A fatal case of extensive arteriovenous malformation.

Arteriovenous malformation (AVM) is a rare congenital vascular anomaly that can progress to severe complications, including high-output heart failure and coagulopathy. We describe an 84-year-old woman with an extensive AVM extending from the right upper limb to the anterior chest. She was admitted with decompensated heart failure and elevated fibrin degradation products. Despite initial improvement, she experienced sudden cardiac arrest on hospital day 13. Resuscitation allowed transient electrocardiographic recording, which showed ST-segment elevation in precordial leads and aVR, suggesting acute coronary syndrome. Autopsy revealed extensive AVM with intralesional thrombi, concentric ventricular hypertrophy, and histological evidence of hyperacute ischemia, but no coronary thrombosis. The findings suggest possible mechanisms including thrombus lysis or distal embolization consistent with myocardial infarction with non-obstructive coronary artery, potentially influenced by AVM-related coagulopathy, as well as the contribution of long-standing pulmonary hypertension. This case underscores the fatal risks of extensive AVM and highlights the importance of recognizing not only heart failure progression but also thromboembolic and pulmonary hypertensive complications, along with consideration of palliative care in advanced disease. Learning objective: Arteriovenous malformation is a rare congenital vascular anomaly that can cause progressive symptoms, including high-output heart failure depending on its size and location. In advanced stage, complications related not only to heart failure but also to coagulation abnormalities should be carefully considered.