A 14 month-old intact microminipig, weighing 8 kg, showed ST-segment elevation in A-B lead electrocardiogram during cardiac catheterization followed by ventricular tachycardia, which degenerated into ventricular fibrillation. Although a direct current defibrillation of 360 J was applied, ventricular tachycardia re-occurred for another 2 times and the direct defibrillation was repeated. After returning to normal sinus rhythm, a marked ST-segment elevation was still observed on leads II, III and aVF together with a remarkable decrease in contractility of inferior wall. The heart was excised for precise macroscopic and histological examinations, but there was no dissection, embolus or thrombus in the coronary arteries. These findings suggest that right coronary artery vasospasm could have caused the ischemic attack, leading to lethal arrhythmias.