The ability of electrical stimulation to provoke rhythm disturbances was tested 4 days after a heart attack in dogs. The heart attack was created in one of 3 ways: by blocking off a coronary artery permanently, by blocking off a coronary artery only temporarily, or by blocking off a coronary artery only temporarily, permanently and removing all blood flowing through the artery via collateral vessels for 2 hours. The group that had only a temporary coronary artery occlusion had far fewer provokable rhythm disturbances. This indicates that restoring patency of the coronary artery after a blockage has occurred may result in fewer rhythm disturbances.