Acute transmural ischemia of the inferior surface of the heart, also referred to as the diaphragmatic surface, is caused by occlusion of the posterior descending coronary artery which arises from the right coronary artery about 75% of the time. In the remainder, it arises from the left circumflex coronary artery or rarely from both. It is associated with ST segment elevation in leads II, III and aVF. These are frequently referred to as the inferior or diaphragmatic leads.