摘要:

Acute pulmonary edema during hypertensive crisis has been attributed to acute left ventriculár systolic failure secondary to increased afterload. We tested the hypothesis that the increase in coronary artery perfusion pressure associated with systemic hypertension could also contribute to increased left ventricular filling pressures by acutely increasing coronary intravascular volume and decreasing left ventricular diastolic compliance. Isolated isovolumic (balloon in left ventricle) normal rabbit hearts (n= 13) with pericardium removed and right ventricle vented were blood perfused at an initial coronary artery perfusion pressure of 100 mm Hg; left ventricular balloon volume was adjusted to produce an initial left ventricular end-diastolic pressure of 15±1 mm Hg; left ventricular systolic pressure was 102±3 mm Hg. When coronary perfusion pressure was increased to 130±l mm Hg to simulate a hypertensive crisis, coronary flow increased from 2.0±0.2 to 3.0±0.2 ml/min/g left ventricle (p< 0.001), left ventricular systolic pressure increased to 116±4 mm Hg, and isovolumic left ventricular end-diastolic pressure increased to 21±1 mm Hg (p< 0.001), which indicated a decrease in left ventricular diastolic compliance. When coronary perfusion pressure was decreased to a physiological level of 70 mm Hg, coronary flow rate decreased to 1.4±0.1 ml/min/g left ventricle (p< 0.001), left ventricular systolic pressure fell to 82±4 mm Hg, and left ventricular end-diastolic pressure fell to 14±1 mm Hg (p< 0.001). The left ventricular diastolic pressure-volume curve was shifted upward and to the left at a coronary perfusion pressure of 130 mm Hg relative to the curve generated at a coronary perfusion pressure of 70 mm Hg, confirming that left ventricular diastolic compliance decreased when coronary perfusion pressure was elevated. Coronary hypertension also resulted in an increase in left ventricular wall thickness as assessed by two-dimensional echocardiogram. Mean endocardial-to-epicardial wall thickness was 5.1±0.6 mm at a coronary perfusion pressure of 130 mm Hg and 4.1±0.4 mm at a coronary perfusion pressure of 70 mm Hg (p< 0.05). Neither peak negative rate of change of pressure (-dP/dt) nor the exponential time constant of ventricular relaxation changed when coronary perfusion pressure was decreased from 130 to 70 mm Hg, which suggests that early diastolic relaxation was unaffected over the range of coronary perfusion pressure studied. The correlation between coronary hypertension, decreased left ventricular diastolic compliance, and increased wall thickness in the normal isolated isovolumic blood-perfused rabbit heart suggests that coronary vascular turgor may be a significant factor altering diastolic compliance of the left ventricle during acute hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The influence of ethanol (alcohol) consumption on blood pressure during and after the development of hypertension was examined by using spontaneously hypertensive rats (SHR) and stroke-prone SHR (SHRSP). Normotensive Wistar-Kyoto (WKY) rats were also used for comparison. Substituting alcohol (5–20%) for drinking water at 1 month of age retarded the age-dependent rise of blood pressure hi all three strains so that, at 7 months, blood pressure measured by a tail-cuff method was 24 mm Hg, 26 mm Hg, and 41 mm Hg lower in the alcohol-treated WKY rats, SHR, and SHRSP, respectively, than in untreated rats. Significant differences in blood pressure were seen in each strain after only 3 months. Withdrawal of alcohol at this stage caused an acute rise of blood pressure then a return to subnormal levels, which persisted for a further 3 months. Administration of 15% alcohol to adult WKY rats and SHR for 2 months had no significant effect on blood pressure. Increasing alcohol content to 20% for a further 2 months prevented rises of blood pressure hi both strains. Thus, although continuous drinking of alcohol does not lower blood pressure, it appears to counteract the development of hypertension in rats.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This study was performed with Dahi salt-sensitive (DS) and Dahi salt-resistant (DR) rats to detect differences hi cardiovascular hemodynamics and renal responses that might be involved hi initiating salt-induced hypertension hi DS rats. The effects of 4 weeks of 8% NaCl diet were studied hi conscious, male DR and DS rats hi which vascular and urinary catheters had been previously implanted. Results were compared with those obtained from control groups of DR and DS rats on 4 weeks of 1% NaCl diet. DR rats on 8% salt diet did not develop hypertension, and cardiac output and blood volume were unchanged; glomerular filtration rate, urinary flow, sodium excretion, and plasma atrial natriuretic factor (ANT) increased. DS rats on 8% salt diet developed hypertension, and cardiac output and blood volume increased; glomerular filtration rate, urinary flow, and sodium excretion did not change, despite an increase hi ANF. DS and DR rats on 1% NaCl diet were subjected to ANF infusion. After ANF infusion DR rats had a decreased blood volume and an increased glomerular filtration rate, urinary flow, and sodium excretion; DS rats showed no significant changes hi blood volume, glomerular filtration rate, urinary flow, or sodium excretion. ANF caused vasodilation hi all regions studied hi DR rats; DS rats showed vasodilation hi all regions except the kidney. After acute volume expansion, although both DR and DS rats responded by an increase hi cardiac output, only DS rats developed prolonged hypertension. This finding suggests an inadequate vasodilatory mechanism in DS rats. In response to acute volume expansion, renal resistance decreased hi DR rats but not hi DS rats. It is concluded that the primary hemodynamic disturbance hi DS rats with salt-Induced hypertension is an increase hi cardiac output caused by blood volume expansion hi the absence of any vasodilation. Comparison of the responses of DS and DR rats to high salt diets, ANF infusion, and acute volume expansion indicates that the salt-induced hypertension in DS rats is initiated by a diminished renal response to ANF.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Plasma catecholamines and blood pressure reactivity were investigated in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats maintained on three levels of dietary calcium: low (0.1%), intermediate (1.0%), or high (2.0%). In the SHR, restricted dietary calcium resulted in elevations of mean arterial pressure that were most pronounced during handling and restraint stress (p< 0.05). There was no difference between SHR on intermediate and high calcium diets and no dietary effects in the WKY rats. Resting and stressed levels of circulating catecholamines did not differ across diet conditions in either strain. The SHR on low calcium diets had significantly larger pressor responses to infused norepinephrine (p< 0.05). There were no differences between the rats on intermediate and high calcium diets. The results indicate that differences observed in blood pressure reactivity across diets in this study may have been a consequence of altered postsynaptic sensitivity rather than an increase in norepinephrine release.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Forty-seven patients with mild hypertension and 48 normotensive patients entered a blinded, parallel study in which they received a placebo, 10 mmol/day calcium carbonate (CaCO3), or 20 mmol/day CaCO3. There were no significant differences in blood pressure changes among the groups. In the hypertensive group and in patients with the highest blood pressure there were individual falls in systolic pressure, particularly in the group receiving 10 mmol daily CaCO3. In the hypertensive group the changes were: with placebo, −3±2/− 2±2 mm Hg; with CaCO3(10 mmol), −7±3/− 2±2 mm Hg; and with CaCO3(20 mmol), −2±3/l±2 mm Hg. No change was significant, and no pressure changes of patients taking CaCO3differed significantly from changes of patients taking placebo. Ten of 33 patients taking placebo, 11 of 31 taking 10 mmol/ day CaCO3, and nine of 31 taking 20 mmol/day CaCO3were classified as responders from their systolic blood pressure fall. These response rates did not differ. Eight patients had falls of systolic blood pressure greater than 15 mm Hg. Five were on 10 mmol/day CaCO3and three on 20 mmol/day CaCO3. This response was significantly different from that with placebo. Univariate analyses failed to reveal any predictive dietary or biochemical parameter. After 3 months of not taking CaCO3, 12 patients classified as responders, including six of the eight with a fall of 15 mm Hg or more, were rerandomized to placebo or to 20 mmol/day CaCO3. In the rechallenge, responses to CaCO3and placebo were similar, neither causing a significant pressure fall. Calcium carbonate did not reduce blood pressure. The apparent response hi a few patients was not verified by rechallenge. The present study does not support calcium supplementation as a useful nonpharmacological measure for reducing elevated blood pressure.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Atrial natriuretic factor was infused in a low dose (0.2 μg/min) during 5 days in six patients with essential hypertension. Atrial natriuretic factor infusion caused plasma levels of atrial natriuretic factor to increase from 49±10 to 106±19 pg/ml. Within 4 hours after the start of the atrial natriuretic factor infusion, urinary sodium excretion increased hi all subjects. Sodium balance was regained after 24 hours with a net loss of 72.3±14.6 mmol. However, systolic as well as diastolic blood pressure started to decrease gradually in all subjects only after 12 hours of atrial natriuretic factor infusion, reaching a stable level after 36 hours with a decrease of 11.5±1.5% and 10.3±0.8%, respectively. Heart rate increased in parallel by 12.6±3.1%. Hematocrit rose 7.1±2.3%. After cessation of atrial natriuretic factor infusion, plasma atrial natriuretic factor levels, sodium balance, and hematocrit returned to baseline within 24 hours, whereas blood pressure slowly returned toward baseline values over 3 days. These data show that chronic atrial natriuretic factor infusion in patients with essential hypertension causes a negative sodium balance and a rise in hematocrit, followed by a smooth decrease in blood pressure with a rise in heart rate until a new equilibrium is reached after approximately 2 days. Thus, atrial natriuretic factor in low doses appears intimately involved in the regulation of sodium balance and blood pressure in humans. Moreover, these data suggest that atrial natriuretic factor-like substances will eventually become useful antihypertensive drugs.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The accuracy of blood pressure values obtained by continuous noninvasive finger blood pressure recording via the FINAPRES device was evaluated by comparison with simultaneous intraarterial monitoring both at rest and during performance of tests known to induce fast and often marked changes in blood pressure. The comparison was performed in 24 normotensive or essential hypertensive subjects. The average discrepancy between finger and intra-arterial blood pressure recorded over a 30-minute rest period was 6.5±2.6 mm Hg and 5.4±2.9 mm Hg for systolic and diastoiic blood pressure, respectively; a close between-method correspondence was also demonstrated by linear regression analysis. The beat-to-beat changes in finger systolic and diastoiic blood pressure were on average similar to those measured intra-arterially during tests that induced a pressor or depressor response (hand-grip, cold pressor test, diving test, Valsalva maneuver, intravenous injections of phenylephrine and trinitroglycerine) as well as during tests that caused vasomotor changes without major variations in blood pressure (application of lower body negative pressure, passive leg raising). The average between-method discrepancy in the evaluation of blood pressure changes was never greater than 4.3 and 2.0 mm Hg for systolic and diastoiic blood pressure, respectively; the corresponding standard deviations ranged between 4.6 and 1.6 mm Hg. Beat-to-beat computer analysis of blood pressure variability over the 30-minute rest period provided standard deviations almost identical when calculated by separate consideration of intra-arterial and finger blood pressure tracings (3.7 and 3.8 mm Hg, respectively). The two methods of blood pressure recording also allowed similar assessments of the sensitivity of baroreceptor control of heart rate (vasoactive drug injections) and blood pressure (neck chamber technique) to be obtained. Thus, beat-to-beat blood pressure recording via FINAPRES provides an accurate estimate of means and variability of radial blood pressure in groups of subjects and represents in most cases an acceptable alternative to invasive blood pressure monitoring during laboratory studies.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID