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Biomedical subjects

R A Vogel

Publications and source records attributed to R A Vogel.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effect of antioxidant vitamins on the transient impairment of endothelium-dependent brachial artery vasoactivity following a single high-fat meal.

CONTEXT: Much has been written about the potential role of antioxidants in the prevention of atherosclerosis. OBJECTIVE: To assess the short-term effect of a single high-fat meal with and without pretreatment with antioxidant vitamins on endothelial function in healthy, normocholesterolemic subjects. DESIGN: Observer-blinded randomized trial. SETTING: University hospital. PARTICIPANTS: Twenty healthy, normocholesterolemic (total and low-density lipoprotein cholesterol <5.2 mmol/L and <3.4 mmol/L [<200 mg/dL and <130 mg/ dL], respectively), male (7) and female (13) hospital employee volunteers, aged 24 to 54 years. INTERVENTION: Three randomly administered breakfasts: (1) a high-fat meal (3766 J [900 calories], 50 g of fat); (2) a low-fat meal (3766 J [900 calories], 0 g of fat); and (3) a high-fat meal and pretreatment with oral administration of vitamins C (1 g) and E (800 IU) (high-fat meal with vitamins). A subgroup of 10 subjects also ate the low-fat meal with the same vitamin pretreatment (low-fat meal with vitamins). MAIN OUTCOME MEASURE: High-resolution ultrasound assessed flow-mediated (endothelium-dependent) brachial artery vasodilation measured as percent diameter change before and hourly for 6 hours following each meal. RESULTS: Flow-mediated vasodilation fell from a mean+/-SD of 20%+/-8% before to 12%+/-6%, 10%+/-6%, and 8%+/-9% at 2, 3, and 4 hours, respectively, after the high-fat meal (P<.001). No significant changes in flow-mediated vasodilation occurred after the low-fat meal, high-fat meal with vitamins, or low-fat meal with vitamins. The change in flow-mediated vasodilation after the low-fat and high-fat meals correlated inversely with the 2-hour postprandial change in triglyceride levels (r=-0.54; P<.001). CONCLUSION: A single high-fat meal transiently reduces endothelial function for up to 4 hours in healthy, normocholesterolemic subjects, probably through the accumulation of triglyceride-rich lipoproteins. This decrease is blocked by pretreatment with antioxidant vitamins C and E, suggesting an oxidative mechanism.

Adult↗
PubMed1997

Effect of a single high-fat meal on endothelial function in healthy subjects.

Although there is a well-established relation between serum cholesterol and coronary artery disease risk, individual and national variations in this association suggest that other factors are involved in atherogenesis. High-fat diet associated triglyceride-rich lipoproteins have also been suggested to be atherogenic. To assess the direct effect of postprandial triglyceride-rich lipoproteins on endothelial function, an early factor in atherogenesis--10 healthy, normocholesterolemic volunteers--were studied before and for 6 hours after single isocaloric high- and low-fat meals (900 calorie; 50 and 0 g fat, respectively). Endothelial function, in the form of flow-mediated vasoactivity, was assessed in the brachial artery using 7.5-MHz ultrasound as percent arterial diameter change 1 minute after 5 minutes of upper-arm arterial occlusion. Serum lipoproteins and glucose were determined before eating and 2 and 4 hours postprandially. Serum triglycerides increased from 94 +/- 55 mg/dl preprandially to 147 +/- 80 mg/dl 2 hours after the high-fat meal (p = 0.05). Flow-dependent vasoactivity decreased from 21 +/- 5% preprandially to 11 +/- 4%, 11 +/- 6%, and 10 +/- 3% at 2, 3, and 4 hours after the high-fat meal, respectively (all p <0.05 compared with low-fat meal data). No changes in lipoproteins or flow-mediated vasoactivity were observed after the low-fat meal. Fasting low-density lipoprotein cholesterol correlated inversely (r = -0.47, p = 0.04) with preprandial flow-mediated vasoactivity, but triglyceride level did not. Mean change in postprandial flow-mediated vasoactivity at 2, 3, and 4 hours correlated with change in 2-hour serum triglycerides (r = -0.51, p = 0.02). These results demonstrate that a single high-fat meal transiently impairs endothelial function. These findings identify a potential process by which a high-fat diet may be atherogenic independent of induced changes in cholesterol.

Adult↗
PubMed1997

Coronary risk factors, endothelial function, and atherosclerosis: a review.

The traditional risk factors for coronary heart disease, which include hypercholesterolemia, hypertension, cigarette smoking, diabetes mellitus, and high-fat diet, have all been associated with impairments in endothelial function. Impaired endothelium function may promote the development of atherosclerosis through its effects on vasoregulation, platelet and monocyte adhesion, vascular smooth muscle cell growth, and coagulation. Increased oxidative stress may be another mechanism by which endothelial dysfunction contributes to atherosclerosis, although controversy exists on this issue. Risk factor modification, particularly lowering elevated concentrations of low-density lipoprotein cholesterol, improves endothelial function. At least seven clinical studies have demonstrated improved endothelial function with cholesterol reductions in patients with markedly elevated or even borderline elevations in cholesterol concentrations, whether or not coronary heart disease is present. Other interventions that improve endothelial function include blood pressure reduction, smoking cessation, and administration of estrogen to postmenopausal women.

Animals↗
PubMed1997

Short-term low dose intracoronary diltiazem administered at the onset of reperfusion reduces myocardial infarct size.

BACKGROUND: Currently, controversy exists regarding the use of calcium-channel blockers in the treatment of acute myocardial infarction (AMI), due to apparent conflicting results from clinical trials and animal models. One hypothesis to explain such a discrepancy proposes that the timing and duration of drug administration might influence its cardioprotective effect. Pretreatment with calcium-channel blockers or their administration during coronary artery occlusion is associated with the diminished infarct size in animal models. While verapamil failed to reduce infarct size when the drug was given at the onset of reperfusion, similar effects of low dose diltiazem are not known. METHODS AND RESULTS: This experiment evaluated the effect of intracoronary short term low dose diltiazem administration given immediately with postischemic myocardial reperfusion. Yorkshire swine underwent thoracotomy and 50 min of left anterior descending (LAD) occlusion, followed by 3 h of reperfusion. In the first group, diltiazem (2.5 mg diluted in 60 cc saline) was infused into the LAD over 12 min, beginning with the onset of reperfusion (n=8). In the second group, animals received saline instead of diltiazem and served as controls (n=6). Infarct size was 0.13+/-0.06 g/kg of body weight for diltiazem group, and 0.42+/-0.04 g/kg for controls (P=0.01). CONCLUSIONS: Short-term low dose diltiazem delivered exclusively during early reperfusion can significantly diminish infarct size in swine. Local intracoronary diltiazem may be valuable adjunct in patients subject to myocardial ischemia/reperfusion during coronary artery bypass grafting, primary angioplasty for AMI, or thrombolysis for AMI if given immediately after restoration of coronary blood flow.

Animals↗
PubMed1996

Performance standards and edge detection with computerized quantitative coronary arteriography. The Lovastatin Restenosis Trial Group.

Quantitative coronary angiography (QCA) has become an important tool for evaluating coronary angiograms. Many methodologic factors, such as the choice of frame to analyze, the selection of the "normal," segment and the method of edge detection used may affect the results of QCA. The sequential steps in performing QCA, including a comparison of visual and automated edge-detection methodologies, were evaluated using 12 precision-drilled phantoms and 20 patient films. Normal diameter, minimal lumen diameter, and diameter stenosis were measured. In the phantom studies, the measurements from both visual and automated systems correlated well with the true measurements of the phantoms and between systems (all r values >0.92). To study the difference between methodologies on QCA results as influenced by the choice of frame and normal segment analyzed, the patient films were analyzed independently in 3 separate rounds of interpretation. In round 1, each system's operator individually chose frames and normal segments for analysis. In round 2, both systems analyzed the same preselected frames, but independently chose normal segments. In round 3, both systems analyzed the same preselected normal segments and frames. The intersystem correlations between visual and automatic systems for rounds 1, 2, and 3 were: normal diameter, r = 0.25, r = 0.37, and r = 0.75, respectively; minimal lumen diameter, r = 0.79, r = 0.86, and r = 0.85, respectively; and diameter stenosis, r = 0.65, r = 0.73, and r = 0.87, respectively. The manual edge-detection and automated edge-detection systems used in this study are reasonably accurate and consistent on phantom studies. In patient studies, the nonautomated processes (choice of frame and normal segment for analysis) produced significant differences in the QCA results, thus illustrating that operator-dependent factors other than edge detection are very important in QCA.

Constriction, Pathologic↗
PubMed1996

Changes in flow-mediated brachial artery vasoactivity with lowering of desirable cholesterol levels in healthy middle-aged men.

Current National Cholesterol Education Program guidelines consider desirable total and low-density lipoprotein cholesterol levels to be < 200 and < 160 mg/dl, respectively, for healthy individuals without multiple coronary risk factors. To determine the extent to which these levels affect vascular function, we assessed flow-mediated (endothelium-dependent) brachial artery vasoactivity noninvasively before, during, and after cholesterol lowering (simvastatin 10 mg/day) in 7 healthy middle-aged men with cholesterol levels meeting current recommendations. Flow-mediated brachial artery vasoactivity was measured using 7.5 MHz ultrasound and expressed as percent diameter change from baseline to hyperemic conditions (1 minute following 5 minutes of blood pressure cuff arterial occlusion). Flow-mediated vasoactivity rose from 5.0 +/- 3.6% at baseline to 10.5 +/- 5.6%, 13.3 +/- 4.3%, and 15.7 +/- 4.9% (all p < 0.05) as cholesterol fell from 200 +/- 12 to 161 +/- 18, 169 +/- 16, and 153 +/- 11 mg/dl after 2, 4, and 12 weeks, respectively, of cholesterol-lowering therapy. Vasoactivity and cholesterol returned to baseline levels 12 weeks after simvastatin discontinuation. Overall, vasoactivity was found to correlate inversely with cholesterol levels (r = -0.47, p = 0.004). These data suggest that flow-mediated brachial artery vasoactivity responds rapidly to changes in cholesterol levels and that endothelial function improves by lowering cholesterol levels below recommendations of current guidelines.

Adult↗
PubMed1996

Comparisons of angiographic core laboratory analyses of phantom and clinical images: interlaboratory variability.

Centralized, quantitative coronary analysis (QCA) has become the standard for determining change in coronary anatomy in clinical investigations. QCA systems and laboratory methods, however, vary among core facilities, and analysis variability among angiographic core laboratories (ACL) has not be studied. We evaluated QCA accuracy and variability among active ACL, using differing QCA systems by comparing analyses of phantom and clinical cinefilm images. Automated, unedited analyses were performed on images of 11 plexiglass phantom lumens (0.67-5.05 mm) acquired under varying radiographic conditions. Analysis differences from actual luminal diameters ranged widely (+0.42 - (-)0.45 mm) among ACL. Measurement of diameters < 1.0 mm were overestimated and diameters > 3.0 mm were underestimated. Measurements of midrange diameters (> 1.0 mm and < 3.0 mm) were most comparable among ACL (93% within +/- 0.2 mm). Clinical image analysis was performed using differing QCA systems and laboratory methodology on 11 randomly selected study films. Comparative analyses revealed significant variability between laboratories in the assessment of minimal lumen diameter (0.22 +/- 0.38 mm P < 0.05). These data describe analysis variability among ACL and demonstrate a need for establishing ACL performance standards.

Clinical Laboratory Techniques↗
PubMed1995

Timing of magnesium therapy affects experimental infarct size.

BACKGROUND: Controversy exists regarding the use of magnesium in the treatment of acute myocardial infarction (AMI) because of apparent conflicting results from clinical trials. One hypothesis to explain the various clinical observations proposes that the timing of magnesium administration significantly influences its therapeutic effect; ie, supraphysiological levels of Mg2+ must be present at the time of reperfusion for magnesium to produce clinical benefit. METHODS AND RESULTS: These experiments evaluated the effect of varying the timing of magnesium administration during AMI. Female Yorkshire swine (34 to 42 kg) underwent thoracotomy and 50 minutes of left anterior descending coronary artery (LAD) occlusion, followed by 3 hours of reperfusion. In the first group, MgSO4 (250 mg of magnesium diluted in 60 cm3 saline) was infused into the LAD over 12 minutes, beginning immediately with the onset of reperfusion (n = 6, Mg-early group). In the second group, MgSO4 was given after 1 hour of reperfusion (n = 6, Mg-late group). Six pigs received saline instead of magnesium and served as the control group. Lethal arrhythmias were significantly reduced in the Mg-early group. Infarct size was determined by vital staining. Infarct size was 0.16 +/- 0.05 g/kg body wt (Mg-early), 0.35 +/- 0.08 g/kg (Mg-late), and 0.42 +/- 0.04 g/kg for the control group. Compared with the control group, significant (P = .029) reduction in infarct size occurred in the Mg-early group but not in the Mg-late group. CONCLUSIONS: We conclude that intracoronary MgSO4 delivered during reperfusion can significantly diminish infarct size in swine, but the timing of administration is critical.

Animals↗
PubMed1995

Quality of care for Medicare patients with acute myocardial infarction. A four-state pilot study from the Cooperative Cardiovascular Project.

OBJECTIVE: To develop and test indicators of the quality of care for patients with acute myocardial infarction (AMI). DESIGN: Retrospective medical record review. SETTING: All acute care hospitals in Alabama, Connecticut, Iowa, and Wisconsin. PATIENTS: All hospitalizations for Medicare patients discharged with a principal diagnosis of AMI between June 1, 1992, and February 28, 1993, were identified (N = 16,869). MAIN OUTCOME MEASURE: Percentage of patients receiving appropriate interventions as defined by 11 quality-of-care indicators derived from clinical practice guidelines that were modified and updated in consultation with a national group of physicians and other health care professionals. RESULTS: We abstracted data from 16,124 (96%) of the hospitalizations, representing 14,108 primary hospitalizations and 2016 hospitalizations resulting from transfers. Potential exclusions to the use of standard treatments in AMI care were common with 90% and 70% of patients having potential exclusions for thrombolytics and beta-blockers, respectively. In cohorts of "ideal candidates" for specific interventions, 83% received aspirin, 69% received thrombolytics, and 70% received heparin during the initial hospitalization; 77% received aspirin and 45% received beta-blockers at discharge. CONCLUSIONS: These data demonstrate that many Medicare patients may not be ideal candidates for standard AMI therapies, but these treatments are underused, even in the absence of discernible contraindications. Hospitals and physicians who apply these quality indicators to their practices are likely to find opportunities for improvement.

Alabama↗
PubMed1995

Correlation of cold pressor and flow-mediated brachial artery diameter responses with the presence of coronary artery disease.

Flow-mediated brachial and coronary artery vasoactivity are abnormal in patients with coronary artery disease (CAD) and cardiac risk factors. Cold pressor coronary artery vasoactivity is abnormal in patients with CAD, but brachial artery responses have not been studied. This study assesses whether cold pressor and flow-mediated brachial artery vasoactivity correlate independently with the presence of CAD. We studied 50 men (27 who were clinically normal, 23 with angiographically proven CAD) aged 23 to 59 years. With use of 7.5 MHz ultrasound, we measured brachial artery diameter and Doppler flow velocity at baseline, during contralateral ice water hand immersion (cold pressor), after 5 minutes of ipsilateral blood pressure cuff occlusion (flow-mediated), and after nitroglycerin administration. During cold pressor stimulation, mean brachial artery diameter increased 0.36 +/- 2.93% in normal subjects but decreased 2.38 +/- 3.32% in the CAD subjects (p = 0.006). Mean flow-mediated diameter increased 9.11 +/- 6.01% and 6.58 +/- 7.50% in normal and CAD subjects, respectively (p = NS). Responses to sublingual nitroglycerin were the same in the 2 groups. Multiple stepwise regression analysis revealed that cold pressor vasoactivity was found to correlate with smoking status (p = 0.0002) and the presence of CAD (p = 0.04). In the 32 nonsmokers undergoing assessment, only the presence of CAD correlated with cold pressor vasoactivity (p = 0.02). The associations of brachial artery vasoactivity with cardiac risk factors and CAD appear to be stimulus-dependent. Cold pressor vasoactivity correlates more closely with the presence of CAD than does flow-mediated vasoactivity.

Adult↗
PubMed1995

The effects of age and gender on brachial artery endothelium-dependent vasoactivity are stimulus-dependent.

Impaired endothelium-dependent vasomotion in response to flow-mediated, cholinergic, and cold pressor stimulation has been demonstrated in the presence of both atherosclerosis and cardiac risk factors. This study investigated the effects of different vasoactive stimuli on brachial artery vasomotion with respect to age and gender. Forty healthy subjects (20 men and 20 women), ages 23 to 52 years, were studied. Using 7.5 MHz ultrasound, brachial artery diameter and Doppler flow velocity at baseline, following 5 min of ipsilateral blood pressure cuff occlusion (flow-mediated), during contralateral hand immersion in ice (cold pressor) and after sublingual nitroglycerin administration, were measured in older subjects (> 40 yrs) and younger subjects (< 40 yrs). Among normal subjects, % diameter change in response to the flow-mediated stimulus was less in older men than in younger men (6.8 +/- 3.2% vs. 11.5 +/- 7.4%, p < 0.05); older and younger women had comparable responses (10.0 +/- 5.3% vs. 11.6 +/- 4.3%, p = NS). With cold pressor, normal older men and older women vasoconstricted (-1.2 +/- 0.9%, -2.2 +/- 4.7%) compared with younger subjects who vasodilated (1.4 +/- 2.5%, 0.6 +/- 2.3%, p < 0.02). The cold pressor test elicited comparable responses among older normal subjects. Nitroglycerin, a non-endothelium-mediated stimulus, induced significant vasodilatation in all the groups. In conclusion, endothelium-mediated responses in subjects of varying age and gender are stimulus-dependent. Flow-mediated vasodilatation could not differentiate older premenopausal women from younger women; cold pressor stimulus could.

Adult↗
PubMed1995

Cardiopulmonary bypass support of high risk coronary angioplasty patients: registry results.

Coronary angioplasty has been increasingly utilized in patients with extensive coronary disease, severe and acute chest pain syndromes, and poor ventricular function. This process has been facilitated in part by use of circulatory support, including perfusion balloons, intraaortic balloon pumps and cardiopulmonary bypass support systems. Percutaneous cannulation has facilitated elective and emergency application of cardiopulmonary bypass support in patients undergoing high risk coronary angioplasty. A National Registry of 25 centers has accumulated data on 801 elective and 210 emergency support angioplasty patients. Standby cardiopulmonary bypass support of elective high risk patients was associated with fewer complications and less in-hospital mortality in patients other than those with left ventricular ejection fraction < or = 20% and possibly older high risk patients. In elective cases, circulatory support was required in only approximately 7% of high risk patients, although need appeared to be unpredictable. Emergency use of cardiopulmonary bypass support, initiated < 20 minutes from the time of circulatory collapse, was associated with improved patient prognosis. Overall, patients undergoing circulatory cardiopulmonary bypass supported angioplasty had a marked reduction in anginal status, improvement in left ventricular ejection fraction and good (80%) 2-year survival. Although used only occasionally, circulatory support remains an important prophylactic interventional tool for the extremely high risk patient (left ventricular ejection fraction < or = 20%) and a lifesaving emergency technique for the occasional patient with circulatory collapse.

Angioplasty, Balloon, Coronary↗
PubMed1995

Technical aspects of evaluating brachial artery vasodilatation using high-frequency ultrasound.

Flow-mediated brachial artery vasoactivity has been recently proposed as a noninvasive means for assessing endothelial function. To better characterize this technique, we measured brachial artery diameter and flow using 7.5-MHz ultrasound following 1, 3, and 5 min of upper arm blood pressure cuff occlusion in 19 normal volunteers and 13 patients with coronary artery disease (CAD). Although similar flow increases were observed with each protocol, statistically significant vasodilatation (12.6 +/- 5.7%) was observed in the normals only after 5 min of occlusion. With the use of this protocol, postocclusion blood flow increased 528 +/- 271 and 481 +/- 247% in the normals and CAD patients, respectively (P = NS). More vasodilatation was observed in the normals compared with the CAD patients (11.3 +/- 5.4 vs. 1.6 +/- 5.2%, P < 0.001). Interestingly, vasodilatation persisted for 20 min despite return of blood flow to baseline in 2 min. With the use of lower arm occlusion, arterial diameter was found to decrease 4.4 +/- 3.9% in response to a 85 +/- 7% decrease in flow. We conclude that 1) longer brachial artery occlusion results in more vasodilatation despite similar hyperemic responses, 2) vasodilatation persists substantially beyond hyperemia, and 3) CAD patients have impaired flow-mediated vasodilatation using this noninvasive technique.

Adult↗