A 43-year-old woman with a long history of heavy cigarette smoking was in good health until she developed fatigue, dyspnea on exertion, and paroxysmal nocturnal dyspnea approximately three months before admission to our hospital. Four weeks before admission, she was admitted to another hospital for the sudden onset of a right hemiparesis. She was noted to be in atrial fibrillation, and cardiac catheterization and angiocardiography revealed triple-vessel coronary arterial disease and moderately severe mitral regurgitation. Because of repeated episodes of paroxysmal nocturnal dyspnea, she was referred to our hospital for cardiac surgery. On admission, an electrocardiogram was recorded (Figure).