Propranolol is a non-selective beta-adrenergic blocker that has some sodium blockade, but primarily exerts its antiarrhythmic effects through antagonism of catecholamine-mediated effects on cardiac conduction. This antagonism results in slowed conduction velocity, increased refractoriness, and reduced automaticity, especially in sinoatrial and atrioventricular nodal tissue. Propranolol is also reported to be effective in SVT [17]. Retrospective reviews have not always found differences in recurrence rates among infants treated with digoxin versus propranolol: some report equal efficacy in preventing recurrent SVT [4, 5, 17], while others report a lower recurrence with propranolol [27-29].