Maintenance of circulation during ventricular fibrillation with the simultaneous use of two "counterpulsation" devices. Two valveless, single orifice counterpulsation devices, with pumping stroke volumes of 65 ml each, were implanted on the ascending aorta and pulmonary artery of seven open chest anesthetized dogs. After completion of the preparation, ventricular fibrillation was induced. The devices were synchronized to pump simultaneously at a rate of 85-100 bpm. The combined use of the counterpulsation devices provided maximal aortic pressure of 111.4 +/- 25.1 mmHg during ventricular fibrillation for a period of 15-60 min. The mean left ventricular pressure was 17.7 +/- 4.4 mmHg, and the cardiac index 64.5 +/- 23.6 ml/kg/min. Cardioversion of ventricular fibrillation to sinus rhythm restored normal hemodynamics. The counterpulsation device implanted on the ascending aorta was not able to maintain circulation for more than 5 min after the induction of ventricular fibrillation, if used alone. In conclusion, the use of two counterpulsation devices implanted on the ascending aorta and pulmonary artery was able to maintain circulation in experimental animals during ventricular fibrillation. 