Subpulmonic obstruction in complete (d) transposition produced by redundant tricuspid tissue.

Two cases are reported in which complete transposition of the great vessels was associated with an unusual form of subpulmonic obstruction. In each case, redundant tricuspid valvular tissue protruded through a ventricular septal defect into the left ventricular outflow tract, producing severe obstruction to the outflow of blood from the left ventricle. The clinical course suggested the presence of left ventricular outflow obstruction. Both patients demonstrated progressive clinical deterioration characterized by increasing cyanosis, respiratory distress, and decrease in intensity of the cardiac murmur. Serial laboratory determinations revealed increasing hemoglobin and decreasing systemic oxygen saturation. The clinical deterioration was relieved only temporarily by atrial balloon septostomy. The angiographic findings appear to be specific for this type of subpulmonic obstruction. In each case, a large asymmetric filling defect was demonstrated at the anterior border of the left ventricular outflow tract below the pulmonic valve. When the clinical and laboratory findings suggest pulmonary or subpulmonary obstruction, careful evaluation of the outflow tract is indicated. If diagnosed clinically, redundant tricuspid tissue could perhaps be resected during a definitive operation, thus relieving the outflow obstruction.