Aurora Health Care, a network of Wisconsin hospitals, doctors, clinics, and pharmacies

Healing Broken Hearts

TAHs have had a long history, but not always a successful one. The first TAH, the Liotta, was implanted in 47-year-old Haskell Karp in Houston, Texas in 1969 as a bridge to transplantation. Karp lived with the artificial heart for about 65 hours, but died shortly after receiving a donor heart transplant.

Then in 1982, a TAH known as the Jarvik-7, intended to be a permanent implant rather than a bridge to transplantation, was first implanted in 61-year-old Barney Clark. He lived for 112 days with the artificial heart, but suffered from complications, seizures , and pneumonia before dying of multiple organ failure.

As of 2005 there were at least ten different VAD or TAH devices available for clinical or research use. In 2006, the AbioCor artificial heart was approved by the US Food and Drug Administration (FDA) for permanent implant.

According to the FDA, recipients of TAHs must fit the following profile:

• Have end-stage heart failure
• Have a life expectancy of less than 30 days
• Be unable to receive a natural heart transplant
• Have no other treatment options

Because only very sick patients receive these hearts, mortality remains quite high. Based on reports in medical journals, few patients with artificial hearts have actually left the hospital. With more experience and better selection of patients, the life-saving effectiveness of this technology may improve.

Pumping Blood Naturally

The human heart is divided into four chambers—the right atrium (upper right chamber), right ventricle (lower right chamber), left atrium (upper left chamber), and left ventricle (lower left chamber). The chambers work together to pump blood. The average human heart pumps blood at a rate of 60-100 beats per minute. To pump the blood, the heart contracts in two stages:

• Stage one: The right and left atria contract simultaneously, pumping blood into the right and left ventricles.
• Stage two: The ventricles contract simultaneously to pump blood out of the heart to the lungs (from the right ventricle) and the rest of the body (from the left ventricle).

Then the heart relaxes and fills up with blood again, preparing for the next contraction.

Pumping Blood With TAH

The AbioCor is a grapefruit-sized device with two ventricle chambers, valves, a hydraulic pumping system, and an electronics system. It is made of titanium and plastic and weighs about two pounds. It is designed to fit completely inside the body, without wires or tubes poking through the skin. The device moves the blood in a rhythm, just like the human heart, and creates a pulse.

The AbioCor is made up of:

• Internal hydraulic pump—Similar to hydraulic pumps used in heavy equipment, this component moves hydraulic fluid from side-to-side of the artificial heart. A rapidly spinning gear inside the pump creates pressure to move the fluid.
• Porting valve—This valve opens and closes, allowing the hydraulic fluid to move from one side of the artificial heart to the other. When fluid moves to the right side of the artificial heart, blood is pumped to the lungs through an artificial ventricle. When fluid moves to the left side of the artificial heart, blood is pumped to the rest of the body.
• Wireless energy transfer system—An internal and external coil transmit power from an external battery, without piercing the surface of the skin. The internal coil picks up the power and sends it to an internal battery and controller unit.
• Internal rechargeable battery—This battery is implanted in the abdomen. It allows people to take part in 30-40 minutes of activity, like swimming and showering, while disconnected from the external battery pack.
• Controller unit—This small, electronic unit is implanted in the abdomen. It monitors and controls the speed at which the heart pumps.

Trying to Save Lives

According to the American Heart Association, over five million people in the US suffer from heart failure. Some patients benefit from VADs or heart transplants. However, only a small percentage can receive donor hearts each year due to a shortage in supply. TAHs may provide another option.