Search Engines to Capture Missing Deaths From Institutional Data Warehouse

INTRODUCTION

Clinical publications use mortality as a hard end point. It is unknown how many patient deaths are under-reported in institutional databases. The objective of this study was to query mortality in our patient cohort from our data warehouse and compare these deaths to those identified in different databases.

METHODS

We passed the first/last name and date of birth of 134 patients through online mortality search engines (Find a Grave Index, US Cemetery and Funeral Home Collection, etc.) to assess their ability to capture patient deaths and compared that to deaths recorded from our institutional data warehouse.

RESULTS

Our institutional data warehouse found approximately one-third of the total patient mortalities. After the Social Security Death Index, we found that the Find a Grave Index captured the most mortalities missed by the institutional data warehouse. These results highlight the advantages of incorporating readily available search engines into institutional data warehouses for the accurate collection of patient mortalities, particularly those that occur outside of index operative admission.

CONCLUSIONS

The incorporation of the mortality search engines significantly augmented the capture of patient deaths. Our approach may be useful for tailored patient outreach and reporting mortalities with institutional data.

Single-Cell RNA sequencing investigation of female-male differences under PAD conditions

Peripheral arterial disease (PAD) is an age-related medical condition affecting mostly muscular arteries of the limb. It is the 3rd leading cause of atherosclerotic morbidity. The mechanical environment of endothelial cells (ECs) in PAD is characterized by disturbed blood flow (d-flow) and stiff extracellular matrices. In PAD, the stiffness of arteries is due to decreased elastin function and increased collagen content. These flow and stiffness parameters are largely missing from current models of PAD. It has been previously proven that ECs exposed to d-flow or stiff substrates lead to proatherogenic pathways, but the effect of both, d-flow and stiffness, on EC phenotype has not been fully investigated. In this study, we sought to explore the effect of sex on proatherogenic pathways that could result from exposing endothelial cells to a d-flow and stiff environment. We utilized the scRNA-seq tool to analyze the gene expression of ECs exposed to the different mechanical conditions both in vitro and in vivo. We found that male ECs exposed to different mechanical stimuli presented higher expression of genes related to fibrosis and d-flow in vitro. We validated our findings in vivo by exposing murine carotid arteries to d-flow via partial carotid artery ligation. Since women have delayed onset of arterial stiffening and subsequent PAD, this work may provide a framework for some of the pathways in which biological sex interacts with sex-based differences in PAD.

Comparison of arterial storage conditions for delayed arterial ring testing

Objective

Arterial ring testing is the gold standard for measuring arterial function. Increased arterial tone through arterial contraction and impaired endothelial relaxation (endothelial dysfunction) are key metrics of impaired arterial health in peripheral arterial disease (PAD). To allow for comparative testing of arteries during standard laboratory hours, storage buffers and conditions have been used to extend the functional life of arteries. Various storage conditions have been compared, but there has not been a robust comparison or validation in human arteries. The objective of this work is to optimize storage of arterial segments for endothelial cell (EC) testing in a murine model and to test EC function in human PAD arteries. We hypothesized that certain storage conditions would be superior to others.

Methods

Healthy murine aortas were harvested from 10- to 14-week-old C57/Bl6J male and female mice and compared under different storage protocols (24 hours) to immediate arterial testing. The storage conditions tested were: Opti-MEM (37°C or 4°C), Krebs-HEPES with 1.8 mmol/L or 2.5 mmol/L calcium (4°C), or Wisconsin (WI) solution at 4°C. Vascular function was evaluated by isometric force testing. Endothelium-dependent and -independent relaxation were measured after precontraction with addition of methacholine or sodium nitroprusside, respectively. Arterial contraction was stimulated with potassium chloride or phenylephrine. Analysis of variance was used to determine significance compared with immediate testing with P < .05. Under institutional review board approval, 28 PAD arteries were collected at amputation and underwent vascular function testing as described. Disturbed flow conditions were determined by indirect (upstream occlusion) flow to the harvested tibial arteries. Stable flow arteries had in-line flow. Arterial calcification was quantified manually as present or not present.

Results

We found that 4°C WI and 37°C Opti-MEM best preserved endothelium-dependent relaxation and performed similarly to immediately testing aortas (termed fresh for freshly tested) (P > .95). Other storage conditions were inferior to freshly tested aortas (P < .05). Vascular smooth muscle function was tested by endothelial-independent relaxation and contractility. All storage conditions preserved endothelial-independent relaxation and contractility similar to freshly tested arteries. However, 4°C WI and 37°C Opti-MEM storage conditions most closely approximated the maximum force of contraction of freshly tested arteries in response to potassium chloride (P > .39). For human arterial testing, 28 tibial arteries were tested for relaxation and contraction with 16 arteries with peripheral artery occlusive disease (PAD with disturbed flow) and 12 without peripheral artery occlusive disease (PAD with stable flow), of which 14 were calcified and 14 were noncalcified. Endothelial-dependent relaxation data was measurable in 9 arteries and arterial contraction data was measurable in 14 arteries. When comparing flow conditions, arteries exposed to disturbed flow (n = 4) had significantly less relaxation (2% vs 59%; P = .03) compared with stable flow conditions (n = 5). In contrast, presence the (n = 6) or absence of calcification (n = 3) did not impact arterial relaxation. Arterial contraction was not different between groups in either comparison by flow (n = 9 disturbed; n = 5 stable) or calcification (n = 6 present; n = 8 absent).

Conclusions

In healthy murine aortas, arterial storage for 24 hours in 4°C WI or 37°C Opti-MEM both preserved endothelium-dependent relaxation and maximum force of contraction. In human PAD arteries stored in 4° WI, flow conditions before arterial harvest, but not arterial calcification, led to differences in arterial relaxation in human PAD arteries. Arterial contractility was more robust (11/28 arteries) compared with arterial relaxation (7/28 arteries), but was not significantly different under flow or calcification parameters. This work defines ideal storage conditions for arterial ring testing and identifies that EC dysfunction from disturbed flow may persist in delayed ex vivo arterial testing.

Effect of Aging, Sex, and Gene (Fbln5) on Arterial Stiffness of Mice: 20 Weeks Adult Fbln5-knockout Mice Have Older Arteries than 100 Weeks Wild-Type Mice

The arterial stiffening is a strong independent predictor of cardiovascular risk and has been used to characterize the biological age of arteries ('arterial age'). Here we revealed that the Fbln5 gene knockout (Fbln5 ^-/- ) significantly increases the arterial stiffening for both male and female mice. We also showed that the arterial stiffening increases with natural aging, but the stiffening effect of Fbln5 ^-/- is much more severe than aging. The arterial stiffening of 20 weeks old mice with Fbln5 ^-/- is much higher than that at 100 weeks in wild-type (Fbln5 ^+/+ ) mice, which indicates that 20 weeks mice (equivalent to ∼26 years old humans) with Fbln5 ^-/- have older arteries than 100 weeks wild-type mice (equivalent to ∼77 years humans). Histological microstructure changes of elastic fibers in the arterial tissue elucidate the underlying mechanism of the increase of arterial stiffening due to Fbln5-knockout and aging. These findings provide new insights to reverse 'arterial age' due to abnormal mutations of Fbln5 gene and natural aging. This work is based on a total of 128 biaxial testing samples of mouse arteries and our recently developed unified-fiber-distribution (UFD) model. The UFD model considers the fibers in the arterial tissue as a unified distribution, which is more physically consistent with the real fiber distribution of arterial tissues than the popular fiber-family-based models (e.g., the well-know Gasser-Ogden-Holzapfel [GOH] model) that separate the fiber distribution into several fiber families. Thus, the UFD model achieves better accuracies with less material parameters. To our best knowledge, the UFD model is the only existing accurate model that could capture the property/stiffness differences between different groups of the experimental data discussed here.

Myoglobinemia, Peripheral Arterial Disease, and Patient Mortality

BACKGROUND

Peripheral arterial disease (PAD) causes leg muscle damage due to inadequate perfusion and increases cardiovascular events and mortality 2- to 3-fold. It is unclear if PAD is a biomarker for high-risk cardiovascular disease or if skeletal muscle injury harms arterial health. The objective of this work is to test if serum myoglobin levels (myoglobinemia) are a marker of PAD, and if so, whether myoglobin impairs vascular health.

STUDY DESIGN

Patient blood samples were collected from PAD and control (no PAD) patients and interrogated for myoglobin concentrations and nitric oxide bioavailability. Patient mortality over time was captured from the medical record. Myoglobin activity was tested on endothelial cells and arterial function.

RESULTS

Myoglobin is a biomarker for symptomatic PAD and was inversely related to nitric oxide bioavailability; 200 ng/mL myoglobin in vitro increased endothelial cell permeability in vitro and decreased nitrate bioavailability. Ex vivo, 100 ng/mL myoglobin increased vascular tone in naive murine aortas approximately 1.5 times, impairing absolute vessel relaxation. In vivo, we demonstrated that myoglobinemia caused impaired flow-mediated dilation in a porcine model. Patients presenting with myoglobin levels of 100 ng/mL or greater had significantly more deaths than those with myoglobin levels of less than 100 ng/mL.

CONCLUSIONS

Using a combination of patient data, in vitro, ex vivo, and in vivo testing, we found that myoglobin is a biomarker for symptomatic PAD and a potent regulator of arterial health that can increase vascular tone, increase vascular permeability, and cause endothelial dysfunction, all of which may contribute to the vulnerability of PAD patients to cardiovascular events and death.

Effect of a Decision Aid on Agreement Between Patient Preferences and Repair Type for Abdominal Aortic Aneurysm: A Randomized Clinical Trial

Importance

Patients with abdominal aortic aneurysm (AAA) can choose open repair or endovascular repair (EVAR). While EVAR is less invasive, it requires lifelong surveillance and more frequent aneurysm-related reinterventions than open repair. A decision aid may help patients receive their preferred type of AAA repair.

Objective

To determine the effect of a decision aid on agreement between patient preference for AAA repair type and the repair type they receive.

Design, Setting, and Participants

In this cluster randomized trial, 235 patients were randomized at 22 VA vascular surgery clinics. All patients had AAAs greater than 5.0 cm in diameter and were candidates for both open repair and EVAR. Data were collected from August 2017 to December 2020, and data were analyzed from December 2020 to June 2021.

Interventions

Presurgical consultation using a decision aid vs usual care.

Main Outcomes and Measures

The primary outcome was the proportion of patients who had agreement between their preference and their repair type, measured using χ2 analyses, κ statistics, and adjusted odds ratios.

Results

Of 235 included patients, 234 (99.6%) were male, and the mean (SD) age was 73 (5.9) years. A total of 126 patients were enrolled in the decision aid group, and 109 were enrolled in the control group. Within 2 years after enrollment, 192 (81.7%) underwent repair. Patients were similar between the decision aid and control groups by age, sex, aneurysm size, iliac artery involvement, and Charlson Comorbidity Index score. Patients preferred EVAR over open repair in both groups (96 of 122 [79%] in the decision aid group; 81 of 106 [76%] in the control group; P = .60). Patients in the decision aid group were more likely to receive their preferred repair type than patients in the control group (95% agreement [93 of 98] vs 86% agreement [81 of 94]; P = .03), and κ statistics were higher in the decision aid group (κ = 0.78; 95% CI, 0.60-0.95) compared with the control group (κ = 0.53; 95% CI, 0.32-0.74). Adjusted models confirmed this association (odds ratio of agreement in the decision aid group relative to control group, 2.93; 95% CI, 1.10-7.70).

Conclusions and Relevance

Patients exposed to a decision aid were more likely to receive their preferred AAA repair type, suggesting that decision aids can help better align patient preferences and treatments in major cardiovascular procedures.

Trial Registration

ClinicalTrials.gov Identifier: NCT03115346.

Abstract 137: Role Of Cellular Communication Network Factor 2 (ccn2) And Male Sex On Flow-mediated Arterial Remodeling And Atherosclerotic Plaque Formation

CCN2 or connective tissue growth factor is up-regulated in response to disturbed flow and arterial stiffening. Carotid artery disease and peripheral arterial disease (PAD) are associated with disturbed flow and arterial stiffening. We have identified a key role for CCN2 in stiffened arterial remodeling and flow-mediated focal atherosclerotic plaque formation in translational models of carotid and PAD and in patient carotid plaques/PAD arteries. The objective of this project was to determine the modifiability of CCN2 pathways in pathologic arterial remodeling and atherosclerosis.

Methods: To test our hypothesis that CCN2 was an important mediator of pathology arterial remodeling in vascular disease , we utilized murine models of stiffened arteries (fibulin-5 KO) in atherogenic conditions (PCSK9 + HFD) and clinical arterial tissue from patients with PAD and carotid artery disease.

Results: Disturbed flow increases EC expression of CCN2 3.5 fold in WT carotid arteries. This is doubled again in Fibulin 5 KO ( KO ) carotid arteries. These KO carotid arteries are ~3x stiffer than littermate control arteries, which is a similar ratio of PAD compared to healthy control arteries ( 1A ). Under disturbed flow and atherogenic conditions KO arteries had more elastin breaks (P=.04), greater plaque area (P=.007) and more lipid deposition (P=.02), and Glagov’s outward remodeling (P=.02) ( 1B/C ). This was most pronounced in male mice. CCN2 staining is significantly increased in PAD arteries and carotid endarterectomy plaques (P<.05) ( 1D/E ). To evaluate the modifiability of CCN2, we utilized CCN2 ECKO animals. We found that male (but not female) CCN2 ECKO animals had significantly less atherosclerotic plaque burden (P=.001) and similar elastin breaks/lipid deposition compared to littermate controls ( 1F/G ).

Conclusion: CCN2 may play an important and modifiable role in flow-mediated pathologic arterial remodeling and focal atherosclerotic plaque burden.

COVID-19-associated venous thromboembolism portends worse survival

Patients with coronavirus disease 2019 (COVID-19) seem to be at high risk for venous thromboembolism (VTE) development, but there is a paucity of data exploring both the natural history of COVID-19-associated VTE and the risk for poor outcomes after VTE development. This investigation aims to explore the relationship between COVID-19-associated VTE development and mortality. A prospectively maintained registry of patients older than 18 years admitted for COVID-19-related illnesses within an academic health care network between March and September 2020 was reviewed. Codes from the tenth revision of the International Classification of Diseases for VTE were collected. The charts of those patients with a code for VTE were manually reviewed to confirm VTE diagnosis. There were 2,552 patients admitted with COVID-19-related illnesses. One hundred and twenty-six patients (4.9%) developed a VTE. A disproportionate percentage of patients of Black race developed a VTE (70.9% VTE v 57.8% non-VTE; P = .012). A higher proportion of patients with VTE expired during their index hospitalization (22.8% VTE v 8.4% non-VTE; P < .001). On multivariable logistic regression analysis, VTE was independently associated with mortality (odds ratio = 3.17; 95% confidence interval, 1.9-5.2; P < .001). Hispanic/Latinx ethnicity was associated with decreased mortality (odds ratio = 0.45; 95% confidence interval, 0.21-1.00; P = .049). Hospitalized patients of Black race with COVID-19 were more prone to VTE development, and patients with COVID-19 who developed in-hospital VTE had roughly nearly threefold higher odds of mortality. Further emphasis should be placed on optimizing COVID-19 anticoagulation protocols to reduce mortality in this high-risk cohort.

Rationale and design of the granulocyte-macrophage colony stimulating factor in peripheral arterial disease (GPAD-3) study

BACKGROUND

Lower extremity peripheral arterial disease (PAD) is a public health problem and many patients with PAD experience claudication despite adequate medical and/or surgical management. Mobilization of endogenous progenitor cells using Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) is a novel therapeutic option that has shown promising results in experimental models and phase I/IIA clinical trials. The GPAD-3 trial will study the effect of two successive administrations of GM-CSF at 3-month interval for improving claudication among patients with lower extremity PAD.

METHODS

We plan to recruit 176 patients in this ongoing randomized, double-blind, placebo-controlled Phase IIB trial. After screening for inclusion and exclusion criteria, eligible subjects undergo a 4-week screening phase where they perform subcutaneous placebo injections thrice weekly and walk at least three times a day until they develop claudication. After the screening phase, eligible subjects undergo baseline testing and are randomized 2:1 to receive 500 μg/day of GM-CSF subcutaneously thrice weekly for three weeks or placebo injections. After 3 months, follow-up endpoint testing is performed and subjects in the GM-CSF group receive the second administration of the drug for three weeks while subjects in placebo group receive matching placebo injections. All participants undergo endpoint testing at six-month and nine-month follow-up. The primary endpoint is change in 6-min walk distance between baseline and 6-month follow-up.

CONCLUSION

GPAD-3 explores a novel approach to address the need for alternative therapies that can alleviate symptoms among patients with lower extremity PAD. If successful, this study will pave the way for a pivotal Phase III trial.

Perfusion Assessment in Critical Limb Ischemia: Principles for Understanding and the Development of Evidence and Evaluation of Devices: A Scientific Statement From the American Heart Association

There are >12 million patients with peripheral artery disease in the United States. The most severe form of peripheral artery disease is critical limb ischemia (CLI). The diagnosis and management of CLI is often challenging. Ethnic differences in comorbidities and presentation of CLI exist. Compared with white patients, black and Hispanic patients have higher prevalence rates of diabetes mellitus and chronic renal disease and are more likely to present with gangrene, whereas white patients are more likely to present with ulcers and rest pain. A thorough evaluation of limb perfusion is important in the diagnosis of CLI because it can not only enable timely diagnosis but also reduce unnecessary invasive procedures in patients with adequate blood flow or among those with other causes for ulcers, including venous, neuropathic, or pressure changes. This scientific statement discusses the current tests and technologies for noninvasive assessment of limb perfusion, including the ankle-brachial index, toe-brachial index, and other perfusion technologies. In addition, limitations of the current technologies along with opportunities for improvement, research, and reducing disparities in health care for patients with CLI are discussed.

The small heat shock protein HSPB1 protects mice from sepsis

In vitro studies have implicated the small heat shock protein HSPB1 in a range of physiological functions. However, its in vivo relevance is unclear as the phenotype of unstressed HSPB1^−/− mice is unremarkable. To determine the impact of HSPB1 in injury, HSPB1^−/− and wild type (WT) mice were subjected to cecal ligation and puncture, a model of polymicrobial sepsis. Ten-day mortality was significantly higher in HSPB1^−/− mice following the onset of sepsis (65% vs. 35%). Ex vivo mechanical testing revealed that common carotid arteries from HSPB1^−/− mice were more compliant than those in WT mice over pressures of 50–120 mm Hg. Septic HSPB1^−/− mice also had increased peritoneal levels of IFN-γ and decreased systemic levels of IL-6 and KC. There were no differences in frequency of either splenic CD4⁺ or CD8⁺ T cells, nor were there differences in apoptosis in either cell type. However, splenic CD4⁺ T cells and CD8⁺ T cells from HSPB1^−/− mice produced significantly less TNF and IL-2 following ex vivo stimulation. Systemic and local bacterial burden was similar in HSPB1^−/− and WT mice. Thus while HSPB1^−/− mice are uncompromised under basal conditions, HSPB1 has a critical function in vivo in sepsis, potentially mediated through alterations in arterial compliance and the immune response.

Reversible secretome and signaling defects in diabetic mesenchymal stem cells from peripheral arterial disease patients

OBJECTIVE

Regenerative medicine seeks to stall or to reverse the pathologic consequences of chronic diseases. Many people with diabetes have peripheral arterial disease (PAD), which increases their already high risk of major amputation. Cellular therapies are a promising regenerative medicine approach to PAD that can be used to focally inject regenerative cells to endangered tissue beds. Mesenchymal stem cells (MSCs) are known to promote tissue regeneration through stromal support and paracrine stimulation of new blood vessels (angiogenesis). Whereas little is known about human diabetic MSCs (dMSCs), particularly those from patients with PAD, dMSCs have a limited expansion capacity but can be improved with human platelet lysate (PL) supplementation. PL is rich in many growth factors, including epidermal growth factor (EGF), which is known to be important to cell proliferation and survival signaling pathways. We hypothesize that dMSCs have a reversible defect in EGF receptor pathways. The objective of this work was to test this hypothesis using dMSCs from PAD patients.

METHODS

The secretome expression of EGF and prominent angiogens was characterized from bone marrow (BM)-derived and adipose tissue-derived (ATD) dMSCs from five patients (six limbs) undergoing major amputation. Western blot was used to characterize the AKT and extracellular signal-regulated protein kinases 1 and 2 expression in dMSCs under standard culture (5% fetal bovine serum plus fibroblast growth factor 2 [FGF2]), 5% human PL, or 5% fetal bovine serum plus EGF. Healthy donor MSCs were control cells. The angiogenic activity of BM- and ATD-dMSCs was tested on human umbilical vein endothelial cells (ECs). Paired t-test, analysis of variance, and Kruskal-Wallis tests were used as appropriate.

RESULTS

Both BM- and ATD-dMSCs had typical MSC surface marker expression and similar expansion profiles, and they did not express EGF in their secretome. PL supplementation of dMSCs improved AKT signaling, but they were resistant to FGF2 activation of extracellular signal-regulated protein kinases 1 and 2. EGF supplementation led to similar AKT expression as with PL, but PL had greater phosphorylation of AKT at 30 and 60 minutes. The conditioned media from both BM- and ATD-dMSCs had robust levels of prominent angiogens (vascular endothelial growth factor, monocyte chemoattractant protein 1, hepatocyte growth factor), which stimulated EC proliferation and migration, and the co-culture of dMSCs with ECs led to significantly longer EC sprouts in three-dimensional gel than EC-alone pellets.

CONCLUSIONS

PL and EGF supplementation improves AKT expression in dMSCs over that of FGF2, but PL improved pAKT over that of EGF. Thus, PL supplementation strategies may improve AKT signaling, which could be important to MSC survival in cellular therapies. Furthermore, BM- and ATD-dMSCs have similar secretomes and robust in vitro angiogenic activity, which supports pursuing dMSCs from both reservoirs in regenerative medicine strategies.

Abstract 717: Sequential Inflow Occlusion and Walking Capacity in Large Animal Model of PAD

Introduction: Peripheral artery disease (PAD) affects over 8 million Americans over 40 years of age. PAD patients are heavily burdened by pain and walking dysfunction. Treatment paradigms for PAD are evolving, but optimal medical therapy, risk factor modification, and supervised exercise therapy (SET) are the first line therapies for these persons. SET improves walking time and may improve skeletal muscle perfusion. However, the mechanisms by which SET and other treatments are not well understood. Translational models of PAD may be useful in developing novel therapeutics for PAD patients.

Objective: The objective of this work is to introduce a large animal (porcine) model of PAD that includes sequential occlusion of inflow that can be used on patient-like treadmills for SET or quantification of walking distance and dysfunction.

Methods: Two female Yorkshire swine were accommodated to our treadmill one week prior to procedure. On day 0, swine underwent endovascular placement of a covered stent (GORE® VIABAHN® endoprosthesis) into the right external iliac artery followed by placement of a vascular plug (AMPLATZER, St. Jude Medical) inside this stent was used in the initial procedure. In order to mimic the common presentation of PAD patients having one leg more severely ischemic than the other, we performed a sequential occlusion of the ipsilateral internal iliac artery and contralateral external iliac artery one week later. Vascular flow were quantified by arteriogram, a modified ankle brachial index, and duplex ultrasound. Animals were walked weekly on a large animal treadmill with a 3.5 KM/HR pace and 10 degree incline until failure (pigs would slide to end of treadmill).

Results: There were no technical failures or complications. One and three weeks after the initial procedure, pigs walked 40% and 45% of pre-procedural maximal walking time. There was sustained depression of the blood pressure ratio of ischemic hindlimb to unaffected forelimb (hindlimb index or HLI), which was significantly inhibited out to 6 weeks ( HLI of 0.4-0.63 ).

Conclusion: We have created a pilot model of PAD that can be used for both SET testing and quantifying maximal walking time/distance. This model may be useful in testing novel therapeutics and validating promising mechanistic findings from small animals.

Association of Statin Dose With Amputation and Survival in Patients With Peripheral Artery Disease

BACKGROUND

Statin dose guidelines for patients with peripheral artery disease (PAD) are largely based on coronary artery disease and stroke data. The aim of this study is to determine the effect of statin intensity on PAD outcomes of amputation and mortality.

METHODS

Using an observational cohort study design and a validated algorithm, we identified patients with incident PAD (2003-2014) in the national Veterans Affairs data. Highest statin intensity exposure (high-intensity versus low-to-moderate-intensity versus antiplatelet therapy but no statin use) was determined within 1 year of diagnosis of PAD. Outcomes of interest were lower extremity amputations and death. The association of statin intensity with incident amputation and mortality was assessed with Kaplan-Meier plots, Cox proportional hazards modeling, propensity score-matched analysis, and sensitivity and subgroup analyses, as well, to reduce confounding.

RESULTS

In 155 647 patients with incident PAD, more than a quarter (28%) were not on statins. Use of high-intensity statins was lowest in patients with PAD only (6.4%) in comparison with comorbid coronary/carotid disease (18.4%). Incident amputation and mortality risk declined significantly with any statin use in comparison with the antiplatelet therapy-only group. In adjusted Cox models, the high-intensity statin users were associated with lower amputation risk and mortality in comparison with antiplatelet therapy-only users (hazard ratio, 0.67; 95% confidence interval, 0.61-0.74 and hazard ratio, 0.74; 95% confidence interval, 0.70-0.77, respectively). Low-to-moderate-intensity statins also had significant reductions in the risk of amputation and mortality (hazard ratio amputation, 0.81; 95% confidence interval, 0.75- 0.86; hazard ratio death, 0.83; 95% confidence interval, 0.81-0.86) in comparison with no statins (antiplatelet therapy only), but effect size was significantly weaker than the high-intensity statins (P<0.001). The association of high-intensity statins with lower amputation and death risk remained significant and robust in propensity score-matched, sensitivity, and subgroup analyses.

CONCLUSIONS

Statins, especially high-intensity formulations, are underused in patients with PAD. This is the first population-based study to show that high-intensity statin use at the time of PAD diagnosis is associated with a significant reduction in limb loss and mortality in comparison with low-to-moderate-intensity statin users, and patients treated only with antiplatelet medications but not with statins, as well.

Human diabetic mesenchymal stem cells from peripheral arterial disease patients promote angiogenesis through unique secretome signatures

BACKGROUND

Diabetic patients are at increased risk of complications from severe peripheral arterial disease. Mesenchymal stem cells (MSC) may be useful in limiting these complications. Our objective is to test the angiogenic potential of diabetic versus healthy MSCs.

METHODS

MSCs' angiogenic potential was tested by endothelial cell (EC) proliferation, migration, and 3-dimensional sprouting. Diabetic conditions were simulated with 5.5, 20, or 40 mM glucose. MSC secretome was quantified by enzyme-linked immunosorbent assay.

RESULTS

Human aortic ECs were most sensitive to glucose conditions and were used for all MSC experiments. Diabetic MSCs had greater 3-dimensional invasion than healthy MSCs (P<.05), but EC sprouting was decreased in high glucose conditions in both diabetic and healthy MSCs. Secretome analysis demonstrated that 20mM glucose stimulated epidermal growth factor (EGF) expression in diabetic and healthy MSCs, but that diabetic MSCs had a unique secretome with increased levels of chemokine (C-X-C motif) ligand 1 (CXCL-1), interleukin six (IL-6), and monocyte chemoattractant protein 1 (MCP-1) (P<.05).

CONCLUSION

Despite having similar in vitro angiogenic activity, diabetic MSCs secrete a unique and inflammatory angiogenic signature that may influence MSC survival and function after transplantation in cell therapy applications. Strategies that normalize secretome in diabetic patients may improve the utility of autologous MSCs in this population of patients.

Race and Socioeconomic Status Independently Affect Risk of Major Amputation in Peripheral Artery Disease

Background

Black race has been shown to be a risk factor for amputation in peripheral artery disease (PAD); however, race has been argued to be a marker for socioeconomic status (SES) rather than true disparity. The aim of this study is to study the impact of race and SES on amputation risk in PAD patients.

Methods and Results

Patients with incident PAD in the national Veterans Affairs Corporate Data Warehouse were identified from 2003 to 2014 (N=155 647). The exposures were race and SES (measured by median income in residential ZIP codes). The outcome was incident major amputation. Black veterans were significantly more likely to live in low‐SES neighborhoods and to present with advanced PAD. Black patients had a higher amputation risk in each SES stratum compared with white patients. In Cox models (adjusting for covariates), black race was associated with a 37% higher amputation risk compared with white race (hazard ratio: 1.37; 95% confidence interval, 1.30–1.45), whereas low SES was independently predictive of increased risk of amputation (hazard ratio: 1.12; 95% confidence interval, 1.06–1.17) and showed no evidence of interaction with race. In predicted amputation risk analysis, black race and low SES continued to be significant risk factors for amputation regardless of PAD presentation.

Conclusions

Black race significantly increases the risk of amputation within the same SES stratum compared with white race and has an independent effect on limb loss after controlling for comorbidities, severity of PAD at presentation, and use of medications.

High hemoglobin A1c associated with increased adverse limb events in peripheral arterial disease patients undergoing revascularization

OBJECTIVE

Diabetes and peripheral arterial disease (PAD) are independently associated with increased risk of amputation. However, the effect of poor glycemic control on adverse limb events has not been studied. We examined the effects of poor glycemic control (high hemoglobin A_1c level) on the risk of amputation and modified major adverse limb events (mMALEs) after lower extremity revascularization.

METHODS

Patients undergoing PAD revascularization who had hemoglobin A_1c (HbA_1c) levels available within 6 months were identified in the Veterans Affairs database of 2003 to 2014 (N = 26,799). The diagnosis of preoperative diabetes mellitus (PreopDM) was defined using diabetes diagnosis codes and evidence of treatment. Amputation and mMALE risk was compared for HbA_1c levels using Kaplan-Meier analysis. Cox proportional hazards models were created to assess the effect of high HbA_1c levels on amputation and mMALE (adjusted for age, gender, race, socioeconomic status, comorbidities, cholesterol levels, creatinine concentration, suprainguinal or infrainguinal procedure, open or endovascular procedure, severity of PAD, year of cohort entry, and medications) for all patients and stratified by PreopDM.

RESULTS

High HbA_1c levels were present in 33.2% of the cohort, whereas 59.9% had PreopDM. Amputations occurred in 4359 (16.3%) patients, and 10,580 (39.5%) had mMALE. Kaplan-Meier curves showed the worst outcomes in patient with PreopDM and high HbA_1c levels. In the Cox model, incremental HbA_1c levels of 6.1% to 7.0%, 7.1% to 8.0%, and >8% were associated with 26% (hazard ratio [HR], 1.26; 95% confidence interval [CI], 1.15-1.39), 53% (HR, 1.53; 95% CI, 1.37-1.7), and 105% (HR, 2.05; 95% CI, 1.87-2.26) higher risk of amputation, respectively. Similarly, the risk of mMALE also increased by 5% (HR, 1.05; 95% CI, 0.99-1.11), 21% (HR, 1.21; 95% CI, 1.13-1.29), and 33% (HR, 1.33, 95% CI, 1.25-1.42) with worsening HbA_1c levels of 6.1% to 7.0%, 7.1% to 8.0%, and >8%, respectively (vs HbA_1c ≤6.0%). In stratified analysis by established PreopDM, the relative risk of amputation or mMALE was much higher with poor glycemic control (HbA_1c >7.0%) in patients without PreopDM.

CONCLUSIONS

PAD patients with worse perioperative glycemic control have a significantly higher risk of amputation and mMALE. Incremental increases in HbA_1c levels are associated with higher hazards of adverse limb outcomes independent of PreopDM status. Poor glycemic control (HbA_1c >7.0%) in patients without a PreopDM diagnosis carries twice the relative risk of amputation and mMALE than in those with good glycemic control. These results suggest that screening of diabetic status and better management of glycemic control could be a target for improvement of perioperative and long-term outcomes in PAD patients.

Disturbed Flow Promotes Arterial Stiffening Through Thrombospondin-1

BACKGROUND

Arterial stiffness and wall shear stress are powerful determinants of cardiovascular health, and arterial stiffness is associated with increased cardiovascular mortality. Low and oscillatory wall shear stress, termed disturbed flow (d-flow), promotes atherosclerotic arterial remodeling, but the relationship between d-flow and arterial stiffness is not well understood. The objective of this study was to define the role of d-flow on arterial stiffening and discover the relevant signaling pathways by which d-flow stiffens arteries.

METHODS

D-flow was induced in the carotid arteries of young and old mice of both sexes. Arterial stiffness was quantified ex vivo with cylindrical biaxial mechanical testing and in vivo from duplex ultrasound and compared with unmanipulated carotid arteries from 80-week-old mice. Gene expression and pathway analysis was performed on endothelial cell-enriched RNA and validated by immunohistochemistry. In vitro testing of signaling pathways was performed under oscillatory and laminar wall shear stress conditions. Human arteries from regions of d-flow and stable flow were tested ex vivo to validate critical results from the animal model.

RESULTS

D-flow induced arterial stiffening through collagen deposition after partial carotid ligation, and the degree of stiffening was similar to that of unmanipulated carotid arteries from 80-week-old mice. Intimal gene pathway analyses identified transforming growth factor-β pathways as having a prominent role in this stiffened arterial response, but this was attributable to thrombospondin-1 (TSP-1) stimulation of profibrotic genes and not changes to transforming growth factor-β. In vitro and in vivo testing under d-flow conditions identified a possible role for TSP-1 activation of transforming growth factor-β in the upregulation of these genes. TSP-1 knockout animals had significantly less arterial stiffening in response to d-flow than wild-type carotid arteries. Human arteries exposed to d-flow had similar increases TSP-1 and collagen gene expression as seen in our model.

CONCLUSIONS

TSP-1 has a critical role in shear-mediated arterial stiffening that is mediated in part through TSP-1's activation of the profibrotic signaling pathways of transforming growth factor-β. Molecular targets in this pathway may lead to novel therapies to limit arterial stiffening and the progression of disease in arteries exposed to d-flow.

A Novel Approach to Assess the In Situ Versus Ex Vivo Mechanical Behaviors of the Coronary Artery

Ex vivo mechanical testing has provided tremendous insight toward prediction of the in vivo mechanical behavior and local mechanical environment of the arterial wall; however, the role of perivascular support on the local mechanical behavior of arteries is not well understood. Here, we present a novel approach for quantifying the impact of the perivascular support on arterial mechanics using intravascular ultrasound (IVUS) on cadaveric porcine hearts. We performed pressure-diameter tests (n = 5) on the left anterior descending coronary arteries (LADCAs) in situ while embedded in their native perivascular environment using IVUS imaging and after removal of the perivascular support of the artery. We then performed standard cylindrical biaxial testing on these vessels ex vivo and compared the results. Removal of the perivascular support resulted in an upward shift of the pressure-diameter curve. Ex vivo testing, however, showed significantly lower circumferential compliance compared to the in situ configuration. On a second set of arteries, local axial stretch ratios were quantified (n = 5) along the length of the arteries. The average in situ axial stretch ratio was 1.28 ± 0.16; however, local axial stretch ratios showed significant variability, ranging from 1.01 to 1.70. Taken together, the data suggest that both the perivascular loading and the axial tethering have an important role in arterial mechanics. Combining nondestructive testing using IVUS with traditional ex vivo cylindrical biaxial testing yields a more comprehensive assessment of the mechanical behavior of arteries.

An endovascular model of ischemic myopathy from peripheral arterial disease

OBJECTIVE

Peripheral arterial disease (PAD) is a significant age-related medical condition with limited pharmacologic options. Severe PAD, termed critical limb ischemia, can lead to amputation. Skeletal muscle is the end organ most affected by PAD, leading to ischemic myopathy and debility of the patient. Currently, there are not any therapeutics to treat ischemic myopathy, and proposed biologic agents have not been optimized owing to a lack of preclinical models of PAD. Because a large animal model of ischemic myopathy may be useful in defining the optimal dosing and delivery regimens, the objective was to create and to characterize a swine model of ischemic myopathy that mimics patients with severe PAD.

METHODS

Yorkshire swine (N = 8) underwent acute right hindlimb ischemia by endovascular occlusion of the external iliac artery. The effect of ischemia on limb function, perfusion, and degree of ischemic myopathy was quantified by weekly gait analysis, arteriography, hindlimb blood pressures, femoral artery duplex ultrasound scans, and histologic examination. Animals were terminated at 5 (n = 5) and 6 (n = 3) weeks postoperatively. Ossabaw swine (N = 8) fed a high-fat diet were used as a model of metabolic syndrome for comparison of arteriogenic recovery and validation of ischemic myopathy.

RESULTS

There was persistent ischemia in the right hindlimb, and occlusion pressures were significantly depressed compared with the untreated left hindlimb out to 6 weeks (systolic blood pressure, 31 ± 21 vs 83 ± 15 mm Hg, respectively; P = .0007). The blood pressure reduction resulted in a significant increase of ischemic myopathy in the gastrocnemius muscle in the treated limb. Gait analysis revealed a functional deficit of the right hindlimb immediately after occlusion that improved rapidly during the first 2 weeks. Peak systolic velocity values in the right common femoral artery were severely diminished throughout the entire study (P < .001), and the hemodynamic environment after occlusion was characterized by low and oscillatory wall shear stress. Finally, the internal iliac artery on the side of the ischemic limb underwent significant arteriogenic remodeling (1.8× baseline) in the Yorkshire but not in the Ossabaw swine model.

CONCLUSIONS

This model uses endovascular technology to produce the first durable large animal model of ischemic myopathy. Acutely (first 2 weeks), this model is associated with impaired gait but no tissue loss. Chronically (2-6 weeks), this model delivers persistent ischemia, resulting in ischemic myopathy similar to that seen in PAD patients. This model may be of use for testing novel therapeutics including biologic therapies for promoting neovascularization and arteriogenesis.

A novel platelet lysate hydrogel for endothelial cell and mesenchymal stem cell-directed neovascularization

Mesenchymal stem cells (MSC) hold promise in promoting vascular regeneration of ischemic tissue in conditions like critical limb ischemia of the leg. However, this approach has been limited in part by poor cell retention and survival after delivery. New biomaterials offer an opportunity to localize cells to the desired tissue after delivery, but also to improve cell survival after delivery. Here we characterize the mechanical and microstructural properties of a novel hydrogel composed of pooled human platelet lysate (PL) and test its ability to promote MSC angiogenic activity using clinically relevant in vitro and in vivo models. This PL hydrogel had comparable storage and loss modulus and behaved as a viscoelastic solid similar to fibrin hydrogels despite having 1/4-1/10th the fibrin content of standard fibrin gels. Additionally, PL hydrogels enabled sustained release of endogenous PDGF-BB for up to 20days and were resistant to protease degradation. PL hydrogel stimulated pro-angiogenic activity by promoting human MSC growth and invasion in a 3D environment, and enhancing endothelial cell sprouting alone and in co-culture with MSCs. When delivered in vivo, the combination of PL and human MSCs improved local tissue perfusion after 8days compared to controls when assessed with laser Doppler perfusion imaging in a murine model of hind limb ischemia. These results support the use of a PL hydrogel as a scaffold for MSC delivery to promote vascular regeneration.

STATEMENT OF SIGNIFICANCE

Innovative strategies for improved retention and viability of mesenchymal stem cells (MSCs) are needed for cellular therapies. Human platelet lysate is a potent serum supplement that improves the expansion of MSCs. Here we characterize our novel PL hydrogel's desirable structural and biologic properties for human MSCs and endothelial cells. PL hydrogel can localize cells for retention in the desired tissue, improves cell viability, and augments MSCs' angiogenic activity. As a result of these unique traits, PL hydrogel is ideally suited to serve as a cell delivery vehicle for MSCs injected into ischemic tissues to promote vascular regeneration, as demonstrated here in a murine model of hindlimb ischemia.

Abstract 109: Statins Have a Dose-dependent Effect on Amputation Risk and Survival in Peripheral Arterial Disease (PAD) Patients

Introduction: Statin dose guidelines for PAD patients are based on coronary artery disease and stroke data. The aim of our study was to determine the effect of statin dose (based on 2013 ACC/AHA guidelines) on PAD outcomes of amputation and mortality.

Methods: Patients with PAD in the Veterans Affairs database were identified from 2003-2014. The exposure was highest statin dose usage (none, low-moderate and high intensity) around diagnosis of PAD (within 1 year). The outcomes were risk of incident amputation (below knee or above knee) and mortality at 1, 3 and 5 years. The effect of statin dose on the two outcomes was also analyzed using Cox proportional hazards modeling to adjust for covariates.

Results: In 208,275 patients with PAD [Males: 98.1%; Mean age: 67.4 yrs (SD 9.9)], 17,643 amputations and 99,951 deaths occurred in a median follow up of 5.2 years. Almost a quarter (27.7%) of patients were not on a statin while 30.4% were on simvastatin 80 mg (no longer recommended due to drug toxicity). The risk of incident amputation declined significantly at the high intensity statin dose as seen in Table 1. In Cox models adjusting for age, gender, race, comorbidities, cholesterol levels and creatinine, the high intensity statins were associated with lower amputation risk and mortality as compared to no statin [HR 0.67; 95% CI (0.63, 0.72) and HR 0.71; 95% CI (0.68, 0.73), respectively]. Low-moderate-dose statins also had significant but smaller reductions in risk of amputation and mortality [HR amputation 0.78 (0.75, 0.82), HR death 0.78 (0.77, 0.80)].

Conclusion: This is one of the largest population based studies to examine the effect of statins on long-term PAD outcomes and the first to explore the dose-dependent effect of statins on amputation and mortality. High intensity statins are associated with a significant reduction in limb loss and mortality in PAD patients followed by a smaller risk reduction by low-moderate intensity statins as compared to no statin therapy.

Posttraumatic Resuscitation Affects Stent Graft Sizing in Patients with Blunt Thoracic Aortic Injury

Patients with blunt aortic injury often present to the emergency department in a relatively hypovolemic state. These patients undergo extensive inhospital resuscitation. The effect of posttraumatic resuscitation on aortic diameter has implications for stent graft sizing. The potential utility of repeat aortic imaging after resuscitation remains unclear. A retrospective chart review of all adult patients presenting to a Level I trauma center between the years 2007 and 2013 was performed. Fifty-three patients were identified with a diagnosis of traumatic aortic injury. Of those, 10 had 2 CT scans before aortic repair and were selected as the study population for analysis. After resuscitation, there was a significant increase in aortic diameter both proximal and distal to the aortic injury: proximal aortic diameter increase of 1.97 mm and distal aortic diameter increase of 1.48 mm. This retrospective study shows that after resuscitation, there is a significant increase in proximal and distal aortic diameter. Interval reimaging of the thoracic aorta may be beneficial after adequate stabilization of the patient's other injuries. In certain cases, more appropriate sizing may prevent a device-related complication.

Posttraumatic Resuscitation Affects Stent Graft Sizing in Patients with Blunt Thoracic Aortic Injury

Patients with blunt aortic injury often present to the emergency department in a relatively hypovolemic state. These patients undergo extensive inhospital resuscitation. The effect of posttraumatic resuscitation on aortic diameter has implications for stent graft sizing. The potential utility of repeat aortic imaging after resuscitation remains unclear. A retrospective chart review of all adult patients presenting to a Level I trauma center between the years 2007 and 2013 was performed. Fifty-three patients were identified with a diagnosis of traumatic aortic injury. Of those, 10 had 2 CT scans before aortic repair and were selected as the study population for analysis. After resuscitation, there was a significant increase in aortic diameter both proximal and distal to the aortic injury: proximal aortic diameter increase of 1.97 mm and distal aortic diameter increase of 1.48 mm. This retrospective study shows that after resuscitation, there is a significant increase in proximal and distal aortic diameter. Interval reimaging of the thoracic aorta may be beneficial after adequate stabilization of the patient's other injuries. In certain cases, more appropriate sizing may prevent a device-related complication.

Late mortality in females after endovascular aneurysm repair

BACKGROUND

Abdominal aortic aneurysm (AAA) rupture is an adverse arterial remodeling event with high mortality risk. Because females have increased rupture risk with smaller AAAs (<5.5 cm), many recommend elective repair before the AAA reaches 5.5 cm. Elective repair improves survival for large AAAs, but long-term benefits of endovascular aneurysm repair (EVAR) for small AAAs in females remain less understood. The objective of this study was to identify if differences in late mortality exist between females undergoing elective EVAR at our institution for small and/or slow-growing AAAs compared with those who meet standard criteria.

METHODS

We retrospectively analyzed all patients that underwent EVAR for infrarenal AAA from June, 2009-June, 2013. We excluded patients that were male, treated emergently or for iliac artery aneurysm, and that received renal and/or mesenteric artery stenting. Patients did not meet anatomic criteria if preoperative AAA diameter was <5.5 cm or enlarged <0.5 cm over 6 mo. Late mortality was assessed from the social security death index.

RESULTS

Thirty-six of 162 elective EVAR patients (22.2%) were female (mean follow-up, 37.2 mo). Twenty patients (55.6%) met AAA size and/or growth criteria, whereas 16 (44.4%) did not meet criteria. Despite comparable demographics, comorbidities, and complications, patients that did not meet criteria had higher late mortality (37.5% versus 5%; P = 0.03) with a trend toward increased reoperation rate (25% versus. 5%; P = 0.48). Meeting size and/or growth criteria decreased odds of late death (odds ratio, 0.09; 95% confidence intervals, 0.01-0.83).

CONCLUSIONS

There is increased late mortality in females receiving elective EVAR at our institution for small and/or slow-growing AAAs. This late mortality may limit the benefits of EVAR for this population.

Hydrogen Sulfide Levels and Nuclear Factor-Erythroid 2-Related Factor 2 (NRF2) Activity Are Attenuated in the Setting of Critical Limb Ischemia (CLI)

Background

Cystathionine γ-lyase, cystathionine β-synthase, and 3-mercaptopyruvate sulfurtransferase are endogenous enzymatic sources of hydrogen sulfide (H₂S). Functions of H₂S are mediated by several targets including ion channels and signaling proteins. Nuclear factor-erythroid 2-related factor 2 is responsible for the expression of antioxidant response element–regulated genes and is known to be upregulated by H₂S. We examined the levels of H₂S, H₂S-producing enzymes, and nuclear factor-erythroid 2-related factor 2 activation status in skeletal muscle obtained from critical limb ischemia (CLI) patients.

Methods and Results

Gastrocnemius tissues were attained postamputation from human CLI and healthy control patients. We found mRNA and protein levels of cystathionine γ-lyase, cystathionine β-synthase, and 3-mercaptopyruvate sulfurtransferase were significantly decreased in skeletal muscle of CLI patients as compared to control. H₂S and sulfane sulfur levels were significantly decreased in skeletal muscle of CLI patients. We also observed significant reductions in nuclear factor-erythroid 2-related factor 2 activation as well as antioxidant proteins, such as Cu, Zn-superoxide dismutase, catalase, and glutathione peroxidase in skeletal muscle of CLI patients. Biomarkers of oxidative stress, such as malondialdehyde and protein carbonyl formation, were significantly increased in skeletal muscle of CLI patients as compared to healthy controls.

Conclusions

The data demonstrate that H₂S bioavailability and nuclear factor-erythroid 2-related factor 2 activation are both attenuated in CLI tissues concomitant with significantly increased oxidative stress. Reductions in the activity of H₂S-producing enzymes may contribute to the pathogenesis of CLI.

Sustained release nitrite therapy results in myocardial protection in a porcine model of metabolic syndrome with peripheral vascular disease

Metabolic syndrome (MetS) reduces endothelial nitric oxide (NO) bioavailability and exacerbates vascular dysfunction in patients with preexisting vascular diseases. Nitrite, a storage form of NO, can mediate vascular function during pathological conditions when endogenous NO is reduced. The aims of the present study were to characterize the effects of severe MetS and obesity on dyslipidemia, myocardial oxidative stress, and endothelial NO synthase (eNOS) regulation in the obese Ossabaw swine (OS) model and to examine the effects of a novel, sustained-release formulation of sodium nitrite (SR-nitrite) on coronary vascular reactivity and myocardial redox status in obese OS subjected to critical limb ischemia (CLI). After 6 mo of an atherogenic diet, obese OS displayed a MetS phenotype. Obese OS had decreased eNOS functionality and NO bioavailability. In addition, obese OS exhibited increased oxidative stress and a significant reduction in antioxidant enzymes. The efficacy of SR-nitrite therapy was examined in obese OS subjected to CLI. After 3 wk of treatment, SR-nitrite (80 mg · kg(-1) · day(-1) bid po) increased myocardial nitrite levels and eNOS function. Treatment with SR-nitrite reduced myocardial oxidative stress while increasing myocardial antioxidant capacity. Ex vivo assessment of vascular reactivity of left anterior descending coronary artery segments demonstrated marked improvement in vasoreactivity to sodium nitroprusside but not to substance P and bradykinin in SR-nitrite-treated animals compared with placebo-treated animals. In conclusion, in a clinically relevant, large-animal model of MetS and CLI, treatment with SR-nitrite enhanced myocardial NO bioavailability, attenuated oxidative stress, and improved ex vivo coronary artery vasorelaxation.

Abstract 193: Analysis of Platelet Lysate Hydrogel and Fibrinogen Gel Intramuscular Injection on Neo-Angiogenesis in Ischemic Limbs

Introduction: We have recently characterized the in vitro benefits of the fibrin-rich pooled human platelet lysate (PL) in gel form on mesenchymal stem cells’ angiogenic activity. This study aimed to investigate the potential angiogenic activity of PL gel compared to a fibrin hydrogel (FG) in a murine model of hind limb ischemia (HLI).

Methods: S129 male and female mice aged 20-weeks (n = 30) underwent right femoral artery ligation to induce HLI and were randomized to five groups: G1) Sham (n=5); G2) HLI-no treatment (n=5); G3) Saline (n=5; G4) PL (N=5); and G5) FG (n=5). The treatment limbs received PL, FG or saline by injection of 200 μL in the adductor muscle at day 0. Perfusion was quantitated with Laser Doppler Perfusion Imaging (LDPI) at 1-day post-procedurally and weekly for 28 days, and reported as ratios of the values in the ischemic limb (IL) to those in the contralateral nonischemic limb (NIL) for the adductor (thigh) and gastrocnemius (calf) areas. We then compared the change in the IL/NIL ratios for each group over the 28 days. Non-parametric analysis of variance with Dunn’s correction test was used to compare results among groups. The level of significance was set at p<0.05.

Results: There were trends in the thigh and calf IL/NIL perfusion ratios at 28 days for mice injected with PL and FG compared to those with saline injections or HLI and no treatment (P>.05). Perfusion in both calf and thigh areas improved from day one to day 28 in all HLI groups. However, only PL and FG groups had significantly increased progression in thigh perfusion, and this was in comparison to sham animals. In the calf, only the FG group demonstrated a significant increase in the perfusion ratio, and this was in comparison to both HLI with no treatment and sham groups (P<.05).

Conclusions: While both FG and PL gel have active angiogenic properties, FG gel alone, and not PL gel, demonstrated superior in vivo angiogenic response in this model of HLI.

Therapeutic potential of sustained-release sodium nitrite for critical limb ischemia in the setting of metabolic syndrome

Nitrite is a storage reservoir of nitric oxide that is readily reduced to nitric oxide under pathological conditions. Previous studies have demonstrated that nitrite levels are significantly reduced in cardiovascular disease states, including peripheral vascular disease. We investigated the cytoprotective and proangiogenic actions of a novel, sustained-release formulation of nitrite (SR-nitrite) in a clinically relevant in vivo swine model of critical limb ischemia (CLI) involving central obesity and metabolic syndrome. CLI was induced in obese Ossabaw swine (n = 18) by unilateral external iliac artery deployment of a full cross-sectional vessel occlusion device positioned within an endovascular expanded polytetrafluoroethylene-lined nitinol stent-graft. At post-CLI day 14, pigs were randomized to placebo (n = 9) or SR-nitrite (80 mg, n = 9) twice daily by mouth for 21 days. SR-nitrite therapy increased nitrite, nitrate, and S-nitrosothiol in plasma and ischemic skeletal muscle. Oxidative stress was reduced in ischemic limb tissue of SR-nitrite- compared with placebo-treated pigs. Ischemic limb tissue levels of proangiogenic growth factors were increased following SR-nitrite therapy compared with placebo. Despite the increases in cytoprotective and angiogenic signals with SR-nitrite therapy, new arterial vessel formation and enhancement of blood flow to the ischemic limb were not different from placebo. Our data clearly demonstrate cytoprotective and proangiogenic signaling in ischemic tissues following SR-nitrite therapy in a very severe model of CLI. Further studies evaluating longer-duration nitrite therapy and/or additional nitrite dosing strategies are warranted to more fully evaluate the therapeutic potential of nitrite therapy in peripheral vascular disease.

Carotid duplex criteria for patients with contralateral occlusion

BACKGROUND

Contralateral occlusion (CLO) occurs in approximately 8% of patients undergoing intervention for carotid artery stenosis. Patients with CLO have increased stroke risk compared with patients without CLO, but standard carotid duplex ultrasonography (CDUS) criteria are not a reliable manner to screen or follow patients with CLO. Because appropriate duplex criteria for these patients are not well understood, this article defines CDUS parameters that accurately predict carotid artery stenosis at our institution.

METHODS

Sixty-five patients with ipsilateral carotid stenosis and CLO were identified from our institutional database. Fifteen of sixty-five patients had arteriography, computed tomography angiography, or magnetic resonance angiography within 6 mo of CDUS. We determined accuracy of our laboratory's criteria for determining stenosis category compared with three-dimensional imaging. Receiver operating characteristic curves were used to determine optimal peak systolic velocity (PSV), end diastolic velocity (EDV), and systolic ratio (SR) cutoff values for diagnosing ≥50% stenosis in this pilot cohort. Finally, the revised criteria were prospectively applied to a validation cohort (n = 8) from the same institution.

RESULTS

Categorization of stenosis by standard PSV, EDV, and SR criteria saw similar accuracy trends in both pilot (46.7, 53.3, and 66.7%) and validation (25, 25, and 62.5%) cohorts. Receiver operating characteristic curve analysis in the pilot cohort identified optimized PSV, EDV, and SR cutoffs (≥250, ≥90, and ≥2.3 cm/s, respectively) for diagnosing ≥50% stenosis. In the pilot cohort, new PSV criteria increased specificity (60%-100%) with minimal decreased sensitivity (90%-80%), whereas new EDV criteria increased specificity (40%-71.4%) and maintained 100% sensitivity. New SR criteria failed to improve sensitivity or specificity above 80%. Similar trends for the new CDUS velocity criteria were observed in the validation cohort.

CONCLUSIONS

Increasingly stringent ultrasound parameters can provide reliable criteria for determining ≥50% carotid stenosis in patients with CLO. Further prospective validation that includes more patients with high-grade ipsilateral stenosis will help identify the role of SR in segregating high-grade versus moderate stenosis in CLO patients.