Identification of the conduction system in corrected transposition and common ventricle at operation.

The high incidence of surgically induced heart block in patients with levotransposition of the great arteries is now better understood because of recent anatomic demonstration of an unusual anterior location of the atrioventricular specialized conducting tissue. The two cases reported herein proved electrophysiologic confirmation of this previously described anatomy. The specialized conducting bundle was easily and consistently identified and then avoided in successful surgical correction in one patient with common ventricle, type A-3, and in another with corrected transposition, large ventricular septal defect, and valvular pulmonary stenosis. Electrophysiologic identification of the atrioventricular conduction tissue at the time of operation may decrease the incidence of heart block and offers additional optimism for successful correction of levotransposition complexes.