Electrophysiologic effects, clinical efficacy and safety of intravenous and oral nadolol in refractory supraventricular tachyarrhythmias

Abstract

The electrocardiographic and electrophysiologic effects, clinical efficacy and safety of intravenous and oral nadolol therapy were examined in 34 patients with recurrent supraventricular tachyarrhythmias (SVT) undergoing electrophysiologic evaluation. Programmed electrical stimulation was performed in the control (drug-free) state, after infusion of intravenous nadolol (mean dose 0.09 ± 0.03 mg/kg) and after chronic oral nadolol therapy in patients who responded to intravenous nadolol (mean dose 83 ± 12 mg for 5 days). Intravenous nadolol administration prolonged mean sinus cycle length (p = 0.009), mean PR interval (p = 0.001) and mean AH interval (p = 0.001), with no significant electrophysiologic effects in the atrium, ventricle or accessory bypass tracts. Oral nadolol had similar electrocardiographic and electrophysiologic effects, but of lesser magnitude. Intravenous nadolol resulted in complete suppression of induced SVT in 78% of patients with sinus and atrioventricular nodal reentrant tachycardia and 11% of patients with atrioventricular (AV) reentrant tachycardia (p < 0.001). Partial responses were frequent in intraatrial or AV reentrant tachycardia (37%). Oral nadolol suppressed induction of SVT in patients who responded to intravenous nadolol. Adverse reactions to intravenous and oral nadolol were infrequent—6% and 8%, respectively—and usually did not require drug withdrawal. Intravenous nadolol is highly effective in sinus and AV nodal reentrant tachycardia, and a successful electrophysiologic response to it predicts efficacy of long-term oral nadolol therapy. It has limited efficacy alone in AV reentrant tachycardia and should be considered in combination with other antiarrhythmic therapy in this type of SVT.