Catastrophic Multiterritorial Arterial Embolization Causing Near-Total Bowel Necrosis in New-Onset Atrial Fibrillation With Thyrotoxicosis.

Acute mesenteric ischemia remains one of the most lethal abdominal emergencies, particularly when bowel necrosis has already occurred at the time of diagnosis. Embolic occlusion of the superior mesenteric artery is most commonly associated with atrial fibrillation. Although hyperthyroidism is a recognized trigger for atrial fibrillation, widespread systemic arterial embolization in this setting is rarely reported. We describe a 77-year-old woman with biochemical thyrotoxicosis and new-onset atrial fibrillation who developed simultaneous superior mesenteric and peripheral arterial occlusions, resulting in near-total small bowel necrosis that was not surgically survivable. Her rapid clinical deterioration underscores the aggressive nature of embolic mesenteric ischemia and the narrow window available for intervention.