ventricular assist device

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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.

Resources

Books

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

Other

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

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.

ven·tric·u·lar as·sist de·vice

any of a variety of mechanical devices that support or replace the pumping function of the left (LVAD) or right ventricle (RVAD). The inflow end of the pump is connected to the ventricle and the outflow end to the aorta (LVAD) or pulmonary artery (RVAD). Most or all of the cardiac output is directed through the device to allow time for recovery of the patient's damaged heart muscle after myocardial infarction or heart surgery. Also used as "a bridge to transplantation," that is, to maintain the patient whose heart will not recover until a donor heart becomes available.

ventricular assist device

Heart surgery A portable, battery-powered device that assists the flow of blood while a Pt is awaiting heart transplant; the VAD is connected at the apex of the left ventricle and pumps the blood past an effete ventricle and aortic valve directly into the aortic arch. Cf Artificial heart, Jarvik-7.

ven·tric·u·lar as·sist de·vice

(VAD) (ven-trik'yū-lăr ă-sist' dĕ-vīs')
A device that supports or replaces the function of a ventricle (LVAD or RVAD indicates which ventricle, i.e., LV = left ventricle, RV right). The device is used in patients with potentially salvageable myocardium, where centrifugal or pneumatic devices can be placed in either heterotopic or orthotopic positions (the latter is termed a total artificial heart). The function of either the left, right, or both ventricles can thus be supported for days to weeks. Either recovery of heart function or need for transplantation then becomes apparent.
References in periodicals archive ?
The Berlin heart ventricular assistance device, which has been developed in Germany, will help keep Tiarna alive for longer than an ECMO machine would have.