Ventricular assist device

Definition

A ventricular assist device (VAD) is a mechanical pump used for temporary blood circulation support. It decreases the workload of the heart while maintaining adequate flow and blood pressure.

Purpose

A VAD is a temporary life-sustaining device. VADs can replace the left ventricle (LVAD), the right ventricle (RVAD), or both ventricles (BIVAD). They are used when the heart muscle is damaged and needs to rest in order to heal or when blood flow from the heart is inadequate. VADs can also be used as a bridge in patients awaiting heart transplantation or in patients who have rejected a transplanted heart.

Examples of patients who might be candidates for a VAD are those who:

• have suffered a massive heart attack

• cannot be weaned from heart-lung bypass after treatment with intravenous fluids, medications, and insertion of a balloon pump in the aorta

• have an infection in the heart wall that does not respond to conventional treatment

• are awaiting a heart transplant and are unresponsive to drug therapy and intravenous fluids

• are undergoing high-risk procedures to clear the blockages in a coronary artery

Although one in five people suffer left side ventricular failure, only a minority are candidates for VADs. To be considered for a VAD, patients must meet specific criteria concerning blood flow, blood pressure, and general health.

Precautions

Poor candidates for a VAD include those with:

• irreversible renal failure

• severe disease of the vascular system of the brain

• cancer that has spread (metastasized)

• severe liver disease

• blood clotting disorders

• severe lung disease

• infections that do not respond to antibiotics

• extreme youth or age

Description

There are four types of VADs, each appropriate for a different condition. Surgery to install a VAD is performed under general anesthesia in a hospital operating room. An incision is made in the chest, then catheters are inserted into the heart and the correct artery. The surgeon sutures the catheters in place, then attaches tubing to connect the catheters to the pump. The pump stays outside the body. Once it is turned on, blood flows out of the diseased ventricle and into the pump, then is returned to the correct blood vessel leaving the heart.

Preparation

Before the operation the patient meets with an anesthesiologist to determine any special conditions that will affect the administration of anesthesia. Standard preoperative blood and urine studies are performed, and the heart is monitored both before and during the operation with an electrocardiograph.

Aftercare

The patient is monitored in intensive care, with follow-up blood, urine, and neurological studies. Blood thinning medications are given to prevent blood clotting.

Except for those patients awaiting a heart transplant, patients are slowly and gradually weaned from the VAD. Even when patients no longer need the VAD, they will require supportive drug therapy and/or a balloon pump inserted in the aorta.

Risks

VAD insertion carries risks of severe complications. Bleeding from surgery is common and occurs in as many as 30-50% of patients. Other complications include the development of blood clots, partial paralysis of the diaphragm, respiratory failure, kidney failure, failure of the VAD, damage to the coronary blood vessels, stroke, and infection.

Sometimes when the left ventricle is supported, the right ventricle begins to need assistance. If VADs are inserted in both ventricles, the heart may become so dependent on their support that they cannot be removed.

Normal results

Because conditions for which VADs are used vary widely and because of the high risks associated with VAD insertion, the outcome of surgery cannot be predicted.

Key Terms

Coronary blood vessels

The arteries and veins that supply blood to the heart muscle.

Diaphragm

The muscle that separates the chest cavity from the abdominal cavity.

Ventricle

The heart has four chambers. The right and left ventricles are at the bottom of the heart and act as the body's main pumps.

For Your Information

Books

• "Ventricular Assist Device." In The Patient's Guide to Medical Tests, ed. Barry L. Zaret, et al. Boston: Houghton Mifflin, 1997.

• "Ventricular Assist Devices." Department of Biological and Agricultural Engineering. New York State University http://www.bae.ncsu.edu

Source: Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group

The Essay Author is Tish Davidson A.M..

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