Abstract Body: Case Presentation:
A 50-year-old man experienced unintended weight loss and required more intensive antihypertensive therapy over the preceding several months prior to presentation, as well as new-onset headaches beginning a few days before presentation. On the day of presentation, he suddenly collapsed while playing a Japanese gambling machine. However, no bystander-initiated cardiopulmonary resuscitation was initiated. Emergency medical services personnel delivered two shocks using a defibrillator. Return of spontaneous circulation was briefly achieved but not sustained. He was transported to an emergency department by ambulance. His refractory ventricular fibrillation prompted the initiation of venoarterial extracorporeal membrane oxygenation as a life-saving measure.

Differential Diagnosis:
Coronary angiography performed immediately after venoarterial extracorporeal membrane oxygenation revealed no significant stenosis. Computed tomography uncovered a large right adrenal mass with a maximum diameter of approximately 95 mm (Image). Abdominal T2-weighted magnetic resonance imaging (MRI) revealed a hyperintense lesion within the right adrenal gland． ¹²³I-meta-iodobenzylguanidine scintigraphy demonstrated intense radiotracer uptake corresponding to the adrenal mass. Furthermore, transthoracic echocardiography identified ventricular septal hypertrophy measuring approximately 19 mm. Cardiac MRI illustrated that the hypertrophy of ventricular septum was relatively uniform. These findings were highly suggestive of pheochromocytoma-induced cardiomyopathy.

Treatment and Management:
Venoarterial extracorporeal membrane oxygenation was successfully weaned on hospital day 3. On hospital day 23, he underwent open right adrenalectomy, and histopathological examination confirmed pheochromocytoma.

Outcome and Follow-up:
To prevent recurrent life-threatening arrhythmia, we implanted a cardioverter–defibrillator on hospital day 35. The postoperative course was uneventful, and he was discharged on hospital day 43.

Discussion/Teaching Points:
Because cardiomyopathy might not quickly resolve after surgery, we implanted a cardioverter–defibrillator in this patient to prevent recurrent cardiac arrest. Although pheochromocytoma-induced cardiomyopathy is relatively rare, most cases are incidentally discovered using clinical images. As the present case illustrates, early detection and rapid therapy could enable the patient to be discharged without any complications.