Page 647 - Cardiac Nursing

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CHAPTER Mechanical Circulatory Assist Devices

Michael A. Chen*

Mechanical circulatory assist devices have been used since the nurses encounter patients requiring IABP support. In addition,
1960s. Intra-aortic balloon pump (IABP) catheters are the most this chapter will describe other types of circulatory assist devices.
commonly used devices. Other circulatory support devices, once
restricted to a few large centers, are now becoming more widely
available for temporary use in the cardiac catheterization labora- INTRA-AORTIC BALLOON PUMP
tory, as an adjunct to cardiac surgery, as well as being implanted COUNTERPULSATION
for short-, intermediate-, and even long-term ventricular assis-
tance (i.e., “destination therapy”). Such devices are used to sup-
port circulation temporarily when the injured (left or right) ven- The IABP was introduced in the late 1960s as a therapy for car-
4
tricular myocardium cannot generate adequate cardiac output. diogenic shock after MI. Since then, its application has expanded
One such device has been used successfully to support a patient to include patients with other etiologies of acute LV failure, in-
1
for nearly seven and a half years. With the aging of the popula- cluding before or after cardiac surgery, from acute myocarditis, and
tion and the improved treatment of coronary artery disease and in patients with chronic heart failure who experience acute hemo-
myocardial infarction (MI), the incidence of heart failure is in- dynamic deterioration. Other indications include support during
creasing; in the coming years the numbers of patients who have high-risk percutaneous coronary intervention (PCI), reducing ma-
5,6
acute severe and end-stage heart failure will increase. Typically, less jor adverse coronary events and procedural complications. They
than 2,500 patients per year receive cardiac transplants in the can be used for patients with unstable angina, refractory ventricu-
United States due to a limited donor pool, making mechanical lar arrhythmias (particularly when ischemia driven), and for pa-
2
assist devices an important long-term therapy as well. In November tients with mechanical complications of acute MI, such as papil-
2002, the Food and Drug Administration approved the use of lary muscle rupture or ventricular septal rupture, as a bridge to
the HeartMate (Thoratec Laboratories, Inc., Pleasanton, CA) left surgical repair. It is estimated that over 70,000 IABP are placed
4
ventricular assist device (LVAD) for permanent or destination each year in the United States alone. Display 26-1 lists the most
therapy in patients who are not appropriate candidates for heart common indications for IABP placement from a review of nearly
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transplantation. 3 17,000 patients who received the therapy from 1996 to 2000.
With early recognition, the often rapid hemodynamic deterio-
ration of patients with acute left ventricular (LV) failure can be Description
arrested with circulatory assist devices. The type of device used
depends on the degree of myocardial injury, the degree of LV The intra-aortic balloon is constructed of a biocompatible, non-
functional impairment, the anticipated length of therapy as well thrombogenic material and mounted on a catheter constructed of
as other factors (including what is available locally). The purpose the same material. An opening at the catheter–balloon connection
of therapy is to stabilize the patient until: (1) the left ventricle re- allows pressurized gas (usually helium) to move in and out of the
covers from acute injury; (2) mechanical problems causing acute balloon, causing inflation and deflation to occur. Most catheters
failure (e.g., ruptured ventricular septum) can be surgically cor- have two lumens: an inner lumen for central pressure monitoring
rected; (3) heart transplantation can be performed; or (4) a deci- at the catheter tip and a second lumen for the gas. Properly posi-
sion is made to place a device as “destination therapy,” for patients tioned, the distal tip of the balloon catheter rests just distal to the
who are not candidates for transplant. The goal of a circulatory as- origin of the left subclavian artery and the proximal end of the bal-
sist device is to stabilize or improve hemodynamics and secondary loon is positioned proximal to the renal arteries. Figure 26-1 illus-
organ function. The major principles governing all devices are trates proper anatomic position of the IABP catheter. (See Figure
that they: (1) decrease or take over LV workload; (2) enhance oxy- 12-3 in Chapter 12.) The tip of the catheter is radio-opaque so that
gen supply to the myocardium; and (3) partially or totally support its position can be verified with a chest x-ray. The catheter is in-
the systemic circulation and thus, other organ perfusion. The ex- serted via a direct femoral or iliac arteriotomy or by percutaneous
tent to which each principle can be achieved depends on the type insertion using the Seldinger technique with or without a sheath.
of device used. An IABP offers only partial support, whereas im- Although a direct arteriotomy approach is rarely used today, prior
plantable right ventricular assist devices (RVADs), LVADs, and designs made it mandatory, and it may still be the optimal choice
BiVADs can assume the total workload of the right, left, or both for a patient with severe peripheral vascular disease (when direct vi-
ventricles, respectively. In addition, there are devices that provide sualization is desired) or for pediatric patients. The approach re-
intermediate levels of support. Most cardiovascular critical care quires an incision in the groin for access to the femoral or iliac ar-
tery. This technique is more invasive and time consuming, and
*Debra Laurent and Julie A. Shinn are authors of Nursing Care Plan 26-1 requires surgical removal. The percutaneous technique is faster, less

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