Clinical and socioeconomic factors associated with unrecognized peripheral artery disease

Depressive Symptoms Associated with Peripheral Artery Disease and Predicting Mortality in Type 2 Diabetes

This retrospective cohort study aimed to assess the mortality risk in patients with type 2 diabetes mellitus (DM) by screening for depressive symptoms and peripheral artery disease (PAD). We enrolled patients aged ≥60 years who had undergone assessments of both the ankle-brachial index (ABI) and the five-item Geriatric Depression Scale (GDS-5). PAD and depression were defined as ABI ≤ 0.90 and GDS-5 ≥ 1, respectively. The primary endpoint was total mortality. In 1673 enrolled patients, the prevalence of PAD was higher in those with depression than in those without depression (8.9% vs. 5.7%, p = 0.021). After a median follow-up of 56.6 months (interquartile range: 47.0-62.3 months), a total of 168 (10.0%) deaths occurred. The patients in the depression and PAD subgroup had the highest hazard ratio of mortality, followed by the PAD without depression subgroup and the depression without PAD subgroup (2.209, 95%CI: 1.158-4.217; 1.958, 95%CI: 1.060-3.618; and 1.576, 95%CI: 1.131-2.196; respectively) in comparison to the patients without depression and PAD after adjustment for associated factors. In conclusion, a combination of depression and PAD predicted the highest mortality risk. Screening for depression and PAD is recommended in patients aged ≥60 years with type 2 DM.

The importance of socio-economic determinants of health in the care of patients with peripheral artery disease: A narrative review from VAS

Socio-economic determinants of health (SDoH) include various nonmedical factors in the socio-economic sphere with a potentially significant impact on health outcomes. Their effects manifest through several mediators/moderators (behavioral characteristics, physical environment, psychosocial circumstances, access to care, and biological factors). Various critical covariates (age, gender/sex, race/ethnicity, culture/acculturation, and disability status) also interact. Analyzing the effects of these factors is challenging due to their enormous complexity. Although the significance of SDoH for cardiovascular diseases is well documented, research regarding their impact on peripheral artery disease (PAD) occurrence and care is less well documented. This narrative review explores to what extent SDoH are multifaceted in PAD and how they are associated with its occurrence and care. Additionally, methodological issues that may hamper this effort are addressed. Finally, the most important question, whether this association may contribute to reasonable interventions aimed at SDoH, is analyzed. This endeavor requires attention to the social context, a whole systems approach, multilevel-thinking, and a broader alliance that reaches out to more stakeholders outside the medical sphere. More research is needed to justify the power in this concept to improve PAD-related outcomes like lower extremity amputations. At the present time, some evidence, reasonable consideration, and intuitive reasoning support the implementation of various interventions in SDoH in this field.

Walking Behaviour of Individuals with Intermittent Claudication Compared to Matched Controls in Different Locations: An Exploratory Study

Individuals with intermittent claudication (IC) are less physically active than their peers, but how this varies with location is unclear. Individuals with IC and matched controls [sex, age ±5 years, home < 5 miles] wore an activity monitor (activPAL) and carried a GPS device (AMOD-AGL3080) for 7 days. GPS data categorised walking events as occurring at home (<=50 m from home co-ordinates) or away from home, and indoors (signal to noise ratio <= 212 dB) or outdoors. Number of walking events, walking duration, steps and cadence were compared between groups and each location pair using mixed model ANOVAs. In addition, the locus of activity (distance from home) at which walking was conducted was compared between groups. Participants (n = 56) were mostly male (64%) and aged 54-89 years. Individuals with IC spent significantly less time walking and took fewer steps than their matched controls at all locations, including at home. Participants spent more time and took more steps away from home than at home, but were similar when walking indoors and outdoors. The locus of activity was significantly smaller for individuals with IC, suggesting that it is not just physical capacity that influences walking behaviour, and other factors (e.g., social isolation) may play a role.

Outcomes among patients with peripheral artery disease in the Aspirin Dosing: A Patient-Centric Trial Assessing Benefits and Long-Term Effectiveness (ADAPTABLE) study

BACKGROUND

We aimed to understand the effects of aspirin dose on outcomes in patients with peripheral artery disease (PAD) as well as their participation in a pragmatic randomized controlled trial.

METHODS

In a subanalysis of the Aspirin Dosing: A Patient-Centric Trial Assessing Benefits and Long-Term Effectiveness (ADAPTABLE) study, we compared aspirin doses (81 vs 325 mg) among participants with PAD and study participation metrics in patients with and without PAD. The primary outcome composite was all-cause mortality, nonfatal myocardial infarction, and nonfatal stroke.

RESULTS

Among 14,662 participants enrolled in ADAPTABLE with PAD status available, 3493 (23.8%) had PAD. Participants with PAD were more likely to experience the primary composite (13.76% vs 5.31%, p < 0.001), all-cause mortality (7.55% vs 3.01%, p < 0.001), myocardial infarction (5.71% vs 2.09%, p < 0.001), stroke (2.45% vs 0.86%, p < 0.001), and major bleeding (1.19% vs 0.44%, p < 0.001). A higher aspirin dose did not reduce the primary outcome in patients with PAD (13.68% vs 13.84% in 81 mg and 325 mg groups; OR 1.05, 95% CI 0.88-1.25). Participants with PAD were less likely to enroll via email (33.0% vs 41.9%, p < 0.0001), less likely to choose internet follow-up (79.2% vs 89.5%, p < 0.0001), and were more likely to change their aspirin doses (39.7% vs 30.7%, p < 0.0001).

CONCLUSIONS

ADAPTABLE participants with PAD did not benefit from a higher dose of aspirin and participated in the study differently from those without PAD. These results reinforce the need for additional PAD-specific research and suggest that different trial strategies may be needed for optimal engagement of patients with PAD. (ClinicalTrials.gov Identifier: NCT02697916).

Social isolation in patients with chronic limb-threatening ischemia: a cross-sectional study

Assistance by family members or friends plays important roles in the course of treating patients with chronic limb-threatening ischemia (CLTI), both during hospitalization and after discharge. The aim of this study was to reveal the prevalence of social isolation and to explore relevant clinical backgrounds in patients with CLTI presenting with tissue loss and requiring revascularization. We analyzed 413 patients registered in a multicenter study in whom revascularization were scheduled for CLTI with tissue loss. Social isolation was analyzed by assessing the residence status of the patients and the involvement of a trusted family member or friend in their daily lives and during hospitalization. Patients living alone accounted for 24.5% (95% confidence interval [CI] 20.1-28.8%) of the study population. Patients receiving welfare were more likely to live alone (P < 0.001). For patients living alone, 21.8% (95% CI 12.8-30.8%) met a trusted family member or friend in their daily lives less than once per year. Younger age and receiving welfare were independently associated with lower frequency of meeting the trusted person in their daily lives (both P < 0.05). The adjusted odds ratio of age and receiving welfare was 0.44 (95% CI 0.29-0.67) per 10-year increase and 3.47 (95% CI 1.43-8.44), respectively. During hospitalization, 9.9% (95% CI 6.8-13.0%) of the patients had no hospital visits by a trusted family member or friend on three key occasions: the patient's first hospital visit, the preoperative explanation regarding the planned operation, and the day of the operation. Younger age and receiving welfare were independently associated with lower frequency of hospital visits by a family member or friend (both P < 0.05). The adjusted odds ratio of age and receiving welfare for no visit versus ≥ 1 visit was 0.51 (0.36-0.74) per 10-year increase and 5.29 (2.46-11.4), respectively. In conclusion, social isolation is common among patients with CLTI, especially younger patients and those on welfare. Practical countermeasures against social isolation are warranted in the management of CLTI.

Comparative evaluation of socioeconomic insecurity in peripheral and coronary artery disease patients

BACKGROUND

Cardiovascular disease represents the leading cause of death worldwide. Socioeconomic deprivation is a risk factor for cardiovascular disease. We have previously shown that precariousness was more frequent in symptomatic peripheral artery disease (PAD) patients than in the general population. According to a previous study, coronary artery disease (CAD) patients have a higher level of education than CAD with PAD, but no study directly compared the level of precariousness in PAD and CAD patients.

AIM

To measure and compare the level of socioeconomic insecurity in patients suffering from symptomatic PAD with those suffering from isolated CAD, i.e without symptomatic PAD.

METHODS

We conducted an observational, cohort, prospective, multicenter study. Patients suffering from symptomatic PAD or CAD were recruited through the medical or surgical vascular or cardiology departments, or the vascular rehabilitation center. The EPICES score and the INSEE parameters were used for analysis. The individual is considered precarious when his or her score is greater than or equal to 30. Cardiovascular risk factors and peripheral arterial disease stages were also collected.

RESULTS

In total, 230 patients were included. According to the EPICES score, 47.8% [95%CI, 38.7-56.7] of patients with symptomatic PAD were in a precarious situation compared to 17.4% [95%CI, 10.5-24.3] of patients suffering from isolated CAD (P<0.001). The mean EPICES score was 33.3 (SD 22.5) in the PAD and 16.9 (SD 17.02) in the CAD population, respectively (P<0.001). In the PAD population, the level of education was low, with an under-representation of patients with a baccalaureate or higher education degree: 21.7% [95%CI, 14.2-29.3] vs. 41.7% [95%CI, 32.7-50.7] in the PAD and CAD populations, respectively. There was also an under-representation of executives and intellectual and intermediate professions in the PAD population, 18.3% [95%CI, 11.2-25.3], compared to the CAD population, 31.3% [95%CI, 22.8-39.8].

CONCLUSION

PAD patients are more precarious than patients suffering from CAD. A better detection of socioeconomic deprivation in patients suffering from peripheral arterial disease could allow comprehensive care and thus hope for an improvement in terms of morbidity and mortality.

Statins and statin intensity in peripheral artery disease

Background: Peripheral artery disease (PAD) affects more than 202 million people worldwide. Several studies have shown that patients with PAD are often undertreated, and that statin utilization is suboptimal. European and American guidelines highlight statins as the first-line lipid-lowering therapy to treat patients with PAD. Our objective with this meta-analysis was to further explore the impact of statins on lower extremities PAD endpoints and examine whether statin dose (high vs. low intensity) impacts outcomes. Patients and methods: We performed a systematic review and meta-analysis according to the PRISMA guidelines. Any study that presented a comparison of use of statins vs. no statins for PAD patients or studies comparing high vs. low intensity statins were considered to be potentially eligible. We excluded studies with only critical limb threatening ischemia (CLTI) patients. The Medline (PubMed) database was searched up to January 31, 2021. A random effects meta-analysis was performed. Results: In total, 39 studies and 275,670 patients were included in this meta-analysis. In total, 136,025 (49.34%) patients were on statins vs. 139,645 (50.66%) who were not on statins. Statin use was associated with a reduction in all cause-mortality by 42% (HR: 0.58, 95% CI: 0.49-0.67, p<0.01) and cardiovascular death by 43% (HR: 0.57, 95% CI: 0.40-0.74, p<0.01). Statin use was associated with an increase in amputation-free survival by 56% (HR: 0.44, 95% CI: 0.30-0.58, p<0.01). The risk of amputation and loss of patency were reduced by 35% (HR: 0.65, 95% CI: 0.41-0.89, p<0.01) and 46% (HR: 0.54, 95% CI: 0.34-0.74, p<0.01), respectively. Statin use was also associated with a reduction in the risk of major adverse cardiovascular events (MACE) by 35% (HR: 0.65, 95% CI: 0.51-0.80, p<0.01) and myocardial infarction rates by 41% (HR: 0.59, 95% CI: 0.33-0.86, p<0.01). Among patients treated with statins, the high-intensity treatment group was associated with a reduction in all cause-mortality by 36% (HR: 0.64, 95% CI: 0.54-0.74, p<0.01) compared to patients treated with low intensity statins. Conclusions: Statin treatment among patients with PAD was associated with a statistically significant reduction in all-cause mortality, cardiovascular mortality, MACE, risk for amputation, or loss of patency. Higher statin dose seems to be associated with improved outcomes.

Evaluation of socio-economic insecurity in peripheral artery disease patients

The social and economic environment has become a major determinant of cardiovascular health. The objective of our study was to assess socio-economic insecurity in patients with symptomatic PAD. The PRECAR study was a non-interventional prospective cohort study. Patients were recruited from the Vascular Medicine and Surgery Departments of Grenoble-Alpes University Hospital or during a consultation as part of the therapeutic education program "On the move! Better understanding and better living with arterial disease". The analysis of socio-economic and environmental data was based on the EPICES score (a reliable index used to measure individual deprivation) and INSEE parameters (level of education and socio-professional category). Cardiovascular risk factors were also recorded. 150 patients with symptomatic PAD were included between November 2017 and June 2018. 84% were men. In our population 54% (CI95% 45.7 - 62.1) were in a precarious situation compared to 40% (CI95% 39.8 - 40.2) in the general population, according to the EPICES score (P<0.001). Levels of education were low and patients with a baccalaureate or higher education degree were under-represented. Executives, intellectuals and intermediate professions were also under-represented in the PAD population. This data opens new perspectives on the social characterisation of patients that may contribute to improving the outcomes of patients with peripheral vascular disease.

A prospective community engagement initiative to improve clinical research participation in patients with peripheral artery disease

Objective:

Patients diagnosed with peripheral artery disease are difficult to recruit into clinical trials. However, there is currently no high-quality, patient-centered information explaining why peripheral artery disease patients choose to participate or not participate in clinical research studies.

Methods:

The current study was a prospective community engagement initiative that specifically asked patients with and without peripheral artery disease: (1) what motivates them to participate in clinical research studies, (2) their willingness to participate in different research procedures, (3) the barriers to participation, (4) preferences about study design, and (5) demographic and disease-related factors influencing participation. Data were gathered through focus groups (n = 19, participants aged 55–79 years) and mailed questionnaires (n = 438, respondents aged 18–85 years).

Results:

More than half of the respondents stated that they would be willing to participate in a study during evening or weekend time slots. Peripheral artery disease patients (n = 45) were more willing than those without peripheral artery disease (n = 360) to participate in drug infusion studies (48% versus 18%, p < 0.001) and trials of investigational drugs (44% versus 21%, p < 0.001). Motivating factors and barriers to participation were largely consistent with previous studies.

Conclusion:

Adults in our geographic region are interested in participating in clinical research studies related to their health; they would like their doctor to tell them what studies they qualify for and they prefer to receive a one-page advertisement that has color pictures of the research procedures. Peripheral artery disease patients are more willing than those without peripheral artery disease to participate in drug infusion studies, trials of investigational drugs, microneurography, and spinal/epidural infusions.

A Targeted Literature Review of the Disease Burden in Patients With Symptomatic Peripheral Artery Disease

Patients with peripheral artery disease (PAD) have an increased risk of cardiovascular (CV) and limb events, but the disease is frequently underdiagnosed and treatment options are limited. This review examines the disease burden of symptomatic PAD as well as key guideline recommendations. Publications were identified using the ProQuest portal to access the Medline, Medline In-Process, and Embase databases. Search terms for symptomatic PAD were combined with terms relevant to epidemiology, burden, treatment practice, and physiopathology. Articles in English published between January 2001 and September 2016 were screened according to the population, interventions, comparator, outcomes, and study design criteria. Relevant publications (n = 200) were identified. The reported incidence and prevalence of PAD varied depending on the definitions used and the study populations. Patients generally had a poor prognosis, with an increased risk of mortality, CV, and limb events and decreased quality of life. Guideline recommendations included ankle–brachial index measurements, exercise testing, and angiography for diagnosis and risk factor modification, antiplatelets, cilostazol, exercise therapy, or surgical interventions for treatment, depending on the patient profile. The clinical, humanistic, and economic burden of disease in patients with symptomatic PAD is substantial and needs to be reduced through improved PAD management.

SCAI 2018 Think Tank Proceedings: "What skillsets are required of vascular interventional cardiologists in evaluating and managing critical limb ischemia (CLI)? What role should SCAI play in supporting interventional cardiologists in their CLI practices, individually and collectively?"

The aim of this article is to discuss the poor outcomes associated with critical limb ischemia (CLI) and the required knowledge needed for optimal care. There is an opportunity for the Society for Cardiovascular Angiography and Interventions (SCAI) to assist interventional cardiologists in enhancing CLI care through creation of training standards and development of educational content.

Consideration of Sex Differences in Design and Reporting of Experimental Arterial Pathology Studies-Statement From ATVB Council

There are many differences in arterial diseases between men and women, including prevalence, clinical manifestations, treatments, and prognosis. The new policy of the National Institutes of Health, which requires the inclusion of sex as a biological variable for preclinical studies, aims to foster new mechanistic insights and to enhance our understanding of sex differences in human diseases. The purpose of this statement is to suggest guidelines for designing and reporting sex as a biological variable in animal models of atherosclerosis, thoracic and abdominal aortic aneurysms, and peripheral arterial disease. We briefly review sex differences of these human diseases and their animal models, followed by suggestions on experimental design and reporting of animal studies for these vascular pathologies.

Peripheral Arterial Disease Genetics: Progress to Date and Challenges Ahead

PURPOSE OF REVIEW

In this paper, we review the progress made thus far in research related to the genetics of peripheral arterial disease (PAD) by detailing efforts to date in heritability, linkage analyses, and candidate gene studies. We further summarize more contemporary genome-wide association studies (GWAS) and epigenetic studies of PAD. Finally, we review current challenges and future avenues of advanced research in PAD genetics including whole genome sequencing studies.

RECENT FINDINGS

Studies have estimated the heritability of PAD to be moderate, though the contribution to this heritability that is independent of traditional cardiovascular risk factors remains unclear. Recent efforts have identified SNPs associated with PAD in GWAS analyses, but these have yet to be replicated in independent studies. Much remains to be discovered in the field of PAD genetics. An improved understanding of the genetic foundation for PAD will allow for earlier diagnosis of disease and a more complete pathophysiological understanding of the mechanisms of the disease leading to novel therapeutic interventions. Future avenues for success will likely arise from very large-scale GWAS, whole genome sequencing, and epigenetic studies involving very well-characterized cohorts.

Interventional treatment of the left subclavian in 2 patients with coronary steal syndrome

In patients with history of coronary artery disease angina pectoris is usually attributed to the progression of atherosclerotic lesions. However, in patients with previous coronary artery bypass graft operation (CABG) using internal mammary artery grafts, great vessel disease should also be considered. Herein we present two patients with history of CABG whose symptoms were suspicious for coronary ischemia. During cardiac catheterization reverse blood flow was observed from the left artery disease to the left internal mammary artery (LIMA) graft in both cases. After angioplasty and stent implantation of the left subclavian artery antegrade flow was restored in the LIMA grafts and both patients had complete resolution of symptoms.

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.

Global, regional, and national disability-adjusted life years (DALYs) for 306 diseases and injuries and healthy life expectancy (HALE) for 188 countries, 1990-2013: quantifying the epidemiological transition

BACKGROUND

The Global Burden of Disease Study 2013 (GBD 2013) aims to bring together all available epidemiological data using a coherent measurement framework, standardised estimation methods, and transparent data sources to enable comparisons of health loss over time and across causes, age-sex groups, and countries. The GBD can be used to generate summary measures such as disability-adjusted life-years (DALYs) and healthy life expectancy (HALE) that make possible comparative assessments of broad epidemiological patterns across countries and time. These summary measures can also be used to quantify the component of variation in epidemiology that is related to sociodemographic development.

METHODS

We used the published GBD 2013 data for age-specific mortality, years of life lost due to premature mortality (YLLs), and years lived with disability (YLDs) to calculate DALYs and HALE for 1990, 1995, 2000, 2005, 2010, and 2013 for 188 countries. We calculated HALE using the Sullivan method; 95% uncertainty intervals (UIs) represent uncertainty in age-specific death rates and YLDs per person for each country, age, sex, and year. We estimated DALYs for 306 causes for each country as the sum of YLLs and YLDs; 95% UIs represent uncertainty in YLL and YLD rates. We quantified patterns of the epidemiological transition with a composite indicator of sociodemographic status, which we constructed from income per person, average years of schooling after age 15 years, and the total fertility rate and mean age of the population. We applied hierarchical regression to DALY rates by cause across countries to decompose variance related to the sociodemographic status variable, country, and time.

FINDINGS

Worldwide, from 1990 to 2013, life expectancy at birth rose by 6·2 years (95% UI 5·6-6·6), from 65·3 years (65·0-65·6) in 1990 to 71·5 years (71·0-71·9) in 2013, HALE at birth rose by 5·4 years (4·9-5·8), from 56·9 years (54·5-59·1) to 62·3 years (59·7-64·8), total DALYs fell by 3·6% (0·3-7·4), and age-standardised DALY rates per 100 000 people fell by 26·7% (24·6-29·1). For communicable, maternal, neonatal, and nutritional disorders, global DALY numbers, crude rates, and age-standardised rates have all declined between 1990 and 2013, whereas for non-communicable diseases, global DALYs have been increasing, DALY rates have remained nearly constant, and age-standardised DALY rates declined during the same period. From 2005 to 2013, the number of DALYs increased for most specific non-communicable diseases, including cardiovascular diseases and neoplasms, in addition to dengue, food-borne trematodes, and leishmaniasis; DALYs decreased for nearly all other causes. By 2013, the five leading causes of DALYs were ischaemic heart disease, lower respiratory infections, cerebrovascular disease, low back and neck pain, and road injuries. Sociodemographic status explained more than 50% of the variance between countries and over time for diarrhoea, lower respiratory infections, and other common infectious diseases; maternal disorders; neonatal disorders; nutritional deficiencies; other communicable, maternal, neonatal, and nutritional diseases; musculoskeletal disorders; and other non-communicable diseases. However, sociodemographic status explained less than 10% of the variance in DALY rates for cardiovascular diseases; chronic respiratory diseases; cirrhosis; diabetes, urogenital, blood, and endocrine diseases; unintentional injuries; and self-harm and interpersonal violence. Predictably, increased sociodemographic status was associated with a shift in burden from YLLs to YLDs, driven by declines in YLLs and increases in YLDs from musculoskeletal disorders, neurological disorders, and mental and substance use disorders. In most country-specific estimates, the increase in life expectancy was greater than that in HALE. Leading causes of DALYs are highly variable across countries.

INTERPRETATION

Global health is improving. Population growth and ageing have driven up numbers of DALYs, but crude rates have remained relatively constant, showing that progress in health does not mean fewer demands on health systems. The notion of an epidemiological transition--in which increasing sociodemographic status brings structured change in disease burden--is useful, but there is tremendous variation in burden of disease that is not associated with sociodemographic status. This further underscores the need for country-specific assessments of DALYs and HALE to appropriately inform health policy decisions and attendant actions.

FUNDING

Bill & Melinda Gates Foundation.

The genetic basis of peripheral arterial disease: current knowledge, challenges, and future directions

Several risk factors for atherosclerotic peripheral arterial disease (PAD), such as dyslipidemia, diabetes mellitus, and hypertension, are heritable. However, predisposition to PAD may be influenced by genetic variants acting independently of these risk factors. Identification of such genetic variants will provide insights into underlying pathophysiologic mechanisms and facilitate the development of novel diagnostic and therapeutic approaches. In contrast to coronary heart disease, relatively few genetic variants that influence susceptibility to PAD have been discovered. This may be, in part, because of greater clinical and genetic heterogeneity in PAD. In this review, we (1) provide an update on the current state of knowledge about the genetic basis of PAD, including results of family studies and candidate gene, linkage as well as genome-wide association studies; (2) highlight the challenges in investigating the genetic basis of PAD and possible strategies to overcome these challenges; and (3) discuss the potential of genome sequencing, RNA sequencing, differential gene expression, epigenetic profiling, and systems biology in increasing our understanding of the molecular genetics of PAD.