Tricuspid atresia. An anatomical study of 17 cases.

This is a report on the anatomical characteristics of 17 cases of tricuspid atresia. Three of these cases had a discrepancy between the type of bulboventricular loop (dextro) and the position of the great arteries (the aorta being to the left of the pulmonary artery). In these a characteristic type of ventricular septal defect, located just beneath the tissue of the semilunar valves was found. In 3 cases with cardiac dextroversion and juxtaposition of the atrial appendages the great arteries were on the same frontal plane and there was a separation between the semilunar and the anterior mitral leaflet. One case was associated with a double outlet left ventricle, a D-malposition of the great arteries, and a bilateral subaortic and subpulmonary conus. Among the 6 cases with transposition of the great arteries, the ventricular septal defect was large in 2 (34.4%) only. In the analysis of the 13 cases with intact ventricular septa (2 cases) or restrictive (small and medium-sized) ventricular septal defects (11 cases) obstructive anomalies of the vessel arising from the right ventricle were found in 12 (92.3%). These anomalies involved the aorta in 4 cases. (34.4%) and the pulmonary artery in 8 (66.6%). In the study of the 4 cases with a large ventricular septal defect, obstructive anomalies in the vessel arising from the right ventricle were present in 2 cases (50%), and were located in the aorta in 1 case (25%) and in the pulmonary artery in the other case (25%). The 2 cases with intact ventricular septum were associated with a hypertrophy of this septum and an absent pulmonary valve. In 1 of these cases, a third ventricular chamber was disclosed within the ventricular septum. This chamber communicated with the right ventricle through a very small opening. In 82.3% of the cases, the projection of the dimple, the rest of the tricuspid orifice, was located either on the ventricular septum or over the left ventricle. In the 3 cases with juxtaposition of the atrial appendages there was a positive transillumination of the floor of the right atrium, which corresponded, to the rest of the tricuspid valve in one case and to the atrioventricular portion of the membranous septum in the other 2.