Beta-blocker therapy for the Wolff-Parkinson-White syndrome

Two types of arrhythmias are associated with the Wolff-Parkinson-White syndrome: those in which the accessory pathway is a required part of the reentrant circuit, e.g., orthodromic atrioventricular reciprocating tachycardia, and those that conduct over the accessory pathway but do not require its activation for maintenance of tachycardia, e.g., atrial flutter/fibrillation. Increased sympathetic tone shortens the refractoriness of atrial and ventricular tissue; however, conduction in the atrium and ventricle is not considered the limiting factor for maintenance of atrioventricular reciprocating tachycardia or conduction over the accessory pathway in atrial arrhythmias. Intravenous beta-adrenergic blockers given to patients in the resting state have a minimal to moderate effect in depressing atrioventricular nodal conduction, but have little or no effect on accessory pathway refractoriness or conduction in most patients. In patients presenting with atrioventricular reentry, intravenous administration of beta-adrenergic blocking drugs often is not effective to terminate tachycardia. However, long-term oral therapy with these agents may be beneficial, especially in patients in whom enhanced sympathetic tone is responsible for the initiation or maintenance of tachycardia.