Electrophysiologic studies after Mustard's operation for d-transposition of the great vessels

Abstract

Electrophysiologic studies were performed in 16 patients after Mustard's operation for d-transposition of the great vessels. Standard 12 lead electrocardiograms showed the following rhythms: “sinus” (10 patients), junctional (4 patients), atrial flutter (1 patient) and alternating sinus and junctional (1 patient). Overdrive atrial stimulation was used to determine sinus nodal recovery time in the 16 patients. Atrial and atrioventricular (A-V) nodal effective refractory periods were determined in 12 patients utilizing the atrial extrastimulus technique. Twenty-four hour Holter electrocardiographic monitoring was performed in 15 patients. Ten (63 percent) of the 16 patients had abnormal sinus nodal recovery time. The atrial effective refractory period was prolonged in 4 (33 percent) of the 12 patients in whom it was measured. All 12 patients had a normal A-V nodal effective refractory period. Previously undetected arrhythmias were found in all patients when the 24 hour Holter electrocardiogram was compared with the standard electrocardiogram. Atropine shortened the sinus nodal recovery time, atrial effective refractory period and A-V nodal effective refractory period in all patients studied. One patient, whose junctional pacemaker was first to recover after termination of atrial pacing, had conversion to sinus rhythm and normal sinus nodal recovery time after administration of atropine. This study indicates (1) that a diseased sinus node and interrupted atrial pathways are involved in the genesis of arrhythmias after Mustard's operation, and (2) that adequate evaluation of arrhythmias in patients after this operation requires not only the standard electrocardiogram, but also a 24 hour Holter monitor, His bundle electrograms and determination of sinus nodal recovery time and atrial and A-V nodal effective refractory periods.