Effects of combination antihypertensive therapy on baroreflex sensitivity and heart rate variability in systemic hypertension

Earlier studies have shown that cardiovascular autonomic regulation is impa ired in untreated or poorly controlled systemic hypertension. The purpose o f this double-blind, randomized parallel trial was to evaluate whether impr oved blood pressure (BP) control can reverse this impairment. The study gro up consisted of 33 patients (age 45 to 63 years) with poor BP control who r eceived randomized metoprolol or enalapril monotherapy. Baroreflex sensitiv ity (BRS) was assessed by phenylephrine test and time- and frequency-domain measurements of heart rate variability (HRV) were analyzed from 24-hour am bulatory electrocardiographic recordings during monotherapy and after 10 we eks of combination therapy with metoprolol + felodipine or enalaril + hydro chlorothiazide to lower casual BP to <140/90 mm Hg, Intensified treatment d ecreased 24-hour systolic and diastolic BP from 139 +/- 12/86 +/- 8 mm Hg t o 126 +/- 8/80 +/- 7 mm Hg (p <0.0001). BRS improved from 6.2 +/- 3.2 ms/mm Hg to 8.9 +/- 4.1 ms/mm Hg (p <0.0001) and measurements of HRV (e.g., SD o f all RR intervals from 128 +/- 45 ms to 145 +/- 46 ms, p <0.001) improved significantly during the combination therapy. Changes in BRS and HRV were s imilar in magnitude in both treatment arms. Mean RR intervals were comparab le before and after intensive antihypertensive therapy (850 +/- 124 ms vs 9 37 +/- 279 ms, p = NS), These data indicate that adequate BP control with m odem antihypertensive combination therapy can improve cardiovascular autono mic function, which may partially explain the reduced cardiac mortality obs erved in patients with intensified antihypertensive therapy. (C) 1999 by Ex cerpta Medica, Inc.