Sequenced external counterpulsation and intraaortic balloon pumping in cardiogenic shock

Sequenced external counterpulsation, a noninvasive technique for ventricular assistance, was compared with intraaortic balloon pumping. With sequenced external counterpulsation external pressure is applied during ventricular diastole to cuffs located from distal to proximal sites on each limb. This procedure causes return of arterial blood to the central circulation which augments central aortic pressure and, possibly, coronary flow. The limb cuffs are rapidly deflated just before ventricular systole so that peripheral resistance is lessened, thereby decreasing left ventricular afterload. The cardiovascular effects of this method have been studied in anesthetized baboons with normal blood pressure and with cardiogenic shock, and in awake human beings with normal blood pressure. Intraaortic balloon pumping was studied in normal dogs and baboons and then in these same animals during cardiogenic shock. Sequenced pulsation caused cardiac output to increase by 25 percent in normal baboons, 17 percent in baboons with cardiogenic shock and 11 percent in normal human volunteers. Intraaortic balloon pumping caused cardiac output to increase by 4 percent in normal animals and 9 percent in animals with cardiogenic shock. Diastolic augmentation of the central aortic pressure pulse was achieved uniformly with both methods. Thus, sequenced external pulsation increased cardiac output to a greater degree than intraaortic balloon pumping, whereas diastolic pressure was augmented equivalently. External counterpulsation probably augments venous return in addition to its effects on the arterial system. Because the technique is totally noninvasive it may play a role in the therapy of patients with cardiogenic shock.