A diagnostic ECG system analyzes lead traces for evidence of ST elevation in the lead signals. The pattern of ST elevation in leads having predetermined vantage points to the electrical activity of the heart and, in some instances, the presence of ST depression in certain other leads, identifies a specific coronary artery or branch as the culprit coronary artery for an acute ischemic event. ECG measurements which are associated with the identity of specific arterial occlusion locations are calculated and used to form a classifier of the probability of occlusion at different locations. The location identified as having the highest probability is indicated to a user as the most likely occlusion location.