PARTIAL REGRESSION OF VASCULAR STRUCTURAL ALTERATIONS IN HYPERTENSIVE PATIENTS TREATED WITH ALPHA-BETA-BLOCKER, LABETALOL

: We studied the structural and functional characteristics of the vascular bed at calf level in 46 middle aged hypertensive patients (20 males and 26 females) treated with different beta-blockers. After one week of placebo, the patients were divided into three groups: group 1 was treated with labetalol, an alpha-beta-blocker (200 mg t.t.d.); group 2 was treated with acebutolol, a cardioselective beta-blocker with intrinsic sympathomimetic activity (ISA) (200 mg t.t.d.); group 2 was treated with acebutolol, a cardioselective beta-blocker with intrinsic sympathomimetic activity (ISA) (200 mg t.t.d.); group 3 was treated with metoprolol, a cardioselective beta-blocker without ISA (100 mg t.t.d.). Before and after placebo, and after three months of active drug treatment, we measured blood pressure, and rest and peak flow at the calf level by strain gauge plethysmography. Basal and minimal vascular resistances were calculated as the ratio between mean blood pressure and rest or peak flow, respectively. A significant decrease in blood pressure was observed in each group. However, basal and minimal vascular resistances decreased only in the labetalol-treated group. These observations indicate that antihypertensive agents that have similar effects on blood pressure, may have different effects on minimal vascular resistance. Therefore, maximum vasodilation of arterioles improves, suggesting that long term treatment with labetalol, but not with other beta-blockers is able to induce a partial regression of vascular structural alterations in hypertensive patients.