Michael Shanks - site 2006: Hearts: Basic Biology

You know it's there, but what exactly is it doing?
A brief guide for those curious minds on natural hearts and some historic replacement hearts.

The Basics

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That heart is often referred to as a muscular pump that delivers blood throughout your body. Why do we need blood? It so happens that blood is an efficient means of transportation for delivering oxygen from the lungs to all the tissues in your body (including the tissue of the heart itself). Blood also carries toxic carbon dioxide from those tissues back to the lungs, where you can exhale the CO2 into the atmosphere. Additionally, it's responsible for transporting nourishment from digestion, hormones (eg, testesterone & estrogen), immunological agents (eg, clotting factors, antibodies), and waste products.

How does blood enter and leave the heart? There are four chambers in the human heart: two atria (right and left) and two ventricles (right and left). Deoxygenated blood travels into the heart through the right atrium, then travels to the right ventricle before it leaves to go to the lungs, where it becomes oxygenated. Oxygenated blood enters the heart through the left atrium, then flows to the left ventricle before leaving circulate blood through the rest of the body.

Here's a little video from Guidant that you can walk through to see you heart in action. Scroll down to the bottom to see the video: http://www.guidant.com/condition/heart/heart_bloodflow.shtml

The Jarvik-7

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Though we often refer to the Jarvik-7 as a total artificial heart, it does not really replace all four chambers. The two pumps of the Jarvik-7 actually act as right and left ventricles that attach to the patient's own right and left atria. The pumping action is powered by air from an external power console about the size of a standard household refrigerator. The heart rate can be varied between 40 and 120 beats per minute (the average resting heart rate is 60-80 bpm), depending on what level of activity the patient is at. The device is made from plastic, aluminum, and a special type of polyester that promotes skin growth around the tubes that penetrate the skin (THI).

The AbioCor

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The AbioCor, the newest and most advanced total artificial heart of today, also acts as a replacement for the right and left ventricles. It's powered by an external battery and is constructed from titanium, plastic, and Angioflex, a special durable plastic designed to withstand millions of heartbeats. While the average heart is 10 ounces, the Abiocor is two pounds, thus making it available to only one half of the male population and one fifth of the female population in the United States. An implanted controller in the abdomen closely monitors the heart rate and automatically signals the AbioCor to speed up or slow down (CSTC).

Here is a video of the AbioCor in action:
http://cumulus.mos.org:8080/ramgen/archives/cst/video_17453_web.rm?usehostname

References
Current Science & Technology Center. The AbioCor Replacement Heart. http://www.mos.org/cst/article/3737/
Purves, WK. Life: The Science of Biology, 7th Ed. Virginia: Sinauer, 2004.
Texas Heart Institute. Jarvik-7 Total Artificial Heart. http://www.tmc.edu/thi/j7tah.html

Ten Things 2006: Projects > Tammy Wang: A New Heart to Heart > Hearts: Let's Begin!