The Ventricular Septal Defect in Tricuspid Atresia: Its Natural History and Surgical Importance

Abstract

We have previously reported anatomic and functional closure of ventricular septal defects (VSDs) in tricuspid atresia. To study this phenomenon further, clinical, angiographic, and pathologic findings in 40 consecutive cases of tricuspid atresia were reviewed. In 14 of these patients, there was evidence of closure of the VSD; in eight it was complete and in the other six partial. Eleven of these VSD closures occurred in type 1 (without transposition) patients and three among type II (with transposition). Progressive cyanosis, increasing polycythemia and/or disappearance of a previously heard murmur were observed in all patients; these signs were more conspicuous in complete than in partial closure. The incidence of closure of VSD in this lesion was 35 percent but when tricuspid atresia patients without VSD are excluded, the incidence increases to 42 percent. Progressive muscular "encroachment" of the margins of the VSD with subsequent fibrosis and covering by endocardial proliferation is the most likely mechanism of closure. Previous surgical shunts played no role in VSD closure. For initial palliation, a Blalock-Taussig shunt (preferably on the left side) is recommended in preference to a Glenn anastomosis, because the latter may leave the left pulmonary circuit without blood supply if the VSD closes. If further palliation is required prior to a Fontan type of operation, a Blalock-Taussig shunt on the right side, Glenn anastomosis or enlargement of VSD could be performed. In type II patients, a large and non-restrictive VSD is essential for survival following a Fontan operation. Therefore, the size of the VSD should be evaluated prior to and at the time of surgical correction. If the VSD is small in type II cases, complete bypass of the VSD and right ventricle either by a pulmonary artery-to-ascending aorta or left ventricle-to-descending aorta conduit should be performed. This is preferable to resection of the ventricular septum or creation of an aortopulmonary window proximal to pulmonary artery banding.