Try digitalPLUS for 10 days for only $0.99
The Baltimore Sun

How do artificial hearts work?

There was a time, back in the 1980s, when artificial hearts were big news. There was daily, front-page media attention around implantable artificial hearts. In 1982, Barney Clark received an artificial heart designed by Robert Jarvik and installed by Dr. William DeVries. Clark lasted almost four months before dying.

The plastic heart that Barney Clark received was a complete replacement heart. Even though it got huge attention, the heart they used had problems. It also needed a big, 400-pound machine to keep the heart running. In other words, it was not very portable or convenient.

The public lost interest in artificial hearts, but the technology has been improving since the 1980s. Today it is fairly common for people to get artificial hearts while they wait for donor hearts. And the whole artificial heart rig has become far more portable. You can find videos on YouTube, for example, that show Europeans with artificial hearts walking around the mall doing some shopping. The patient wheels along a cart about the size of a suitcase that keeps the heart pumping.

Today there are also devices that assist the ailing heart, rather than replacing it. The patient's heart remains in place and an extra pump is attached to it to carry some of the load.

The need for an artificial heart usually comes after a severe heart attack or some other form of heart disease. The heart is a big muscle. In a heart attack, part of the muscle dies from lack of oxygen. In a severe heart attack, enough of the muscle can die to severely limit what the heart can do.

In that case, the only long-term solution right now is a heart transplant. But the number of possible recipients for a heart transplant outstrips the supply of donor hearts. Also, a person always needs to wait some period of time for a match to become available. Artificial hearts try to fill the gap between supply and demand.

When most people think about an artificial heart, they think about the complete replacement heart. These heart mechanisms do their best to replicate the action of a real heart. In other words, these hearts have two pumping areas like a human heart does, and they pump blood in pulses (they beat) like a human heart does. In a real human heart, the heart muscle squeezes to pump the blood through a ventricle. In an artificial heart, there is a flexible membrane inside each pumping area that inflates to compress and pump the blood.

The newest replacement hearts are self-contained inside the patient. There are no wires or tubes poking through the skin. The computer control unit is inside the body, along with a small battery. Electrical power is sent through the skin using induction to keep that battery charged. Outside the body is a computer display panel that connects wirelessly to the internal computer, and the inductive charging system that can be either battery powered or plugged into the wall.

The problem with these complete replacement hearts is that they are still fairly large, and people do not tend to live for more than a few months after the heart is installed. So there is now an alternative called the Left Ventricle Assist Device, or LVAD. Dick Cheney has probably been the most famous person to receive an LVAD, but dozens of others are living their lives with LVADs implanted in their chests.

The most successful LVADs are continuous flow pumps that pick up blood before it reaches the heart, then pump that blood around the heart and directly into the artery. The patient's heart is still in place and still pumping as best it can. The LVAD is just helping it out.

LVADs are much smaller that complete replacement hearts, and less complicated. They are easier and less traumatic to install. Patients routinely leave the house using a backpack or side pack holding the battery. LVADs also offer less risk. If the LVAD were to fail, the patient's heart is still there and still beating as best it can.

In the future, complete artificial hearts and LVADs will improve. There is also intense research around the idea of growing replacement hearts in the lab using stem cells. If the technique can ever be perfected, there is a good chance that the supply problem for heart transplants will be eliminated.

For extra info on this or the scoop on other fascinating topics, go to Contact Marshall Brain, founder of HowStuffWorks, at

Copyright © 2015, The Baltimore Sun