Electrophysiologic Identification of the Specialized Conduction System in Corrected Transposition of the Great Arteries

Abstract

Electrophysiologic identification of the specialized conduction system was performed during open-heart surgery in two cases of corrected transposition of the great arteries (1-TGA) with situs solitus, dextrocardia or dextroversion and membranous ventricular septal defect (VSD). In one case there was accompanying subvalvlar pulmonary stenosis and in the other there was an Ebstein-like deformity of the systemic atrioventricular (A-V) valve. Electrograms were recorded throughout the right atrium and morphologic left ventricle in the case with subvalvar pulmonary stenosis and throughout the left atrium and morphologic right ventricle in the case with the Ebstein-like deformity of the systemic A-V valve. Specialized conduction system electrograms were recorded exclusively at sites anterior to the membranous VSD in both cases and at no other sites in the respective atrium or ventricle studied. There was first degree A-V block in both cases and in each the site within the specialized conduction system of this delay was proximal to the specialized fiber electrogram recording sites and thus probably proximal to the bifurcation of the bundle branches. In addition, on, the Ebstein-like deformity of the systemic A-V valve present in one case was confirmed by directly recording ventricular electrograms in an area of "atrialized-ventricle above the valve.