ABSTRACT
The obstructive lesions in the outflow tracts of hearts with complete transposition of the great arteries determine the clinical evolution, prognosis, and the selection of surgical procedures. Their knowledge is basic to interpret the imaging findings. From the pathologic specimens collection of the Instituto Nacional de CardiologÝa "Ignacio Chßvez", seventy-tree hearts with this cardiopathy were studied morphologically with the sequential segmental system. Thirty-two hearts had outflow tracts anomalies, being obstructive twenty-eight; among these lesions were: malposition of the infundibular septum, hipertrophyc left infundibulum, prolapse of tricuspid valve tissue through a ventricular septal defect, accessory mitral valve tissue, septal hipertrophy at the left outflow tract level, abnormal insertion of cord tendinae of the mitral valve, anticlockwise malposition of the mitral valve (first report in the literature). The left outflow tract presented obstructive lesions (92.85) more frequently than the right one. These lesions produce left ventricular hipertrophy, a fundamental feature for the anatomic surgical procedures to be made.