The U.S. Food and Drug Administration today approved a heart assist device with a novel design that is the first to mechanically support the weakened heart of a small-sized adult man or woman with heart failure who is at risk of dying while awaiting a heart transplant.

Heart assist devices are surgically implanted mechanical pumps that help the heart's ventricle do its work of pumping blood to the rest of the body. Previous models were too large to be placed in the upper abdomen of some women and small-sized men. But the Thoratec HeartMate II Left Ventricular Assist System employs a first-of-a-kind design. Instead of the standard pulsatile pump that simulates the action of the heart, the device uses a continuous flow pump that constantly moves blood with a single moving part, a spinning rotor. This allows the device to be slimmed down to a mere three inches in length and a weight of approximately one pound.

"The HeartMate II is an important advance in mechanical heart technology," said Daniel Schultz, M.D., director of FDA's Center for Devices and Radiological Health. "Until now, some heart transplant candidates have been underserved due to the large size of previously approved heart assist devices."

An electrical cable that powers the blood pump passes through the patient's skin to an external controller that the patient wears on his or her waist. The controller is powered either by batteries or connected to an electrical power outlet. Blood flow is set through the pump based on the patient's need, and the controller monitors pump performance, sounding alarms if it detects dangerous conditions or a possible malfunction. The system can operate on two external batteries, allowing the patient to move freely for up to three hours.

In a clinical study of 126 patients at 26 transplant centers, 57 percent of patients with the HeartMate II survived to heart transplant, which is comparable to the survival of patients treated with currently approved heart assist devices.

The product's manufacturer, Thoratec Corporation of Pleasanton, Calif., is required to conduct a post-approval study to further evaluate the HeartMate II's performance during commercialization.