A 24-year-old man with Ebstein anomaly underwent a bidirectional Glenn shunt and closure of an atrial septal defect. Postsurgical prulent mediastinitis was treated by irrigation and drainage, but was followed by rupture of the ascending aorta. During emergency surgery, hypothermic circulatory arrest became necessary due to massive bleeding. Since he had undergone a bidirectional Glenn shunt, left heart venting was essential to obtain deep hypothermic circulatory arrest without cardiac distention and was successfully performed via an anterior thoracotomy approach. The perforated site of the ascending aorta was repaired with a Xeromedica patch. The anterior mediastinum was wrapped with the omentum. Transthoracic left heart venting via an anterior thoracotomy is an useful approach when hypothermic circulatory arrest is required to perform a median sternotomy and to approach the heart.