Venoarterial shunting from inferior vena cava to left atrium in atrial septal defects with normal right heart pressures. Report of two cases

Two unusual cases of atrial septal defect are presented with right to left shunting occurring from functional drainage of the inferior vena cava into the left atrium. The first had been unrecognized in a teenage boy who previously had undergone successful closed pulmonary valvotomy for congenital pulmonary valvular stenosis. The second occurred following a right pneumonectomy for bronchogenic carcinoma in a man with a previously undetected atrial septal defect. The respiratory embarrassment developing postoperatively was related to dislocation of the heart resulting in an anatomic shift of the atrial septum so that the inferior cava emptied directly into the septum secundum defect. Both patients had normal right heart pressures, and in each the diagnosis was established by selective dye-dilution curves and confirmed by selective cineangiography. Blood gas studies were instrumental in the second case in pointing toward a right to left shunt subsequently confirmed by dye-dilution studies. The importance of blood pH, pCO₂, and pO₂ studies and selective indicator-dilution studies in the evaluation of patients with unexplained cyanosis or respiratory distress is emphasized.