.
In all calculations, the average systolic pressure of the right and left brachial artery was used as the denominator (however, in case of discrepancies of ≥10 mmHg, the higher reading was used). As nominators, the following pressures were used: the highest arterial ankle pressure of each leg (method #1), the lowest pressure (#2), only the systolic pressure of the tibial posterior artery (#3), only the systolic pressure of the tibial anterior artery (#4), and the systolic pressure of the tibial posterior artery after exercise (#5). An ABI < 0.9 was regarded as evidence of PAD.
The estimated prevalence of PAD was lowest using method #1 (18.0%) and highest using method #2 (34.5%), while the differences in methods #3–#5 were less pronounced. Method #1 resulted in the most accurate estimation of PAD prevalence in the general population. Using the different approaches, the odds ratio for the association of PAD and cardiovascular (CV) events varied between 1.7 and 2.2.
The data demonstrate that different methods for ABI determination clearly affect the estimation of PAD prevalence, but not substantially the strength of the associations between PAD and CV events. Nonetheless, to achieve improved comparability among different studies, one mode of calculation should be universally applied, preferentially method #1.
PMCID: PMC1950873  PMID: 18293542
18.  The association of the ankle-brachial index with incident coronary heart disease: the Atherosclerosis Risk In Communities (ARIC) study, 1987–2001 
Peripheral arterial disease (PAD), defined by a low ankle-brachial index (ABI), is associated with an increased risk of cardiovascular events, but the risk of coronary heart disease (CHD) over the range of the ABI is not well characterized, nor described for African Americans.
The ABI was measured in 12186 white and African American men and women in the Atherosclerosis Risk in Communities Study in 1987–89. Fatal and non-fatal CHD events were ascertained through annual telephone contacts, surveys of hospital discharge lists and death certificate data, and clinical examinations, including electrocardiograms, every 3 years. Participants were followed for a median of 13.1 years. Age- and field-center-adjusted hazard ratios (HRs) were estimated using Cox regression models.
Over a median 13.1 years follow-up, 964 fatal or non-fatal CHD events accrued. In whites, the age- and field-center-adjusted CHD hazard ratio (HR, 95% CI) for PAD (ABI<0.90) was 2.81 (1.77–4.45) for men and 2.05 (1.20–3.53) for women. In African Americans, the HR for men was 4.86 (2.76–8.47) and for women was 2.34 (1.26–4.35). The CHD risk increased exponentially with decreasing ABI as a continuous function, and continued to decline at ABI values > 1.0, in all race-gender subgroups. The association between the ABI and CHD relative risk was similar for men and women in both race groups. A 0.10 lower ABI increased the CHD hazard by 25% (95% CI 17–34%) in white men, by 20% (8–33%) in white women, by 34% (19–50%) in African American men, and by 32% (17–50%) in African American women.
African American members of the ARIC cohort had higher prevalences of PAD and greater risk of CHD associated with ABI-defined PAD than did white participants. Unlike in other cohorts, in ARIC the CHD risk failed to increase at high (>1.3) ABI values. We conclude that at this time high ABI values should not be routinely considered a marker for increased CVD risk in the general population. Further research is needed on the value of the ABI at specific cutpoints for risk stratification in the context of traditional risk factors.
PMCID: PMC1784111  PMID: 17227586
19.  Associations of Diabetes Mellitus and Other Cardiovascular Disease Risk Factors with Decline in the Ankle Brachial Index 
We compared associations of diabetes mellitus (DM) and other cardiovascular disease (CVD) risk factors with decline in the ankle brachial index (ABI) over four years in participants with and without peripheral artery disease (PAD).
Five hundred sixty-six participants, 300 with PAD, were followed prospectively for four years.
Mean (SD) baseline ABI values were 0.70 (0.13) for participants with both PAD and DM, 0.67 (0.14) for participants with only PAD, 1.10 (0.13) for participants with only DM, and 1.10 (0.10) for participants with neither PAD nor DM. After adjusting for age, gender, and baseline ABI, corresponding ABI change from baseline to 4-year follow-up were -0.02, -0.04, +0.05, and +0.05 respectively. Compared to participants with neither PAD nor DM, participants with only PAD showed significantly more ABI decline (P < .01), while the decline in participants with both PAD and DM was borderline non-significant (P = .06). After adjustments for baseline ABI, age, gender, African-American ethnicity, and other cardiovascular disease (CVD) risk factors; independent factors associated with ABI decline in participants with PAD in the lower ABI leg were older age and elevated D-dimer. DM was not related to ABI decline.
Despite being an important risk factor for PAD, DM was not independently associated with ABI decline. This could reflect the effect of DM promoting both PAD and lower extremity arterial stiffness, resulting in a small decline in the ABI over time. In conclusion, ABI change over time in persons with diabetes may not accurately reflect underlying atherosclerosis.
PMCID: PMC4515111  PMID: 25358555
Peripheral artery disease; Ankle brachial index; Diabetes
20.  Lower Extremity Nerve Function in Patients With Lower Extremity Ischemia 
Archives of internal medicine  2006;166(18):1986-1992.
We determined whether lower extremity ischemia, as measured by the ankle brachial index (ABI), is associated with impaired lower extremity nerve function.
Participants included 478 persons with peripheral arterial disease (PAD) identified from noninvasive vascular laboratories and 292 persons without PAD identified from a general medicine practice and noninvasive vascular laboratories. Peripheral arterial disease was defined as an ABI lower than 0.90 (mild PAD: ABI, 0.70 to <0.90; moderate PAD: ABI, 0.50 to <0.70; and severe PAD: ABI, <0.50). The ABI and electrophysiologic measures of the peroneal, sural, and ulnar nerves were obtained.
Among 546 participants without diabetes, PAD participants had significantly impaired peripheral nerve function in the upper and lower extremities compared with non-PAD participants. After adjusting for age, sex, race, smoking, height, body mass index, recruitment source, alcohol use, disk disease, spinal stenosis, cardiac disease, and cerebrovascular disease, these associations were not statistically significant. After adjusting for confounders among nondiabetic participants, those with severe PAD (ABI, <0.50) had poorer peroneal nerve conduction velocity (NCV) compared with participants without PAD (42.6 vs 44.8 m/s; P=.003) and poorer peroneal NCV compared with participants with mild PAD (42.6 vs 45.0 m/s; P=.001) or moderate PAD (42.6 vs 44.1 m/s; P=.03). Among 224 participants with diabetes, after adjusting for confounders, PAD was associated with poorer peroneal NCV (40.8 vs 43.5 m/s; P=.01), sural nerve amplitude (3.1 vs 4.8 μV; P=.045), and ulnar NCV (47.6 vs 50.2 m/s; P=.03) compared with those without PAD.
Our findings suggest that leg ischemia impairs peroneal nerve function. This association is less strong in patients with diabetes, perhaps because of the overriding influence of diabetes on peripheral nerve function. Clinicians should consider screening for PAD in patients with idiopathic peroneal nerve dysfunction. Peripheral arterial disease–associated nerve dysfunction may contribute to PAD-associated functional impairment.
PMCID: PMC2645651  PMID: 17030832
21.  Prevalence of peripheral arterial disease in high-risk patients using ankle-brachial index in general practice: a cross-sectional study 
The deleterious nature of peripheral arterial disease (PAD) is compounded by a status of underdiagnosed and undertreated disease. We evaluated the prevalence and predictive factors of PAD in high-risk patients using the ankle-brachial index (ABI).
The ABI was measured by general practitioners in France (May 2005–February 2006) in 5679 adults aged 55 years or older and considered at high risk. The primary outcome was prevalence of PAD (ABI strictly below 0.90).
In all, 21.3% patients had signs or symptoms suggestive of PAD, 42.1% had previous history of atherothrombotic disease and 36.6% had two or more cardiovascular risk factors. Prevalence of PAD was 27.8% overall, ranging from 10.4% in patients with cardiovascular risk factors only to approximately 38% in each other subgroup. Prevalence differed depending on the localization of atherothrombotic events: it was 57.1–75.0% in patients with past history of symptomatic PAD; 24.6–31.1% in those who had experienced cerebrovascular and/or coronary events. Regarding the classical cardiovascular risk factors, PAD was more frequent when smoking and hypercholesterolemia history were reported. PAD prevalence was also higher in patients with history of abdominal aortic aneurysm, renal hypertension or atherothrombotic event. Intermittent claudication, lack of one pulse in the lower limbs, smoking, diabetes and renovascular hypertension were the main factors predictive of low ABI.
Given the elevated prevalence of PAD in high-risk patients and easiness of diagnosis using ABI in primary care, undoubtedly better awareness would help preserve individual cardiovascular health and achieve public health goals.
PMCID: PMC2705819  PMID: 19125994
22.  Utility of digital pulse oximetry in the screening of lower extremity arterial disease 
The aim of this study was to evaluate screening methods in the lower extremities by measurement of the digital pulse oximetry (oxygen percent saturation [SpO2]) of toes for peripheral arterial disease (PAD).
A prospective study was performed among 49 patients (98 limbs) with lower extremity arterial occlusive disease. We attempted to measure the ankle-brachial index (ABI), digital pulse oximetry (SpO2), and computerized tomographic angiography (CTA). Patients were divided into three groups by the traditional Fontaine classification system by symptom and CTA criteria: 1) Critical limb ischemia (Fontaine III and IV), 2) Claudication; (Fontaine II), and 3) asymptomatic limbs (Fontaine I).
The sensitivity, specificity, positive and negative predictive values between active treatment groups (group I and II; endovascular and open surgery) and conservative group (group III) are all statistically significant. ABI; 55.09%, 94%, 96.7%, 39.02% (R = 12.54, P < 0.000) SpO2; 87.06%, 87.8%, 84.3%, 90% (R = 40.11, P < 0.000). Pre-SpO2 and pre-ABI all show statistically significant correlation in group I vs. group II, symptomatic PAD (group I and II) vs. asymptomatic PAD (group III), and the total PAD comparison. The Pearson's correlation coefficient between SpO2 and ABI all show significant correlation in group II. Pre-SpO2 vs. Pre-ABI show strong positive correlation except asymptomatic group (group III).
Digital pulse oximetry can be a useful, simple, noninvasive screening device as well as ABI in PAD.
PMCID: PMC3278641  PMID: 22347711
Peripheral arterial disease; Digital; Pulse oximetry; Ankle-brachial index
23.  Exercise-Ankle Brachial Pressure Index with One-Minute Treadmill Walking in Patients on Maintenance Hemodialysis 
Annals of Vascular Diseases  2012;6(1):52-56.
Background: The ankle-brachial pressure index (ABI) is widely used as a standard screening method for arterial occlusive lesion above the knee. However, the sensitivity of ABI is low in hemodialysis (HD) patients. Exercise stress (Ex-ABI) may reduce the false negative results.
Patients and Methods: After measuring resting ABI and toe-brachial pressure index (TBI), ankle pressure and ABI immediately after walking (Post-AP, Post-ABI) were measured using one-minute treadmill walking in 52 lower limbs of 26 HD patients. The definition of peripheral arterial occlusive disease (PAD) required an ABI value of less than 0.90, TBI value of less than 0.60, and decrease of more than 15% of the Post-ABI value and 20 mmHg of Post-AP in Ex-ABI. Computed tomographic angiography (CTA) was performed in 32 lower limbs of 16 HD patients. PAD is defined as presence of stenosis of more than 75% in the case of lesions from an iliac artery to knee on CTA.
Results: The accuracy of Ex-ABI (Sensitivity, 85.7%; Specificity, 77.7%) was higher than those of ABI (Sensitivity, 42.9%; Specificity, 83.3%) or TBI (Sensitivity, 78.6%; Specificity, 61.1%).
Conclusion: Ex-ABI with one-minute treadmill walking is the most useful tool for the screening of arterial occlusive lesions above the knee in maintenance HD patients.
PMCID: PMC3635000  PMID: 23641284
peripheral arterial disease; exercise; diagnosis; screening; hemodialysis
24.  Evaluation of Cuff-Induced Ischemia in the Lower Extremity by Magnetic Resonance Oximetry 
The aim of this study was to evaluate vascular function in the lower extremities by making direct time-course measurement of oxygen saturation in the femoral/popliteal arteries and veins during cuff-induced reactive hyperemia with MRI-based oximetry.
MRI-based oximetry is a new calibration-free technique taking advantage of the paramagnetic nature of blood that depends on the volume fraction of deoxyhemoglobin in red blood cells.
We compared postocclusive blood oxygenation time-course of femoral/popliteal vessels in (1) young healthy subjects (YH, N =10; mean ABI 1.0 ± 0.1, mean age 30 ± 7 y), (2) peripheral arterial disease patients (PAD, N = 12; mean ABI 0.6 ± 0.1, mean age 71 ± 9 y) and 3) age-matched healthy controls (AHC, N = 8; mean ABI 1.1 ± 0.1, mean age 68 ± 9 y). Blood oxygenation was quantified at 3T field strength with a field mapping pulse sequence yielding the magnetic susceptibility difference between blood in the vessels and surrounding muscle tissue from which the intravascular blood oxygen saturation is computed as %HbO2.
Significantly longer washout time (42 ± 16 vs. 14 ± 4 s; p < 0.0001) and lower upslope (0.60 ± 0.20 vs. 1.32 ± 0.41 %HbO2/s; p = 0.0008) were observed for PADs compared to healthy subjects (YH and AHC combined). Further, greater overshoot was observed in YH than in AHC (21 ± 8 vs. 10 ± 5 %HbO2; p = 0.0116).
Postocclusive transient changes in venous blood oxygenation may provide a new measure of vascular competence, which was found to be reduced in subjects with abnormal ABI, manifesting in prolonged recovery during the early phase of hyperemia.
PMCID: PMC2833093  PMID: 20152564
peripheral arterial disease; magnetic resonance oximetry; blood oxygen saturation; reactive hyperemia; phase image
25.  Dietary fatty acids and peripheral artery disease in adults 
Atherosclerosis  2012;222(2):545-550.
Peripheral artery disease (PAD) is a debilitating condition involving atherosclerosis. Although saturated, monounsaturated and polyunsaturated fatty acids have strong associations with atherosclerosis, it is unclear if diets high in these fatty acids affect PAD.
We studied 6,352 adults aged 40 years and older who participated in the U.S. National Health and Nutrition Examination Survey between 1999 and 2004. Ankle-brachial index (ABI) was assessed by standardized blood pressure measurements, and we defined PAD as an ABI <0.9. Fatty acid intake was assessed by validated 24-hour dietary recall. We used multivariable linear and logistic regression to estimate associations between intakes of dietary saturated fatty acids (SFAs), monounsaturated fatty acids (MFAs), marine omega-3 fatty acids (N-3), linolenic acid (LNA), and omega-6 fatty acids (N-6) and ABI/PAD.
The prevalence and 95% confidence interval (CI) of PAD was 5.2% (95% CI 4.6–5.8). There were no associations between ABI and intakes of marine N-3 (p=0.83) or N-6 (p=0.19) in adjusted models. In contrast, LNA was associated with higher ABI (p=0.04) and SFA tended to be associated with lower ABI (p=0.06) in adjusted models. In addition, higher SFA was associated with a higher prevalence of PAD: adjusted odds ratio 1.30 (95% CI 1.01–1.67; p=0.04) and a trend toward slower gait speed (p=0.08).
In this nationally representative sample, higher dietary intakes of LNA and SFAs were associated with higher and lower ABI, respectively. Prospective studies are needed to confirm the potential protective effects of dietary LNA and detrimental effects of dietary SFAs on PAD.
PMCID: PMC3361545  PMID: 22552117
Fatty acids; peripheral arterial disease; linolenic acid; saturated fat

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