Effect of increased left atrial pressure and a positive inotropic agent upon asynergic left ventricle which was produced by acute occlusion of LAD were examined in 8 open-chest dogs. Systolic bulging in ischemic area was qualified by ESL/EDL in percentage. Left atrial pressure was controlled by the reservoir connected to left atrial appendage with a large bore tubing. Cardiac output and aortic pressure were decreased following coronary occlusion without change in isometric developed tension in nonischemic area of left ventricle. Increase of left atrial pressure from 5 mmHg to 14 mmHg produced rise in stroke volume to 191% and rise in aortic pressure to 156% in asynergic left ventricle respectively. These increases were not accompanied by change in ESL/EDL. Therefore, extracardiac factors were assumed to explain the prominent increase in left ventricular stroke work by elevation of left atrial pressure in asynergic left ventricle. Isoproterenol enhanced total cardiac performance by increasing the function of nonischemic area without deterious effect on the ischemic area.