Left ventricular assist device
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. The left ventricle is the large, muscular chamber of the heart that pumps blood out to the body. A left ventricular assist device (LVAD) is a battery-operated, mechanical pump-type device that's surgically implanted. It helps maintain the pumping ability of a heart that can't effectively work on its own.
A ventricular assist device is used to aid the pumping action of a weakened heart ventricle (a major pumping chamber of the heart). VADs were originally intended for short-term use to support failing hearts until donor hearts became available. Some VADs are now used for long-term (destination) therapy in severe heart failure patients who are not candidates for heart transplants.
A ventricular assist device does not replace the heart. Instead, it works with the patient's own heart to pump sufficient blood throughout the body. The VAD consists of a pump, a control system, and an energy supply. Some VADs rely on a battery for their energy supply; others use compressed air (pneumatic). The energy supply and the control system are located outside the body; the pump can be either inside or outside the body. In a VAD, blood flows from the ventricles into a pump. A left ventricular assist device (LVAD) receives blood from the left ventricle and delivers it to the aorta -- the large artery that carries the blood from the heart to the rest of the body. A right ventricular assist device (RVAD) receives blood from the right ventricle and delivers it to the pulmonary artery – the artery that carries blood from the heart to the lungs.
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. A common type of LVAD has a tube that pulls blood from the left ventricle into a pump. The pump then sends blood into the aorta (the large blood vessel leaving the left ventricle). This effectively helps the weakened ventricle. The pump is placed in the upper part of the abdomen. Another tube attached to the pump is brought out of the abdominal wall to the outside of the body and attached to the pump's battery and control system. LVADs are now portable and are often used for weeks to months. Patients with LVADs can be discharged from the hospital and have an acceptable quality of life while waiting for a donor heart to become available.
Typically, an LVAD has two tubes connected to an electric pump, an electronic controller and an energy supply. One tube goes into the left ventricle, pulling blood from the ventricle into the pump. The pump then sends blood into the aorta, the large blood vessel leaving the ventricle, effectively "bypassing" the weakened ventricle. The pump is placed in the upper part of the abdomen. Another tube attached to the pump is brought out of the wall of the abdomen to the outside of the body and attached to the control system for the pump.
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.