A Ventricular assist device, or VAD, is mechanical device that 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 implanted permanently 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 disease and 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 fibrin and does not require long term anticoagulation.

The major complications of VAD implantation include infection, immunosuppression, clotting with resultant stroke, and bleeding secondary to anticoagulation. It is interesting to note that some of the polyurethane components used in the devices cause the deletion of a subset of immune cells when blood comes in contact with them. This predisposes the patient to fungal and some viral infections 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.

Current types of VADs on the market today are somewhat bulky. One type of VAD currently being developed relies on magnetic levitation to drive the rotor within the pump, thereby minimizing the wear and reducing the size of the pump substantially. The first magnetically levitating pump has recently been implanted for clinical trials in Greece and is expected to begin US Clinical Trials in 2007. Magnetic levitation technologies are expected to result in small pediatric VADs within the coming decade.

External links

• http://cardiacsurgery.ctsnetbooks.org/cgi/content/full/2/2003/1491?ck=nck
• Health Center Online VAD
• Mayo Clinic VAD
• FDA VAD

Implants | Cardiology