Chapter 63: Intra-aortic Balloon Pump

INTRODUCTION

An intra-aortic balloon pump (IABP) is a temporary endovascular mechanical device that is placed within the proximal descending aorta to augment cardiac output in a failing heart. Through the principle of counterpulsation, an IABP improves myocardial oxygen supply and decreases myocardial oxygen demand. The pump can also increase cardiac output, ejection fraction, and systemic perfusion while at the same time decreasing heart rate, pulmonary capillary wedge pressure and systemic vascular resistance.

TECHNIQUE

The intra-aortic balloon is an inflatable cylinder made of polyethylene that rests in the aorta several centimeters distal to the left subclavian artery. It is approximately 23–28 cm in length and holds a volume of between 30 and 40 mL. There is a central lumen used for guide-wire placement and central arterial pressure monitoring, alleviating the need for placement of a separate arterial line. A console beside the patient’s bed is used to control the balloon. It has a pressurized gas reservoir and several monitors, including electrocardiography, pressure wave recording, inflation/deflation timing, and triggering selection switches. It also contains an on-board battery that allows the pump to function for up to two hours while unplugged.

A channel surrounds the central lumen in which gas, usually helium, is infused rapidly to expand the balloon. Helium, and occasionally carbon dioxide, is used to inflate the pump because it has a low density and viscosity, which allows for rapid flow rates. Furthermore, if a rare occurrence of balloon rupture were to occur, there is lower risk of air embolism with helium and carbon dioxide since these gases are rapidly absorbed into the bloodstream.

The balloon can be placed in a cardiac catheterization laboratory, where fluoroscopy is used to confirm the position of the balloon. More commonly, it is placed blindly at the patient’s bedside. The balloon is mounted onto a catheter and inserted via the femoral artery using the Seldinger technique. The balloon is advanced so that the tip rests approximately two centimeters distal to the takeoff of the left subclavian artery, which can be approximated by the second rib. The proximal end of the balloon should rest above the takeoff of the renal arteries, located approximately at a level between the first and second lumbar vertebral bodies.

After blind placement, a chest radiograph is used to confirm proper positioning of the balloon. A small radiolucent “tag” enables the clinician to locate the tip of the balloon on the chest radiograph.

INDICATIONS

• Refractory unstable angina

• Acute myocardial infarction (AMI)

  • Cardiogenic shock

  • Acute mitral regurgitation

  • Ventricular septal defect/perforation

  • Thrombolytic therapy

• Failure to separate from cardiopulmonary bypass

• Refractory ventricular dysrhythmias

• Decompensated congestive heart failure or aortic stenosis

• Preoperative placement for high-risk patients (e.g., ejection fraction less than 35% or greater than 70% stenosis of a main coronary artery) undergoing noncardiac surgery

• High-risk coronary artery bypass grafting