[Comparative study of the effect of the calcium antagonist nifedipine, the beta receptor blockers acebutolol and propranolol and their combination on electrophysiologic parameters in the human].

It is well known that in the isolated atrium, nifedipine, verapamil and diltiazem slow down the spontaneous frequency and conduction velocity in the sinus- and in the atrioventricular node. Using therapeutic doses in man, we studied the influence of the calcium-antagonist nifedipine, the beta-blockers acebutolol and propranolol and a combination of these on sinus-node parameters (spontaneous cycle length AA, sinus-node recovery time SNRT, corrected sinus-node recovery time CSNRT, sinoatrial conduction time SACT), and on the intracardiac conduction time (PA-, AH-, HV-interval). Both beta-blockers slowed the spontaneous frequency of depolarization of the sinus-node, but lengthened sinus-node recovery time and sinoatrial conduction time (acebutolol: AA + 6% n.s.; SNRT +5% n.s.; CSNRT +2% n.s.; SACT +33% s.; propranolol: AA +9% n.s.; SNRT +15% s.; CSNRT +37% n.s.; SACT +32% n.s.). Simultaneously PA-, AH and HV-interval lengthened (acebutolol: PA +16% n.s.; AH +7% s.; HV +15% s.; propranolol: PA +19% n.s.; AH +16% s.; HV +9% s.). Nifedipine caused essentially no change in sinus-node parameters nor in intracardiac conduction time in man (AA -11% s.; SNRT -12% s.; CSNRT -7% n.s.; SACT +35% n.s.; PA +4% n.s., AH -2% n.s.; HV +5% n.s.). This is in contrast to results obtained in the isolated atrium, and is different from other calcium-antagonists such as verapamil, gallopamil and diltiazem. The effect of acebutololinduced beta-blockade is not intensified by nifedipine (AA -3% n.s.; SNRT -6% s.; CSNRT -12% s.; SACT -19% n.s.; PA -5% n.s.; AH +3% n.s.; HV +9% n.s.).