Overriding tricuspid valve: echocardiographic and angiocardiographic features.

Eight cases are presented in which the diagnosis of overriding of the tricuspid valve was made during life and the electrocardiographic, echocardiographic and angiographic features of the defect are presented. Four of the patients had dextrotransposition of the great arteries, three had normally related great arteries and one had corrected transposition. In each case there was hypoplasia of the right ventricle and a ventricular septal defect of the atrioventricular (A-V) canal type. The electrocardiogram in the cases with d-transposition was characterized by diminished right ventricular forces, left ventricular forces, left ventricular hypertrophy and a superior leftward frontal plane axis. The echocardiogram in seven cases demonstrated a septal leaflet of the tricuspid valve opening posterior to the septum into the left ventricle. In four cases the anterior leaflet of the tricuspid valve was shown crossing the plane of the interventricular septum as it opened in diastole. The diagnosis in five cases was made angiographically by a left ventricular injection in the left anterior oblique projection. In this view the septum was viewed tangentially and in diastole the negative silhouette of the tricuspid valve was seen straddling the interventricular septum. The presence of an overriding tricuspid valve can greatly complicate repair of intracardiac defects. The diagnosis of this A-V valve anomaly can be accurately made with the use of echocardiography and selective left ventricular angiography.