Still being developed, a total artificial heart (TAH) is an experimental device designed to replace a patient’s own failing heart. By eliminating the need for a heart transplant, TAHs could literally be lifesavers for the thousands of Americans for whom a suitable heart donor cannot be found in time. Currently, there are two basic models of TAH being developed: the CardioWest TAH (formerly Jarvik) and the AbioCor TAH.

A TAH should not be confused with a ventricular assist device (or VAD), which is often called a “mechanical” heart. Unlike a TAH, which completely replaces a heart, a VAD helps the patient’s own heart pump blood. It is most often used as a bridging device for patients waiting for a heart transplant. Recent research has shown that long-term therapy with VADs may help heart failure patients recover their native heart function to the point where they are removed from the heart transplant list. By contrast, the goal of a total artificial heart is to completely replace the native heart.

The first total artificial heart, a Jarvik model, kept an animal alive for 90 minutes in 1957. Pioneering attempts were made with the Jarvik heart in human patients by the Texas Heart Institute in 1969 and then again in 1982, when patient Barney Clark lived for 112 days on a Jarvik 7. Unfortunately, these early attempts at developing a TAH suffered from a critical flaw. The early models relied on wires and tubes that broke the skin barrier. As a result there was greater risk of infection and blood clots.

Between 1982 and the first years of the new millennium, researchers continued to work on various models of the Jarvik heart, which was renamed CardioWest in the early 1990s. Finally, in October 2004, the CardioWest TAH-t (for temporary) was approved as the first temporary total artificial heart. This device is currently approved only for use as a bridge to transplantation among patients who would soon die without immediate intervention. There are less than 30 transplant centers in the world that are approved to use this technology.

Attempts to improve on the TAH also resulted in the AbioCor artificial heart. This unit solved the problem of breaking the skin barrier by operating on both internal and external batteries. The internal lithium batteries are recharged by an external unit that transmits power through the skin. On July 2, 2001, a human patient received the first self-contained, fully implantable AbioCor artificial heart. The device, about the size of a grapefruit and weighing 4 pounds, had no tubes or wires going through skin. Although the patient died more than 4 months after the implant, the results from the experimental device exceeded physicians’ expectations.

The AbioCor TAH continued to undergo revisions, and in 2006, was approved by the Food & Drug Administration under a Humanitarian Device Exception. This special designation allows the device to be used when there are no other alternatives. Currently, this device is only approved for use if the following conditions are met:

• The patient is less than 75 years old
• The patient requires life support systems
• The patient is not a candidate for a VAD
• The patient cannot be weaned from temporary heart support, if it's being used

In addition, there are few centers of excellence in the United States that can perform the complicated procedure.