A man in his 80s was transferred to our hospital after losing consciousness and receiving shock delivered from an automated external defibrillator (AED). He was conscious on arrival with a blood pressure of 93/60 mm Hg and a heart rate (HR) of 125 beats per minute. An electrocardiogram (ECG) showed atrial fibrillation, with an HR of 50 to 121 beats per minute and a QTc of 434 ms and no evidence of a Brugada ECG pattern. He had a history of right kidney nephrectomy for retroperitoneal liposarcoma and transurethral resection of a bladder tumor. Blood test results indicated nonelevated troponin T levels and an absence of electrolyte disturbances. Echocardiography revealed an ejection fraction of 31% and severe aortic valve stenosis (aortic valve area, 0.60 cm2; velocity, 3.4 m/s). No significant coronary stenosis was found on computed tomography angiography. He had no family history of sudden cardiac death (SCD). He did not take any proarrhythmic agents and had no syncopal episodes. He was admitted to and treated in the intensive care unit; however, he died of pump failure 2 days after admission.