Electrophysiologic effects of propranolol on sinus node function in children.

Little is known regarding the effects of propranolol (P) on sinus node function in children. In this study, corrected sinus node recovery time (CSNRT) and estimated sinoatrial conduction time (SACT) were measured in 10 children (ages 3 to 16 years; mean 8.3 years) without clinical evidence of sinus node dysfunction before and after intravenous P. The spontaneous sinus cycle length (SCL) increased after P(0.1 mg/kg) in all patients. Mean SCL increased 13.4% from 635 +/- 200 msec (+/- SD) to 720 +/- 202 msec (p less than 0.01). Maximum CSNRT increased in nine patients after P and mean CSNRT increased 63% from 203 +/- 61 msec to 330 +/- 190 msec (p less than 0.05). SACT changed in a random fashion after P. Mean SACT did not change significantly. We conclude that P significantly suppresses sinus node automaticity in children with normal sinus node function but has little or no effect on sinoatrial conduction.