A 55-year-old man underwent surgical replacement of a mitral valve 10 years earlier. In a retrospective evaluation of a chest radiograph, the diaphragm was intact at the time of initial surgery. He was then admitted to our emergency room with a complaint of vertigo. During evaluation, he developed decreased consciousness. Ventricular fibrillation was diagnosed, and external massage and full cardiopulmonary resuscitation were performed. After 20 minutes, his sinus rhythm returned and hemodynamic status stabilized with inotropic drugs. Transthoracic echocardiography showed normal valvular function and no evidence of left cardiac malfunction or clot. Electrocardiography showed ST elevation in inferior leads, and levels of cardiac enzymes were elevated. Angiography showed an embolic lesion in the mid right coronary artery that was treated with percutaneous coronary intervention (PCI) and insertion of a stent. After 24 hours, the patient was extubated in good condition, but had mild dyspnea that progressed to CO2 narcosis and subsequent reintubation. Post-extubation chest radiography showed herniation of abdominal organs into the right hemithorax. The diaphragmatic defect was closed with a polytetrafluoroethylene patch by a thoracic surgeon, and the postoperative course was uncomplicated.