Former Vice President Dick Cheney's announcement this week that he has been implanted with a left ventricular assist device (LVAD) to aid his ailing heart highlights one of several technologies available to people suffering from heart failure. Earlier this week, Scientific American wrote about a new six-kilogram portable artificial heart driver from SynCardia Systems, Inc. that has given three cardiac patients the freedom to await a possible transplant at home, rather than being tethered to a 180-kilogram driver in the hospital.

Cheney's LVAD differs significantly from SynCardia's artificial heart and driver—the latter works only if a recipient's heart can continue to function to some degree on its own. LVADs, which have been on the market since 1994, generally consist of a tube that pulls blood from the damaged heart's left ventricle into a pump, which then sends blood into the aorta, assisting the weakened ventricle. The pump, placed in the upper part of the abdomen, has a second tube that extends outside the body through the abdominal wall, where it is attached to the pump's battery and control system.

It's unclear who makes the LVAD Cheney had implanted, although there are several makers of such devices. In January, the U.S. Food and Drug Administration approved a second-generation device made by Thoratec Corp. in Pleasanton, Calif., according to USA Today. Thoratec's HeartMate II is designed to be used for a lifetime (as opposed to being a life-sustaining bridge only until a transplant heart can be found). Two-year survival is reportedly about 60 percent, about the same as a transplant. Other LVADs include the HeartAssist5 made by Houston's MicroMed Cardiovascular Inc. and the Jarvik 2000 FlowMaker made by Jarvik Heart, Inc. in New York City.

Cardiac surgeon Michael DeBakey was the first to use an LVAD successfully in a patient. In 1966, he implanted such a device to sustain a patient for 10 days while his heart healed following surgery. Initially, LVADs served to keep cardiac patients alive while they waited weeks or months for a transplant organ. As the technology has matured, LVADs have been able to serve patients for years without failure. This is significant because there are typically about twice as many people in the U.S. awaiting donor hearts as there are available organs at any given time.

Newer LVAD designs seek to shrink the device by using a rotor to continuously stream blood without the need for a pump. The hope is that smaller LVADs can be used in heart patients who until now have been too thin or two short to receive an implanted pump, which can be 10 to 15 inches in diameter, with connection tubes 12 to 20 inches long, Wray Herbert wrote in a December 2007 article for Scientific American Body.

The 69-year-old Cheney has suffered five heart attacks since the age of 37, the most recent in February. He previously had a defibrillator implanted to monitor his heart and shock it back into a normal rhythm if abnormal beating occurred, according to Reuters. Cheney's surgery took place last week at Inova Fairfax Heart and Vascular Institute in Washington's northern Virginia suburbs, The New York Times reported.

LVAD diagram courtsey of Madhero88, via Wikimedia Commons