Electrophysiological abnormalities after Mustard's operation for transposition of the great arteries.

Because of the frequent occurrence of significant dysrhythmias after Mustard's operation for transposition of the great arteries, electrophysiological studies were performed in i6 patients during postoperative cardiac catheterization. Intracavitary electricalpotentials were recordedfrom the conduction system in all i6patients. In 9 of these patients, the stability of the atrioventricular conduction system during rapid atrial pacing was tested, as well as the subsequent promptness ofpacemaker recovery. The pacemaker recovery time, corrected for cycle length, was significantly prolonged in 4 of 9 patients studied. After atrialpacing, an escapejunctional rhythmpreceded the resumption of sinus rhythm in 3 patients. No intra-atrial block was found between the upper and lower intra-atrial electrograms. In 4 patients, an early electrical activity was recorded inside the pulmonary venous (new left) atrium, above the tricuspid valve. This electrical activity occurred during the T-P interval and was unrepresented on the surface electrocardiogram. No significant abnormalities ofconduction were observed in the atrioventricular node or the His Purkinje system. Furthermore, rapid atrial pacing caused no abnormal atrioventricular block. The abnormal pacemaker recovery time and the absence of conduction disturbances in the atria, atrioventricular node, and His-Purkinje system confirm the hypothesis that injury to the sinoatrial node is the main