A friend had severe chest pain. His ecg was little abnormal. Angiography showed only 40% blockage in one of the arteries. The pain contrinued. Ultrasound showed gallblader stones. He died of cardiac arrest during endoscopy procedure. His BP before starting the procedure was 130/80. His lipid profile etc. were all normal. Other than slight history of BP for which he was taking regular medicine, there was no other ailment. What was the complication?