A 5-day-old boy with mitral atresia and restrictive interatrial communication underwent an anastomosis between the left atrial appendage and left superior vena cava draining to the right atrium after unsuccessful balloon atrial septostomy. Consequent reduction of left atrial pressure improved the child's clinical condition, enabling palliative surgery. This procedure may be done safely without cardiopulmonary bypass in a seriously ill patient with combined elevated left atrial pressure and persistent left superior vena cava.