Changes and significance of subtype function of beta-adrenoreceptors in left ventricular remodeling of hypertension.

Abstract

Changes in the density of myocardium and blood lymphocyte beta-adrenoceptors (beta-AR) in left ventricular (LV) geometry have been found in patients with essential hypertension (EH). However, it is not known whether intrinsic beta-AR subtype function changes during left ventricular remodeling of hypertension. The purpose of this study was to further investigate the changes and clinical significance of beta-AR subtype function in LV remodeling in patients with EH. One hundred and thirty-four men (mean age, 53 years) with EH as defined in the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure grades 1 to 2 and 40 normotensives were studied. Based on the echocardiographic LV mass index and relative wall thickness, four patterns of LV geometry, ie, normal left ventricle, concentric remodeling, eccentric hypertrophy, and concentric hypertrophy were identilied. beta-Adrenoreceptor subtype responsiveness was measured by a treadmill exercise test (to measure cardiac beta1-adrenoreceptor responsiveness) and by Salbutamol injection test (to measure cardiac beta2-adrenoreceptor responsiveness) in 134 male patients with EH. Forty normotension subjects were also studied as controls. In patients with EH in the groups of concentric remodeling, concentric hypertrophy, and eccentric hypertrophy, heart rate in response to the treadmill test (peak exercise-resting rate) was significantly higher (P < 0.05, P < 0.01. P < 0.01, respectively) than that in the control group. In the concentric remodeling and concentric hypertrophy group, the chronotropic doses of salbutamol required to increase the heart rate by 30 beats/min (CD30) were significantly lower (P < 0.05, P < 0.01, respectively) than that in the control group. However, in the eccentric hypertrophy group. CD30 was higher significantly (P < 0.01) than that in the control group. In the concentric remodeling, concentric hypertrophy, and eccentric hypertrophy groups, beta1-AR responsiveness significantly increased them in the normotensive group, whereas beta2-AR responsiveness significantly increased in the concentric remodeling and concentric hypertrophy groups them in the normotensive group, and significantly decreased in the eccentric hypertrophy them in the normotensive group. The results suggest that non-beta-selective blocker may be beneficial for normal morphology, concentric remodeling and concentric hypertrophy, while beta1-selective blockers may be beneficial for eccentric hypertrophy in patients with EH.