In tests on dogs specially devised cardiac massage appliances and a monitoring system synchronizing the mechanical massage with the R wave on the ECG were used in carrying out a synchronous mechanical chest massage in conditions of an experimentally induced incompetence of the cardiac ventricles. Optimal parameters of the hemodynamics were recorded with the massage proceeding in such a manner, when mechanical action on the cardiac ventricles coincided with termination of the maximum pressure period of the myocardium. The synchronous ancillary cardiac massage effected under conditions of ventricular incompetence was found to be attended by a rise of cardiac output and increased aortic pressure, falling tension in the auricles and normalization of the acid-base equilibrium figures. Synchronization of the massaging appliance operation with cardiac contractions is an effective method of assisted circulation in acute incompetence of the heart valves.