Regression of myocardial hypertrophy and influence of adrenergic system

Studies of regression of myocardial hypertrophy in spontaneously hypertensive rats (SHR) suggest that the adrenergic system may play an important role in the reversal of hypertrophy. The effect of propranolol on reversal of hypertrophy, however, is still controversial. This study describes the effect of propranolol, given alone or in combination with hydralazine in different ratios for 4 wk, on blood pressure (BP), ventricular weight, and myocardial catecholamine (MC) concentrations. The data show that a certain ratio of propranolol to hydralazine (750:30) leads to moderate BP control (196-156 mmHg) without increased MC (634 vs. 552 ng/g) and moderately reduced hypertrophy. Reduction of BP alone with increased MC (hydralazine alone) or reduction of MC without BP control (propranolol alone) failed to reduce hypertrophy. A significant correlation between both ventricular weight and heart rate with MC (r = 0.6) was obtained by multiple regression analysis. This study suggests that adrenergic factors seem to play an important role in modulating structural cardiac response to variations in arterial pressure.