THE HIGH mortality which has been associated with the conventional methods of treatment of acute coronary occlusion associated with shock1 has stimulated consideration of surgical treatment for the lesion. Indeed, clinical attempts to remove acute coronary artery obstruction have already been made on a few occasions2,3 but without prolonged success. Because of the high risks attendant upon operations of this nature, coronary endarterectomy, to be considered, must be based upon accurate preoperative diagnosis with a means available to support the circulation during and following an operative procedure and with the knowledge that restoration of flow to the ischemic area can effect immediate or prolonged improvement in reversible changes which may have occurred in the myocardium subsequent to the occlusion. A closed method of left heart bypass4-8 has been described and has been clinically used to support the failing heart. At present, there is insufficient experimental evidence to