By: Subhan Khan, Takeshi Tsubouchi, and Ellen B. Morrison

Each year, about 8000 people worldwide are added to lists of heart failure patients waiting for donor hearts. These patients have the most severe form of heart failure—end-stage left ventricular failure (LVF), or what the New York Heart Association defines as “Class IV” disease. In these patients, the left ventricle—the heart’s major pumping chamber—is unable to meet the body’s requirement for oxygenated blood. With donor hearts scarce (about 3000 worldwide per year), physicians face the challenge of keeping patients alive until a compatible heart becomes available. Treatment options are drug therapy or drug therapy in combination with mechanical pumping support, and research shows the latter to be the better of the two.1

Although some patients have undergone replacement of the native heart with an artificial heart, most physicians opt to leave the diseased heart in place and supplement its pumping strength with a surgically implanted left ventricular assist device (LVAD) or system (LVAS). These systems feature a small, compact pump connected by tubing to an opening in the bottom (apex) of the left ventricle. Blood flows from the left ventricle into the pump, where it is propelled into an outflow conduit attached to the aorta—the pipeline that transports blood to all major arteries in the body. A cable (drive line) tunneled through an exit port in the abdominal wall, links the pump to a portable external monitor and power source.

In the United States, the majority of LVAS manufacturers first seek a bridge-to-transplant indication, meaning that their products are initially approved solely for temporary support in patients awaiting a donor heart. However, the goal of most manufacturers is to demonstrate that their pumps are sufficiently durable for long-term support, or destination therapy, in patients who are not eligible for cardiac transplantation.

Since the first implantation of an artificial pump in the early 1980s, these devices have undergone significant transformation. Large, first-generation pulsatile pumps were followed by second-generation axial-flow pumps. Centrifugal-flow pumps, such as the DuraHeart LVAS, which has a magnetically levitated impeller, represent the latest generation of these devices. This impeller is designed to avoid all mechanical contacts within the pump chamber, thereby reducing wear and tear on the pump components. Even more important, new impeller designs are addressing two of the more common safety issues associated with circulatory support pumps: red blood cell rupture (hemolysis), caused by friction within the pump chamber, and clot formation (thrombosis) due to blood pooling along the sides of the chamber.