Ventricular assist device

A Ventricular assist device, or VAD, is mechanical devicethat is used to partially or completely replace the function of a failing heart. The devices are generally designed to replace or assist cardiac function temporarily, but recently devices are becoming available that can be implantedpermanently for so called "destination therapy". Most patients using the devices, however, are awaiting heart transplant.

VADs are designed to assist either the right or left ventricle, or both at once. The choice of device depends on the underlying heart diseaseand the pulmonary arterial resistance which determines the load on the right ventricle. Generally when pulmonary arterial resistance is high, right ventricular assist becomes necessary. Because the devices generally result in blood flowing over a non biologic surface, predisposing the blood to clotting, there is need for anticoagulation. There is one device, the Heartmate, which provides a biologic surface derived from fibrinand does not require long term anticoagulation.

The major compications of VAD implantation include infection, immunosuppression, clotting with resultant stroke, and bleedingsecondary to anticoagulation. It is interesting to note that some of the polyurethanecomponents used in the devices cause the deletion of a subset of immune cellswhen blood comes in contact with them. This predisposes the patient to fungaland some viralinfections necessitating appropriate prophylactic therapy.

VADs need to be clearly distinguished from artificial hearts, which are designed to completely take over cardiac function and generally require the removal of the patient's heart. There is, as yet, no device of that type that can be used for long-term therapy of heart failure.

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It uses material from the http://en.wikipedia.org/wiki/Ventricular+assist+device Wikipedia article Ventricular assist device.