[Transposition of the great arteries: anatomic types of left ventricular outflow tract obstruction (author's transl)].

A postmortem investigation has been carried out in 48 heart specimens with transposition of the great arteries (TGA) to evaluate incidence and type of left ventricular outflow tract obstruction. The frequence of pulmonary stenosis in our series (23%) is similar to those reported from previous studies. Cases have been divided in two groups according to presence or absence of ventricular septal defect. In cases with intact ventricular septum the obstruction was determined by asymmetric hypertrophy of the septum (1 observation) and by abnormal attachement of clefted anterior mitral leaflet to the interventricular septum (2 observations). In the specimens with ventricular septal defect, 4 presented a stenosis due to malalignment of the infundibular septum, associated with valvular stenosis in 1 case and with valvular stenosis and fibrous subvalvular ring in 2. Another case presented a stenotic pulmonary valve and a parachute mitral valve. The remaining 3 showed a cleft of the anterior leaflet of the mitral valve. The high incidence of infundibular malalignment obstruction is underlined together with its association with A-P or L-position of the aorta. This peculiar relation of the great arteries could be angiocardiographically employed as indicative for the presence of this type of left outflow tract obstruction in TGA.