Effects of Sotalol on His-Purkinje Conduction and Refractoriness in Humans

BACKGROUND: The effects of sotalol on refractoriness in human ventricular and atrial muscles have been well established, but the drug's effect on the electrical properties of the His-Purkinje system in humans is not known, especially whether sotalol's effect is due solely to its action on prolonging repolarization or in combination with its beta-blocking properties. We studied the electrophysiologic effects of intravenous sotalol and propranolol in patients undergoing electrophysiologic studies of cardiac arrhythmias. METHODS AND RESULTS: We studied 22 patients (19 men, 3 women; mean age, 60 +/- 6 years) who had coronary artery disease and assessable anterograde, retrograde, or both, His-Purkinje system function. Fifteen patients underwent electrophysiologic studies before and after intravenous sotalol (1.5 mg/kg), and 7 patients underwent electrophysiologic studies before and after intravenous propranolol (0.15 mg/kg). Both sotalol and propranolol had no significant effect on the H-V interval, but sotalol significantly increased ventricular refractoriness and His-Purkinje refractoriness, both in anterograde and retrograde conduction, whereas propranolol did not, Sotalol's effect on His-Purkinge refractoriness also caused atrioventricular block distal to the His bundle during atrial pacing at a moderately fast rate. Sotalol was not effective in preventing bundle branch re-entry tachycardia, nevertheless, it increased cycle length of bundle branch re-entry tachycardia by increasing refractoriness. CONCLUSIONS: Sotalol increased His-Purkinje refractoriness in humans but had no effect on His-Purkinje conduction. The drug must be used judiciously in patients with a diseased His-Purkinje system because it may cause atrioventricular block distal to His at fast heart rates. Sotalol had no effect on macrore-entry utilizing bundle branches.