Right-to-left shunt through the cardiac veins after the Fontan procedure.

We found right-to-left shunts through the cardiac veins postoperatively in 2 patients who had undergone the Fontan procedure. In one of the patients, channels were present through the cardiac veins independent of the coronary sinus. In the other patient, an atretic orifice for the coronary sinus, coupled with a persistent left-sided superior caval vein, complicated the postoperative course.