PubMed Health⌕ Search

Biomedical subjects

Mark A Creager

Publications and source records attributed to Mark A Creager.

At least 55 records · Page 3Linked to original sources
PubMed2004

The relationship of cigarette smoking to peripheral arterial disease.

Cigarette smoking is one of the most important risk factors for peripheral arterial disease (PAD). Smoking increases the risk of PAD by several fold and is a more influential risk factor for PAD than for coronary artery disease. Multiple pathophysiologic mechanisms may account for the prevalence of atherosclerosis in cigarette smokers. These include abnormalities of endothelial function, lipoprotein metabolism, coagulation, and platelet function. Smoking cessation decreases the risk of cardiovascular morbidity and mortality, and may improve functional capacity in patients with PAD. Therapies to promote smoking cessation include counseling, nicotine replacement, and bupropion. Healthcare providers must enhance their efforts and target smoking cessation as a modifiable risk factor in patients with PAD and other manifestations of atherosclerosis.

Arteriosclerosis↗
PubMed2003

Cholesterol reduction with atorvastatin improves walking distance in patients with peripheral arterial disease.

BACKGROUND: Cholesterol modification reduces cardiovascular events in patients with atherosclerosis, including those with peripheral arterial disease. The purpose of this study was to determine whether cholesterol lowering with atorvastatin improves walking performance in patients with intermittent claudication. METHODS AND RESULTS: This randomized, double-blind, parallel-design study included 354 persons with claudication attributable to peripheral arterial disease. Patients were treated with placebo, atorvastatin (10 mg per day), or atorvastatin (80 mg per day) for 12 months. The outcome measures included change in treadmill exercise time and patient-reported measures of physical activity and quality of life based on questionnaires. Maximal walking time after 12 months of treatment with atorvastatin did not change significantly. However, there was improvement in pain-free walking time after 12 months of treatment for the 80-mg (P=0.025) group compared with placebo. A physical activity questionnaire demonstrated improvement in ambulatory ability for the 10- and 80-mg groups (P=0.011), whereas 2 quality of life instruments, the Walking Impairment Questionnaire and Short Form 36 Questionnaire, did not show significant change. CONCLUSIONS: Atorvastatin improves pain-free walking distance and community-based physical activity in patients with intermittent claudication. When treated with atorvastatin, patients with peripheral arterial disease may experience improvement in symptoms to complement the anticipated reduction in cardiovascular events reported in other studies of statins.

Aged↗
PubMed2003

Oral antioxidant therapy improves endothelial function in Type 1 but not Type 2 diabetes mellitus.

Oxidative stress decreases the bioavailability of endothelium-derived nitric oxide in diabetic patients. We investigated whether impaired endothelium-dependent vasodilation (EDV) in diabetes can be improved by long-term administration of oral antioxidants. Forty-nine diabetic subjects [26 Type 1 (T1) and 23 Type 2 (T2)] and 45 matched healthy control subjects were randomized to receive oral vitamin C (1,000 mg) and vitamin E (800 IU) daily or matching placebo for 6 mo. Vascular ultrasonography was used to determine brachial artery EDV and endothelium-independent vasodilation (EIV). EDV was decreased in both T1 (4.9 +/- 0.9%, P = 0.015) and T2 (4.1 +/- 1.0%, P < 0.01) subjects compared with control subjects (7.7 +/- 0.7%). EIV was decreased in T2 (15.0 +/- 1.2%, P < 0.01) but not T1 subjects (18.5 +/- 2.3%, P = 0.3) compared with controls (21.8 +/- 1.8%). Administration of antioxidant vitamins increased EDV in T1 (by 3.4 +/- 1.4%, P = 0.023) but not T2 subjects (by 0.5. +/- 0.4%, P = 0.3). Antioxidant therapy had no significant affect on EIV. Oral antioxidant therapy improves EDV in T1 but not T2 diabetes. These results are consistent with the lack of clinical benefit in studies that have included primarily T2 diabetic patients.

Administration, Oral↗
PubMed2003

Endothelin-1 and vascular tone in subjects with atherogenic risk factors.

Endothelin-1 (ET-1) is a potent vasoconstrictor that increases vascular tone in the resistance vessels of subjects with hypertension. It is unclear whether endogenous ET-1 affects resistance-vessel function equally in patients with other cardiovascular risk factors. Vasoconstriction to ET-1 is mediated principally via the endothelin-A (ETA) receptor on vascular smooth muscle cells. Accordingly, we used an ETA-specific antagonist, BQ-123, to test the hypothesis that endogenous ET-1 increases vascular resistance selectively in subjects with hypertension compared with other risk factors. BQ-123 was infused at 100 nmol/min for 80 minutes into the brachial artery of 10 subjects with hypertension (mean+/-SEM arterial pressure, 106+/-5 mm Hg), 12 subjects with hypercholesterolemia (mean+/-SEM total cholesterol, 7.1+/-0.2 mmol/L), 10 active smokers (mean+/-SEM, 42+/-11 pack-years), and 11 healthy, age-matched individuals. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. BQ-123 dilated resistance arterioles in hypertensive subjects, with FBF's increasing by 46+/-7% from baseline (P<0.001). BQ-123 increased FBF to a lesser extent in hypercholesterolemic (24+/-5%, P<0.001) and healthy (20+/-8%, P=0.007) individuals but did not affect FBF significantly in smokers (10+/-8%, P=0.185). The vasodilator response in hypertensive subjects, but not in hypercholesterolemic patients or smokers, was significantly greater than that in healthy individuals (P=0.012). Endogenous ET-1, acting via the ETA receptor, increases resistance-vessel tone in subjects with hypertension more than in subjects with hypercholesterolemia or in smokers. These results indicate that ET-1 contributes more to the pathophysiology of hypertension than of other risk factors in subjects without overt atherosclerosis.

Arteriosclerosis↗
PubMed2003

Pharmacotherapy and behavioral intervention for peripheral arterial disease.

Lower-extremity peripheral arterial disease is a chronic disease process resulting from atherosclerotic obstruction of major vessels supplying the legs. A significant manifestation of systemic atherosclerosis, it is estimated to affect more than 10 million adults in the United States alone. The reported incidence is a conservative estimate, because many patients who suffer from symptoms of peripheral arterial disease attribute them to "normal aging" and may not report them to their physician. Additionally, physicians may miss the diagnosis if a comprehensive history and vascular examination are not a routine part of their assessment. The hallmark symptom of peripheral arterial disease is intermittent claudication, defined as reproducible muscular leg pain that is precipitated by exercise and relieved by rest. Intermittent claudication not only limits functional capacity and adversely affects quality of life but is also an ominous predictor of increased risk for myocardial infarction, stroke, and cardiovascular death. Due to the chronicity of atherosclerosis, medical intervention is most successful when a comprehensive team approach is utilized, involving the patient, family, and vascular health professionals. Treatment for peripheral arterial disease is aimed at first, minimizing symptoms and disease progression via smoking cessation, supervised exercise therapy, pharmacotherapy, and/or revascularization, and second, minimizing the risk of cardiovascular mortality via risk factor identification and reduction, and the use of antiplatelet therapy.

Arterial Occlusive Diseases↗
PubMed2002

Homocysteine impairs coronary microvascular dilator function in humans.

OBJECTIVES: We sought to use positron emission tomography (PET) to test the hypothesis that hyperhomocysteinemia adversely effects coronary microvascular dilator function. BACKGROUND: Hyperhomocysteinemia is associated with abnormal endothelium-dependent vasodilation in peripheral human arteries. However, its effect on the coronary circulation is not known. METHODS: Eighteen healthy humans, age 24 to 56 years, were enrolled in a double-blind, crossover trial. Basal and adenosine-stimulated myocardial blood flow (MBF) was determined by PET: after ingestion of placebo and after methionine-induced hyperhomocysteinemia. Further, brachial ultrasonography was used to assess flow-mediated vasodilation. Additionally, to assess the role of nitric oxide (NO) in adenosine-mediated vasodilation, the MBF response to adenosine was measured in the presence and absence of the NO synthase antagonist NG-monomethyl-l-arginine (l-NMMA) (0.3 mg/kg/min intravenously). RESULTS: Hyperhomocysteinemia resulted in a reduction in the MBF dose-response curve to adenosine (p < 0.05). This was most apparent with low dose adenosine, where MBF augmentation was significantly blunted during hyperhomocysteinemia (1.06 +/- 1.00 ml/min/g vs. 0.58 +/- 0.78 ml/min/g, placebo vs. methionine, p < 0.05). Similarly, flow-mediated brachial artery vasodilation was impaired during hyperhomocysteinemia (4.4 +/- 2.6% vs. 2.6 +/- 2.3%, placebo vs. methionine, p < 0.05). In a separate series of experiments, MBF during adenosine was reduced in the presence of l-NMMA (p < 0.05 analysis of variance). This was most apparent at the low dose of adenosine, where MBF response to adenosine was blunted in the presence of l-NMMA (2.08 +/- 1.34 ml/min/g vs. 1.48 +/- 1.32 ml/min/g, placebo vs. l-NMMA, p < 0.05). CONCLUSION: The data, therefore, support the hypothesis that acute hyperhomocysteinemia impairs microvascular dilation in the human coronary circulation as a result of reduced NO bioavailability.

Adenosine↗
PubMed2002

Diabetes and atherosclerosis: epidemiology, pathophysiology, and management.

CONTEXT: Complications of atherosclerosis cause most morbidity and mortality in patients with diabetes mellitus. Despite the frequency and severity of disease, proven medical therapy remains incompletely understood and underused. OBJECTIVE: To review the epidemiology, pathophysiology, and medical and invasive treatment of atherosclerosis in patients with diabetes mellitus. DATA SOURCES: Using the index terms diabetes mellitus, myocardial infarction, peripheral vascular diseases, cerebrovascular accident, endothelium, vascular smooth muscle, platelets, thrombosis, cholesterol, hypertension, hyperglycemia, insulin, angioplasty, and coronary artery bypass, we searched the MEDLINE and EMBASE databases from 1976 to 2001. Additional data sources included bibliographies of identified articles and preliminary data presented at recent cardiology conferences. STUDY SELECTION: We selected original investigations and reviews of the epidemiology, pathophysiology, and therapy of atherosclerosis in diabetes. We selected randomized, double-blind, controlled studies, when available, to support therapeutic recommendations. Criteria for data inclusion (168 of 396) included publication in a peer-reviewed journal or presentation at a national cardiovascular society-sponsored meeting. DATA EXTRACTION: Data quality was determined by publication in peer-reviewed literature. Data extraction was performed by one of the authors. DATA SYNTHESIS: Diabetes mellitus markedly increases the risk of myocardial infarction, stroke, amputation, and death. The metabolic abnormalities caused by diabetes induce vascular dysfunction that predisposes this patient population to atherosclerosis. Blood pressure control, lipid-lowering therapy, angiotensin-converting enzyme inhibition, and antiplatelet drugs significantly reduce the risk of cardiovascular events. Although diabetic patients undergo revascularization procedures because of acute coronary syndromes or critical limb ischemia, the outcomes are less favorable than in nondiabetic cohorts. CONCLUSIONS: Since most patients with diabetes die from complications of atherosclerosis, they should receive intensive preventive interventions proven to reduce their cardiovascular risk.

Arteriosclerosis↗
PubMed2002

Guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery: a report of the International Brachial Artery Reactivity Task Force.

Endothelial function is thought to be an important factor in the pathogenesis of atherosclerosis, hypertension and heart failure. In the 1990s, high-frequency ultrasonographic imaging of the brachial artery to assess endothelium-dependent flow-mediated vasodilation (FMD) was developed. The technique provokes the release of nitric oxide, resulting in vasodilation that can be quantitated as an index of vasomotor function. The noninvasive nature of the technique allows repeated measurements over time to study the effectiveness of various interventions that may affect vascular health. However, despite its widespread use, there are technical and interpretive limitations of this technique. State-of-the-art information is presented and insights are provided into the strengths and limitations of high-resolution ultrasonography of the brachial artery to evaluate vasomotor function, with guidelines for its research application in the study of endothelial physiology.

Brachial Artery↗
PubMed2002

Inhibition of protein kinase Cbeta prevents impaired endothelium-dependent vasodilation caused by hyperglycemia in humans.

The bioavailability of nitric oxide is decreased in animal models and humans with diabetes mellitus. Hyperglycemia, in particular, attenuates endothelium-dependent vasodilation in healthy subjects. In vitro and in vivo animal studies implicate activation of protein kinase Cbeta as an important mechanism whereby hyperglycemia decreases endothelium-derived nitric oxide. Accordingly, this study tested the hypothesis that inhibition of protein kinase Cbeta would prevent impairment of endothelium-dependent vasodilation in healthy humans exposed to hyperglycemia. This study was a randomized, double-blind, placebo-controlled, crossover trial. Healthy subjects were treated with an orally active, selective, protein kinase Cbeta inhibitor, LY333531, or matching placebo once a day for 7 days before vascular function testing. Forearm blood flow was measured using venous-occlusion, strain-gauge plethysmography. Endothelium-dependent vasodilation was measured via incremental brachial artery administration of methacholine chloride (0.3 to 10 microg/min) during euglycemia and after 6 hours of hyperglycemic clamp. The forearm blood flow dose-response curve to methacholine was significantly attenuated by hyperglycemia after placebo treatment (P=0.009 by ANOVA, euglycemia versus hyperglycemia) but not after treatment with LY333531. Inhibition of protein kinase Cbeta prevents the reduction in endothelium-dependent vasodilation induced by acute hyperglycemia in healthy humans in vivo. These findings suggest that hyperglycemia impairs endothelial function, in part, via protein kinase Cbeta activation.

Adult↗
PubMed2002

Peripheral arterial disease: medical care and prevention of complications.

Peripheral arterial disease (PAD) is a common but under-recognized problem affecting older patients. Intermittent claudication is the most frequent symptom of PAD, although the diagnosis of PAD is often overlooked until the patient presents with limb-threatening ischemia. Importantly, PAD is a marker for generalized atherosclerosis and is closely associated with coronary and cerebrovascular disease. The severity of PAD has been correlated with an increased risk of myocardial infarction, stroke, and cardiovascular death. The recognition and diagnosis of PAD, combined with its appropriate medical management, may well reduce the overall risk of cardiovascular morbidity. When diagnosed early, both exercise and pharmacotherapy can ameliorate symptoms of claudication, augment functional performance, and improve quality of life.

Aged↗
PubMed2002

Contribution of endothelin to pulmonary vascular tone under normoxic and hypoxic conditions.

The contribution of endothelin to resting pulmonary vascular tone and hypoxic pulmonary vasoconstriction in humans is unknown. We studied the hemodynamic effects of BQ-123, an endothelin type A receptor antagonist, on healthy volunteers exposed to normoxia and hypoxia. Hemodynamics were measured at room air and after 15 min of exposure to hypoxia (arterial PO(2) 99.8 +/- 1.8 and 49.4 +/- 0.4 mmHg, respectively). Measurements were then repeated in the presence of BQ-123. BQ-123 decreased pulmonary vascular resistance (PVR) 26% and systemic vascular resistance (SVR) 21%, whereas it increased cardiac output (CO) 22% (all P < 0.05). Hypoxia raised CO 28% and PVR 95%, whereas it reduced SVR 23% (all P < 0.01). During BQ-123 infusion, hypoxia increased CO 29% and PVR 97% and decreased SVR 22% (all P < 0.01). The pulmonary vasoconstrictive response to hypoxia was similar in the absence and presence of BQ-123 [P = not significant (NS)]. In vehicle-treated control subjects, hypoxic pulmonary vasoconstriction did not change with repeated exposure to hypoxia (P = NS). Endothelin contributes to basal pulmonary and systemic vascular tone during normoxia, but does not mediate the additional pulmonary vasoconstriction induced by acute hypoxia.

Acute Disease↗