We report a 20-year-old patient with Shone's complex and severe diastolic dysfunction of his small left ventricle (LV) in whom severe pulmonary hypertension and biventricular failure developed while he was awaiting combined heart-lung transplantation. We performed a percutaneous balloon atrial septostomy and a modified Potts shunt (13-mm graft from left pulmonary artery to descending aorta), with the aim of decompressing the hypertensive right ventricle (RV) by reducing left ventricular preload and left atrial hypertension. The procedures were uneventful. The patient's condition improved rapidly and biventricular function was restored. In contrast to a Potts shunt in other conditions, patients with pulmonary hypertension caused by left ventricular disease may benefit from an additional atrial left-to-right shunt.