counterpulsation

a technique for assisting the circulation and decreasing the work of the heart by synchronizing the force of an external pumping device with cardiac systole and diastole. External counterpulsation is a noninvasive procedure in which the legs are encased in rigid tubular bags filled with air or water and connected to a pumping unit. Internal counterpulsation requires insertion of an intra-aortic balloon-tipped catheter, the distal end of which is attached to a pump that inflates the balloon. (See also intra-aortic balloon pump.)

External counterpulsation is less effective than internal counterpulsation, but it is easier to use and less hazardous to the patient. It employs the same general principles as internal counterpulsation by applying pressure against the blood vessels of the legs during diastole and release of pressure during systole. This has the effect of increasing venous return and enhancing systolic unloading of the left ventricle. The end result of external counterpulsation is that of augmenting coronary circulation and improving blood flow to the myocardium, improving systemic circulation, and reducing the workload of the heart, thereby lessening myocardial demand for and consumption of oxygen. Indications for external counterpulsation include cardiogenic shock and severe heart failure in acute situations such as myocardial infarction and open-heart surgery. It is a temporary measure that does not benefit patients with chronic heart failure.