Prevalence and significance of unrecognized lower extremity peripheral arterial disease in general medicine practice*

Hydrophilic Coating Microstructure Mediates Acute Drug Transfer in Drug-Coated Balloon Therapy

Drug-coated balloon (DCB) therapy is a promising endovascular treatment for obstructive arterial disease. The goal of DCB therapy is restoration of lumen patency in a stenotic vessel, whereby balloon deployment both mechanically compresses the offending lesion and locally delivers an antiproliferative drug, most commonly paclitaxel (PTX) or derivative compounds, to the arterial wall. Favorable long-term outcomes of DCB therapy thus require predictable and adequate PTX delivery, a process facilitated by coating excipients that promotes rapid drug transfer during the inflation period. While a variety of excipients have been considered in DCB design, there is a lack of understanding about the coating-specific biophysical determinants of essential device function, namely, acute drug transfer. We consider two hydrophilic excipients for PTX delivery, urea (UR) and poly(ethylene glycol) (PEG), and examine how compositional and preparational variables in the balloon surface spray-coating process impact resultant coating microstructure and in turn acute PTX transfer to the arterial wall. Specifically, we use scanning electron image analyses to quantify how coating microstructure is altered by excipient solid content and balloon-to-nozzle spray distance during the coating procedure and correlate obtained microstructural descriptors of coating aggregation to the efficiency of acute PTX transfer in a one-dimensional ex vivo model of DCB deployment. Experimental results suggest that despite the qualitatively different coating surface microstructures and apparent PTX transfer mechanisms exhibited with these excipients, the drug delivery efficiency is generally enhanced by coating aggregation on the balloon surface. We illustrate this microstructure-function relation with a finite element-based computational model of DCB deployment, which along with our experimental findings suggests a general design principle to increase drug delivery efficiency across a broad range of DCB designs.

Novel Payloads to Mitigate Maladaptive Inward Arterial Remodeling in Drug-Coated Balloon Therapy

Drug-coated balloon therapy is a minimally invasive endovascular approach to treat obstructive arterial disease, with increasing utilization in the peripheral circulation due to improved outcomes as compared to alternative interventional modalities. Broader clinical use of drug-coated balloons is limited by an incomplete understanding of device- and patient-specific determinants of treatment efficacy, including late outcomes that are mediated by postinterventional maladaptive inward arterial remodeling. To address this knowledge gap, we propose a predictive mathematical model of pressure-mediated femoral artery remodeling following drug-coated balloon deployment, with account of drug-based modulation of resident vascular cell phenotype and common patient comorbidities, namely, hypertension and endothelial cell dysfunction. Our results elucidate how postinterventional arterial remodeling outcomes are altered by the delivery of a traditional anti-proliferative drug, as well as by codelivery with an anti-contractile drug. Our findings suggest that codelivery of anti-proliferative and anti-contractile drugs could improve patient outcomes following drug-coated balloon therapy, motivating further consideration of novel payloads in next-generation devices.

Understudied factors in drug-coated balloon design and evaluation: A biophysical perspective

Drug-coated balloon (DCB) percutaneous interventional therapy allows for durable reopening of the narrowed lumen via physical tissue expansion and local anti-restenosis drug delivery, providing an alternative to traditional uncoated balloons or a permanent indwelling implant such as a conventional metallic drug-eluting stent. While DCB-based treatment of peripheral arterial disease (PAD) has been incorporated into clinical guidelines, DCB use has been recently curtailed due to reports that showed evidence of increased mortality risk in patients treated with paclitaxel (PTX)-coated balloons. Given the United States Food and Drug Administration's 2019 consequent warning regarding PTX-eluting DCBs and the subsequent marked reduction in clinical DCB use, there is now a critical need to better understand the compositional and mechanical factors underlying DCB efficacy and safety. Most work to date on DCB refinement has focused on designing both the enabling balloon catheter and alternate coatings composed of various drugs and excipients, followed by device evaluation in preclinical and clinical studies. We contend that improvement in DCB performance will require a better understanding of the biophysical factors operative during and following balloon deployment, and moreover that the elaboration and demonstrated control of these factors are needed to address current concerns with DCB use. This article provides a perspective on the biophysical interactions that govern DCB performance and offers new design strategies for the development of next-generation DCB devices.

Machine Learning-Based Peripheral Artery Disease Identification Using Laboratory-Based Gait Data

Peripheral artery disease (PAD) manifests from atherosclerosis, which limits blood flow to the legs and causes changes in muscle structure and function, and in gait performance. PAD is underdiagnosed, which delays treatment and worsens clinical outcomes. To overcome this challenge, the purpose of this study is to develop machine learning (ML) models that distinguish individuals with and without PAD. This is the first step to using ML to identify those with PAD risk early. We built ML models based on previously acquired overground walking biomechanics data from patients with PAD and healthy controls. Gait signatures were characterized using ankle, knee, and hip joint angles, torques, and powers, as well as ground reaction forces (GRF). ML was able to classify those with and without PAD using Neural Networks or Random Forest algorithms with 89% accuracy (0.64 Matthew's Correlation Coefficient) using all laboratory-based gait variables. Moreover, models using only GRF variables provided up to 87% accuracy (0.64 Matthew's Correlation Coefficient). These results indicate that ML models can classify those with and without PAD using gait signatures with acceptable performance. Results also show that an ML gait signature model that uses GRF features delivers the most informative data for PAD classification.

[Evolution of the prevalence of peripheral artery disease in clinical practice: A descriptive population study with real databases (SIDIAP-CMBD)]

OBJECTIVE

To evaluate, with real world data (SIDIAP and CMBD), the evolution of the prevalence of peripheral arterial disease (PAD) in the Catalan population and the cardiovascular risk factors present in people with this pathology.

DESIGN

Longitudinal descriptive population study. SITE: Primary health care.

PARTICIPANTS

Patients listed in SIDIAP and CMBD with a diagnosis of peripheral artery disease between 2008 and 2018 ≥ 35 years, as well as those without a diagnosis, but with an ABI < 0.9 in SIDIAP.

INTERVENTIONS AND MAIN MEASUREMENTS

Main variable AP (ICD-9, ICD-10). Sociodemographic data, risk factors and cardiovascular disease, drug use and prevalent cardiovascular events at the time of diagnosis.

RESULTS

141,520 patients were studied. 75% had hypertension, 58% were smokers or former smokers, and 23% had a myocardial infarction. The global prevalence increased from 1.15% in 2008 to 3.10% in 2018. The prevalence of PAD increased with age, with a moderate increase at younger ages, and more pronounced in > 55 years, exceeding 10% in > 85 years.

CONCLUSION

This is a population study where it is observed that the evolution of the prevalence of peripheral artery disease has presented a constant increase during the years 2008-2018, being higher in men, especially from 55 years of age. Studies with large databases can facilitate the design and implementation of new policies in national health systems.

Development of a polygenic risk score to improve detection of peripheral artery disease

INTRODUCTION

Peripheral artery disease (PAD) is a major cause of cardiovascular morbidity and mortality, yet timely diagnosis is elusive. Larger genome-wide association studies (GWAS) have now provided the ability to evaluate whether genetic data, in the form of genome-wide polygenic risk scores (PRS), can help improve our ability to identify patients at high risk of having PAD.

METHODS

Using summary statistic data from the largest PAD GWAS from the Million Veteran Program, we developed PRSs with genome data from UK Biobank. We then evaluated the clinical utility of adding the best-performing PRS to a PAD clinical risk score.

RESULTS

A total of 487,320 participants (5759 PAD cases) were included in our final genetic analysis. Compared to participants in the lowest 10% of PRS, those in the highest decile had 3.1 higher odds of having PAD (95% CI, 3.06-3.21). Additionally, a PAD PRS was associated with increased risk of having coronary artery disease, congestive heart failure, and cerebrovascular disease. The PRS significantly improved a clinical risk model (Net Reclassification Index = 0.07, p < 0.001), with most of the performance seen in downgrading risk of controls. Combining clinical and genetic data to detect risk of PAD resulted in a model with an area under the curve of 0.76 (95% CI, 0.75-0.77).

CONCLUSION

We demonstrate that a genome-wide PRS can discriminate risk of PAD and other cardiovascular diseases. Adding a PAD PRS to clinical risk models may help improve detection of prevalent, but undiagnosed disease.

Medial Arterial Calcification: A Significant and Independent Contributor of Peripheral Artery Disease

Over 200 million individuals worldwide are estimated to have peripheral artery disease (PAD). Although the term peripheral can refer to any outer branch of the vasculature, the focus of this review is on lower-extremity arteries. The initial sequelae of PAD often include movement-induced cramping pain in the hips and legs or loss of hair and thinning of the skin on the lower limbs. PAD progresses, sometimes rapidly, to cause nonhealing ulcers and critical limb ischemia which adversely affects mobility and muscle tone; acute limb ischemia is a medical emergency. PAD causes great pain and a high risk of amputation and ultimately puts patients at significant risk for major adverse cardiovascular events. The negative impact on patients' quality of life, as well as the medical costs incurred, are huge. Atherosclerotic plaques are one cause of PAD; however, emerging clinical data now shows that nonatherosclerotic medial arterial calcification (MAC) is an equal and distinct contributor. This ATVB In Focus article will present the recent clinical findings on the prevalence and impact of MAC in PAD, discuss the known pathways that contribute specifically to MAC in the lower extremity, and highlight gaps in knowledge and tools that limit our understanding of MAC pathogenesis.

Principal predictors of major adverse limb events in diabetic peripheral artery disease: A narrative review

Background and aims

The increasing prevalence of diabetes mellitus is causing a massive growth of peripheral artery disease incidences, a disabling complication of diabetic atherosclerosis, which leads often to the amputation of the affected limb. Critical limb ischemia is the terminal disease stage, which requires a prompt intervention to relieve pain and save limbs. However, patients undergoing revascularization often suffer from cardiovascular, cerebrovascular and major adverse limb events with poor outcomes. Furthermore, the same procedure performed in apparently similar patients has various outcomes and lack of an outcome predictive support causes a high lower limb arterial revascularization rate with disastrous effects for patients. We collected the main risk factors of major adverse limb events in a more readable and immediate format of the topic, to propose an overview of parameters to manage effectively peripheral artery disease patients and to propose basics of a new predictive tool to prevent from disabling vascular complications of the disease.

Methods

Most recent and updated literature about the prevalence of major adverse limb events in peripheral artery disease was reviewed to identify possible main predictors.

Results

In this article, we summarized major risk factors of limb revascularization failure and disabling vascular complications collecting those parameters principally responsible for major adverse limb events, which provides physio-pathological explanation of their role in peripheral artery disease.

Conclusion

We evaluated and listed a panel of possible predictors of MALE (Major Adverse Limb Event) in order to contribute to the development of a predictive score, based on a summary of the main risk factors reported in scientific articles, which could improve the management of peripheral artery disease by preventing vascular accidents.

Effects of Postoperative Percutaneous Coronary Intervention, Pharmacologic Treatment, and Predisposing Factors on Clinical Outcomes in Patients With and Without Type 2 Diabetes Along With Critical Limb Ischemia

PURPOSE

Critical limb ischemia (CLI) has been identified as being connected to rates of cardiovascular mortality and lower extremity amputation (LEA). This prospective study investigated the effects of percutaneous coronary intervention (PCI), pharmacologic treatment, and predisposing factors on clinical outcomes in patients with and without type 2 diabetes mellitus (DM) along with CLI after endovascular intervention.

METHODS

249 consecutive patients with CLI (Fontaine stages III-IV) received pharmacologic treatment after successful endovascular intervention. Their primary patency rates of infrapopliteal lesions and cardiovascular and amputation events during a 36-month follow-up period were assessed.

FINDINGS

Patients with DM were more likely to be younger (P = 0.026); 50% (n = 63), 42.9% (n = 54), 52.4% (n = 66), and 77% (n = 97) of DM patients had arterial calcification, end-stage renal disease, diabetic neuropathy, and Fontaine stage IV (P < 0.001, P < 0.001, P < 0.001, and P = 0.019, respectively). The primary patency rates were 61%, 48.8%, and 42.3% at 12, 24, and 36 months, in the patients without DM (P = 0.034, P = 0.013, and P = 0.005). Patients with DM had higher risks of 36-month coronary artery disease, cerebrovascular accident, mortality, and LEA (P = 0.005, P = 0.042, P = 0.042, and P < 0.001). Patients with CLI receiving long-term cilostazol treatment had a better primary patency and amputation-free survival, and a lower risk of mortality at 36 months (P < 0.001, P < 0.001, and P = 0.001). Statin use was associated with 36-month amputation-free survival but not with primary patency (P = 0.032 and P = 0.088). Subgroup multivariate Cox analyses showed that primary patency was independently associated with long-term cilostazol treatment, PCI in the first postoperative year, and direct revascularization in the DM group, whereas in the control group, long-term cilostazol treatment was the main independent factor. The risk of amputation was independently associated with a high high-sensitivity chronic reactive protein level, diabetic neuropathy, sole use of an oral hypoglycemic agent, and lack of supervised exercise.

IMPLICATIONS

Long-term cilostazol treatment, aggressive management of dyslipidemia, and meticulous assessment and prevention of postoperative unstable coronary artery disease should be considered in CLI patients with and without DM to maximize clinical outcomes. PCI in the first postoperative year may be a predisposing factor for patency failure in patients with CLI, especially those with DM. A large-scale prospective randomized trial should be conducted to confirm these findings (TVGH IRB No. 2013-08-020B).

Long-Term Cilostazol Treatment and Predictive Factors on Outcomes of Endovascular Intervention in Patients with Diabetes Mellitus and Critical Limb Ischemia

INTRODUCTION

Despite improvements in endovascular interventions and multidisciplinary approaches, improving clinical outcomes and increasing limb salvage have become increasingly challenging. This prospective study investigated the associations of cilostazol treatment with clinical outcomes and predictive factors in patients with diabetes mellitus (DM) and critical limb ischemia (CLI) after endovascular revascularization of the affected angiosome.

METHODS

In this study, 172 consecutive patients with CLI (Fontaine levels III-IV) received cilostazol treatment after successful endovascular intervention according to the angiosome concept, and their primary patency rates and cardiovascular and amputation events during a 24-month follow-up period were assessed.

RESULT

The 24-month primary patency rate, mortality rate, and amputation rate were better in the patients under long-term cilostazol treatment (P < 0.001, P = 0.029, and P = 0.014). Weighted multivariate Cox analyses with a propensity scoring-based method showed that long-term cilostazol treatment [hazard ratio (HR) 0.2, 95% confidence interval (CI) 0.11-0.36, P < 0.001], direct revascularization (DR) (HR 0.46, 95% CI 0.28-0.74, P = 0.002), and supervised exercise (HR 0.4, 95% CI 0.24-0.66, P < 0.001) were independently associated with primary patency. Patients with lower-extremity amputation (LEA) had a higher risk of coronary artery disease (CAD) and mortality. Cellulitis and neuropathy were independently associated with LEA events (cellulitis: HR 2.89, 95% CI 1.66-5.05, P < 0.001; neuropathy: HR 2.2, 95% CI 1.31-3.7, P = 0.003).

CONCLUSION

Our results showed that patients with DM who received cilostazol treatment for more than 3 months had significantly better outcomes and decreased amputation and mortality rates after DR, and cellulitis and neuropathy were highly associated with the risk of limb loss. A large-scale randomized trial should be conducted in the future to confirm these results.

TRIAL REGISTRATION

Taipei Veterans General Hospital (TVGH) IRB no. 2013-08-020B. Registered 30 August 2013.

Pilot screening program for lower extremities atherosclerotic disease in a population of central Greece

BACKGROUND

Screening program in lower extremity atherosclerotic disease (LEAD) has not been widely implemented from health systems. The aim of this study was to assess the incidence of LEAD in Greece though a pilot LEAD screening program.

METHODS

Males >60 years old without known diagnosis of LEAD or chronic renal disease were invited through public primary health care institutions to participate in a pilot screening program in Central Greece. Demographics, atherosclerotic risk factors and other comorbidities were recorded. LEAD was defined as ankle-brachial pressure index (ABPI) of <0.9 or >1.4.

RESULTS

Among a total of 1152 individuals (invitation acceptance 70%; 1152/1638) LEAD was detected in 13% (148); including 7% with ABPI<0.9 and 6% with ABPI>1.4. Comparing the groups with ABPI<0.9 vs. normal ABPI, abnormal ABPI was associated with older age (P=0.001), hypertension (HT) (P=0.037), smoking (P=0.002), duration of smoking (P=0.01), packs/year (P=0.002), coronary artery disease (P=0.02), chronic obstructive pulmonary disease (P=0.028) and cerebrovascular disease (P=0.001). After multivariate analysis, increased age (0.94, CI: 0.026-5.2; P=0.022), history of HT (2.4, CI: 0.44- 3.7; P=0.05) and longer duration of smoking (0.9, CI: 0.01-6.1; 0.013) were associated with ABPI <0.9. Abnormally higher ABPI (>1.4) was not associated with any factor. Among those without known CAD or CVD (96/148), 37.5% (36/96) were on statins and 21% (20/96) on antiplatelets.

CONCLUSIONS

Incidence of LEAD was 13% in a male >60 years-old population of central Greece; these individuals maybe undertreated. ABPI<0.9 was diagnosed in 7% and was associated with older age, HT and duration of smoking.

Predicting Future Cardiovascular Events in Patients With Peripheral Artery Disease Using Electronic Health Record Data

BACKGROUND

Patients with peripheral artery disease (PAD) are at risk of major adverse cardiac and cerebrovascular events. There are no readily available risk scores that can accurately identify which patients are most likely to sustain an event, making it difficult to identify those who might benefit from more aggressive intervention. Thus, we aimed to develop a novel predictive model-using machine learning methods on electronic health record data-to identify which PAD patients are most likely to develop major adverse cardiac and cerebrovascular events.

METHODS AND RESULTS

Data were derived from patients diagnosed with PAD at 2 tertiary care institutions. Predictive models were built using a common data model that allowed for utilization of both structured (coded) and unstructured (text) data. Only data from time of entry into the health system up to PAD diagnosis were used for modeling. Models were developed and tested using nested cross-validation. A total of 7686 patients were included in learning our predictive models. Utilizing almost 1000 variables, our best predictive model accurately determined which PAD patients would go on to develop major adverse cardiac and cerebrovascular events with an area under the curve of 0.81 (95% CI, 0.80-0.83).

CONCLUSIONS

Machine learning algorithms applied to data in the electronic health record can learn models that accurately identify PAD patients at risk of future major adverse cardiac and cerebrovascular events, highlighting the great potential of electronic health records to provide automated risk stratification for cardiovascular diseases. Common data models that can enable cross-institution research and technology development could potentially be an important aspect of widespread adoption of newer risk-stratification models.

Screening for Peripheral Artery Disease Using the Ankle-Brachial Index: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

Peripheral artery disease (PAD) is associated with a high risk for cardiovascular events and poor ambulatory function, even in the absence of symptoms. Screening for PAD with the ankle-brachial index (ABI) may identify patients in need of treatment to improve health outcomes.

OBJECTIVE

To systematically review evidence for the US Preventive Services Task Force on PAD screening with the ABI, the diagnostic accuracy of the test, and the benefits and harms of treatment of screen-detected PAD.

DATA SOURCES

MEDLINE, PubMed, and the Cochrane Central Register of Controlled Trials for relevant English-language studies published between January 2012 and May 2, 2017. Surveillance continued through February 7, 2018.

STUDY SELECTION

Studies of unselected or generally asymptomatic adults with no known cardiovascular disease.

DATA EXTRACTION AND SYNTHESIS

Independent critical appraisal and data abstraction by 2 reviewers.

MAIN OUTCOMES AND MEASURES

Cardiovascular morbidity; PAD morbidity; mortality; health-related quality of life; diagnostic accuracy; and serious adverse events.

RESULTS

Five studies (N = 5864 participants) were included that examined the indirect evidence for the benefits and harms of screening and treatment of screen-detected PAD. No population-based screening trials evaluated the direct benefits or harms of PAD screening with the ABI alone. A single diagnostic accuracy study of the ABI compared with magnetic resonance angiography gold-standard imaging (n = 306) found low sensitivity (7%-34%) and high specificity (96%-100%) in a screening population. Two adequately powered trials (n = 4626) in asymptomatic populations with and without diabetes with a variably defined low ABI (≤0.95 or ≤0.99) showed no statistically significant effect of aspirin (100 mg daily) for composite CVD outcomes (adjusted hazard ratio [HR], 1.00 [95% CI, 0.81-1.23] and HR, 0.98 [95% CI, 0.76-1.26]). One trial (n = 3350) demonstrated no statistically significant increase in major bleeding events with the use of aspirin (adjusted HR, 1.71 [95% CI, 0.99- 2.97]) and no statistically significant increase in major gastrointestinal bleeding (relative risk, 1.13 [95% CI, 0.44-2.91]). Two exercise trials (n = 932) in screen-relevant populations reported no differences in quality of life, Walking Impairment Questionnaire walking distance, or symptoms at 12 and 52 weeks; no harms were reported.

CONCLUSIONS AND RELEVANCE

There was no direct evidence and limited indirect evidence on the benefits of PAD screening with the ABI in unselected or asymptomatic populations. Available studies suggest low sensitivity and lack of beneficial effect on health outcomes, but these studies have important limitations.

The use of machine learning for the identification of peripheral artery disease and future mortality risk

OBJECTIVE

A key aspect of the precision medicine effort is the development of informatics tools that can analyze and interpret "big data" sets in an automated and adaptive fashion while providing accurate and actionable clinical information. The aims of this study were to develop machine learning algorithms for the identification of disease and the prognostication of mortality risk and to determine whether such models perform better than classical statistical analyses.

METHODS

Focusing on peripheral artery disease (PAD), patient data were derived from a prospective, observational study of 1755 patients who presented for elective coronary angiography. We employed multiple supervised machine learning algorithms and used diverse clinical, demographic, imaging, and genomic information in a hypothesis-free manner to build models that could identify patients with PAD and predict future mortality. Comparison was made to standard stepwise linear regression models.

RESULTS

Our machine-learned models outperformed stepwise logistic regression models both for the identification of patients with PAD (area under the curve, 0.87 vs 0.76, respectively; P = .03) and for the prediction of future mortality (area under the curve, 0.76 vs 0.65, respectively; P = .10). Both machine-learned models were markedly better calibrated than the stepwise logistic regression models, thus providing more accurate disease and mortality risk estimates.

CONCLUSIONS

Machine learning approaches can produce more accurate disease classification and prediction models. These tools may prove clinically useful for the automated identification of patients with highly morbid diseases for which aggressive risk factor management can improve outcomes.

Identifying Unrecognized Peripheral Arterial Disease Among Asymptomatic Patients in the Primary Care Setting

National initiatives to enhance recognition of the detrimental impact of peripheral arterial disease on the health of adult Americans have been advocated. The objective of this study was to evaluate a strategy for identifying patients with unrecognized peripheral arterial disease from among persons without known atherosclerotic disease in the primary care setting. A cross-sectional design was used. Participants were patients receiving care from a multispecialty group practice in Massachusetts between July 2002 and July 2003, with a scheduled appointment with a primary care physician. Persons 70 years of age or older who were not already known to have atherosclerotic disease were enrolled. In addition, persons aged 50-69 with a diagnosis of diabetes mellitus, dyslipidemia, hypertension, and/or smoking based on information derived from administrative databases, and not known to have atherosclerotic disease, were enrolled. Before the scheduled appointment, potential study participants completed a telephone interview to ascertain their medical history. The ankle-brachial index (ABI) of eligible patients was measured at the time of the scheduled primary care office visit. Peripheral arterial disease was diagnosed if 1 or both legs had an ABI of ≤0.90. Also assessed was the time spent in performing ABI testing in a convenience sample of the study participants. ABI testing was performed on 717 patients. Among 359 study subjects aged ≥70 years, 45 (12.5%) were diagnosed with peripheral arterial disease. Nine (2.5%) of 358 subjects aged 50-69 years were diagnosed with peripheral arterial disease. The average total time (n=52) for ABI testing was 13.7 (SD: ±3.3) minutes. Patients aged ≥70 years required more time for ABI testing compared to those aged 50-69 (mean: 15.0 vs 13.0 minutes, p=0.04). Unrecognized asymptomatic peripheral arterial disease can be commonly detected among patients in the primary care setting who are not already known to have atherosclerotic disease. The yield from screening is substantially greater among unselected older patients compared with younger patients specifically identified as having risk factors for PAD. These findings should help inform the development and implementation of new initiatives to enhance the early detection of peripheral arterial disease among asymptomatic patients in the primary care setting.

Limitation of the resting ankle-brachial index in symptomatic patients with peripheral arterial disease

Peripheral arterial disease (PAD) has been demonstrated to be prevalent in the primary care setting. However, it has also been shown to be unrecognized and under-treated. Owing to the association with cardiovascular disease it has been recommended to screen high-risk patients for PAD in the primary care setting using the ankle-brachial index (ABI). ABI has been demonstrated to be highly sensitive and specific in diagnosing PAD in patients with significant stenosis. However, the utility in patients with less severe stenosis and calcified vessels is in question. The aims of this study were to determine the diagnostic utility of measuring the ABI at rest in patients referred to the vascular laboratory for evaluation of suspected PAD, and to assess the added value of pulse volume recordings and post-exercise studies in patients with a normal ABI. A computerized vascular diagnostic laboratory database was queried for symptomatic outpatients referred for measurement of segmental blood pressure, the ABI or pulse volume recordings by physicians not specialized in the evaluation and management of patients with peripheral vascular disease. Of 707 patients undergoing outpatient physiologic arterial evaluations between February 1, 2003 and July 31, 2004, 396 met these inclusion criteria. Data recorded included resting ABI, ABI following treadmill exercise test and the presence of abnormal pulse volume recordings. The study population ( n = 396) consisted of equal numbers of men and women (mean age 69 years, range 19-100 years). Among 396 studies, resting ABI values were normal in 183 (46.2%) and abnormal in 159 (40.2%). Of the 138 patients who underwent exercise testing, 84 had normal ABI readings at rest. In the 84 patients who had a normal ABI at rest and underwent exercise testing, the ABI fell below 0.9 after exercise in 26 (31%). Arterial non-compressibility was detected in 54 (13.6%) patients, whose average age was 67 years. Thirteen (24%) of those with non-compressible vessels had abnormal pulse volume recording (PVR) results, compared to five with normal resting ABI who had abnormal PVR findings (2.7%). In conclusion, this study demonstrated that nearly half of patients referred to the outpatient vascular laboratory because of suspected arterial disease had a normal resting ABI. While it is recommended that the ABI be measured at rest in patients at risk of PAD in primary care practice, these findings suggest that patients with symptoms of PAD should be more completely evaluated in a vascular laboratory. Furthermore, when the ABI is normal at rest in patients with symptoms of intermittent claudication, exercise testing is recommended to enhance the sensitivity for detection of PAD.

Intensive walking exercise for lower extremity peripheral arterial disease: A systematic review and meta-analysis

BACKGROUND

Supervised treadmill exercise is the recommended therapy for peripheral arterial disease (PAD) patients with intermittent claudication (IC). However, most PAD patients do not exhibit typical symptoms of IC. The aim of the present study was to explore the efficacy and safety of intensive walking exercise in PAD patients with and without IC.

METHODS

The PubMed, Embase and Cochrane Library databases were systematically searched. Randomized controlled trials comparing the effects of intensive walking exercise with usual care in patients with PAD were included for systematic review and meta-analysis.

RESULTS

Eighteen trials with 1200 patients were eligible for the present analysis. Compared with usual care, intensive walking exercise significantly improved the maximal walking distance (MWD), pain-free walking distance, and the 6-min walking distance in patients with PAD (P < 0.00001 for all). Subgroup analyses indicated that a lesser improvement in MWD was observed in the subgroup with more diabetes patients, and that the subgroup with better baseline walking ability exhibited greater improvement in walking performance. In addition, similar improvements in walking performance were observed for exercise programs of different durations and modalities. No significant difference was found in adverse events between the intensive walking and usual care groups (relative risk 0.84; 95% confidence interval 0.51, 1.39; P = 0.50).

CONCLUSIONS

Regardless of exercise length and modality, regularly intensive walking exercise improves walking ability in PAD patients more than usual care. The presence of diabetes may attenuate the improvements in walking performance in patients with PAD following exercise.

Risk of lower extremity arterial disease in a cohort of workers occupationally exposed to ionizing radiation over a prolonged period

In this study the incidence risk of lower extremity arterial disease (LEAD; international classification of diseases version 9 code 440.2) was assessed in a cohort of workers occupationally exposed to radiation over a prolonged period. The study cohort includes 22,377 workers of the Mayak Production Association (25% of whom are females) first employed at one of the main facilities in 1948-1982 and followed up to the end of 2008. Dose estimates used in the study are provided by Mayak Worker Dosimetry System 2008. The mean total dose from external gamma-rays is 0.54 Gy for males and 0.44 Gy for females. The mean absorbed liver dose from internal alpha-radiation due to incorporated plutonium is 0.23 Gy in males and 0.44 Gy in females. Relative risks and excess relative risks per unit dose (ERR/Gy) are calculated based on maximum likelihood. A total of 943 cases of LEAD are registered in the study cohort during the follow-up of 512,801 person-years. A significant association of LEAD incidence with total dose from external gamma-rays (based on a linear model) was revealed, and the ERR/Gy is 0.27 (95% confidence interval (CI) 0.11; 0.48). It turned out that a linear-exponential model provides a better fit of the data (∆AIC = 9.957). Inclusion of an adjustment for internal alpha-radiation dose resulted in the reduction of the ERR/Gy to 0.19 (95% CI 0.05; 0.39), but the risk remains significant. No association of LEAD incidence with dose from internal alpha-radiation was found in the study worker cohort. It is concluded that this study provides evidence for an association of LEAD incidence with dose from external gamma-rays taking non-radiation factors into account.

[Diagnostic accuracy of dual energy CT angiography in patients with diabetes mellitus]

OBJECTIVES

Peripheral arterial disease (PAD) represents a major and highly prevalent complication in patients with diabetes mellitus. The diagnostic, non-invasive work-up by computed tomography angiography (CTA) is limited in the presence of extensive calcification. The aim of the study was to determine the diagnostic accuracy of dual energy CTA (DE-CTA) for the detection and characterization of PAD in patients with diabetes mellitus.

MATERIAL AND METHODS

In this study 30 diabetic patients with suspected or known PAD were retrospectively included in the analysis. All subjects underwent DE-CTA (Somatom Definition Flash, Siemens Healthcare, Erlangen, Germany) prior to invasive angiography, which served as the reference standard. Blinded analysis included assessment of the presence and degree of peripheral stenosis on curved multiplanar reformatting (MPR) and maximum intensity projections (MIP). Conventional measures of diagnostic accuracy were derived.

RESULTS

Among the 30 subjects included in the analysis (83% male, mean age 70.0 ± 10.5 years, 83% diabetes type 2), the prevalence of critical stenosis in 331 evaluated vessel segments was high (30%). Dual energy CT identified critical stenoses with a high sensitivity and good specificity using curved MPR (100% and 93.1%, respectively) and MIP images (99% and 91.8%, respectively). In stratified analysis, the diagnostic accuracy was higher for stenosis pertaining to the pelvic and thigh vessels as compared with the lower extremities (curved MPR accuracy 97.1% vs. 99.2 vs. 90.9%; respectively, p < 0.001).

CONCLUSION

The use of DE-CTA allows reliable detection and characterization of peripheral arterial stenosis in patients with diabetes mellitus with higher accuracy in vessels in the pelvic and thigh regions compared with the vessels in the lower legs.

Blood flow restriction training and the exercise pressor reflex: a call for concern

Blood flow restriction (BFR) training (also known as Kaatsu training) is an increasingly common practice employed during resistance exercise by athletes attempting to enhance skeletal muscle mass and strength. During BFR training, blood flow to the exercising muscle is mechanically restricted by placing flexible pressurizing cuffs around the active limb proximal to the working muscle. This maneuver results in the accumulation of metabolites (e.g., protons and lactic acid) in the muscle interstitium that increase muscle force and promote muscle growth. Therefore, the premise of BFR training is to simulate and receive the benefits of high-intensity resistance exercise while merely performing low-intensity resistance exercise. This technique has also been purported to provide health benefits to the elderly, individuals recovering from joint injuries, and patients undergoing cardiac rehabilitation. Since the seminal work of Alam and Smirk in the 1930s, it has been well established that reductions in blood flow to exercising muscle engage the exercise pressor reflex (EPR), a reflex that significantly contributes to the autonomic cardiovascular response to exercise. However, the EPR and its likely contribution to the BFR-mediated cardiovascular response to exercise is glaringly missing from the scientific literature. Inasmuch as the EPR has been shown to generate exaggerated increases in sympathetic nerve activity in disease states such as hypertension (HTN), heart failure (HF), and peripheral artery disease (PAD), concerns are raised that BFR training can be used safely for the rehabilitation of patients with cardiovascular disease, as has been suggested. Abnormal BFR-induced and EPR-mediated cardiovascular complications generated during exercise could precipitate adverse cardiovascular or cerebrovascular events (e.g., cardiac arrhythmia, myocardial infarction, stroke and sudden cardiac death). Moreover, although altered EPR function in HTN, HF, and PAD underlies our concern for the widespread implementation of BFR, use of this training mechanism may also have negative consequences in the absence of disease. That is, even normal, healthy individuals performing resistance training exercise with BFR are potentially at increased risk for deleterious cardiovascular events. This review provides a brief yet detailed overview of the mechanisms underlying the autonomic cardiovascular response to exercise with BFR. A more complete understanding of the consequences of BFR training is needed before this technique is passively explored by the layman athlete or prescribed by a health care professional.

Impedance plethysmography as an alternative method for the diagnosis of peripheral arterial disease

BACKGROUND AND OBJECTIVE

In the diagnosis of peripheral artery disease (PAD), the ankle-brachial index (ABI) is considered as the standard, and other noninvasive methods have received too little attention. Therefore, the aim of the study was to determine the diagnostic accuracy of impedance plethysmography in diagnosing PAD and to compare this method with other methods.

MATERIALS AND METHODS

A total of 66 patients with a mean age of 76.1±9.6 years who had been treated for various cardiovascular diseases at Kaunas Clinical Hospital during 2011-2012 were enrolled into the study. All the patients were screened for PAD. Impedance plethysmography was performed with a new-generation Niccomo™ device. The receiver operating characteristic analysis was employed to determine the diagnostic accuracy of 4 parameters of impedance plethysmography: crest time (CT), crest width (CW), pulse amplitude (Pampl), and alternating blood flow (ABF).

RESULTS

There were a significant correlation between the ABI and the CT (r=-0.699, P<0.001), between the ABI and the ABF (r=0.552; P<0.001), and between the ABI and the Pampl only among men (r=0.652; P<0001). No correlation was found between the ABI and the CW. Among all the parameters, the CT had the highest sensitivity and specificity (73.2% and 96.0%, respectively). Other parameters had the following sensitivities and specificities: ABF, 61.0% and 96.0%; and Pampl, 90.0% and 20.0%, respectively.

CONCLUSIONS

Impedance plethysmography, especially its parameter CT, is an alternative noninvasive method in diagnosing PAD and could be used for the screening of patients with PAD.

Peripheral artery questionnaire improves ankle brachial index screening in symptomatic patients with peripheral artery disease

AIM

The peripheral artery questionnaire (PAQ) is a disease-specific health status measure of patients with peripheral artery disease (PAD). Whether the PAQ scores are associated with a PAD diagnosis among patients with symptoms suspicious for PAD is unknown and could help increase the pretest probability of ankle brachial index (ABI) screening among patients with suspicious symptoms.

METHODS

The PAQ was completed by 567 patients evaluated for potential intermittent claudication at six tertiary centres. Demographics, medical history, physical examination findings and the PAQ domain scores were compared with ABI. A diagnostic threshold < 0.90 for a PAD diagnosis was assessed with a ROC of PAQ scores. The correlation between the PAQ Summary Score and ABI was also calculated.

RESULTS

The PAQ Summary Score was significantly lower in patients with low ABI as compared with those having a normal ABI (37.6 ± 19.0 vs. 70.1 ± 22.7, p < 0.001). The PAQ Summary Score and ABI were highly correlated (r = 0.56, p < 0.001) and the optimal PAQ Summary Score for predicting low ABI was 50.3 (AUC = 0.86, sensitivity 80.3%, specificity 78.3%).

CONCLUSIONS

The PAQ Summary Score was associated with an increased likelihood of PAD in patients with suspected PAD symptoms, and a low summary score (≤ 50.3) was an optimal threshold for predicting PAD among patients referred for ABI.

Clinical and socioeconomic factors associated with unrecognized peripheral artery disease

Peripheral artery disease (PAD) is a highly prevalent condition that frequently goes undetected and untreated. Socioeconomic factors associated with unrecognized PAD are not known. The ankle-brachial index (ABI) was calculated in 1656 study participants undergoing non-emergent coronary angiography with PAD defined as an ABI <0.9. Subjects were followed for mortality and cardiovascular outcomes. Compared to those without PAD, those with unrecognized PAD at enrollment were older, had higher rates of cardiovascular comorbidities, and had higher major adverse cardiovascular events (MACE) (p<0.03 for all). Among those enrolling without a reported history of PAD, there was a higher prevalence of PAD with decreasing income (p=0.004), education level (p<0.001), social isolation (p=0.027) and depression (p=0.034); 50% of these individuals reported symptoms suggestive of claudication. In conclusion, the prevalence of unrecognized PAD is high amongst a cohort of high-risk individuals referred for coronary angiography. A profile of lower socioeconomic status is associated with unrecognized PAD. These subjects will report symptoms suggestive of claudication and impaired walking ability when directly queried.

Clinical application of vascular regenerative therapy for peripheral artery disease

Prognosis of peripheral artery disease (PAD), especially critical limb ischemia, is very poor despite the development of endovascular therapy and bypass surgery. Many patients result in leg amputation and, therefore, vascular regenerative therapy is expected in this field. Gene therapy using vascular endothelial growth factor is the first step of vascular regenerative therapy, but did not confirm effectiveness in a large-scale randomized comparative study. Based on animal experiments, bone marrow mononuclear cells (MNCs), peripheral blood MNCs were used as the cell source for regenerative therapy. Those cells were confirmed to be effective to decrease rest pain and ulcer size, but its effect was not fully satisfied. Mesenchymal stem cells (MSCs) are expected as an effective cell source for vascular regeneration and clinical studies are ongoing, because the cells are able to differentiate into various cell types and produce a significant amount of vascular growth factors. Of vascular regeneration therapy, peripheral MNCs and bone marrow MNCs were recognized as advanced medical technology but do not attain to the standard therapy. However, clinical use of MSCs have already started, and induced pluripotent stem cells are surely promising tool for vascular regeneration therapy although further basic studies are required for clinical application.

Factors associated with mobility outcomes in older people post-ankle fracture: an observational cohort study focussing on peripheral vessel function

INTRODUCTION

There are increasing numbers of older persons sustaining ankle fractures. This injury often results in a degree of functional limitation, particularly in older patients. There is currently limited research into factors associated with mobility outcomes.

DESIGN

Observational cohort study.

SETTING

Hospital Trauma Department, UK.

PARTICIPANTS

Persons aged 60 years or over who sustained an unstable ankle fracture with no established peripheral arterial disease pre-injury.

METHODS

This study investigated the association between ankle-brachial pressure index (ABPI) and extended timed 'up and go' (TUG) measures. Associations between TUG outcomes and age, pre-morbid functional mobility (Olerud-Molander Ankle Score) and fracture severity (number of malleoli injured) were also explored.

ANALYSIS

Complete cases (n=76; 84% of cohort) were entered into univariate and multivariate linear regression.

RESULTS

No association was found between ABPI and TUG at 6 months in unadjusted and adjusted analyses. Pre-morbid functional mobility (B=-0.34, 95% confidence interval (CI) -0.45 to -0.23, p<0.001) and age (B=0.46, 95% CI 0.25-0.66, p<0.001) were associated with extended TUG values (r2=0.53, p<0.001). Fracture severity was not a significant independent predictor variable.

CONCLUSIONS

Peripheral vessel function and fracture severity may have a limited independent influence on mobility outcome after ankle fracture in those patients who do not have established pre-injury peripheral arterial disease. Age and pre-morbid mobility gave an indication of mobility outcome, but a substantial amount of variance remains unexplained. Limitations of this study, including missing data and potential residual confounding, indicate the need for caution in generalising these results. The study provides a basis on which to plan larger studies of the factors associated with mobility outcome after ankle fracture in older populations.

Cell therapy of peripheral arterial disease: from experimental findings to clinical trials

The age-adjusted prevalence of peripheral arterial disease in the US population was estimated to approach 12% in 1985, and as the population ages, the overall population having peripheral arterial disease is predicted to rise. The clinical consequences of occlusive peripheral arterial disease include intermittent claudication, that is, pain with walking, and critical limb ischemia (CLI), which includes pain at rest and loss of tissue integrity in the distal limbs, which may ultimately lead to amputation of a portion of the lower extremity. The risk factors for CLI are similar to those linked to coronary artery disease and include advanced age, smoking, diabetes mellitus, hyperlipidemia, and hypertension. The worldwide incidence of CLI was estimated to be 500 to 1000 cases per million people per year in 1991. The prognosis is poor for CLI subjects with advanced limb disease. One study of >400 such subjects in the United Kingdom found that 25% required amputation and 20% (including some subjects who had required amputation) died within 1 year. In the United States, ≈280 lower-limb amputations for ischemic disease are performed per million people each year. The first objective in treating CLI is to increase blood circulation to the affected limb. Theoretically, increased blood flow could be achieved by increasing the number of vessels that supply the ischemic tissue with blood. The use of pharmacological agents to induce new blood vessel growth for the treatment or prevention of pathological clinical conditions has been called therapeutic angiogenesis. Since the identification of the endothelial progenitor cell in 1997 by Asahara and Isner, the field of cell-based therapies for peripheral arterial disease has been in a state of continuous evolution. Here, we review the current state of that field.

Evaluation of asymptomatic peripheral arterial disease by ankle- brachial index in patients with concomitant coronary arterial disease

BACKGROUND

Peripheral arterial disease is associated with adverse cardiovascular outcomes. As such, it is found that screening for peripheral arterial disease (PAD) improves risk assessment. Thus, intensive risk factor modification and medical treatment in these patients are necessary.

OBJECTIVES

The purpose of this study was to determine the prevalence of asymptomatic peripheral arterial disease in patients with concomitant coronary arterial disease.

METHODS

Asymptomatic peripheral arterial disease was investigated in 400 patients (60% males, 40% females, aged 59.7± 11.3) with a documented coronary arterial disease.

RESULTS

Among patients with documented CAD, 12% had asymptomatic PAD with the ABI ratio of less than 0.9.

CONCLUSIONS

It is advisable to screen for PAD not only as a disease but also as a risk assessment method for atherosclerosis.

A Study on the Relationship between Serum Beta 2-Microglobulin Levels, Underlying Chronic Kidney Disease, and Peripheral Arterial Disease in High-Vascular-Risk Patients

BACKGROUND

Serum beta 2-microglobulin (B2M) levels have been found to be increased in patients with peripheral arterial disease (PAD), yet it is still unknown whether B2M correlates with PAD intensity.

OBJECTIVES

We aim to evaluate the correlation between B2M and the ankle-brachial index (ABI) values in high-vascular-risk patients.

METHODS

This is a cross-sectional study of 63 high-vascular-risk patients admitted to the Cardiology Department or evaluated as outpatients in the Internal Medicine Department of our institution. Patients were classified into two groups according to their ABI: patients without PAD (n = 44, ABI values between 0.9 and 1.4) and patients with PAD (n = 19, ABI values lower than 0.9 or higher than 1.4). We performed univariate and multivariate analysis based on a multiple linear regression model.

RESULTS

Serum B2M levels were higher in patients with pathological ABI values than in those without PAD (2.36 ± 1.13 vs. 1.80 ± 0.65 mg/L; P<0.05). We found no correlation between B2M and ABI in our total population (r = -0.12) or in patients with PAD (r = -0.09; NS for both comparisons). Age, gender, arterial hypertension, estimated glomerular filtration rate (eGFR), uric acid, total cholesterol, and LDL-cholesterol correlated with B2M in the univariate analysis. In the final linear regression model, eGFR, uric acid and total cholesterol correlated independently with B2M (P<0.01).

CONCLUSION

We found no correlation between B2M levels and ABI values in high-vascular-risk patients that could usefully help in the subsequent diagnosis of PAD. However, we observed a significant correlation between B2M and eGFR, even when renal function was only slightly impaired.

Chapter II: Diagnostic methods

Non-invasive vascular studies can provide crucial information on the presence, location, and severity of critical limb ischaemia (CLI), as well as the initial assessment or treatment planning. Ankle-brachial index with Doppler ultrasound, despite limitations in diabetic and end-stage renal failure patients, is the first-line evaluation of CLI. In this group of patients, toe-brachial index measurement may better establish the diagnosis. Other non-invasive measurements, such as segmental limb pressure, continuous-wave Doppler analysis and pulse volume recording, are of limited accuracy. Transcutaneous oxygen pressure (TcPO(2)) measurement may be of value when rest pain and ulcerations of the foot are present. Duplex ultrasound is the most important non-invasive tool in CLI patients combining haemodynamic evaluation with imaging modality. Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are the next imaging studies in the algorithm for CLI. Both CTA and MRA have been proven effective in aiding the decision-making of clinicians and accurate planning of intervention. The data acquired with CTA and MRA can be manipulated in a multiplanar and 3D fashion and can offer exquisite detail. CTA results are generally equivalent to MRA, and both compare favourably with contrast angiography. The individual use of different imaging modalities depends on local availability, experience, and costs. Contrast angiography represents the gold standard, provides detailed information about arterial anatomy, and is recommended when revascularisation is needed.

Gender divergence on the impact of multiple cardiovascular risk factors on the femoral artery intima-media thickness in asymptomatic young adults: the Bogalusa Heart Study

INTRODUCTION

Gender divergence on the impact of multiple cardiovascular risk factors on the femoral artery intima-media thickness (IMT) has not been studied in a biracial (black-white) community-based asymptomatic young adults.

METHODS

Femoral IMT was measured by B-mode ultrasonography in 1080 individuals (age, 24-43 years; 71% white; 43% men) enrolled in the Bogalusa Heart Study.

RESULTS

Femoral IMT showed a gender difference (men > women; P = 0.001), but no racial difference. In a multivariate model, age, cigarette smoking, systolic blood pressure and total cholesterol to high-density lipoprotein cholesterol ratio related independently, in that order, to IMT in women, and age and low-density lipoprotein cholesterol in men. In women, mean IMT increased with increasing number of risk factors defined as values above the age-, race- and gender-specific 75th percentile of systolic blood pressure, waist circumference, total cholesterol to high-density lipoprotein cholesterol ratio and insulin along with positive smoking status (P for trend = 0.001), with respective mean IMT (mm) values of 0.61, 0.65, 0.72 and 0.77, for 0, 1 to 2, 3 and 4 to 5 risk factors. There was no such significant trend in men.

CONCLUSIONS

Although men versus women had thicker IMT, the observed increasing trend of femoral IMT with increasing number of risk factors in asymptomatic young women suggests that women may be relatively more susceptible to the burden of multiple risk factors.

A phase II dose-ranging study of the phosphodiesterase inhibitor K-134 in patients with peripheral artery disease and claudication

BACKGROUND

Phosphodiesterase inhibitors have been shown to improve claudication-limited exercise performance in patients with peripheral artery disease. K-134, a novel phosphodiesterase inhibitor, was evaluated in a phase II trial incorporating an adaptive design to assess its safety, tolerability, and effect on treadmill walking time.

DESIGN

Patients with peripheral artery disease were randomized to receive placebo (n = 87), K-134 at a dose of 25 mg (n = 42), 50 mg (n = 85), or 100 mg (n = 84), or cilostazol at a dose of 100 mg (n = 89), each twice daily for 26 weeks. Peak walking time (PWT) was assessed using a graded treadmill protocol at baseline and after 14 and 26 weeks of treatment. A Data and Safety Monitoring Board-implemented adaptive design was used that allowed early discontinuation of unsafe or minimally informative K-134 arms.

RESULTS

As determined by the prospectively defined adaptive criteria, the 25-mg K-134 arm was discontinued after 42 individuals had been randomized to the arm. During the 26-week treatment period, PWT increased by 23%, 33%, 37%, and 46% in the placebo, 50-mg K-134, 100-mg K-134, and cilostazol arms, respectively (primary analysis placebo vs 100-mg K-134 arm not statistically significant, P = .089). Secondary analyses showed that cilostazol significantly increased PWT after 14 weeks of treatment and that the 100-mg K-134 dose and cilostazol both increased PWT vs placebo after 14 and 26 weeks in those individuals who completed the 26-week trial and were compliant with the study drug, or when the data were analyzed using a mixed-effects model incorporating all time points. K-134 had tolerability and adverse effect profiles similar to that of cilostazol. Both drugs were associated with an increase in withdrawals before study completion due to adverse events compared with placebo.

CONCLUSIONS

K-134 was generally well tolerated. K-134 at a dose of 100 mg twice daily did not affect PWT according to the primary analysis, but K-134 and cilostazol both increased PWT when analyzed using a mixed-effects model and in the per-protocol population.

Lower extremity nerve function, calf skeletal muscle characteristics, and functional performance in peripheral arterial disease

OBJECTIVES

To determine whether poor lower extremity nerve function is associated with less-favorable calf muscle characteristics and greater functional impairment in people with and without peripheral arterial disease (PAD).

DESIGN

Cross-sectional.

SETTING

Three Chicago-area medical centers.

PARTICIPANTS

Four hundred thirteen participants with PAD (ankle-brachial index (ABI) < 0.90) and 255 without.

MEASUREMENTS

Electrodiagnostic testing of the peroneal nerve was performed. Calf muscle cross-sectional area and percentage fat were measured using computed tomography at 66.7% of the distance between the distal and proximal tibia. Six-minute walk performance was measured.

RESULTS

Adjusting for age, sex, race, ABI, leg symptoms, smoking, physical activity, comorbidities, and other covariates, lower peroneal nerve conduction velocity (NCV) was associated with lower calf muscle area (first quartile 4,770.3 mm(2) , fourth quartile 5,571 mm(2) , P < .001) and poorer 6-minute walk distance (first quartile 989.2 feet, fourth quartile 1,210.8 feet, P < .001) in participants without diabetes mellitus with PAD. Lower peroneal NCV was associated with lower calf muscle area (first quartile 5,166.0 mm(2) , fourth quartile 6,003.8 mm(2) , P = .01) and poorer 6-minute walk distance (first quartile 866.4 feet, fourth quartile 1,082.5 feet, P = .01) in participants with diabetes mellitus and PAD as well. In participants without PAD, lower peroneal NCV was not associated with lower calf muscle area but was associated with poorer 6-minute walk distance only in participants without diabetes mellitus (first quartile 1,317.0 feet, fourth quartile 1,570.4 feet, P-trend < .001).

CONCLUSION

Lower peroneal nerve function is associated with smaller calf muscle area and greater functional impairment in individuals with PAD. Future study is needed to determine whether improving peroneal NCV prevents loss of calf muscle and functional decline in people with PAD.

Characteristics of peripheral arterial disease and its relevance to the diabetic population

Peripheral arterial disease (PAD) is very frequent in diabetics, and it increases with age. Foot examination contributes poorly to diagnosis of PAD. The ankle-brachial index (ABI) measurement is considered the most accurate noninvasive diagnostic method when evaluating PAD: ABI evaluation is recommended in all diabetics aged >50 years. Many diabetic patients with PAD have a concomitant sensitive neuropathy: as a consequence, perception of ischemic pain is remarkably reduced or completely blocked. The result is that the prevalence of claudication in the diabetic population with PAD is lower than the prevalence of critical limb ischemia (CLI) in this population. CLI is a major risk factor for lower extremity amputation without revascularization. Ankle and toe pressures and oxygen tension at the foot are the noninvasive diagnostic parameters of CLI though the medial artery calcification inhibits accurate determination of the ankle and toe pressures, especially when a forefoot ulcer is present. In diabetics, the anatomical localization is mainly distal; arterial wall calcification is frequently observed and occlusion occurs more frequently than stenosis. Such anatomical features, along with the difficulties in the diagnostic approach, account for the fundamental role of CLI as the main prognostic indicator for major amputation. PAD is an expression of systemic atherosclerotic disease. Prognosis of patients with PAD is related to the presence and extent of underlying coronary artery disease (CAD) but also to the severity of PAD: in particular, patients in whom revascularization is not feasible have the highest mortality rate.

Outcomes and Risk Prediction Model for Peripheral Arterial Disease in Patients with Stable Coronary Artery Disease

We used the National Heart, Lung, and Blood Institute Limited Access Dataset of Prevention of Events with Angiotensin-Converting Enzyme Inhibition (PEACE) Trial (n = 8290) which included patients with stable coronary artery disease (CAD) and preserved ejection fraction (>40%). We identified risk factors for the development of critical peripheral arterial disease (PAD; those needing angioplasty, bypass grafting, or aneurysm repair) and formulated a risk score by multivariate analyses. A total of 220 patients (2.8%) developed critical PAD over a mean follow-up of 4.7 years. Significant predictors of critical PAD were history of intermittent claudication, smoking, hypertension (HTN), coronary-artery bypass grafting (CABG), diabetes, age, serum cholesterol, and body mass index (BMI). Incident critical PAD was associated with increased composite outcome of cardiovascular death, myocardial infarction, percutaneous transluminal coronary angioplasty, or CABG (hazard ratio 1.82, 95% CI 1.50-2.22, P < .001). Risk assessment using our score may identify CAD patients at risk for critical PAD events.

Sex differences in the prevalence of peripheral artery disease in patients undergoing coronary catheterization

To determine whether there are sex differences in the prevalence of peripheral artery disease, we performed an observational study of 1014 men and 547 women, aged ≥ 40 years, referred for elective coronary angiography. Women were slightly older, more obese, had higher low-density lipoprotein cholesterol (LDL-C) levels and systolic blood pressure (BP), and were more likely to be African American. Women had higher high-density lipoprotein cholesterol (HDL-C) levels, lower diastolic BP, and were less likely to smoke or to have a history of cardiovascular disease. Women had less prevalent (62% vs 81%) and less severe coronary artery disease (CAD) (p < 0.001 for both) by coronary angiography, but more prevalent peripheral artery disease (PAD) as determined by the ankle-brachial index (ABI) than men (23.6% versus 17.2%). Independent predictors of lower ABI were female sex, black race, older age, tobacco use, CAD, diabetes, and triglyceride level. In a full multivariable logistic regression model, women had a risk-adjusted odds ratio for PAD of 1.78 (95% CI 1.25-2.54) relative to men. Among patients referred for coronary angiography, women have less prevalent and less severe CAD, but more prevalent PAD, a sex difference that is not explained by traditional cardiovascular disease risk factors or CAD severity. Clinical Trial Registration-URL: http://clinicaltrials.gov. Unique identifier: NCT00380185.

Quantitative analysis of the postcontractile blood-oxygenation-level-dependent (BOLD) effect in skeletal muscle

Previous studies show that transient increases in both blood flow and magnetic resonance image signal intensity (SI) occur in human muscle after brief, single contractions, and that the SI increases are threefold larger in physically active compared with sedentary subjects. This study examined the relationship between these transient changes by measuring anterior tibial artery flow (Doppler ultrasound), anterior muscle SI (3T, one-shot echo-planar images, TR/TE = 1,000/35), and muscle blood volume and hemoglobin saturation [near-infrared spectroscopy (NIRS)] in the same subjects after 1-s-duration maximum isometric ankle dorsiflexion contractions. Arterial flow increased to a peak 5.9 ± 0.7-fold above rest (SE, n = 11, range 2.6-10.2) within 7 s and muscle SI increased to a peak 2.7 ± 0.6% (range 0.0-6.0%) above rest within 12 s after the contractions. The peak postcontractile SI change was significantly correlated with both peak postcontractile flow (r = 0.61, n = 11) and with subject activity level (r = 0.63, n = 10) estimated from 7-day accelerometer recordings. In a subset of 7 subjects in which NIRS data acquisition was successful, the peak magnitude of the postcontractile SI change agreed well with SI calculated from the NIRS blood volume and saturation changes (r = 0.80, slope = 1.02, intercept = 0.16), confirming the blood-oxygenation-level-dependent (BOLD) mechanism underlying the SI change. The magnitudes of postcontractile changes in blood saturation and SI were reproduced by a simple one-compartment muscle vascular model that incorporated the observed pattern of postcontractile flow, and which assumed muscle O(2) consumption peaks within 2 s after a brief contraction. The results show that muscle postcontractile BOLD SI changes depend critically on the balance between O(2) delivery and O(2) consumption, both of which can be altered by chronic physical activity.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Leveraging informatics for genetic studies: use of the electronic medical record to enable a genome-wide association study of peripheral arterial disease

BACKGROUND

There is significant interest in leveraging the electronic medical record (EMR) to conduct genome-wide association studies (GWAS).

METHODS

A biorepository of DNA and plasma was created by recruiting patients referred for non-invasive lower extremity arterial evaluation or stress ECG. Peripheral arterial disease (PAD) was defined as a resting/post-exercise ankle-brachial index (ABI) less than or equal to 0.9, a history of lower extremity revascularization, or having poorly compressible leg arteries. Controls were patients without evidence of PAD. Demographic data and laboratory values were extracted from the EMR. Medication use and smoking status were established by natural language processing of clinical notes. Other risk factors and comorbidities were ascertained based on ICD-9-CM codes, medication use and laboratory data.

RESULTS

Of 1802 patients with an abnormal ABI, 115 had non-atherosclerotic vascular disease such as vasculitis, Buerger's disease, trauma and embolism (phenocopies) based on ICD-9-CM diagnosis codes and were excluded. The PAD cases (66+/-11 years, 64% men) were older than controls (61+/-8 years, 60% men) but had similar geographical distribution and ethnic composition. Among PAD cases, 1444 (85.6%) had an abnormal ABI, 233 (13.8%) had poorly compressible arteries and 10 (0.6%) had a history of lower extremity revascularization. In a random sample of 95 cases and 100 controls, risk factors and comorbidities ascertained from EMR-based algorithms had good concordance compared with manual record review; the precision ranged from 67% to 100% and recall from 84% to 100%.

CONCLUSION

This study demonstrates use of the EMR to ascertain phenocopies, phenotype heterogeneity and relevant covariates to enable a GWAS of PAD. Biorepositories linked to EMR may provide a relatively efficient means of conducting GWAS.

Incidence and risk factors of peripheral arterial occlusive disease in a prospective cohort of 700 adult elderly men followed for 5 years

OBJECTIVE

This study was designed to assess the incidence of peripheral arterial occlusive disease (PAOD) in a population-based cohort of men aged 55-74 years and to establish a predictive function based on risk factors for the disease.

METHODS

This was a prospective study of 699 men representative of an urban population. Cardiovascular risk factors, history of cardiovascular events, and ankle-brachial index (ABI) at baseline and at 5 years were measured. PAOD was defined as a confirmed ABI <0.9.

RESULTS

A total of 468 (67%) subjects could be evaluated at 5 years. In the remaining 233 subjects, 94 had PAOD at baseline, 66 died during the study, and 73 were lost to follow-up. At the end of the 5-year study period, 56 (12%) subjects developed PAOD (21.4% ABI <0.6, 78.6% ABI between 0.61 and 0.9). Independent predictors for PAOD were age older than 70 years at baseline (odds ratio [OR] 2.5, P = 0.004), smoking history more than 40 pack-year (OR = 2.27, P = 0.007), history of cerebrovascular disease (OR = 3.49, P = 0.02), and symptomatic coronary disease (OR = 3.36, P = 0.004). The 5-year incidence of PAOD was 22.4% for subjects older than 70 years, 21.5% for heavy smokers, 29.4% for those with previous cerebrovascular events, and 25% for subjects with ischemic heart disease. The risk for PAOD in subjects without risk factors was 6%.

CONCLUSIONS

Twelve percent of adult men aged between aged 55 and 74 years developed PAOD during a follow-up of 5 years. Besides subjects with history of cardiovascular disease, men older than aged 70 years and heavy smokers constituted a high-risk group for PAOD and, therefore, the object of directed efforts of primary prevention.

Peripheral artery disease: current insight into the disease and its diagnosis and management

Peripheral artery disease (PAD), which comprises atherosclerosis of the abdominal aorta, iliac, and lower-extremity arteries, is underdiagnosed, undertreated, and poorly understood by the medical community. Patients with PAD may experience a multitude of problems, such as claudication, ischemic rest pain, ischemic ulcerations, repeated hospitalizations, revascularizations, and limb loss. This may lead to a poor quality of life and a high rate of depression. From the standpoint of the limb, the prognosis of patients with PAD is favorable in that the claudication remains stable in 70% to 80% of patients over a 10-year period. However, the rate of myocardial infarction, stroke, and cardiovascular death in patients with both symptomatic and asymptomatic PAD is markedly increased. The ankle brachial index is an excellent screening test for the presence of PAD. Imaging studies (duplex ultrasonography, computed tomographic angiography, magnetic resonance angiography, catheter-based angiography) may provide additional anatomic information if revascularization is planned. The goals of therapy are to improve symptoms and thus quality of life and to decrease the cardiovascular event rate (myocardial infarction, stroke, cardiovascular death). The former is accomplished by establishing a supervised exercise program and administering cilostazol or performing a revascularization procedure if medical therapy is ineffective. A comprehensive program of cardiovascular risk modification (discontinuation of tobacco use and control of lipids, blood pressure, and diabetes) will help to prevent the latter.