Developing current procedural terminology codes that describe the work performed by machines

The “Taxonomy of Artificial Intelligence for Medical Services and Procedures” became part of the Current Procedural Terminology (CPT®) code set effective January 1, 2022. It provides a framework for discrete and differentiable CPT codes which; are consistent with the features of the devices’ output, characterize interaction between the device and the physician or other qualified health care professional, and foster appropriate payment. Descriptors include “Assistive”, “Augmentative”, and “Autonomous”. As software increasingly augments the provision of medical services the taxonomy will foster consistent language in coding enabling patient, provider, and payer access to the benefits of innovation.

Plasma Gut Microbe-Derived Metabolites Associated with Peripheral Artery Disease and Major Adverse Cardiac Events

Cardiovascular diseases are associated with gut dysbiosis, but the role of microbe-derived metabolites as biomarkers or modulators of cardiovascular disease are not well understood. This is a targeted metabolomics study to investigate the association of nine microbe-derived metabolites with lower extremity peripheral artery disease (PAD), a form of atherosclerosis, and major adverse cardiac events (MACE). The study cohort consists of individuals with intermittent claudication and ankle-brachial index (ABI) < 0.9 (N = 119) and controls without clinically-apparent atherosclerosis (N = 37). The primary endpoint was MACE, a composite endpoint of myocardial infarction, coronary revascularization, stroke, transient ischemic attack, or cardiac-related death. Plasma metabolite concentrations differed significantly between the PAD and control groups. After adjustment for traditional atherosclerosis risk factors, kynurenine, hippuric acid, indole-3-propionic acid (IPA), and indole-3-aldehyde (I3A) concentrations were negatively associated with PAD, whereas indoxyl sulfate and 3-hydroxyanthranilic acid were positively associated. Hippuric acid, IPA, and I3A correlated with ABI, a surrogate for atherosclerotic disease burden. Those in the highest I3A concentration quartile had significantly improved freedom from MACE during follow-up compared to those in the lowest quartile. This study identifies specific indole- and phenyl-derived species impacted by gut microbial metabolic pathways that could represent novel microbiome-related biomarkers of PAD.

Foundational Considerations for Artificial Intelligence Using Ophthalmic Images

IMPORTANCE

The development of artificial intelligence (AI) and other machine diagnostic systems, also known as software as a medical device, and its recent introduction into clinical practice requires a deeply rooted foundation in bioethics for consideration by regulatory agencies and other stakeholders around the globe.

OBJECTIVES

To initiate a dialogue on the issues to consider when developing a bioethically sound foundation for AI in medicine, based on images of eye structures, for discussion with all stakeholders.

EVIDENCE REVIEW

The scope of the issues and summaries of the discussions under consideration by the Foundational Principles of Ophthalmic Imaging and Algorithmic Interpretation Working Group, as first presented during the Collaborative Community on Ophthalmic Imaging inaugural meeting on September 7, 2020, and afterward in the working group.

FINDINGS

Artificial intelligence has the potential to improve health care access and patient outcome fundamentally while decreasing disparities, lowering cost, and enhancing the care team. Nevertheless, substantial concerns exist. Bioethicists, AI algorithm experts, as well as the Food and Drug Administration and other regulatory agencies, industry, patient advocacy groups, clinicians and their professional societies, other provider groups, and payors (i.e., stakeholders) working together in collaborative communities to resolve the fundamental ethical issues of nonmaleficence, autonomy, and equity are essential to attain this potential. Resolution impacts all levels of the design, validation, and implementation of AI in medicine. Design, validation, and implementation of AI warrant meticulous attention.

CONCLUSIONS AND RELEVANCE

The development of a bioethically sound foundation may be possible if it is based in the fundamental ethical principles of nonmaleficence, autonomy, and equity for considerations for the design, validation, and implementation for AI systems. Achieving such a foundation will be helpful for continuing successful introduction into medicine before consideration by regulatory agencies. Important improvements in accessibility and quality of health care, decrease in health disparities, and lower cost thereby can be achieved. These considerations should be discussed with all stakeholders and expanded on as a useful initiation of this dialogue.

Depression Predicts Non-Home Discharge After Abdominal Aortic Aneurysm Repair

BACKGROUND

Mental health's impact on vascular surgical patients has long been overlooked. While outside the expertise of most surgeons, understanding the role that depression plays in the postoperative course could provide additional insight into opportunities to improve surgical outcomes and healthcare value. Additionally, non-home discharge (NHD) to a rehabilitation or skilled nursing facility after surgery is associated with impaired quality of life and higher postdischarge complications, readmissions, and mortality. We hypothesized that depression would be associated with an increased risk for NHD following abdominal aortic aneurysm (AAA) repair.

METHODS

Nonruptured AAA repair cases were identified from the National Inpatient Sample (NIS) using ICD-9 codes between 2005 and 2014. Depression, comorbidities, postoperative complications, and discharge destination were evaluated using statistical tests as appropriate to the data. A hierarchical multivariable logistic regression controlling for hospital level variation was used to examine the independent association between depression, and the primary outcome of NHD controlling for median income and confounders meeting P < 0.05 on univariate analysis.

RESULTS

There were 99,934 total cases analyzed, of which 4,755 (4.8%) were diagnosed with depression and 10,618 (11.9%) required NHD. Patients with depression were younger, more likely to be women, white, have diabetes, chronic obstructive pulmonary disease, hypertension, tobacco use, and more likely to experience a postoperative complication. On adjusted multivariable analysis, patients with depression were more likely to require NHD (odds ratio [OR] 1.87, 95% confidence interval [CI]: 1.68-2.08, c-statistic = 0.82). On stratified analysis by operative approach, depression had a larger effect estimate in endovascular repair (OR 2.19; 95% CI: 1.90-2.52) versus open repair (OR 1.60; 95% CI: 1.38-1.87).

CONCLUSIONS

In a nationally representative sample, patients with depression were more likely to require NHD after AAA repair. This study highlights the importance that depression plays in postoperative outcomes after AAA repair. Furthermore, addressing mental health preoperatively has the potential to improve outcomes in patients undergoing AAA repair.

Patients with depression are less likely to go home after critical limb revascularization

BACKGROUND

Although often overlooked during the preoperative evaluation, recent evidence has suggested that depression in patients with peripheral artery disease is associated with increased postoperative complications, including decreased primary and secondary patency after revascularization and an increased risk of major amputation and mortality. Postoperative nonhome discharge (NHD) is an important outcome for patients and has also been associated with other adverse outcomes; however, the effect that depression has on NHD after vascular surgery has remained unexplored. We hypothesized that depression would be associated with an increased risk of NHD after revascularization for chronic limb threatening ischemia (CLTI).

METHODS

Endovascular, open, and hybrid (combined open and endovascular) cases of revascularization for CLTI were identified from the 2012 to 2014 National (Nationwide) Inpatient Sample. CLTI, diagnoses of depression, and medical comorbidities were defined using the corresponding International Classification of Diseases, Ninth Revision, Clinical Modification codes. A hierarchical multivariable binary logistic regression controlling for hospital level variation and for confounders meeting P <.01 on bivariate analysis was used to examine the association between depression and NHD. A sensitivity analysis after coarsened exact matching for baseline characteristics that differed between the two groups was performed to reduce any imbalance.

RESULTS

A total of 64,817 cases were identified, of which 5472 (8.4%) included a diagnosis of depression and 16,524 (25.5%) NHD. The patients with depression were younger and more likely to be women and white, have multiple comorbidities and a nonelective admission, and experience a postoperative complication (P <.05). On unadjusted analyses, patients with depression had an 8% absolute increased risk of requiring NHD (32.1% vs 24.9%; P <.001). On multivariable analysis, patients with depression had an increased odds for NHD (odds ratio [OR], 1.50; 95% confidence interval [CI], 1.40-1.61; c-statistic, 0.81) compared with those without depression. After stratification by operative approach, depression had a larger effect estimate in endovascular revascularization (OR, 1.57; 95% CI, 1.42-1.74) compared with open (OR, 1.45; 95% CI, 1.30-1.62). A test for interaction between depression and gender identified that men with depression had greater odds of NHD compared with women with depression (OR, 1.68; 95% CI, 1.51-1.88; vs OR, 1.37; 95% CI, 1.25-1.51; interaction P <.01). A sensitivity analysis after coarsened exact matching confirmed these findings.

CONCLUSIONS

To the best of our knowledge, the present study is the first to identify an association between depression and NHD after revascularization for CLTI. These results provide further evidence of the negative effects that comorbid depression has on patients undergoing revascularization for CLTI. Future studies should examine whether treating depression can improve the outcomes in this patient population.

Treatment With a Marine Oil Supplement Alters Lipid Mediators and Leukocyte Phenotype in Healthy Patients and Those With Peripheral Artery Disease

Background

Peripheral artery disease (PAD) is an advanced form of atherosclerosis characterized by chronic inflammation. Resolution of inflammation is a highly coordinated process driven by specialized pro‐resolving lipid mediators endogenously derived from omega‐3 fatty acids. We investigated the impact of a short‐course, oral, enriched marine oil supplement on leukocyte phenotype and biochemical mediators in patients with symptomatic PAD and healthy volunteers.

Methods and Results

This was a prospective, open‐label study of 5‐day oral administration of an enriched marine oil supplement, assessing 3 escalating doses in 10 healthy volunteers and 10 patients with PAD. Over the course of the study, there was a significant increase in the plasma level of several lipid mediator families, total specialized pro‐resolving lipid mediators, and specialized pro‐resolving lipid mediator:prostaglandin ratio. Supplementation was associated with an increase in phagocytic activity of peripheral blood monocytes and neutrophils. Circulating monocyte phenotyping demonstrated reduced expression of multiple proinflammatory markers (cluster of differentiation 18, 163, 54, and 36, and chemokine receptor 2). Similarly, transcriptional profiling of monocyte‐derived macrophages displayed polarization toward a reparative phenotype postsupplementation. The most notable cellular and biochemical changes over the study occurred in patients with PAD. There were strong correlations between integrated biochemical measures of lipid mediators (specialized pro‐resolving lipid mediators:prostaglandin ratio) and phenotypic changes in circulating leukocytes in both healthy individuals and patients with PAD.

Conclusions

These data suggest that short‐term enriched marine oil supplementation dramatically remodels downstream lipid mediator pathways and induces a less inflammatory and more pro‐resolution phenotype in circulating leukocytes and monocyte‐derived macrophages. Further studies are required to determine the potential clinical relevance of these findings in patients with PAD.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02719665.

Association of comorbid depression with inpatient outcomes in critical limb ischemia

There is a growing body of evidence that peripheral artery disease (PAD) may be impacted by depression. The objective of this study is to determine whether outcomes, primarily major amputation, differ between patients with depression and those without who presented to hospitals with critical limb ischemia (CLI), the end-stage of PAD. A retrospective cohort of patients hospitalized for CLI during 2012 and 2013 was identified from the National Inpatient Sample (NIS) using ICD-9 codes. The primary outcome was major amputation and secondary outcomes were length of stay and other complications. The sample included 116,008 patients hospitalized for CLI, of whom 10,512 (9.1%) had comorbid depression. Patients with depression were younger (64 ± 14 vs 67 ± 14 years, p < 0.001) and more likely to be female (55% vs 41%, p < 0.001), white (73% vs 66%, p < 0.001), and tobacco users (46% vs 41%, p < 0.001). They were also more likely to have prior amputations (9.8% vs 7.9%, p < 0.001). During the hospitalization, the rate of major amputation was higher in patients with comorbid depression (11.5% vs 9.1%, p < 0.001). In multivariable analysis, excluding patients who died prior to/without receiving an amputation ( n = 2621), comorbid depression was associated with a 39% increased odds of major amputation (adjusted OR 1.39, 95% CI 1.30, 1.49; p < 0.001). Across the entire sample, comorbid depression was also independently associated with a slightly longer length of stay (β = 0.199, 95% CI 0.155, 0.244; p < 0.001). These results provide further evidence that depression is a variable of interest in PAD and surgical quality databases should include mental health variables to enable further study.

Predicting the effects of supplemental EPA and DHA on the omega-3 index

BACKGROUND

Supplemental long-chain omega-3 (n-3) fatty acids (EPA and DHA) raise erythrocyte EPA + DHA [omega-3 index (O3I)] concentrations, but the magnitude or variability of this effect is unclear.

OBJECTIVE

The purpose of this study was to model the effects of supplemental EPA + DHA on the O3I.

METHODS

Deidentified data from 1422 individuals from 14 published n-3 intervention trials were included. Variables considered included dose, baseline O3I, sex, age, weight, height, chemical form [ethyl ester (EE) compared with triglyceride (TG)], and duration of treatment. The O3I was measured by the same method in all included studies. Variables were selected by stepwise regression using the Bayesian information criterion.

RESULTS

Individuals supplemented with EPA + DHA (n = 846) took a mean ± SD of 1983 ± 1297 mg/d, and the placebo controls (n = 576) took none. The mean duration of supplementation was 13.6 ± 6.0 wk. The O3I increased from 4.9% ± 1.7% to 8.1% ± 2.7% in the supplemented individuals ( P < 0.0001). The final model included dose, baseline O3I, and chemical formulation type (EE or TG), and these explained 62% of the variance in response (P < 0.0001). The model predicted that the final O3I (and 95% CI) for a population like this, with a baseline concentration of 4.9%, given 850 mg/d of EPA + DHA EE would be ∼6.5% (95% CI: 6.3%, 6.7%). Gram for gram, TG-based supplements increased the O3I by about 1 percentage point more than EE products.

CONCLUSIONS

Of the factors tested, only baseline O3I, dose, and chemical formulation were significant predictors of O3I response to supplementation. The model developed here can be used by researchers to help estimate the O3I response to a given EPA + DHA dose and chemical form.

Peripheral Artery Disease Is Associated with a Deficiency of Erythrocyte Membrane n-3 Polyunsaturated Fatty Acids

Population-based data suggest that individuals who consume large dietary amounts of n-3 polyunsaturated fatty acids (PUFA) have lower odds of peripheral artery disease (PAD); however, clinical studies examining n-3 PUFA levels in patients with PAD are sparse. The objective of this study is to compare erythrocyte membrane fatty acid (FA) content between patients with PAD and controls. We conducted a cross-sectional study of 179 vascular surgery outpatients (controls, 34; PAD, 145). A blood sample was drawn and the erythrocyte FA content was assayed using capillary gas chromatography. We calculated the ratio of the n-3 PUFA eicosapentaenoic acid (EPA) to the n-6 PUFA arachidonic acid (ARA) as well as the omega-3 index (O3I), a measure of erythrocyte content of the n-3 PUFA, EPA, and docosahexaenoic acid (DHA), expressed as a percentage of total erythrocyte FA. Compared with controls, patients with PAD smoked more and were more likely to have hypertension and hyperlipidemia (p < 0.05). Patients with PAD had a lower mean O3I (5.0 ± 1.7% vs 6.0 ± 1.6%, p < 0.001) and EPA:ARA ratio (0.04 ± 0.02 vs 0.05 ± 0.05, p < 0.001), but greater mean total saturated fats (39.5 ± 2.5% vs 38.5 ± 2.6%, p = 0.01). After adjusting for several patient characteristics, comorbidities, and medications, an absolute decrease of 1% in the O3I was associated with 39% greater odds of PAD (odds ratio [OR] 1.39, 95% confidence interval [CI] 1.03-1.86, and p = 0.03). PAD was associated with a deficiency of erythrocyte n-3 PUFA, a lower EPA:ARA ratio, and greater mean total saturated fats. These alterations in FA content may be involved in the pathogenesis or development of poor outcomes in PAD.

Radial Artery Tonometry is Associated With Major Adverse Cardiac Events in Patients With Peripheral Artery Disease

BACKGROUND

Peripheral artery disease (PAD) is associated with increased arterial stiffness, as measured by an increasing radial artery augmentation index (AIX). However, it has not yet been clearly demonstrated whether AIX is associated with adverse cardiovascular outcomes in a PAD population.

MATERIALS AND METHODS

Seventy-two patients with PAD were recruited between 2011 and 2016. Radial artery applanation tonometry was performed at a baseline visit, and the central AIX, normalized to 75 beats/min, and the peripheral AIX were calculated using pulse wave analysis. Incident major adverse cardiac events (MACEs) were identified by subsequent chart review.

RESULTS

Study subjects had comorbidities commonly associated with PAD including a high prevalence of hypertension (93%), hyperlipidemia (85%), coronary artery disease (39%), and diabetes mellitus (39%). During a median follow-up period of 34 mo (interquartile range 29-38), 14 patients experienced a MACE. In a univariate Cox proportional hazards model, a 10-unit increase in the peripheral AIX was significantly associated with a 54% increased rate of MACE (hazard ratio [HR] 1.54, 95% confidence interval [CI] 1.06-2.22, P = 0.02), but central AIX, normalized to 75 beats/min, was not (HR 1.33, 95% CI 0.71-2.47, P = 0.37). In a multivariable model adjusted for coronary artery disease, age, and Rutherford category the peripheral AIX remained significantly associated with MACE (HR 1.70, 95% CI 1.10-2.62, P = 0.02).

CONCLUSIONS

Increased arterial stiffness, as measured by the peripheral AIX, was independently associated with an increased rate of MACE in patients with PAD. The use of radial artery tonometry should be contemplated as a tool for risk stratification in patients with PAD.

Fish Oil Increases Specialized Pro-resolving Lipid Mediators in PAD (The OMEGA-PAD II Trial)

BACKGROUND

N-3 polyunsaturated fatty acid (PUFA) supplementation has been associated with reduced mortality and inflammation in patients with cardiovascular disease. There are limited data on the effects of n-3 PUFA supplementation in patients with peripheral artery disease (PAD).

MATERIALS AND METHODS

The OMEGA-PAD II trial was a double-blinded, randomized, placebo-controlled trial to assess the effect of 3 mo of high-dose oral n-3 PUFA supplementation on inflammation, endothelial function, and walking ability in patients with PAD.

RESULTS

Twenty-four patients with claudication received 4.4 g/d of fish oil or placebo for 3 mo. Outcomes measured included high-sensitivity C-reactive protein levels, the omega-3 index, endothelial function as measured via flow-mediated vasodilation, walking impairment questionnaire, and a 6-min walk test. Plasma levels of specialized pro-resolving lipid mediators (SPMs) were measured by liquid-chromatography-tandem mass spectrometry. In patients treated with fish oil, the absolute mean omega-3 index significantly increased from baseline (fish oil: 7.2 ± 1.2%, P < 0.001; placebo: -0.4 ± 0.9%, P = 0.31; between-group P < 0.001). Furthermore, there were significant increases in several pathway markers of SPM biosynthesis, including several mono-hydroxyeicosapentaenoic acids and mono-hydroxydocosahexaenoic acids. We also observed significant increases in the SPM lipoxin A₅ (fish oil: 0.57 ± 0.70 pg/mL, P = 0.05; placebo: 0.01 ± 0.38 pg/mL, P = 0.93; between-group P = 0.04) and resolvin E3 (fish oil: 154 ± 171 pg/mL, P = 0.04; placebo: 32 ± 54 pg/mL, P = 0.08; between-group P = 0.04). There were no significant changes in high-sensitivity C-reactive protein, flow-mediated vasodilation, walking impairment questionnaire, or 6-min walk test in the fish oil group.

CONCLUSIONS

Fish oil increases SPMs in plasma of patients with PAD. Further studies are required to determine whether these early changes translate to clinical improvements in patients with PAD.

Leptinemia is Associated With Peripheral Artery Disease

BACKGROUND

Leptin, adiponectin, and resistin are in a class of hormones called adipokines that are produced by adipocytes and have been implicated in the causal pathway of atherosclerosis. We examined the association between adipokine levels and peripheral artery disease (PAD), hypothesizing that after adjusting for fat mass, leptin and resistin would be higher, whereas adiponectin would be lower, in patients with PAD.

METHODS

A cross-sectional sample of 179 predominately male (97%) vascular surgery outpatients was recruited from the San Francisco Veterans Affairs Medical Center (SFVAMC). PAD was defined as either an ankle-brachial index < 0.9 plus symptoms of claudication or prior revascularization for symptomatic PAD (n = 141). Controls had an ankle-brachial index ≥0.9 and no history of atherosclerotic disease (n = 38). Adipokines were assayed using commercially available ELISA kits and values were log-transformed. Fat mass was measured using bioelectrical impedance.

RESULTS

In an analysis adjusting for body mass index (BMI) and atherosclerotic risk factors, higher serum leptin was associated with PAD (OR 2.54, 95% CI 1.07-6.01, P = 0.03), whereas high molecular weight adiponectin was inversely associated, though not significantly (OR 0.60, 95% CI 0.33-1.08, P = 0.09). Resistin was not associated with PAD. Sensitivity analyses using fat mass/height² rather than BMI yielded similar results.

CONCLUSIONS

These results indicate that after adjusting for BMI or fat mass, serum leptin levels are positively and independently associated with PAD, whereas high molecular weight adiponectin might be inversely associated. Using a more representative, nonveteran sample, further investigations should focus on the potential role of adipokines in the pathophysiology of PAD as well as determine whether leptin levels have clinical utility in predicting PAD outcomes.

Serum resistin is associated with impaired endothelial function and a higher rate of adverse cardiac events in patients with peripheral artery disease

OBJECTIVE

Resistin is a hormone that has been associated with metabolic syndrome and cardiovascular disease. The role of resistin in patients with peripheral artery disease (PAD) has not been fully explored. This study seeks to understand the relationship between serum resistin, vascular function, and cardiovascular outcomes in patients with PAD.

METHODS

There were 106 patients with PAD who were recruited between 2011 and 2016. Patients attended a baseline visit during which a comprehensive vascular physiology assessment including medical and surgical history, radial artery tonometry, and flow mediated-vasodilation (FMD) was completed. A blood sample was drawn, and serum resistin was assayed using enzyme-linked immunosorbent assay kits. Using the time of study enrollment as the time of origin, incident major adverse cardiac events (MACEs) were identified by subsequent chart review and defined as a composite end point of myocardial infarction, coronary revascularization, transient ischemic attack, stroke, or death from a cardiac cause.

RESULTS

Patients had a mean age of 68 ± 8 years, were largely white (75%), and had comorbidities commonly associated with PAD including hypertension (92%), hyperlipidemia (87%), coronary artery disease (37%), and diabetes mellitus (38%). After stratification by resistin quartile, higher resistin quartiles were significantly associated with an older age, a greater number of pack-years smoked, and a lower estimated glomerular filtration rate. Despite similar comorbidities and medication use, endothelial function, as measured by FMD, was significantly lower with increasing resistin quartile (I, 9.1% ± 3.3%; II, 7.1% ± 3.5%; III, 5.8% ± 4.0%; IV, 5.6% ± 3.5%; P = .002). In multivariable linear regression, higher resistin quartiles (III and IV) were associated with lower FMD relative to quartile I after adjusting for several patient characteristics, medications, and comorbidities (III, -2.26 [95% confidence interval (CI), -4.51 to -0.01; P = .05]; IV, -2.53 [95% CI, -4.87 to -0.20; P = .03]). During a median follow-up period of 36 months (interquartile range, 29-45 months), 21 patients experienced the primary end point. In a Cox proportional hazards model adjusted for smoking status, coronary artery disease, and age, each 1 ng/mL increase in resistin was associated with a 10% increased risk of MACEs (hazard ratio, 1.10; 95% CI, 1.00-1.20; P = .04).

CONCLUSIONS

In patients with PAD, higher levels of resistin were associated with impaired endothelial function and an increased rate of MACEs. These results suggest that resistin may be a marker or effector of impaired vascular physiology and adverse cardiac outcomes in patients with PAD. Further research is needed to determine the potential mechanisms by which resistin may impair endothelial function and increase MACEs in this population.

The association of comorbid depression with mortality and amputation in veterans with peripheral artery disease

OBJECTIVE

Peripheral artery disease (PAD) is an increasing health concern with rising incidence globally. Previous studies have shown an association between PAD incidence and depression. The objective of the study was to determine the association of comorbid depression with PAD outcomes (amputation and all-cause mortality rates) in veterans.

METHODS

An observational retrospective cohort of 155,647 patients with incident PAD (2003-2014) from nationwide U.S. Veterans Health Administration hospitals was conducted using the national Veterans Affairs Corporate Data Warehouse. Depression was measured using concurrent International Classification of Diseases, Ninth Revision diagnosis codes 6 months before or after PAD diagnosis. The main outcomes were incident major amputation and all-cause mortality. Crude associations were assessed with Kaplan-Meier plots. The effects of depression adjusted for covariates were analyzed using Cox proportional hazards models.

RESULTS

Depression was present in 16% of the cohort, with the occurrence of 9517 amputations and 63,287 deaths (median follow-up, 5.9 years). Unadjusted hazard ratios (HRs) of comorbid depression for amputations and all-cause mortality were 1.32 (95% confidence interval [CI], 1.25-1.39) and 1.02 (95% CI, 0.99-1.04), respectively. After adjustment for covariates in Cox regression models, a diagnosis of comorbid depression at the time of PAD diagnosis was associated with a 13% higher amputation (HR, 1.13; 95% CI, 1.07-1.19) and 17% higher mortality (HR, 1.17; 95% CI, 1.14-1.20) risk compared with patients with no depression. On stratification by use of antidepressants, depressed patients not taking antidepressants had a 42% higher risk of amputation (HR, 1.42; 95% CI, 1.27-1.58) compared with those without depression. Patients taking antidepressants for depression still had increased risk of amputation but only 10% higher compared with those without depression (HR, 1.10; 95% CI, 1.03-1.17). Interestingly, patients taking antidepressants for other indications also had a higher risk of amputation compared with those not having depression or not taking antidepressants (HR, 1.08; 95% CI, 1.03-1.14). Having any diagnosis of depression or the need for antidepressants increased the mortality risk by 18% to 25% in the PAD cohort compared with those without depression and not taking antidepressants for any other indication.

CONCLUSIONS

PAD patients with comorbid depression have a significantly higher risk of amputation and mortality than PAD patients without depression. Furthermore, untreated depression was associated with an increased amputation risk in the PAD population, more so than depression or other mental illness being treated by antidepressants. The underlying mechanisms for causality, if any, remain to be determined. The association of antidepressant treatment use with amputation risk should prompt further investigations into possible mechanistic links between untreated depression and vascular dysfunction.

Depression severity is associated with increased inflammation in veterans with peripheral artery disease

The present study examines the association between depressive symptoms and inflammatory markers in peripheral artery disease (PAD) to better understand the mechanistic relationship between depression and PAD. A cross-sectional sample of 117 patients with PAD (97% male, 76% Caucasian) was recruited from the San Francisco Veterans Affairs Medical Center. Patients were categorized into three subgroups based upon current depressive symptom severity, as defined by Patient Health Questionnaire-8 scores: no symptoms (score of 0-4, n = 62), mild symptoms (score of 5-9, n = 33), and moderate/severe symptoms (score ≥ 10, n = 22). Serum levels of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), soluble intercellular adhesion molecule-1 (ICAM-1), and tumor necrosis factor-alpha (TNF-α) were assayed and log-transformed for multivariable analysis. To decrease the possibility of Type 1 errors, inflammatory markers were standardized and summed to create a total inflammatory score. In a multivariable analysis controlling for demographics, PAD severity, and atherosclerotic risk factors, mild and moderate/severe depressive symptoms were predictive of a higher total inflammatory score when compared to the group with no symptoms (mild symptoms p = 0.04, moderate/severe symptoms p = 0.007). Exploratory multivariable analyses of individual inflammatory markers found IL-6 levels were significantly higher in the moderate/severe symptoms group ( p = 0.006) than in the no symptoms group. Moreover, hs-CRP and ICAM-1 trended upwards with increasing depression severity. TNF-α was not associated with depression severity. We conclude that depressive symptom severity was independently associated with greater inflammation in PAD. Future research should examine the strength and directionality of this association through larger prospective cohort studies, as well as investigate the pathophysiological mechanisms responsible.

Review of biologic and behavioral risk factors linking depression and peripheral artery disease

The incidence of depression has been rising rapidly, and depression has been recognized as one of the world’s leading causes of disability. More recently, depression has been associated with an increased risk of symptomatic atherosclerotic disease as well as worse perioperative outcomes in patients with cardiovascular disease. Additionally, recent studies have demonstrated an association between depression and peripheral artery disease (PAD), which has been estimated to affect more than 200 million people worldwide. These studies have identified that depression is associated with poor functional and surgical outcomes in patients with PAD. Although the directionality and specific mechanisms underlying this association have yet to be clearly defined, several biologic and behavioral risk factors have been identified to play a role in this relationship. These factors include tobacco use, physical inactivity, medical non-adherence, endothelial and coagulation dysfunction, and dysregulation of the hypothalamic-pituitary-adrenal axis, autonomic system, and immune system. In this article, we review these potential mechanisms and the current evidence linking depression and PAD, as well as future directions for research and interventional strategies. Understanding and elucidating this relationship may assist in preventing the development of PAD and may improve the care that patients with PAD and comorbid depression receive.

Frailty Is Associated with an Increased Risk of Major Adverse Cardiac Events in Patients with Stable Claudication

BACKGROUND

Frailty, a syndrome characterized by decreased physiologic reserves and resistance to stressors, is associated with disability, poor surgical outcomes, and mortality. We evaluated the impact of frailty on cardiovascular disease (CVD) events in peripheral arterial disease (PAD) patients with intermittent claudication.

METHODS

We conducted a retrospective review of patients with stable intermittent claudication enrolled in the OMEGA-PAD study between 2010 and 2015. The modified frailty index (mFI) is a retrospectively validated index of frailty derived from the Canadian Study of Health and Aging and was used in this study to categorize frailty as low, medium, or high. Our outcome was time to occurrence of a major adverse cardiac event (MACE), defined as a composite endpoint of myocardial infarction, coronary revascularization, stroke, or CVD-related death. Cox proportional hazards models were used to calculate relative hazards ratio.

RESULTS

There were 129 subjects with a mean age of 67 years, 97% were men, 36% were diabetic, and 33% had known coronary heart disease. When the mFI criteria were applied, 38 subjects were "low" frailty, 72 were "medium" frailty, and 19 were "high" frailty. During the median follow-up period of 34 months (interquartile range: 25-43), 29 subjects experienced a MACE. When compared to the lowest mFI, patients with medium frailty were 2.8 times more likely to have an event (95% confidence interval [CI]: 0.95-8.46, P = 0.06), whereas patients with a high mFI were 4.8 times as likely (95% CI: 1.43-15.8, P = 0.01). In a model adjusted for age, smoking status, and presence of diabetes, those with a medium mFI were 4.3 times more likely to have an event (95% CI: 1.37-13.7, P = 0.01) and those with a high mFI were 9.2 times as likely (95% CI: 2.6-32.4, P = 0.001).

CONCLUSIONS

Higher mFI category is associated with a significantly increased risk of MACE in PAD patients with stable claudication. Frailty may serve as a useful adjunct for assessment of overall cardiac risk, particularly as treatment options are being contemplated.

Characterizing the relationship between flow-mediated vasodilation and radial artery tonometry in peripheral artery disease

BACKGROUND

Arterial stiffness, measured by the augmentation index (AIX) from radial artery tonometry, and endothelial dysfunction, measured by brachial-artery flow-mediated vasodilation (FMD), have each been associated with increased risk of cardiovascular events. However, their interrelationship in peripheral artery disease (PAD) patients is poorly understood.

MATERIALS AND METHODS

In a cross-sectional analysis of 123 vascular surgery outpatients, the association between FMD and AIX was examined in controls with atherosclerotic risk factors (n = 32) and patients with PAD (n = 91). PAD was defined as claudication symptoms with an ankle-brachial index of <0.9 or a history of revascularization for symptomatic PAD. Controls had an ankle-brachial index ≥0.9 and no history of atherosclerotic vascular disease.

RESULTS

Compared to controls, patients with PAD had lower FMD (6.3 ± 3.8 versus 8.4 ± 3.7, P = 0.008), while central AIX normalized to 75 beats per minute (25.5 ± 9.0 versus 19.3 ± 8.6, P = 0.001) and peripheral AIX (91.3 ± 14.5 versus 81.3 ± 11.4, P = 0.001) were higher. FMD was not significantly correlated with either central or peripheral AIX (central AIX: P = 0.58; peripheral AIX: P = 0.89) across the entire cohort, or in either the patients with PAD (central AIX: P = 0.48; peripheral AIX: P = 0.23) or controls (central AIX: P = 0.43; peripheral AIX: P = 0.92). In a multivariate model including FMD, higher AIX remained independently associated with PAD.

CONCLUSIONS

In an analysis of vascular surgery outpatients, no correlation between FMD and AIX was detected. Larger prospective studies are needed to determine whether the inclusion of both parameters improves predictive models for the early identification and potential risk stratification of PAD patients.

Increased circulating blood cell counts in combat-related PTSD: Associations with inflammation and PTSD severity

Inflammation is reported in post-traumatic stress disorder (PTSD). Few studies have investigated circulating blood cells that may contribute to inflammation. We assessed circulating platelets, white blood cells (WBC) and red blood cells (RBC) in PTSD and assessed their relationship to inflammation and symptom severity. One-hundred and sixty-three male combat-exposed veterans (82 PTSD, 81 non-PTSD) had blood assessed for platelets, WBC, and RBC. Data were correlated with symptom severity and inflammation. All cell counts were significantly elevated in PTSD. There were small mediation effects of BMI and smoking on these relationships. After adjusting for these, the differences in WBC and RBC remained significant, while platelet count was at trend level. In all subjects, all of the cell counts correlated significantly with inflammation. Platelet count correlated with inflammation only in the PTSD subjects. Platelet count, but none of the other cell counts, was directly correlated with PTSD severity ratings in the PTSD group. Combat PTSD is associated with elevations in RBC, WBC, and platelets. Dysregulation of all three major lineages of hematopoietic cells in PTSD, as well as their significant correlation with inflammation, suggest clinical significance of these changes.

Association between arterial stiffness and peripheral artery disease as measured by radial artery tonometry

OBJECTIVE

Arterial stiffness and peripheral artery disease (PAD) are both associated with an elevated risk of major adverse cardiac events; however, the association between arterial stiffness and PAD is less well characterized. The goal of this study was to examine the association between parameters of radial artery tonometry, a noninvasive measure of arterial stiffness, and PAD.

METHODS

We conducted a cross-sectional study of 134 vascular surgery outpatients (controls, 33; PAD, 101) using arterial applanation tonometry. Central augmentation index (AIX) normalized to 75 beats/min and peripheral AIX were measured using radial artery pulse wave analysis. Pulse wave velocity was recorded at the carotid and femoral arteries. PAD was defined as symptomatic claudication with an ankle-brachial index of <0.9 or a history of peripheral revascularization. Controls had no history of atherosclerotic vascular disease and an ankle-brachial index ≥0.9.

RESULTS

Among the 126 participants with high-quality tonometry data, compared with controls (n = 33), patients with PAD (n = 93) were older, with higher rates of hypertension, hyperlipidemia, diabetes, and smoking (P < .05). Patients with PAD also had greater arterial stiffness as measured by central AIX, peripheral AIX, and pulse wave velocity (P < .05). In a multivariable model, a significantly increased odds of PAD was associated with each 10-unit increase in central AIX (odds ratio, 2.1; 95% confidence interval, 1.1-3.9; P = .03) and peripheral AIX (odds ratio, 1.9; 95% confidence interval, 1.2-3.2; P = .01). In addition, central and peripheral AIX were highly correlated (r₁₂₀ = 0.76; P < .001).

CONCLUSIONS

In a cross-sectional analysis, arterial stiffness as measured by the AIX is independently associated with PAD, even when adjusting for several atherosclerotic risk factors. Further prospective data are needed to establish whether radial artery tonometry could be a tool for risk stratification in the PAD population.

Relationship between the omega-3 index and specialized pro-resolving lipid mediators in patients with peripheral arterial disease taking fish oil supplements

BACKGROUND

Oral supplementation with n-3 polyunsaturated fatty acids (PUFA) increases the omega-3 index, a biomarker of red blood cell eicosapentaenoic acid and docosahexaenoic acid, and plasma levels of biosynthesis pathway markers and potent lipid mediators involved in the resolution of inflammation among patients with peripheral arterial disease (PAD).

OBJECTIVE

We aimed to quantify the association between an upstream change in the omega-3 index and downstream changes in lipid mediator production.

METHODS

We conducted a secondary analysis of the OMEGA-PAD I Trial, a randomized, placebo controlled trial investigating high-dose n-3 PUFA oral supplementation in PAD patients. Eighty subjects were randomized to either 4.4 g of fish oil or placebo for 1 month. Regression analyses using generalized estimating equation techniques were used to investigate the relationship between changes in the omega-3 index and changes in lipid mediators, pre- and post-intervention.

RESULTS

In the fish oil group, there was a significant increase in the omega-3 index (5 ± 1% to 9 ± 2%, P < .001) as well as in the plasma levels of several downstream lipid mediator pathway markers of resolution, which are involved with the regulation of leukocyte effector function and host defense. A doubling of the omega-3 index correlated with increases of 2.3-fold in 18-hydroxy-eicosapentaenoic acid (HEPE; P < .0001), 1.7-fold in 15-HEPE (P = .03), 1.9-fold in 5-HEPE (P = .04), and 3.6-fold in 4-hydroxy-docosahexaenoic acid (P < .001).

CONCLUSION

Among subjects with symptomatic PAD who took oral fish oil supplements for 1 month, observed changes in the omega-3 index were strongly associated with increases in downstream mediators in the biochemical pathways of resolution.

Abstract 20: Resolution Phenotype of Monocytes and Macrophages is Altered in Peripheral Arterial Disease

Introduction: Peripheral arterial disease (PAD) is a chronic disease characterized by systemic inflammation. Monocytes (Mo) and macrophages play a central role in vascular inflammation and its resolution. We hypothesize that impaired resolution in PAD results in poor clinical outcomes.

Methods: Resolution phenotype was assessed by phagocytic activity of leukocytes, Mo cell surface markers, and cytokine profiling of Mo-derived macrophages (MDM). Phagocytosis and cell-surface markers were determined by flow cytometry. MDMs were generated from peripheral blood mononuclear cells via density gradient centrifugation. Cytokines were measured by ELISA following MDM differentiation and subsequent stimulation with LPS.

Results: Circulating Mo and neutrophils (PMN) isolated from PAD patients (n=9) demonstrated significantly lower phagocytic activity (Mo: >30%, p<.001; PMN: >25%, p<.01, Fig. 1) as compared to healthy subjects (HS) (n=14). Cell-surface marker analysis demonstrated a higher proportion of the pro-inflammatory intermediate Mo subset (CD14 ++ 16 + , 1.8-fold, p=.04) in PAD compared to HS. MDM from PAD subjects retain their intrinsic inflammatory program by producing more IL-6 (PAD 3138±2676 ng/mL, HS 731±854 ng/mL p=.03) and IL-1β (PAD 244±236 ng/mL, HS 24.1±23.8 ng/mL p=.04) than those from HS. Upon stimulation with LPS, MDM from PAD subjects secrete more IL-6 (PAD 23353±22483 ng/mL, HS 5097±5836 ng/mL p=.05) than those from HS.

Conclusions: Circulating Mo and PMN in patients with PAD have substantially lower phagocytic activity as well as a greater proportion of the pro-inflammatory intermediate Mo subset compared to HS. MDM preserve their elevated inflammatory state throughout culture and retain a heightened response upon latter stimulatory cues. Collectively these data demonstrate a heightened inflammatory and impaired resolution phenotype in PAD that has potential implications for disease progression and response to interventions.

Chronic stress is associated with reduced circulating hematopoietic progenitor cell number: A maternal caregiving model

BACKGROUND

Chronic psychological stress is a risk factor for cardiovascular disease and mortality. Circulating hematopoietic progenitor cells (CPCs) maintain vascular homeostasis, correlate with preclinical atherosclerosis, and prospectively predict cardiovascular events. We hypothesize that (1) chronic caregiving stress is related to reduced CPC number, and (2) this may be explained in part by negative interactions within the family.

METHODS

We investigated levels of stress and CPCs in 68 healthy mothers - 31 of these had children with an autism spectrum disorder (M-ASD) and 37 had neurotypical children (M-NT). Participants provided fasting blood samples, and CD45⁺CD34⁺KDR⁺ and CD45⁺CD133⁺KDR⁺ CPCs were assayed by flow cytometry. We averaged the blom-transformed scores of both CPCs to create one index. Participants completed the perceived stress scale (PSS), the inventory for depressive symptoms (IDS), and reported on daily interactions with their children and partners, averaged over 7 nights.

RESULTS

M-ASD exhibited lower CPCs than M-NT (Cohen's d=0.83; p⩽0.01), controlling for age, BMI, and physical activity. Across the whole sample, positive interactions were related to higher CPCs, and negative interactions to lower CPCs (allp's<0.05). The adverse effects of group on CPCs were significantly mediated through negative interactions with the child (indirect β=-0.24, p⩽0.01). In the full model, greater age (β=-0.19, p=0.04), BMI (β=-0.18, p=0.04), and negative interactions with the child (β=-0.33, p<0.01) were independently associated with lower CPCs. M-ASD had a less healthy lipid profile (total cholesterol/HDL), which in turn, was associated with lower CPCs.

CONCLUSIONS

Chronic stress adversely impacts CPC number, an early-stage biomarker that predicts subclinical atherosclerosis and future CVD events, independent of traditional cardiovascular risk factors and inflammatory factors. Among maternal caregivers, child-related interpersonal stress appears to be a key psychological predictor of stress-related CVD risk.

Increased pro-inflammatory milieu in combat related PTSD - A new cohort replication study

INTRODUCTION

Several lines of evidence indicate that increased inflammation is associated with Post-Traumatic Stress Disorder (PTSD). We have previously reported that peripheral inflammatory markers are significantly higher in combat-exposed veterans with than without PTSD. This study was designed to replicate these findings in a new study cohort using the same population and recruitment strategies.

METHODS

Sixty-one male war veterans (31 PTSD and 30 control subjects) were included in this replication study. Levels of Interleukin-6, Tumor Necrosis Factor-alpha, Gamma interferon, and high-sensitivity C-reactive protein were quantified in blood samples. A standardized "total pro-inflammatory score" was calculated to limit the number of statistical comparisons. The Clinician Administered PTSD Scale (CAPS) rating scale was used to assess PTSD symptom severity.

RESULTS

PTSD subjects had significantly higher total pro-inflammatory scores compared to non-PTSD subjects in unadjusted analysis (Cohen's d=0.75, p=0.005) as well as after adjusting for potentially confounding effects of age, BMI, smoking, and potentially interfering medications and somatic co-morbidities (p=0.023). There were no significant correlations between inflammatory markers and severity of symptoms within the PTSD group.

CONCLUSIONS

We replicated, in a new sample, our previous finding of increased inflammatory markers in combat-exposed PTSD subjects compared to combat-exposed non-PTSD controls. These findings strongly add to the growing literature suggesting that immune activation may be an important aspect of PTSD pathophysiology, although not directly correlated with current PTSD symptom levels in the PTSD group.

Predictors of change in omega-3 index with fish oil supplementation in peripheral artery disease

BACKGROUND

The omega-3 index represents the red blood cell (RBC) content of two major long-chain n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid, and docosahexaenoic acid. We sought to determine factors associated with a favorable response to fish oil treatment and to characterize changes in RBC PUFAs associated with fish oil supplementation.

METHODS

This study was a secondary analysis of the OMEGA-PAD I trial, a randomized, double-blinded, placebo-controlled trial investigating short-duration, high-dose n-3 PUFA oral supplementation on endothelial function and inflammation in subjects with peripheral arterial disease. Patients with mild to severe claudication received either 4.4 g of fish oil providing 2.6 g of eicosapentaenoic acid and 1.8 g of docosahexaenoic acid daily (n = 40) or placebo capsules (n = 40) for 1 mo. The RBC fatty acid content was measured by gas chromatography and expressed as a percent of total fatty acids. The change in omega-3 index was calculated as the difference between pre- and post-supplementation in the fish oil and placebo groups. Univariate analysis identified predictors of change in omega-3 index, with these variables included in our multivariable model.

RESULTS

In the fish oil group, there was an increase in the omega-3 index (5.1± 1.3% to 9.0± 1.8%; P < 0.0001), whereas there was no change in the control group. Factors associated with a favorable response (i.e., greater than the median change of 4.06%) included a lower body mass index and higher concentrations of low-density lipoproteins. Other demographic and/or lifestyle factors such as age, race, or smoking status were unrelated to the response. Oral n-3 PUFA supplementation also decreased the n-6 PUFA content in RBCs.

CONCLUSIONS

Short-term, high-dose n-3 PUFA supplementation increases the omega-3 index to a greater extent in patients with a lower body mass index and higher total and low-density lipoprotein cholesterol levels.

Posttraumatic Stress Disorder Is Associated With Worse Endothelial Function Among Veterans

Background

Current research in behavioral cardiology reveals a significant association between posttraumatic stress disorder (PTSD) and increased risk for cardiovascular disease and mortality; however, the underlying mechanisms remain poorly understood. We hypothesized that patients with PTSD would exhibit endothelial dysfunction, a potential mechanism involved in the development and progression of cardiovascular disease.

Methods and Results

A total of 214 outpatients treated at the San Francisco Veterans Affairs Medical Center underwent tests of endothelial function and evaluation for PTSD. Flow‐mediated vasodilation of the brachial artery was performed to assess endothelial function, and current PTSD status was defined by the PTSD Checklist, based on the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition), with a score ≥40. Multivariable linear regression models were used to estimate the association between PTSD status and endothelial function. Patients with PTSD (n=67) were more likely to be male (99% versus 91%, P=0.04) and to have depression (58% versus 8%, P<0.0001) and were less likely to be on an angiotensin‐converting enzyme inhibitor (17% versus 36%, P=0.007) or β‐blocker treatment (25% versus 41%, P=0.03). Univariate analysis demonstrated that patients with PTSD had significantly lower flow‐mediated vasodilation (5.8±3.4% versus 7.5±3.7%; P=0.003); furthermore, lower flow‐mediated vasodilation was associated with increasing age (P=0.008), decreasing estimated glomerular filtration rate (P=0.003), hypertension (P=0.002), aspirin (P=0.03), and β‐blocker treatments (P=0.01). In multivariable analysis, PTSD remained independently associated with lower flow‐mediated vasodilation (P=0.0005).

Conclusions

After adjusting for demographic, comorbidity, and treatment characteristics, PTSD remained associated with worse endothelial function in an outpatient population. Whether poor endothelial function contributes to the higher risk of cardiovascular disease in patients with PTSD deserves further study.

Short-Term, High-Dose Fish Oil Supplementation Increases the Production of Omega-3 Fatty Acid-Derived Mediators in Patients With Peripheral Artery Disease (the OMEGA-PAD I Trial)

Background

Patients with peripheral artery disease (PAD) experience significant morbidity and mortality. The OMEGA-PAD I Trial, a randomized, double-blinded, placebo-controlled trial, addressed the hypothesis that short-duration, high-dose n-3 polyunsaturated fatty acids (n-3 PUFA) oral supplementation improves endothelial function and inflammation in PAD.

Methods and Results

Eighty patients with stable claudication received 4.4 g of fish oil or placebo for 1 month. The primary end point was endothelial function as measured by brachial artery flow-mediated vasodilation. Secondary end points included biomarkers of inflammation, n-3 polyunsaturated fatty acids metabolome changes, lipid profile, and walking impairment questionnaires. Although there was a significant increase in FMD in the fish oil group following treatment (0.7±1.8% increase from baseline, P=0.04), this response was not different then the placebo group (0.6±2.5% increase from baseline, P=0.18; between-group P=0.86) leading to a negative finding for the primary endpoint. There was, however, a significant reduction in triglycerides (fish oil: −34±46 mg/dL, P<0.001; placebo −10±43 mg/dL, P=0.20; between-group differential P-value: 0.02), and an increase in the omega-3 index of 4±1% (P<0.001) in the fish oil group (placebo 0.1±0.9%, P=0.49; between-group P<0.0001). We observed a significant increase in the production of pathway markers of specialized pro-resolving mediators generated from n-3 polyunsaturated fatty acids in the fish oil group.

Conclusions

High-dose, short-duration fish oil supplementation did not lead to a different response in the primary end point of endothelial function between the treatment and placebo group, but improved serum triglycerides and increased the production of downstream n-3 polyunsaturated fatty acids–derived products and mediators in patients with PAD.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique identifier: NCT01310270.

Analysis of nutritional habits and intake of polyunsaturated fatty acids in veterans with peripheral arterial disease

Inadequate nutrient intake may contribute to the development and progression of peripheral arterial disease (PAD). This study’s aim was to assess intake of essential fatty acids and nutrients among veterans with PAD. All 88 subjects had ankle–brachial indices of <0.9 and claudication. A validated food frequency questionnaire evaluated dietary intake, and values were compared to guidelines established by the American Heart Association (AHA) and American College of Cardiology (ACC), as well as the AHA/ACC endorsed Dietary Approaches to Stop Hypertension (DASH) eating plan. The mean age was 69 ± 8 years. Compared to the AHA/ACC guidelines, subjects with PAD had an inadequate intake of long-chain polyunsaturated fatty acids ( n-3 PUFA; 59% consumed >1 gram daily). Our subjects with PAD had an increased intake of cholesterol (31% met the cut-off established in the DASH plan), total fat (5%) and sodium (53%). They had an inadequate intake of magnesium (3%), calcium (5%), and soluble fiber (3%). Dietary potassium intake met the recommended guidelines. In our subjects with PAD, intake of critical nutrients deviated substantially from the recommended amounts. Further prospective studies should evaluate whether PAD patients experience clinical benefit if diets are modified to meet the AHA/ACC recommendations.

Spaceflight impairs antigen-specific tolerance induction in vivo and increases inflammatory cytokines

The health risks of a dysregulated immune response during spaceflight are important to understand as plans emerge for humans to embark on long-term space travel to Mars. In this first-of-its-kind study, we used adoptive transfer of T-cell receptor transgenic OT-II CD4 T cells to track an in vivo antigen-specific immune response that was induced during the course of spaceflight. Experimental mice destined for spaceflight and mice that remained on the ground received transferred OT-II cells and cognate peptide stimulation with ovalbumin (OVA) 323-339 plus the inflammatory adjuvant, monophosphoryl lipid A. Control mice in both flight and ground cohorts received monophosphoryl lipid A alone without additional OVA stimulation. Numbers of OT-II cells in flight mice treated with OVA were significantly increased by 2-fold compared with ground mice treated with OVA, suggesting that tolerance induction was impaired by spaceflight. Production of proinflammatory cytokines were significantly increased in flight compared with ground mice, including a 5-fold increase in IFN-γ and a 10-fold increase in IL-17. This study is the first to show that immune tolerance may be impaired in spaceflight, leading to excessive inflammatory responses.

Advancing beyond the "heart-healthy diet" for peripheral arterial disease

OBJECTIVE

Peripheral arterial disease (PAD) is a burdensome cardiovascular condition that results from chronic inflammatory insults to the arterial vasculature. Key risk factors include age, gender, type 2 diabetes mellitus, hypertension, hypercholesterolemia, hyperhomocysteinemia, smoking, lack of physical fitness, and poor diet, the latter three being modifiable in the development and progression of PAD. A growing body of evidence indicates that imbalanced nutrient intake may contribute to the development and progression of PAD. The purpose of this review is to summarize current knowledge about nutritional patterns among patients with PAD and to ascertain whether certain health-promoting foods and nutrients could benefit patients with this condition.

METHODS

We conducted a comprehensive literature review to examine primary source evidence for or against the nutrients that are commonly associated with PAD and their potential utility as therapies.

RESULTS

We summarized nine categories of nutrients, as well as four diets endorsed by the American Heart Association that may be prescribed to patients with or at risk for PAD. The nutrients reviewed included omega-3 polyunsaturated fatty acids (n-3 PUFAs), folate and B-series vitamins, and antioxidants. The diet plans described include the Dietary Approaches to Stop Hypertension (DASH) diet, Mediterranean diet, low-fat diet, low carbohydrate diet, Dr Dean Ornish's Spectrum Diet and Dr Andrew Weil's Anti-Inflammatory Diet.

CONCLUSIONS

PAD is a chronic inflammatory condition that is associated with longstanding poor nutrition habits. We advocate for an intensified use of diet in PAD therapy, and we specifically recommend following eating patterns that are rich in nutrients with anti-inflammatory and antioxidant properties.

Ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery in clinical research

The vascular endothelium is a monolayer of cells that cover the interior of blood vessels and provide both structural and functional roles. The endothelium acts as a barrier, preventing leukocyte adhesion and aggregation, as well as controlling permeability to plasma components. Functionally, the endothelium affects vessel tone. Endothelial dysfunction is an imbalance between the chemical species which regulate vessel tone, thombroresistance, cellular proliferation and mitosis. It is the first step in atherosclerosis and is associated with coronary artery disease, peripheral artery disease, heart failure, hypertension, and hyperlipidemia. The first demonstration of endothelial dysfunction involved direct infusion of acetylcholine and quantitative coronary angiography. Acetylcholine binds to muscarinic receptors on the endothelial cell surface, leading to an increase of intracellular calcium and increased nitric oxide (NO) production. In subjects with an intact endothelium, vasodilation was observed while subjects with endothelial damage experienced paradoxical vasoconstriction. There exists a non-invasive, in vivo method for measuring endothelial function in peripheral arteries using high-resolution B-mode ultrasound. The endothelial function of peripheral arteries is closely related to coronary artery function. This technique measures the percent diameter change in the brachial artery during a period of reactive hyperemia following limb ischemia. This technique, known as endothelium-dependent, flow-mediated vasodilation (FMD) has value in clinical research settings. However, a number of physiological and technical issues can affect the accuracy of the results and appropriate guidelines for the technique have been published. Despite the guidelines, FMD remains heavily operator dependent and presents a steep learning curve. This article presents a standardized method for measuring FMD in the brachial artery on the upper arm and offers suggestions to reduce intra-operator variability.

Relationship between kidney disease and endothelial function in peripheral artery disease

OBJECTIVE

We have previously shown that peripheral artery disease (PAD) is associated with marked impairment of endothelial function (EF). Given that poor EF is associated with functional status of PAD patients as well as with increased morbidity and mortality in patients undergoing vascular procedures, determination of factors associated with poor EF in a PAD cohort is important. We hypothesized that decreased kidney function is associated with impaired EF in patients with PAD.

METHODS

This was a cross-sectional study of PAD patients presenting to a vascular surgery outpatient clinic at the San Francisco Veterans Affairs Medical Center including patients enrolled in the OMEGA-PAD I trial (NCT01310270) and the OMEGA-PAD Cohort. Brachial artery flow-mediated vasodilation was performed to assess EF. Kidney function was characterized by estimated glomerular filtration rate with the abbreviated Modification of Diet in Renal Disease formula. Linear regression was performed to assess the relationship between EF and kidney function in claudicants.

RESULTS

Ninety-seven patients with intermittent claudication participated in this study. Mean age was 69 ± 8 years, 97% were male, and 79% were white. Comorbidities included hypertension (91%), dyslipidemia (87%), coronary artery disease (42%), and diabetes mellitus (38%). Mean ankle-brachial index was 0.73 ± 0.14 and mean flow-mediated vasodilation was 7.0% ± 3.8%, indicating impaired EF. Linear regression showed an association between kidney function and EF (by 10 mL/min/1.73 m(2); β, 0.12; confidence interval, 0.05-0.20; P = .001). After multivariable regression adjusting for age, race, log tumor necrosis factor α, hypertension, dyslipidemia, and diabetes, estimated glomerular filtration rate remained significantly associated with EF (P = .033).

CONCLUSIONS

In patients with PAD, decreased kidney function is associated with endothelial dysfunction. Further longitudinal studies are needed to better understand the impact of kidney function on PAD progression and the role of endothelial dysfunction in this process.

Women's health in spaceflight

OBJECTIVE

To review the current state of knowledge with regards to clinical challenges related to women's health during spaceflight.

METHODS

Articles were reviewed relevant to "women", "sex," and "gender" in "microgravity," "weightlessness," and "spaceflight" in the English and Russian languages.

RESULTS

There were 50 papers identified. Studies have shown that crewmembers suffer from space motion sickness, but gender discrepancies have not been explored. Nearly all women experience orthostatic intolerance in space, which may be due to differences in female cardiovascular response. Immunosuppression in spaceflight results in susceptibility to opportunistic infections, but no studies have investigated gender differences. Finally, radiation exposure and germ cell viability influence the reproductive health of astronauts.

CONCLUSIONS

With changes in space access offered by commercial space activities, research areas devoted to women's health in microgravity should become one of the priorities for safe space exploratory efforts.

Clinical correlates of red blood cell omega-3 fatty acid content in male veterans with peripheral arterial disease

OBJECTIVE

Despite available medical therapies, patients with peripheral arterial disease (PAD) remain at high risk for cardiovascular events. The n-3 polyunsaturated fatty acids (PUFA), derived from marine sources, have been shown to improve cardiovascular mortality. The Omega-3 Index (O3I), a proportion of the n-3 PUFA eicosapentaenoic acid and docosahexaenoic acid in the red blood cell membrane, correlates with cardiovascular risk. Previous investigations have found that n-3 PUFA supplementation, fish consumption, older age, and smoking history affect the O3I in different patient populations, although similar correlations have never been explored in PAD. We hypothesized that in our PAD cohort, blood content of omega-3 fatty acids would directly and positively correlate with a history of fish oil supplementation and older age and inversely correlate with a smoking history and obesity.

METHODS

This cross-sectional study included 111 patients who had an ankle-brachial index of <0.9 associated with claudication symptoms. We used linear regression to determine the association between clinical factors and the O3I.

RESULTS

The mean age of the cohort was 69 ± 8 years; 37% had diabetes mellitus (hemoglobin A1c, 7% ± 1%), and 94% reported current smoking or a history of smoking. The mean O3I was 5% ± 2%. In multivariate linear regression analysis, the O3I was associated with older age, increasing body mass index, and a history of smoking and fish oil intake.

CONCLUSIONS

This is the first report of the relation between blood content of omega-3 fatty acids and clinical factors in a PAD population. In patients with PAD, older age, elevated body mass index, and prior fish oil supplementation predicted a higher O3I. A history of smoking correlated with a lower O3I. These results demonstrate that the O3I is a reliable measure of dietary n-3 PUFA intake and that clinical factors related to the O3I in PAD are similar to those observed in other populations.

Abstract 318: Determinants of Red Blood Cell Omega-3-Fatty Acid Content in Patients With Peripheral Arterial Disease

Objectives: Despite available medical therapies, patients with peripheral arterial disease (PAD) remain at high risk for cardiovascular events. n-3 polyunsaturated fatty acids (PUFAs), derived from marine sources, have been shown to improve cardiovascular mortality. The omega-3 index (O3I), a proportion of the n-3 PUFAs eicosapentanoic acid and docosahexanoic acid in the red blood cell membrane, correlates with cardiovascular risk. We sought to determine the clinical factors associated with the O3I in patients with PAD.

Methods: This cross-sectional study included 111 patients, who had an ankle-brachial index of < 0.9 associated with claudication symptoms. We used linear regression to determine the association between demographic and lifestyle factors and the O3I.

Results: The mean age of the cohort was 69 ± 8 years, 37% had diabetes mellitus (Hemoglobin A1c: 7 ± 1%), and 94% had smoked. The mean O3I was 5 ± 2%. Table 1 shows the variables associated with O3I in regression analyses. In a multivariate model, an independent association was maintained with increasing age, BMI, and a history of smoking and fish oil intake.

Conclusions: In a cohort of patients with PAD, older age, elevated BMI, and prior fish oil supplementation predicted a higher O3I. A history of smoking correlated with a lower O3I. Our findings suggest that targeting nutrition and tobacco use with therapeutic interventions has potential to reduce cardiovascular risk among PAD patients.

Effects of gravitational mechanical unloading in endothelial cells: association between caveolins, inflammation and adhesion molecules

Mechanical forces including gravity affect endothelial cell (ECs) function, and have been implicated in vascular disease as well as physiologic changes associated with low gravity environments. The goal of this study was to investigate the impact of gravitational mechanical unloading on ECs phenotype as determined by patterns of gene expression. Human umbilical vascular endothelial cells were exposed to 1-gravity environment or mechanical unloading (MU) for 24 hours, with or without periods of mechanical loading (ML). MU led to a significant decrease in gene expression of several adhesion molecules and pro-inflammatory cytokines. On the contrary, eNOS, Caveolin-1 and -2 expression were significantly increased with MU. There was a decrease in the length and width of the cells with MU. Addition of ML during the MU period was sufficient to reverse the changes triggered by MU. Our results suggest that gravitational loading could dramatically affect vascular endothelial cell function.

Peripheral arterial disease, gender, and depression in the Heart and Soul Study

BACKGROUND

Despite the high prevalence of peripheral arterial disease (PAD) in women, risk factors for PAD in women are not well understood.

METHODS

Gender-specific risk factors for PAD were examined in a prospective cohort study of 1024 patients (184 women and 840 men) with stable coronary artery disease who were recruited between 2000 and 2002. Logistic regression models were used to evaluate associations between traditional and nontraditional risk factors and PAD in men and women.

RESULTS

PAD was found in 11% of women and in 13% of men. Women with PAD had a similar prevalence of traditional risk factors (hypertension, hyperlipidemia, and smoking) compared with women without PAD and were significantly more likely to suffer from depression than women without PAD. Men with PAD were more likely to have hypertension, diabetes mellitus, a history of smoking, a worse lipid profile, and higher levels of inflammatory biomarkers than men without PAD. A multivariate model showed depression was the strongest independent factor associated with PAD in women, whereas smoking and elevated fibrinogen were independently associated with PAD in men.

CONCLUSIONS

The current findings suggest there are gender differences in risk factors for the development of PAD. Further research is needed to understand the role of depression in PAD.

Short-term physical inactivity impairs vascular function

BACKGROUND

Sedentarism, also termed physical inactivity, is an independent risk factor for cardiovascular diseases. Mechanisms thought to be involved include insulin resistance, dyslipidemia, hypertension, and increased inflammation. It is unknown whether changes in vascular and endothelial function also contribute to this excess risk. We hypothesized that short-term exposure to inactivity would lead to endothelial dysfunction, arterial stiffening, and increased vascular inflammation.

METHODS

Five healthy subjects (four men and one woman) underwent 5 d of bed rest (BR) to simulate inactivity. Measurements of vascular function (flow-mediated vasodilation to evaluate endothelial function; applanation tonometry to assess arterial resistance), inflammation, and metabolism were made before BR, daily during BR, and 2 d after BR recovery period. Subjects maintained an isocaloric diet throughout.

RESULTS

BR led to significant decreases in brachial artery and femoral artery flow-mediated vasodilation (brachial: 11 ± 3% pre-BR versus 9 ± 2% end-BR, P = 0.04; femoral: 4 ± 1% versus 2 ± 1%, P = 0.04). The central augmentation index increased with BR (-4 ± 9% versus 5 ± 11%, P = 0.03). Diastolic blood pressure increased (58 ± 7 mm Hg versus 62 ± 7 mm Hg, P = 0.02), whereas neither systolic blood pressure nor heart rate changed. 15-Hydroxyeicosatetraenoic acid, an arachidonic acid metabolite, increased but the other inflammatory and metabolic biomarkers were unchanged.

CONCLUSIONS

Our findings show that acute exposure to sedentarism results in decreased endothelial function, arterial stiffening, increased diastolic blood pressure, and an increase in 15-hydroxyeicosatetraenoic acid. We speculate that inactivity promotes a vascular "deconditioning" state characterized by impaired endothelial function, leading to arterial stiffness and increased arterial tone. Although physiologically significant, the underlying mechanisms and clinical relevance of these findings need to be further explored.

Walking disability in patients with peripheral artery disease is associated with arterial endothelial function

OBJECTIVE

Patients with peripheral artery disease (PAD) have varying degrees of walking disability that do not completely correlate with ankle-brachial index (ABI) or angiographic anatomy. We hypothesized that endothelial function (EF) is an independent predictor of symptom severity in PAD patients.

METHODS

This was a cross-sectional study of 100 PAD patients presenting to a vascular surgery clinic. All patients received ABI testing and brachial artery flow-mediated, endothelium-dependent vasodilation (FMD) to assess arterial EF. Symptom severity and walking disability reported by Rutherford category was based on the patient's self-report during the clinic visit and recorded by the investigator-vascular surgeons. Demographic, biochemical, and physiologic parameters were entered into regression equations to determine association with symptom severity.

RESULTS

Patients were a mean age of 66 ± 8 years, and 43% had diabetes. Mean FMD was 7.4%, indicating impaired EF. EF progressively declined as Rutherford category increased (P = .01). Brachial artery FMD, ABI, systolic blood pressure, C-reactive protein, low-density lipoprotein, high-density lipoprotein, β-blocker use, and a history of diabetes or coronary artery disease were all associated with Rutherford category (all P < .05). Multivariable regression showed EF (P < .02) and ABI (P < .0001) were independently associated with walking disability. When the cohort was restricted to claudicant patients (n = 73), EF remained associated with walking disability after adjustment for other covariates (P = .0001).

CONCLUSIONS

Symptom severity in PAD is multifactorial, reflecting impaired hemodynamics and vascular dysfunction. This is the first report demonstrating that walking disability in PAD is associated with arterial EF. The mechanistic link underlying these observations remains to be defined.

Safety and feasibility of adjunctive dexamethasone infusion into the adventitia of the femoropopliteal artery following endovascular revascularization

OBJECTIVE

Restenosis following endovascular treatment of the femoropopliteal segment is associated with the inflammatory response produced in the artery wall at the time of the procedure. Although local drug delivery to the superficial femoral and popliteal arteries promises improved patency, data are currently limited. We hypothesized that improved percutaneous delivery of an anti-inflammatory compound into the adventitia of the femoropopliteal at the time of endovascular treatment would be safe, feasible, and decrease the inflammatory response.

METHODS

This was a prospective, investigator-initiated, phase I, first-in-man study testing the safety and feasibility of percutaneous adventitial delivery of dexamethasone. Following successful intervention, an adventitial microinfusion catheter was advanced over a 0.014-inch wire to the treated segment. Its microneedle (0.9 mm long × 140-μm diameter) was deployed into the adventitia to deliver dexamethasone (4 mg/mL) mixed with contrast agent (80:20 ratio), providing fluoroscopic visualization. The primary safety outcome measure was freedom from vessel dissection, thrombosis, or extravasation while the primary efficacy outcome was duplex-determined binary restenosis defined as a peak systolic velocity ratio >2.5.

RESULTS

Twenty patients with Rutherford clinical category 2-5 enrolled in this study. The mean age was 66, and 55% had diabetes mellitus. Treated lesion length was 8.9 ± 5.3 cm, and 50% were chronic total occlusions. Eighty percent of treated lesions were in the distal superficial femoral or popliteal arteries. All lesions were treated by balloon angioplasty with provisional stenting (n = 6) for suboptimal result. Three patients were treated with atherectomy as well. A mean of 1.6 ± 1.1 mg (0.5 ± 0.3 mL) of dexamethasone sodium phosphate was injected per centimeter of lesion length. In total, a mean of 12.1 ± 6.1 mg of dexamethasone was injected per patient. The mean number of injections required per lesion was 3.0 ± 1.3 cm, minimum one and maximum six injections. There was 100% technical success of drug delivery and no procedural or drug-related adverse events. The mean Rutherford score decreased from 3.1 ± .7 (median, 3.0) preoperatively to .5 ± .7 at 6 months (median, 0.0; P < .00001). Over this same time interval, the index leg ankle-brachial index increased from .68 ± .15 to .89 ± .19 (P = .0003). The preoperative C-reactive protein in this study was 6.9 ± 8.5 indicating severe baseline inflammation, which increased to 14.0 ± 23.1 mg/L (103% increase) at 24 hours following the procedure. However, this increase did not reach statistical significance of P = .14. Two patients met the primary efficacy end point of loss of primary patency by reoccluding their treated segment of the index lesion during the follow-up period.

CONCLUSIONS

Adventitial drug delivery via a microinfusion catheter is a safe and feasible alternative to intimal-based methods for adjunctive treatment in the femoropopliteal segment. The 6-month preliminary results suggest perivascular dexamethasone treatment may improve outcomes following angioplasty to the femoral and popliteal arteries, and support further clinical investigation of this approach.