Cardiac involvement in hypertension

Maximal exercise hemodynamics and risk of mortality in apparently healthy men and women

The purpose of this investigation was to determine the association of maximal exercise hemodynamic responses with risk of mortality due to all-causes, cardiovascular disease (CVD), and coronary heart disease (CHD) in a population of apparently healthy individuals. Study participants were 20,387 men (mean age = 42.2 yr) and 6,234 women (mean age = 41.9 yr), patients of a preventive medicine center in Dallas, TX, examined between 1971 and 1989. Maximal heart rate and maximal systolic blood pressure (SBP) measured during the maximal exercise test were related to risk of all-cause, CVD, and CHD mortality. During an average of 8.1 yr of follow-up, there were 348 deaths in men and 66 deaths in women. Among men, after adjustment for confounding variables, risks (and 95 percent confidence interval (CI)) of all-cause mortality for quartiles of maximal SBP, relative to the lowest quartile, were: 0.96 (0.70-1.33), 1.36 (1.01-1.85), and 1.37 (0.98-1.92) for quartiles 2-4, respectively. Similarly adjusted risks for maximal heart rate were: 0.61(0.44-0.85), 0.69 (0.51-0.93), and 0.60 (0.41-0.87). Similar results were seen for risk of CVD and CHD death. In women, similar trends in adjusted risks of all-cause and CVD mortality across maximal SBP and heart rate categories were observed. For maximal heart rate, a 35 bpm higher value was associated with a 36 percent decreased risk of CVD mortality in men (RR = 0.63,95 percent CI = 0.34-0.71) and an 8 percent lower risk in women (RR = 0.92,95 percent CI = 0.18-4.63). These results suggest that an exaggerated SBP or an attenuated heart rate response to maximal exercise may indicate an elevated risk for mortality in this apparently healthy population.

Effects of long-term treatment with prazosin on left ventricular diastolic function in mild to moderate hypertension

It is not well established if blood pressure control is associated with an improvement in diastolic function, whose impairment represents an early marker of cardiac involvement in systemic hypertension. The purpose of this study was to evaluate whether a prolonged treatment with an alpha 1-blocking agent can lead to a reversal of the abnormalities of left ventricular filling. Eleven never-treated patients with mild to moderate essential hypertension were examined before and after at least six months of treatment with prazosin. Cardiac function and left ventricular mass were measured by means of radionuclide ventriculography and echocardiography. Average blood pressure values significantly decreased during the treatment period: from 163.54 +/- 17.80 mm Hg to 146.81 +/- 13.14 mm Hg for systolic blood pressure and from 106.09 +/- 6.96 mm Hg to 92.90 +/- 8.93 mm Hg for diastolic blood pressure. All the indices of left ventricular mass showed a trend toward reduction, but the differences with respect to the baseline values did not reach statistical significance. Average value of ejection fraction was normal before treatment and did not change significantly after treatment. All indices of diastolic function were significantly lower than normal controls' values at the beginning of the study and tended to worsen at the end of the study. Our findings suggest that diastolic function is not consistently affected by the therapy with alpha 1-adrenoreceptor antagonists despite good blood pressure control.

Upward shift of the lower range of coronary flow autoregulation in hypertensive patients with hypertrophy of the left ventricle

BACKGROUND

At any given perfusion pressure, coronary reserve is expressed by the difference between autoregulated and maximally vasodilated flow. In hypertension the raised coronary resistance reduces the steepness of the pressure-flow relationship at maximal vasodilatation. In the presence of cardiac hypertrophy the line of autoregulated flow becomes higher. For these reasons coronary reserve is reduced and the point at which baseline flow approaches the maximal achievable flow might be shifted to a higher perfusion pressure. Thus, any reduction below this elevated and critical value of pressure would lower the coronary flow.

METHODS AND RESULTS

The investigated patients were normotensive (controls, nine) and hypertensive with normal (group I, seven) or augmented LV mass index because of concentric LV hypertrophy (group II, eight). All had effort-induced angina and angiographically normal left epicardial branches. Flow in the great cardiac vein was measured by thermodilution in the baseline and during stepwise (5 mm Hg every 5 minutes) decrease of the coronary perfusion pressure with a titrated nitroprusside i.v. infusion; perfusion pressures of 60 mm Hg in the controls and 70 mm Hg in the hypertensives were taken as end points. Baseline flow averaged 102 ml/min in normotensives, 104 ml/min in hypertensive group I and 148 ml/min in hypertensive group II. At the end points flow was similar to baseline in the controls and group I. In group II coronary flow started to decline and myocardial O2 extraction started to slightly but significantly rise at perfusion pressures of 90-80 mm Hg; at the end point flow was reduced by 26% (p less than 0.01 from baseline). The perfusion patterns did not seem to be related to the changes in tension-time index and heart rate.

CONCLUSIONS

The association of high blood pressure (reduced ability of the coronary arterioles to dilate) and hypertrophy of the myocardium (augmented baseline coronary flow) may shift the point of exhaustion of coronary reserve to a higher perfusion pressure and make the myocardium vulnerable to treatment-induced relative hypertension.

1,2-diacylglycerol content in myocardium from spontaneously hypertensive rats during the development of hypertension

1,2-Diacylglycerol (DAG) has been considered to play an important role as an activator of protein kinase C in the signal transduction of inositol phospholipid metabolism. To examine the relation of 1,2-DAG in heart tissues to cardiac hypertrophy associated with hypertension, we measured the amount of 1,2-DAG in spontaneously hypertensive rat (SHR) hearts at 4, 10 and 20 weeks of age, and in age-matched normotensive Wistar-Kyoto (WKY) rat hearts using thin-layer chromatography with flame ionization detection (TLC-FID). Significant cardiac hypertrophy was found in 4-week-old SHR, while SHR did not yet have significant hypertension. Major phospholipids such as phosphatidylcholine and phosphatidylethanolamine increased from 4 to 20 weeks in the myocardium, but there was no difference between the two strains. The cholesterol levels of 4- and 20-week-old SHR were significantly higher than WKY rats. The 1,2-DAG contents of SHR hearts were significantly higher than WKY rats at 4 weeks. An increase in the RNA content was also observed in 4-week-old SHR hearts. However, analysis of the fatty acid composition of 1,2-DAG revealed no difference between the two strains. However, there was no significant difference in the 1,2-DAG content or in its fatty acid composition between SHR and WKY rat hearts at 10 and 20 weeks of age. It is suggested that an increase in the 1,2-DAG content of SHR hearts during the early stages appears related to the initiation of cardiac hypertrophy in SHR hearts before developed hypertension.