Counterpulsation: A technique for assisting the circulation by decreasing the afterload of the left ventricle and augmenting the diastolic pressure. It may be achieved by intra-aortic balloon, or by implanting a special pumping device in the chest, or externally by applying a negative pressure to the lower extremities during cardiac systole.Intra-Aortic Balloon Pumping: Counterpulsation in which a pumping unit synchronized with the patient's electrocardiogram rapidly fills a balloon in the aorta with helium or carbon dioxide in early diastole and evacuates the balloon at the onset of systole. As the balloon inflates, it raises aortic diastolic pressure, and as it deflates, it lowers aortic systolic pressure. The result is a decrease in left ventricular work and increased myocardial and peripheral perfusion.Assisted Circulation: Pumping that aids the natural activity of the heart. (Dorland, 27th ed)Shock, Cardiogenic: Shock resulting from diminution of cardiac output in heart disease.Coronary-Subclavian Steal Syndrome: A complication of INTERNAL MAMMARY-CORONARY ARTERY ANASTOMOSIS whereby an occlusion or stenosis of the proximal SUBCLAVIAN ARTERY causes a reversal of the blood flow away from the CORONARY CIRCULATION, through the grafted INTERNAL MAMMARY ARTERY (internal thoracic artery), and back to the distal subclavian distribution.Angina Pectoris: The symptom of paroxysmal pain consequent to MYOCARDIAL ISCHEMIA usually of distinctive character, location and radiation. It is thought to be provoked by a transient stressful situation during which the oxygen requirements of the MYOCARDIUM exceed that supplied by the CORONARY CIRCULATION.Heart-Assist Devices: Small pumps, often implantable, designed for temporarily assisting the heart, usually the LEFT VENTRICLE, to pump blood. They consist of a pumping chamber and a power source, which may be partially or totally external to the body and activated by electromagnetic motors.Myocardial Infarction: NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION).Coronary Circulation: The circulation of blood through the CORONARY VESSELS of the HEART.