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Biomedical subjects

Julian P J Halcox

Publications and source records attributed to Julian P J Halcox.

8 recordsLinked to original sources
PubMed2005

Vasculopathy in Turner syndrome: arterial dilatation and intimal thickening without endothelial dysfunction.

CONTEXT: Women with Turner syndrome (TS) have an increased cardiovascular mortality rate from both structural and ischemic heart disease, especially aortic dissection. OBJECTIVE: We hypothesized that TS women have a fundamental arterial wall defect that may be due to genetic factors or estrogen deficiency. DESIGN, SETTING, AND PATIENTS: TS women (n = 93) were compared with normal controls (n = 25) and women with 46,XX primary amenorrhea (PA) (n = 11) with a similar history of estrogen deficiency. Clinical parameters, aortic root diameter, extraaortic arterial structure [common carotid (CD), brachial artery diameter, and carotid intima-media thickness (IMT)], arterial stiffness (pulse-wave velocity, augmentation index), and endothelial function (flow-mediated dilatation) were assessed. MAIN OUTCOME MEASURES: These included arterial diameters and vascular physiology parameters. RESULTS: Differences in arterial structure were observed among TS, normal controls, and 46,XX PA women: IMT (0.61 +/- 0.07 vs. 0.55 +/- 0.06 vs. 0.60 +/- 0.05 mm, respectively; P < 0.001), CD (5.71 +/- 0.64 vs. 5.27 +/- 0.34 vs. 5.22 +/- 0.38 mm; P < 0.001), and brachial artery diameter (3.29 +/- 0.44 vs. 3.06 +/- 0.36 vs. 2.97 +/- 0.30 mm; P = 0.006). Aortic root diameter was greater in TS than normal control women. TS status, height, weight, and IMT were independently associated with increased CD after multivariate adjustment (P < 0.05). TS status, age, diastolic blood pressure, and CD remained independently associated with increased IMT after multivariate adjustment (P < 0.05). Pulse-wave velocity and flow-mediated dilatation were similar among the three groups. CONCLUSION: Women with TS have greater IMT and conduit artery diameters than normal controls. Similarly, increased IMT in TS and 46,XX PA women suggests that estrogen deficiency contributes to intimal thickening. Interventional studies are required to determine the extent to which blood pressure and estrogen deficiency may be appropriate therapeutic targets to reduce cardiovascular risk in TS.

Adult↗
PubMed2005

Stem cells as future therapy in cardiology.

This article focuses on the key studies relevant to the clinical application of stem-cell research in cardiovascular disease. The authors also discuss current and future directions in clinical cardiovascular stem-cell research, including the potential problems and pitfalls that must be addressed to ensure the safety, as well as the efficacy, of treatment regimens in this rapidly evolving therapeutic field.

Cardiovascular Diseases↗
PubMed2004

Beyond the laboratory: clinical implications for statin pleiotropy.

Results from large-scale clinical trials of lipid lowering with 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) have led to a revolution in the management of atherosclerosis. In addition to their potent effect on serum lipid levels, statins influence several other cellular pathways, including those involving inflammatory, oxidative, and thrombotic processes. These effects clearly have the potential to beneficially modify the atherogenic process, and it has been suggested that they contribute to the impressive results seen in the clinical trials. We review the clinical evidence for benefits of statin therapy that are distinct from their effect on lipid biology. In particular, we address three key issues: the role of statins in diseases not traditionally associated with elevated cholesterol levels; whether clinical benefits are seen with statin therapy before an effect on lipid levels; and whether the magnitude of clinical benefit observed with statin therapy is unrelated to the degree of cholesterol reduction. At present, low-density-lipoprotein lowering seems to be the primary mechanism underlying the clinical benefits of statin therapy and should remain the focus of risk-reduction strategies in clinical practice.

Arteriosclerosis↗
PubMed2003

Circulating endothelial progenitor cells, vascular function, and cardiovascular risk.

BACKGROUND: Cardiovascular risk factors contribute to atherogenesis by inducing endothelial-cell injury and dysfunction. We hypothesized that endothelial progenitor cells derived from bone marrow have a role in ongoing endothelial repair and that impaired mobilization or depletion of these cells contributes to endothelial dysfunction and cardiovascular disease progression. METHODS: We measured the number of colony-forming units of endothelial progenitor cells in peripheral-blood samples from 45 men (mean [+/-SE] age, 50+/-2 years). The subjects had various degrees of cardiovascular risk but no history of cardiovascular disease. Endothelium-dependent and endothelium-independent function was assessed by high-resolution ultrasonography of the brachial artery. RESULTS: We observed a strong correlation between the number of circulating endothelial progenitor cells and the subjects' combined Framingham risk factor score (r=-0.47, P=0.001). Measurement of flow-mediated brachial-artery reactivity also revealed a significant relation between endothelial function and the number of progenitor cells (r=0.59, P<0.001). Indeed, the levels of circulating endothelial progenitor cells were a better predictor of vascular reactivity than was the presence or absence of conventional risk factors. In addition, endothelial progenitor cells from subjects at high risk for cardiovascular events had higher rates of in vitro senescence than cells from subjects at low risk. CONCLUSIONS: In healthy men, levels of endothelial progenitor cells may be a surrogate biologic marker for vascular function and cumulative cardiovascular risk. These findings suggest that endothelial injury in the absence of sufficient circulating progenitor cells may affect the progression of cardiovascular disease.

Adult↗
PubMed2002

The effect of sildenafil on human vascular function, platelet activation, and myocardial ischemia.

OBJECTIVE: We studied the effects of sildenafil, a phosphodiesterase 5 inhibitor, on coronary and peripheral vascular function, platelet activation, and myocardial ischemia. BACKGROUND: Nitric oxide vasodilates and inhibits platelet activation by generating cyclic guanosine 5'-monophosphate, which is metabolized by phosphodiesterase type 5. METHODS: The effect of oral sildenafil on resting coronary vascular tone, endothelium-dependent and -independent function and platelet activation was measured in 24 patients. An additional 24 patients with coronary artery disease (CAD) and ischemia during exercise, and 12 control subjects received either 100 mg of sildenafil, 10 mg of isosorbide dinitrate (ISDN) or placebo during exercise on three separate days in a randomized, double-blind manner. Flow-mediated dilation of the brachial artery was measured, and CAD patients underwent treadmill exercise testing. RESULTS: Sildenafil (100 mg) vasodilated epicardial coronary arteries (+6.9 +/- 1.3%, p < 0.0001). Coronary epicardial and microvascular responses with acetylcholine and cold-pressor testing improved, with a greater enhancement in patients with CAD and endothelial dysfunction. Verapamil responses were unchanged. Both resting and adenosine diphosphate-stimulated platelet IIb/IIIa receptor activation was inhibited by sildenafil (p < 0.05). Brachial arteries dilated in response to sildenafil in controls. Peak flow-mediated dilation was similar, but the duration of hyperemia was prolonged after sildenafil administration (p < 0.001). Compared with placebo, ISDN improved myocardial ischemia during exercise (p < 0.05), whereas the effect of sildenafil was intermediate between the two. CONCLUSIONS: Sildenafil dilates epicardial coronary arteries, improves endothelial dysfunction and inhibits platelet activation in patients with CAD. It has an intermediate effect on myocardial ischemia compared with ISDN and placebo.

Adult↗
PubMed2002

Prognostic value of coronary vascular endothelial dysfunction.

BACKGROUND: Whether patients at increased risk can be identified from a relatively low-risk population by coronary vascular function testing remains unknown. We investigated the relationship between coronary endothelial function and the occurrence of acute unpredictable cardiovascular events (cardiovascular death, myocardial infarction, stroke, and unstable angina) in patients with and without coronary atherosclerosis (CAD). METHODS AND RESULTS: We measured the change in coronary vascular resistance (DeltaCVR) and epicardial diameter with intracoronary acetylcholine (ACh, 15 micro g/min) to test endothelium-dependent function and sodium nitroprusside (20 micro g/min) and adenosine (2.2 mg/min) to test endothelium-independent vascular function in 308 patients undergoing cardiac catheterization (132 with and 176 without CAD). Patients underwent clinical follow-up for a mean of 46+/-3 months. Acute vascular events occurred in 35 patients. After multivariate analysis that included CAD and conventional risk factors for atherosclerosis, DeltaCVR with ACh (P=0.02) and epicardial constriction with ACh (P=0.003), together with increasing age, CAD, and body mass index, were independent predictors of adverse events. Thus, patients in the tertile with the best microvascular responses with ACh and those with epicardial dilation with ACh had improved survival by Kaplan-Meier analyses in the total population, as did those in the subset without CAD. Similar improvement in survival was also observed when all adverse events, including revascularization, were considered. Endothelium-independent responses were not predictive of outcome. CONCLUSIONS: Epicardial and microvascular coronary endothelial dysfunction independently predict acute cardiovascular events in patients with and without CAD, providing both functional and prognostic information that complements angiographic and risk factor assessment.

Angina, Unstable↗
PubMed2002

Predisposition to atherosclerosis by infections: role of endothelial dysfunction.

BACKGROUND: Several microorganisms have been implicated in the pathogenesis of atherosclerosis. We hypothesized that infections may predispose to atherosclerosis by inflicting endothelial injury. METHODS AND RESULTS: Of 375 patients undergoing coronary angiography, 218 had assessment of endothelial function using intracoronary acetylcholine (ACH) and of endothelium-independent function with sodium nitroprusside and adenosine. Immunoglobulin-G antibody titers to cytomegalovirus, Chlamydia pneumoniae, Helicobacter pylori, hepatitis A virus, and herpes simplex virus-1 were measured. Pathogen burden was defined as the number of positive antibodies. Although positive serology to individual pathogens tended to be associated with increased incidence of coronary arteriosclerosis (CAD), the pathogen burden correlated with the presence of CAD, even after adjustment for risk factors (OR 1.3; 95% CI, 1.05 to 1.6, P=0.018). Moreover, the severity of CAD was independently associated with the pathogen burden (P=0.001). Pathogen burden was an independent predictor of endothelial dysfunction, determined as the percent change in coronary vascular resistance in response to ACH (P=0.009) but not the responses to sodium nitroprusside or adenosine. Pathogen burden was also an independent determinant of endothelial function in the subgroup with angiographically normal coronary arteries. CONCLUSIONS: The immunoglobulin-G antibody response to multiple pathogens (pathogen burden) is an independent risk factor for endothelial dysfunction and the presence and severity of CAD. Endothelial dysfunction provides the crucial link by which pathogens may contribute to atherogenesis.

Adenosine↗