In January 1986, Dr. O.H. Frazier of the Texas Heart Institute (THI) initiated clinical trials for the Thoratec HeartMate IP LVAS (implantable pneumatic). THI was the first center to take part in these studies, and its surgeons and researchers played a key role in establishing that the pumps could sustain patients with heart failure. In October 1994, final marketing approval was received from the US Food and Drug Administration. Today, the Thoratec HeartMate IP LVAS is used worldwide as a bridge to heart transplantation. The HeartMate can greatly improve the clinical status of bridge-to-transplant patients. Most patients who are in New York Heart Association Functional Class IV (very severe heart failure) before receiving the HeartMate can improve to Class I while supported by the device. Meanwhile, they can be rehabilitated physically. When patients are supported by the HeartMate for more than 30 days, the outcome of transplantation improves.
The pneumatic (air-driven) LVAS is a titanium alloy pump that weighs 570 grams and consists of a blood chamber, an air chamber, a drive-line, and inflow and outflow conduits. Each conduit is a titanium cage that contains a 25-mm porcine (pig) valve within a woven Dacron™-fabric graft. A flexible polyurethane diaphragm separates the blood chamber and the air chamber. Textured surfaces within the blood chamber promote the development of a cellular lining, which helps prevent blood clots and infection. With a stroke volume of 83 milliliters and a maximum pumping rate of 140 beats per minute, the IP LVAS can provide flow rates of up to 12 liters per minute.
The HeartMate console powers and controls the implanted IP LVAS blood pump. A 6-foot cable joins the blood pump to the drive console. Another 6-foot long tubing connects from the pump to the console to push air into the pump chamber. A front panel display gives a continuous readout of the pump rate, stroke volume, and total blood flow. The system can operate in three modes: automatic mode, fixed-rate mode, and external (synchronous) mode. The drive console is easy to operate and can be transported on a wheeled cart, allowing patients to move about the hospital.
For more information, you can read an article entitled, "Improved Mortality and Rehabilitation of Transplant Candidates Treated with a Long-Term Implantable Left Ventricular Assist System," which appears in Volume 222 (1995) of the journal Annals of Surgery (pp. 327-338).