A 75-year old woman with chronic atrial fibrillation presented to the hospital with a 2-day of colicky abdominal pain. The physical examination revealed hypoactive bowel sounds and diffuse abdomina tenderness. Laboratory tests showed a white cell count of 19,400 per cubic millimeter with 92 /o neutrophils, a blood urea nitrogen level of 42 mg per deciliter (15 jimol per liter) and a syrum creatinine level of 3.0 mg per deciliter (267 per liter). The common cause for this problem would be-