A synthetic replacement for the heart remains one of the holy grails of modern medicine. Although the heart is conceptually simple it embodies subtleties that defy straightforward emulation with synthetic materials and power supplies. Consequences of these issues include severe foreign-body rejection and external batteries that limit patient mobility. These complications limited the lifespan of early human recipients to hours or days.
There are two types of artificial heart:
1. Total Artificial Heart (TAH) implantation involves the removal of the native heart. It is a surgical procedure similar to heart transplantation with a human donor heart.
2. Cardiac (heart) assist devices differ, in that the patient’s heart is not removed during implantation. Assist devices may include either a Left Ventricular Assist Device (LVAD) or a Right Ventricular Assist Device (RVAD) or both. As opposed to TAH implantation, the assist device serves to provide only a part of the total cardiac output of the patient’s heart.
Patients who have some remaining heart function but who can no longer live normally may be candidates for ventricular assist devices which do not replace the heart, but boost its output. The first heart assist device was FDA approved in 1994, and two more received approval in 1998. While the original assist devices emulated the pulsating heart newer versions, such as the Heartmate II, developed by the Texas Heart Institute of Houston, Texas, provide continuous flow. These pumps (which may be cetrifugal or axial flow) are smaller and potentially more durable and long-lasting than the current generation of total heart replacement pumps. Several continuous flow ventricular assist devices have been approved for use in the European Union and as at August 2007 were undergoing clinical trials for FDA approval.
