Intra-aortic balloon pump

The intra-aortic balloon pump (IABP) is a mechanical device that increases myocardial oxygen perfusion and indirectly increases cardiac output through afterload reduction. It consists of a cylindrical polyurethane balloon that sits in the aorta, approximately from the left subclavian artery. The balloon inflates and deflates via counter pulsation, meaning it actively deflates in systole and inflates in diastole. Systolic deflation decreases afterload through a vacuum effect and indirectly increases forward flow from the heart. Diastolic inflation increases blood flow to the coronary arteries via retrograde flow. These actions combine to decrease myocardial oxygen demand and increase myocardial oxygen supply. A computer-controlled mechanism inflates the balloon with helium from a cylinder during diastole, usually linked to either an electrocardiogram (ECG) or a pressure transducer at the distal tip of the catheter; some IABPs, such as the Datascope System 98XT, allow asynchronous counterpulsation at a set rate, though this setting is rarely used. Helium is used to inflate the balloon as its low density means there is little turbulent flow, so the balloon can inflate quickly and deflate slowly. It is also relatively benign and eliminated quickly if there is a leak or rupture in the balloon. The following situations may benefit from this device. Cardiogenic shock when used alone as treatment for myocardial infarction. 9–22% survive the first year. Reversible intracardial mechanical defects complicating infarction, i.e. acute mitral regurgitation and septal perforation. Unstable angina pectoris benefits from counterpulsation. Post cardiothoracic surgery—most common and useful is counterpulsation in weaning patients from cardiopulmonary bypass after continued perioperative injury to myocardial tissue. Preoperative use is suggested for high-risk patients such as those with unstable angina with stenosis greater than 70% of main coronary artery, in ventricular dysfunction with an ejection fraction less than 35%.