Metoprolol significantly increased tonic and reflex vagal cardiac activity, whereas ramipril did not affect vagal cardiac control, despite both drugs similarly decreasing blood pressure.
RCT (n=12)
Crossover
Does metoprolol compared to ramipril improve vagal cardiac activity and lower blood pressure in untreated stage 1-2 essential hypertensive patients?
Metoprolol, but not ramipril, increases tonic and reflex vagal cardiac activity in essential hypertension, which correlates with and may contribute to its blood pressure-lowering effects.
Cardiovascular parasympathetic activity is attenuated in essential hypertension. Both beta-adrenoceptor antagonists and angiotensin converting enzyme inhibitors have been reported to increase vagal modulation of heart rate and baroreflex sensitivity, but the relations between the antihypertensive and vagal cardiac effects of these drugs have remained unclear in essential hypertension. In the present study we evaluated the effects of a 4-week crossover monotherapy with metoprolol and ramipril on spectrum analysis indices of heart rate variability in the supine rest and head-up tilted positions, baroreflex sensitivity (phenylephrine method), and 24-h ambulatory blood pressure (BP) in 12 formerly untreated stage 1-2 essential hypertensive patients. Compared to the pretreatment values, both drugs decreased BP similarly and significantly. However, the drugs showed different effects on cardiac vagal activity: metoprolol increased significantly mean R-R interval, R-R interval total, and high-frequency variability at supine rest and baroreflex sensitivity, but ramipril did not significantly affect these variables. The metoprolol-induced decrease in ambulatory BP correlated with the prolongation of the R-R interval and the increase of high-frequency variability at supine rest. The present data show that 4-week treatment with metoprolol increases tonic and reflex vagal cardiac activity, whereas ramipril does not affect vagal cardiac control in essential hypertension. Increase in vagal activity may contribute to the BP-lowering effect of metoprolol in hypertensive patients.
VESALAINEN et al. (1998) conducted an RCT in Essential hypertension (n=12). Metoprolol vs. Ramipril was evaluated on Spectrum analysis indices of heart rate variability, baroreflex sensitivity, and 24-h ambulatory blood pressure. Metoprolol significantly increased tonic and reflex vagal cardiac activity, whereas ramipril did not affect vagal cardiac control, despite both drugs similarly decreasing blood pressure.