ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The mechanism by which myocardial blood flow varies in response to metabolic demand is obscure. One hypothesis is a countercurrent regulation of arterial caliber by diffusible substances carried in venous blood. To study the anatomic basis for blood flow regulation, we performed combined arterial and venous injections in 20 human hearts and studied left ventricular intramyocardial vessels with radiography, 100 μm thick sections, and reconstructions of serial histologic sections. Penetrating arteries lie in interstitial spaces and are closely related to accompanying veins. These interstitial veins partially surround and are indented by branch arteries. A second system of veins lies within muscle fascicles between interstitial spaces and is not related to arteries. The isolated veins have collateral connections with interstitial veins and join them in the subepicardium. This vascular anatomy could allow arterial caliber to be regulated by diffusible substances carried in the interstitial veins. Arterial dilatation might prolong this effect by partial obstruction of interstitial veins, with the isolated venous system providing an alternative pathway for venous drainage and washout. The study shows that a vascular arrangement is present in human left ventricular myocardium that could provide a countercurrent regulation of blood flow with diffusible substances carried in venous blood.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The reduced responsiveness of the renin-angiotensin system to hemodynamic changes in patients with congestive heart failure (CHF) could be due to a defect of the juxtaglomerular apparatus. To test this hypothesis, the responses to viprostol, an analog of prostaglandin E2(PGE2) that is known to stimulate both the macula densa and the juxtaglomerular cells, and to nitroprusside were compared in patients with CHF. An average fall in mean arterial pressure (MAP) of 6 mm Hg with viprostol was associated with a fivefold increase in plasma renin activity (PRA) from 11.4 + 6.4 to 47.9 31.0 ng/ml/hr; in contrast PRA did not change with nitroprusside, despite a significant decrease in preload and an average decrease in MAP of 16 mm Hg. These data demonstrate that (1) the reninangiotensin system could be activated by PGE2in patients with CHF, (2) this activation is not related to the global hemodynamic changes induced by PGE2, and (3) the previously reported unresponsiveness of the renin-angiotensin system in patients with CHF cannot be attributed to a defective response of the juxtaglomerular apparatus.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We used Doppler echocardiography to quantitate the changes in intracardiac blood flow velocities and right and left ventricular stroke volumes in 80 normal human fetuses from 19 to 40 weeks gestation. Blood flow velocity spectra across the aortic, pulmonary, tricuspid, and mitral valves were digitized to obtain peak velocities (m/sec) and flow velocity integrals. Aortic and pulmonary diameters were measured at valve level from two-dimensional echocardiographic images and cross-sectional area was calculated assuming a circular orifice. Ventricular stroke volume was calculated as the product of the cross-sectional area of a great vessel and the flow velocity integral through that vessel. The pulmonary arterial and aortic diameters increased linearly with gestational age (r= .82,r= .84), and pulmonary arterial diameter consistently exceeded aortic diameter. There was a positive relationship between stroke volume and gestational age: stroke volume increased exponentially from 0.7 ml at 20 weeks to 7.6 ml at 40 weeks for the right ventricle (r= .87) and from 0.7 ml at 20 weeks to 5.2 ml at 40 weeks for the left ventricle (r= .91). Similar results were obtained for right and left ventricular and combined cardiac outputs. In 44% of the fetuses it was possible to quantitate both right and left ventricular stroke volumes. There was a close correlation between right and left ventricular stroke volumes in these fetuses (r= .96) and right ventricular stroke volume exceeded left ventricular stroke volume by 28%. Flow velocity across the tricuspid and mitral valves was consistently greater during atrial systole (A wave) than during rapid ventricular filling (E wave) (0.52 0.07 vs 0.37 + 0.08 m/sec and 0.45 ± 0.07 vs 0.33 ± 0.06 mlsec). The E/A ratios for the mitral and tricuspid valves were similar throughout the period of gestation studied, indicating equivalent diastolic ventricular function. This study demonstrates that right and left ventricular stroke volumes increase by approximately 10- fold from 20 to 40 weeks gestation in the normal human fetus. It also demonstrates, within the limitations of the equipment, that right ventricular stroke volume exceeds that of the left ventricle, thus confirming right ventricular dominance in utero.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Plasma levels of high-density lipoprotein cholesterol (HDL-C) at entry and subsequent changes from these baseline levels were inversely predictive of coronary heart disease (CHD) end points in hypercholesterolemic men followed for 7 to 10 years in the Lipid Research Clinics Coronary Primary Prevention Trial, especially in the 1907 participants receiving cholestyramine. When the men in this cohort were compared, each 1 mg/dl increment in baseline HDL-C (mean 44.3 mg/dl) was associated with a 5.5% decrement in risk of “definite” CHD death or myocardial infarction (Z = − 5.4), and each 1 mg/dl increase from baseline HDL-C levels (mean increase = 1.6 mg/dl) during the trial was associated with a 4.4% risk reduction (Z = −2.2). In the 1899 participants receiving placebo, the corresponding risk decrements were 3.4% and 1.1%. Although baseline HDL-C level (mean = 44.4 mg/dl) remained a significant risk predictor (Z = −3.8) in the placebo cohort, increases in HDLC (mean increase 0.5 mg/dl) were not significantly predictive of CHD (Z = −0.6) unless “suspect” as well as “definite” end points were analyzed (Z = − 2.0). When the associations between HDL-C (baseline plus change) and incidence of definite CHD end points within each treatment cohort were compared, their difference approached nominal significance (Z = 1. 9). The results suggest a synergistic interaction, in which cholestyramine treatment reduced CHD risk most substantially in men maintaining the highest HDL-C levels.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The cross-sectional relationship of endogenous androgens (testosterone, androstenedione, and dehydroepiandrosterone sulfate [DHEA-S]), estrogen (estradiol) and progestin (progesterone) to serum levels of lipoprotein cholesterol (very low-density [VLDL], low-density [LDL], and high-density lipoprotein [HDL]) and apolipoproteins (apo A-I and apo B) were studied in white (n 251) and black (n = 258) adolescent boys, ages 1 1 to 17 years, as part of the Bogalusa Heart Study. Black boys had significantly higher levels of estradiol, HDL cholesterol, and apo A-I, and lower levels of androstenedione and VLDL cholesterol than white boys, independent of age and adiposity. Age was correlated strongly with testosterone and androstenedione, and moderately with DHEA-S and estradiol levels in both races. However, only in white boys was age consistently related to VLDL cholesterol (positively), HDL cholesterol (negatively), and apo A-I (negatively). Overall, testosterone was associated inversely with HDL cholesterol and apo A-I in white boys. while progesterone was related positively to apo A-I in both races after adjusting for age and adiposity. However, these relationships were found to differ with age. Partial correlations between levels of sex hormones and lipoproteins adjusted for age and adiposity showed no associations in the 11 to 12 year age group in boys of either race. A significant positive relation of testosterone to VLD, 2holesterol, and inverse relations of testosterone to HDL cholesterol and apo A-I and DHEA-S to HDL cholesterol were apparent only in white boys in the 13 to 14 year age group. Among the older subjects (15 to 17 years old), the relationships of testosterone to HDL cholesterol and androstenedione to apo A-I were positive only in black boys. In addition, a significant positive association between progesterone and apo A-I was noted for both races among boys in the older age group. That the sex hormone-lipoprotein associations vary among different age groups suggests the influence of sexual maturation-related hormonal makeup on lipoproteins. Inherent metabolic differences between the races may account for some of the divergent sex hormone-lipoprotein associations.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To assess the best method of quantitating progression of coronary disease, we studied four measurements in 114 coronary segments from 35 medically treated patients from whom angiograms were obtained 5 years apart. Only stenoses of less than 70% that were visualized in nearly identical projections on both angiograms were evaluated. Vessel edges were measured by use of catheter calibration and an automated computer algorithm yielding two “absolute dimensions” (mean and minimum diameters) and two measurements (percent stenosis and atheroma area) that required a “normal reference” diameter. The coefficient of variation for repeated segment measurements was less for mean and minimum diameter than for percent stenosis and area of atheroma. The best measure of progression of coronary disease as determined by t test comparison of different methods was the change in mean diameter over time (6.7 14.1% decrease), whether calculated on a per coronary segment or per patient basis (p< .001). Based on this measurement and its standard deviation of progression of coronary disease in this patient subset with relatively benign disease, it is estimated that 470 patients per group would be required for an interventional study to demonstrate a 33% reduction in disease progression (207 patients for 50% reduction) at a 95% confidence level and 90% power.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To investigate the action of calcitonin gene-related peptide (CGRP) on human epicardial coronary arteries, six patients received intracoronary CGRP at doses of 50, 100, and 200 ng/min. The effect of CGRP was measured angiographically with a computerized analysis system. A dose-dependent increase in coronary arterial diameter was observed. At the highest dose there were 34%, 7%, 38%, and 40% mean increases in the diameters of the circumflex, proximal, mid, and distal left anterior descending arteries, respectively. No further increase in diameter was found after a subsequent dose of 1 mg intracoronary isosorbide dinitrate. Prior infusion of CGRP did not prevent coronary arterial spasm induced by ergonovine in two patients with variant angina, but a subsequent bolus of CGRP partially relieved the spasm. We propose that CGRP has a role in the regulation of coronary vascular smooth muscle tone.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID