Robert T. Eberhardt

Endothelial dysfunction in a murine model of mild hyperhomocyst(e)inemia

Homocysteine is a risk factor for the development of atherosclerosis and its thrombotic complications. We have employed an animal model to explore the hypothesis that an increase in reactive oxygen species and a subsequent loss of nitric oxide bioactivity contribute to endothelial dysfunction in mild hyperhomocysteinemia. We examined endothelial function and in vivo oxidant burden in mice heterozygous for a deletion in the cystathionine beta-synthase (CBS) gene, by studying isolated, precontracted aortic rings and mesenteric arterioles in situ. CBS(-/+) mice demonstrated impaired acetylcholine-induced aortic relaxation and a paradoxical vasoconstriction of mesenteric microvessels in response to superfusion of methacholine and bradykinin. Cyclic GMP accumulation following acetylcholine treatment was also impaired in isolated aortic segments from CBS(-/+) mice, but aortic relaxation and mesenteric arteriolar dilation in response to sodium nitroprusside were similar to wild-type. Plasma levels of 8-epi-PGF(2alpha) (8-IP) were somewhat increased in CBS(-/+) mice, but liver levels of 8-IP and phospholipid hydroperoxides, another marker of oxidative stress, were normal. Aortic tissue from CBS(-/+) mice also demonstrated greater superoxide production and greater immunostaining for 3-nitrotyrosine, particularly on the endothelial surface. Importantly, endothelial dysfunction appears early in CBS(-/+) mice in the absence of structural arterial abnormalities. Hence, mild hyperhomocysteinemia due to reduced CBS expression impairs endothelium-dependent vasodilation, likely due to impaired nitric oxide bioactivity, and increased oxidative stress apparently contributes to inactivating nitric oxide in chronic, mild hyperhomocysteinemia.

Chronic Venous Insufficiency

Chronic venous disease is often overlooked by primary and cardiovascular care providers because of an underappreciation of the magnitude and impact of the problem. The importance of chronic venous disease is related to the number of people with the disease and the socioeconomic impact of its more severe manifestations. Unfortunately, the literature concerning the prevalence and incidence of chronic venous disease has varied greatly because of differences in the methods of evaluation, criteria for definition, and the geographic regions analyzed. The most common manifestations of chronic venous disease are dilated cutaneous veins, such as telangiectases and reticular veins, and varicose veins. The term chronic venous insufficiency (CVI) describes a condition that affects the venous system of the lower extremities with venous hypertension causing various pathologies including pain, swelling, edema, skin changes, and ulcerations. Although the term CVI is often used to exclude uncomplicated varicose veins, varicose veins have incompetent valves with increased venous pressure leading to progressive dilation and tortuosity. We will use the term CVI to represent the full spectrum of manifestations of chronic venous disease. Varicose veins have an estimated prevalence between 5% to 30% in the adult population, with a female to male predominance of 3 to 1, although a more recent study supports a higher male prevalence.1 The Edinburgh Vein Study screened 1566 subjects with duplex ultrasound for reflux finding CVI in 9.4% of men and 6.6% of women, after age adjustment, which rose significantly with age (21.2% in men >50 years old, and 12.0% in women >50 years old).2 The San Valentino Vascular Screening Project found among the 30 000 subjects evaluated by clinical assessment and duplex ultrasound a prevalence of 7% for varicose veins and 0.86% for “symptomatic” CVI.3 As in previous studies, CVI was more common with increasing age, but …

Predictive Value of Reactive Hyperemia for Cardiovascular Events in Patients With Peripheral Arterial Disease Undergoing Vascular Surgery

Objective— Reactive hyperemia is the compensatory increase in blood flow that occurs after a period of tissue ischemia, and this response is blunted in patients with cardiovascular risk factors. The predictive value of reactive hyperemia for cardiovascular events in patients with atherosclerosis and the relative importance of reactive hyperemia compared with other measures of vascular function have not been previously studied. Methods and Results— We prospectively measured reactive hyperemia and brachial artery flow-mediated dilation by ultrasound in 267 patients with peripheral arterial disease referred for vascular surgery (age 66±11 years, 26% female). Median follow-up was 309 days (range 1 to 730 days). Fifty patients (19%) had an event, including cardiac death (15), myocardial infarction (18), unstable angina (8), congestive heart failure (6), and nonhemorrhagic stroke (3). Patients with an event were older and had lower hyperemic flow velocity (75±39 versus 95±50 cm/s, P=0.009). Patients with an event also had lower flow-mediated dilation (4.5±3.0 versus 6.9±4.6%, P<0.001), and when these 2 measures of vascular function were included in the same Cox proportional hazards model, lower hyperemic flow (OR 2.7, 95% CI 1.2 to 5.9, P=0.018) and lower flow-mediated dilation (OR 4.2, 95% CI: 1.8 to 9.8, P=0.001) both predicted cardiovascular events while adjusting for other risk factors. Conclusions— Thus, lower reactive hyperemia is associated with increased cardiovascular risk in patients with peripheral arterial disease. Furthermore, flow-mediated dilation and reactive hyperemia incrementally relate to cardiovascular risk, although impaired flow-mediated dilation was the stronger predictor in this population. These findings further support the clinical relevance of vascular function measured in the microvasculature and conduit arteries in the upper extremity.

Heterozygous Cellular Glutathione Peroxidase Deficiency in the Mouse Abnormalities in Vascular and Cardiac Function and Structure

Background—Oxidant stress has been implicated in the pathogenesis of atherothrombosis and other vascular disorders accompanied by endothelial dysfunction. Glutathione peroxidases (GPx) play an important role in the cellular defense against oxidant stress by utilizing glutathione (GSH) to reduce lipid hydroperoxides and hydrogen peroxide to their corresponding alcohols. Cellular GPx (GPx-1) is the principal intracellular isoform of GPx. We hypothesized that GPx-1 deficiency per se induces endothelial dysfunction and structural vascular abnormalities through increased oxidant stress. Methods and Results—A murine model of heterozygous deficiency of GPx-1 (GPx+/−) was investigated to examine this hypothesis. Mesenteric arterioles in GPx-1+/− mice demonstrated vasoconstriction to acetylcholine compared with vasodilation in wild-type mice (maximal change in vessel diameter, −13.0±2.8% versus 13.2±2.8%, P <0.0001). We also noted an increase in the plasma and aortic levels of the isoprostane iPF2&agr;-III, a marker of oxidant stress, in GPx-1+/− mice compared with wild-type mice (170.4±23 pg/mL plasma versus 98.7±7.1 pg/mL plasma, P <0.03; 11.7±0.87 pg/mg aortic tissue versus 8.2±0.55 pg/mg aortic tissue, P <0.01). Histological sections from the coronary vasculature of GPx-1+/− mice show increased perivascular matrix deposition, an increase in the number of adventitial fibroblasts, and intimal thickening. These structural abnormalities in the myocardial vasculature were accompanied by diastolic dysfunction after ischemia-reperfusion. Conclusions—These findings demonstrate that heterozygous deficiency of GPx-1 leads to endothelial dysfunction, possibly associated with increased oxidant stress, and to significant structural vascular and cardiac abnormalities. These data illustrate the importance of this key antioxidant enzyme in functional and structural responses of the mammalian cardiovascular system.

Guidelines for Performing Ultrasound Guided Vascular Cannulation: Recommendations of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists

TABLE OF CONTENTS PAGEIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . .46Methodology and Evidence Review . . . . . . .46Ultrasound-Guided Vascular Cannulation . . . . . . . . . . . . . . . . . . . . . . . . . . . .47Ultrasound Principles for Needle-Guided Catheter Placement . . . .

Early fasciotomy in patients with extremity vascular injury is associated with decreased risk of adverse limb outcomes: A review of the National Trauma Data Bank

INTRODUCTION AND OBJECTIVES Lower extremity (LE) arterial trauma and its treatment may lead to extremity compartment syndrome (ECS). In that setting, the decision to perform fasciotomies is multifactoral and is not well delineated. We evaluated the outcomes of patients with surgically treated LE arterial injury who underwent early or delayed fasciotomies. METHODS The National Trauma Data Bank (NTDB) was retrospectively reviewed for patients who had LE arterial trauma and underwent both open vascular repair and fasciotomies. Exclusion criteria were additional non-LE vascular trauma, head or spinal cord injuries, crush injuries, burn injuries, and declaration of death on arrival. Patients were divided into those who had fasciotomies performed within 8h (early group) or >8h after open vascular repair (late group). Comparative analyses of demographics, injury characteristics, complications, and outcomes were performed. RESULTS Of the 1469 patient admissions with lower extremity arterial trauma that met inclusion criteria there were 612 patients (41.7%) who underwent fasciotomies. There were 543 and 69 patients in the early and late fasciotomy groups, respectively. There was no significant difference in age, injury severity, mechanism of injury, associated injuries, and type of vascular repair between the groups. A higher rate of iliac artery injury was observed in the late fasciotomy group (23.2% vs. 5.9%, P<.001). Patients in the early fasciotomy group had lower amputation rate (8.5% vs. 24.6%, P<.001), lower infection rate (6.6% vs. 14.5%, P = .028) and shorter total hospital stay (18.5 ± 20.7 days vs. 24.2 ± 14.7 days, P = .007) than those in the late fasciotomy group. On multivariable analysis, early fasciotomy was associated with a 4-fold lower risk of amputation (Odds Ratio 0.26, 95% CI 0.14-0.50, P<.0001) and 23% shorter hospital LOS (Means Ratio 0.77, 95% CI 0.64-0.94, P = .01). CONCLUSION Early fasciotomy is associated with improved outcomes in patients with lower extremity vascular trauma treated with surgical intervention. Our findings suggest that appropriate implementation of early fasciotomy may reduce amputation rates in extremity arterial injury.

The Effect of L-Arginine and Creatine on Vascular Function and Homocysteine Metabolism

Abstract Studies with l-arginine supplementation have shown inconsistent effects on endothelial function. The generation of guanidinoacetate (GAA) from l-arginine with subsequent formation of creatine and homocysteine and consumption of methionine may reduce the pool of l-arginine available for nitric oxide generation. Experimental studies suggest that creatine supplementation might block this pathway. We sought to determine the effects of l-arginine, creatine, or the combination on endothelium-dependent vasodilation and homocysteine metabolism in patients with coronary artery disease. Patients with coronary artery disease were randomized to l-arginine (9 g/day), creatine (21 g/day), l-arginine plus creatine, or placebo for 4 days (n = 26–29/group). Brachial artery flow-mediated dilation and plasma levels of l-arginine, creatine, homocysteine, methionine, and GAA were measured at baseline and follow-up. l-Arginine and creatine supplementation had no effects on vascular function. l-Arginine alone increased GAA (p < 0.01) and the ratio of homocysteine to methionine (p < 0.01), suggesting increased methylation demand. The combination of creatinine and l-arginine did not suppress GAA production or prevent the increase in homocysteine-to-methionine ratio. Unexpectedly, creatine supplementation (alone or in combination with l-arginine) was associated with an 11–20% increase in homocysteine concentration (p < 0.05), which was not attributable to worsened renal function, providing evidence against an effect of creatine on decreasing methylation demand. In conclusion, the present study provides no evidence that l-arginine supplementation improves endothelial function and suggests that l-arginine may increase methylation demand. Creatine supplementation failed to alter the actions of l-arginine on vascular function or suppress methylation demand. The unexpected increase in homocysteine levels following creatine supplementation could have adverse effects and merits further study, since creatine is a commonly used dietary supplement.

A randomized phase II trial of Arginine Butyrate with standard local therapy in refractory sickle cell leg ulcers

Sickle cell leg ulcers are often debilitating, refractory to healing, and prone to recurrence. Healing of leg ulcers was incidentally observed during dose‐ranging trials of Arginine Butyrate in beta haemoglobinopathies. Here, a controlled Phase II trial was performed in sickle cell patients who had lower extremity ulcers refractory to standard care for at least 6 months. Patients were randomized to receive standard local care alone (Control Arm) or standard care with Arginine Butyrate administered 5 d/week (Treatment Arm), for 12 weeks. Ulcers were photographed weekly, traced, and ulcer areas were calculated by computerized planimetry and compared between the two study arms. Twenty‐seven study courses were evaluated. Control Arm subjects had 25 ulcers with a mean area of 25·7 cm2 initially and 23·2 cm2 after 12 weeks; 2/25 (8%) healed completely. Treatment Arm subjects had 37 ulcers with a mean area of 50·6 cm2 initially and 28·3 cm2 at 12 weeks; 11/37 of these (30%) healed completely. After 3 months, proportions of ulcers which healed were 6/25 (24%) and 29/37 (78%), in the Control and Treatment Arms respectively (P < 0·001). These findings strongly suggest that Arginine Butyrate merits further evaluation for the treatment of refractory sickle cell leg ulcers in larger trials.

Low-Renin Hypertension With Relative Aldosterone Excess Is Associated With Impaired NO-Mediated Vasodilation

Recent studies suggest that hypertension associated with low renin status and hyperaldosteronism is associated with increased risk for end-organ damage and cardiovascular events compared with other forms of hypertension. Additionally, experimental studies have demonstrated impaired nitric oxide-mediated bioactivity in these states. To investigate the relation between renin/aldosterone status and resistance vessel function, we examined plasma renin activity, serum aldosterone level, and forearm blood flow responses to the endothelium-dependent vasodilator methacholine and the endothelium-independent vasodilators sodium nitroprusside and verapamil using venous occlusion plethysmography in 130 volunteers (43 hypertensive, 87 normotensive). Low renin status was associated with impaired responses to methacholine and nitroprusside in patients with hypertension. Peak methacholine response was 8.7±5.6 mL/min per dL in the lowest renin quartile (0.1 to 0.3 ng/mL per hour) versus 14.3±7.3 mL/min per dL in the highest 3 renin quartiles combined (0.4 to 4.6 ng/mL per hour; P<0.001). Peak nitroprusside response was 5.6±2.3 mL/min per dL in the lowest renin quartile versus 13.3±4.1 mL/min per dL in the highest 3 renin quartiles combined (P<0.001). Blood pressure and other clinical characteristics were similar in all 4 quartiles. Vasodilator responses to verapamil did not relate to renin activity. Methacholine and nitroprusside responses did not relate to renin status in normotensive controls (P=0.34). Importantly, hypertensive patients with a high aldosterone/renin ratio also had impaired responses to methacholine. This study demonstrates that low-renin hypertension is associated with marked impairment of nitric oxide-mediated vasodilation of resistance vessels in the forearm vasculature of humans. This impairment could contribute to adverse outcomes in patients with low-renin hypertension and relative aldosterone excess.

Endovascular management of the popliteal artery: comparison of atherectomy and angioplasty.

Purpose: Symptomatic atherosclerotic disease of the popliteal artery presents challenges for endovascular therapy. We evaluated the technical success, complications, and midterm outcomes of atherectomy and angioplasty involving the popliteal segment. Methods: We conducted a retrospective review of outcomes of popliteal artery intervention using atherectomy or angioplasty performed between 2003 and 2008. Results: A total of 56 patients (36% women, age 72.8 ± 12.2 years, 77% critical limb ischemia) underwent popliteal atherectomy (n = 18) or angioplasty (n = 38). These patients had similar clinical characteristics, TransAtlantic Intersociety Consensus (TASC)/ TASC II classification, mean lesion length, and runoff scores. We observed a trend toward higher rates of technical success defined as <30% residual stenosis after atherectomy compared to angioplasty (94% vs 71%, P = .08). While angioplasty was associated with a higher frequency of arterial dissection (23% vs 0%, P = .003), atherectomy was associated with a higher rate of thromboembolic events (22% vs 0%, P = 0.01). Adjunctive stenting was used more frequently following angioplasty compared to atherectomy (45% vs 6%, P = .005). Thrombolysis was used to treat embolization in 4 patients in the atherectomy group. The improvement in the ankle-brachial index (ABI) was similar between the 2 treatment groups. Primary patency of the popliteal artery at 3, 6, and 12 months was 94%, 88%, and 75% in the atherectomy group and 89%, 82%, and 73% in the angioplasty group (P = not significant [NS]). There were no significant differences in limb salvage and freedom from reintervention at 1 year between the atherectomy and angioplasty groups. Conclusions: Our experience with popliteal artery endovascular therapy indicates a distinct pattern of procedural complications with atherectomy compared to angioplasty but similar midterm patency, limb salvage, and freedom from intervention.