Researchers from the Texas Heart Institute have successfully replaced the human heart with a 10,000-RPM artificial pump, which leaves its patients with absolutely no pulse. [...]
Many have tried to make a metal and plastic heart that is capable of beating, but many were unable to continuously beat beyond an 18-month period. Also, metal and plastic have many limitations, such as the requirement of an air compressor outside of the body [...]
Cohn and Frazier's continuous-flow left ventricular assist device (LVAD), however, can replace the heart and doesn't require a compressor because the researchers discovered that recreating the pulse wasn't necessary. [...]
One of the turbines used in the artificial heart has been running in a lab continuously for eight years, and it runs on a small battery that the patient can easily carry on their shoulder.
http://www.dailytech.com/article.aspx?newsid=24157
Hm, imagine the pranks some patients might pull.