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Mechanical circulatory support devices (MCSDs) are flow pumps designed to augment function of the failing ventricle. These devices can be used to support either or both ventricles, and may be for temporary or long-term use. Based on their underlying mechanics, they may be classified as counterpulsation pumps, pneumatic pumps, centrifugal pumps, or axial-flow pumps1 (Tables 21-1 and 21-2). Though most MCSDs will neither be placed nor present to an emergency department (ED), knowledge of them can be helpful. In this chapter, we begin with a brief description of the various MCSDs, then focus specifically on the complications and emergencies associated with the device seen most in the ED: the left ventricular assist device (LVAD).
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TYPES OF MECHANICAL CIRCULATORY DEVICES
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1. Intra-Aortic Balloon Pump
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The Intra-Aortic Balloon Pump (IABP) is a counterpulsation device commonly used for temporary circulatory support. The term “counterpulsation” refers to the inflation of the balloon in diastole and deflation in systole.
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Mechanics: The IABP device consists of two major components: a double-lumen 8.0–9.5 French catheter, with a 25- to 50-ml polyethylene balloon attached at its distal end; and a console with a pump to drive the balloon. The appropriate balloon size is selected on the basis of the patient's height. The IABP catheter is inserted percutaneously, most commonly into the femoral artery. Under fluoroscopic guidance, it is advanced into the descending thoracic aorta, with its tip 2 to 3 cm distal to the origin of the left subclavian artery (at the level of the carina). The outer lumen of the catheter is used to inflate the balloon with helium gas up to 80% to 90% of the diameter of the descending aorta. The inner lumen is used for monitoring systemic arterial pressure. The inflation of the balloon leads to volume displacement of the blood proximally and distally. This augments the coronary blood flow by augmenting the natural “Windkessel Effect” of the aorta, and potentially ...