ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We determined the prevalence of mitral valve prolapse (MVP) in presumably healthy young men by studying 107 male house officers and medical students with cardiac auscultation in the supine, sitting and standing positions. Echocardiograms were performed at rest in the supine position before and after amylnitrite inhalation and were obtainable in 101 subjects. Eleven of the 101 subjects had abnormal findings on auscultation: four had an isolated click and seven had a click and late systolic murmur. Correlation of the independent auscultatory and echocardiographic data in the 101 subjects showed that all seven of the subjects with a click and a murmur had echocardiographic evidence of prolapse. None of the 90 subjects with normal auscultation or the four with an isolated click had an abnormal echocardiogram. All seven subjects with MVP had thoracic skeletal abnormalities, but only one was symptomatic. These data suggest that the prevalence of MVP in healthy young males is similar to the reported 6-10% prevalence in healthy young females

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Cardiovascular complications are a major source of morbidity and mortality in hypertensive patients. To assess the prevalence of anatomic and functional abnormalities of the heart in such patients, we studied 234 asymptomatic subjects with mild-to-moderate systemic hypertension by echocardiography. After adjusting the echocardiographic values for age and body surface area, we found abnormally increased ventricular septal and/or posterobasal free-wall thickness in 61% of the hypertensive subjects. We found increased left atrial, aortic root, and left ventricular internal dimension (at end-diastole) in 5-7%, and decreased mitral valve closing velocity (E-F slope) and left ventricular ejection fraction were noted in six and 15% of the subjects, respectively. Four percent of the patients had disproportionate septal thickening (i.e., ventricular septal-to-left ventricular free-wall thickness ratio > 1.3). In contrast to the high prevalence of cardiac abnormalities detected by echocardiography, less than 10% of the hypertensive subjects had abnormal 12-lead ECGs or abnormal chest x-rays. These findings demonstrate a high prevalence of cardiac abnormalities in a population of asymptomatic hypertensive subjects. These abnormalities can be detected by echocardiography before they are otherwise apparent

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Carotid baroreflex function was assessed in 10 normotensive young men and 20 age-matched subjects with borderline hypertension (successive blood pressures above and below 140/90 mm Hg) by measuring sinus node responses to brief neck suction. Subjects with borderline hypertension were divided into two equal groups according to their average systolic arterial pressures. Baroreflex responses were reset to function at higher pressure levels than normal in subjects with mild borderline hypertension, but reflex sensitivity was normal. Responses were also reset in subjects with more severe borderline hypertension, but reflex sensitivity was subnormal. The results suggest that a gradation of baroreflex responsiveness exists among patients classified as having borderline hypertension: Subnormal responsiveness was found in those subjects whose resting average systolic arterial pressure was 140 mm Hg

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We assessed the release of neuronal and adrenomedullary catecholamines in response to various stimuli of the sympathetic nervous system in normal subjects. Plasma catecholamines and their urinary metabolites, normetanephrine and metanephrine, were measured. Sodium restriction increased supine plasma norepinephrine by 37% and ambulatory plasma norepinephrine by 22%, with urinary normetanephrine excretion increased 29%. The sodium restriction did not elevate plasma epinephrine or urinary metanephrine. The most potent stimuli of norepinephrine were treadmill exercise, orthostasis, caffeine, the cold pressor test, sodium restriction and handgrip exercise, in descending order. Plasma epinephrine was increased by caffeine, treadmill exercise, the cold pressor test, handgrip exercise and the Valsalva maneuver, in that order. Syncope resulted in profound changes in plasma epinephrine but only modest changes in plasma norepinephrine. We conclude that in man, there is frequent dissociation between the effects of different stimuli on neuronal and adrenomedullary catecholamine release

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

We studied the blood pressure, natriuretic, kaliuretic and humoral responses of 347 normal subjects after volume expansion and volume contraction to examine possible differences among whites, blacks and subjects of different ages. According to outpatient 24-hour urine collections, blacks excreted less sodium and potassium than whites. After similar states of sodium intake were achieved among all subjects, 2 liters normal saline were given i.v. Blacks and subjects 40 years excreted less sodium than whites or subjects > 40 years, over a 24-hour period. In addition, blacks excreted less potassium. The delay in sodium excretion occurred during the first 12 hours after the salt load. Blacks had a greater suppression of plasma renin activity than whites 24 hours after saline. Blacks also had higher blood pressures than whites after saline administration; their pressure remained elevated until furosemide was given. Furosemide, 120 mg over 24 hours, evoked greater natriuresis, but less kaliuresis in blacks than in whites. The greater prevalence of hypertension in both blacks and older subjects may be related to relatively blunted natriuretic responses when these groups engage in the high sodium-low potassium intake characteristic of our society.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The purpose of this study was to document the cardiovascular response to submaximal isometric handgrip (IHG) exercise in 32 normal adolescents. Left ventricular (LV) dimensions and systolic time intervals were recorded using echocardiography; blood pressure was measured by sphygmomanometry both at rest and during IHG exercise at 25% maximum contraction. This level of isometric exercise produced significant (p>0.001) increases in mean heart rate, systolic, diastolic and mean blood pressures. Despite this response LV diastolic and systolic dimensions remained unchanged during exercise; hence, stroke volume remained constant. Cardiac index increased by 22% (p>0.001) due to the increase in heart rate. Systemic vascular resistance did not change significantly. LV ejection indices, including shortening fraction, mean Vcf and systolic time intervals also remained unchanged, except for an increase in LV ejection time index (p>0.025). These data indicate that the cardiovascular response to submaximal isometric exercise in normal adolescents is similar to that reported in adults. This study demonstrates that sustained isometric stress testing in adolescents is safe and provides normal hemodynamic values.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Studies in man produce conflicting evidence of the role of the Frank-Starling mechanism in increasing cardiac output during exercise, though animal studies indicate that it may help to improve cardiac performance during severe exertion. Twelve healthy volunteers (mean age 35.8 i 2.8 years) performed graded exercise to exhaustion on a bicycle ergometer in the semisupine position for 8.9 i 0.9 minutes (maximum work load 900 kg-m/min). Echocardiographic recordings of left ventricular dimensions were obtained continuously and end-expiratory tracings digitized. Heart rate increased from 64 ± 3 to 152 ± 4 beats/min. At peak exercise, end-diastolic diameter increased from 4.52 ± 0.20 to 5.24 ± 0.17 cm sec-1 at peak exercise (p>0.0005). Maximum rates of change in diameter in systole and diastole, and normalized maximum diastolic rate of change all increased progressively and significantly throughout the exercise period. These results suggest that severe semisupine exertion causes an increase in left ventricular end-diastolic diameter, stroke dimension and percent change in diameter, but no change in end-systolic diameter measured at end-expiration. Increases in indices of left ventricular fiber shortening and rates of lengthening appear earlier in exercise than does an increase in end-diastolic fiber length, suggesting that during lower levels of exertion cardiac output rises primarily by increases in heart rate. The Frank-Starling effect appears, under the conditions of this study, to be reserved for augmenting cardiac performance during severe semisupine exertion.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

Curves relating left ventricular end-diastolic pressure (LVEDP) to echocardiographically determined end-diastolic diameter (LVEDD) were obtained before and after ischemic arrest in 15 patients during open heart surgery. LVEDP ranged from 0-20 mm Hg during routine operation of the heart-lung machine. Ischemic arrest ranged from 0-94 minutes.In eight patients averaging 21 ± 7 (SEM) minutes of arrest, we saw no change in LVEDP-LVEDD curves. In five patients averaging 55 ± 15 minutes of arrest, we noted temporary alterations in EDP-EDD curves (p>0.05). The curves returned to normal within 30-60 minutes after ischemia. In two patients with an average of 66 minutes of arrest, we observed changes in the EDP-EDD curves which did not revert to normal. Available data did not allow us to distinguish between impaired ventricular relaxation and a true change in ventricular compliance as a cause of the shift in the EDP-EDD curve, but ischemia appears to be a major factor in the observed changes.Increased LVEDP after ischemic arrest during open heart surgery may reflect a decrease in left ventricular compliance, rather than an increase in heart size. The probability of altered LVEDP-LVEDD relations appears to depend on the duration of ischemic arrest.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID

摘要:

The sequence for the onset of segmental contraction of the left ventricle was studied in 25 normal patients by analyzing sequential frames obtained at 16.7-msec intervals of right anterior oblique (RAO) ventriculograms by two independent methods. In the first method, we compared the times of onset of contraction of the hemidiameters associated with each of 54 segments with the time of onset of contraction of the average of all the hemidiameters for the ventricular contour. In the second method we used a radial coordinate system and determined relative phase relationships by plotting the motion of each of 54 segments against the average motion of all segments.The resulting pattern showed that, on the average, the midregion of the inferior wall began to contract 25 msec before the apex and the midregion of the anterior wall began contraction 18 msec before the apex. In 12 of 25 patients the interior and anterior walls both began to contract before the apex. In only one of 25 patients did the apex begin to contract first. This sequence of contraction corresponds to the reported sequence of electrical activation for normal human left ventricles.

ISSN:0009-7322    

出版商:OVID    

年代:1979

数据来源: OVID