Implant Powered by Heart's Lub Dub

Dec. 19, 2007 -- Even the most advanced batteries that power implanted defibrillators and pacemakers must be surgically replaced after four to seven years.

But now researchers have invented a power generator that converts the mechanical motion of a beating heart into useable electrical energy. The solution could not only increase the lifetime of current implantable cardiac devices, it could also reduce the need for operations to replace devices with failed batteries.

"Re-operations are undesirable because they can increase patient complications and add substantial financial expense to the health care system, estimated at $1.2 billion dollars annually," said David Tran a medical student at Stanford University who is working on developing a prototype with fellow medical student Afraaz Irani and Mark Bianco, a mechanical engineer at MicroCube in Freemont, Ca.

Pacemakers, which keep a diseased heart beating at a healthy pace, and defibrillators, which shock irregular beating hearts into a regular rhythm, are both battery-operated electronic devices. They each consist of a pulse generator that contains a battery and circuitry. And each are implanted under the skin near a patient's collarbone.

One or more wire-like leads runs from the device through veins and arteries to the heart, where the lead's screw-shaped end helps anchor it to the muscle. The leads are used to sense heart activity and to carry the electrical charge from the device to the organ.

Tran, Irani, and Bianco invented a tiny device meant to sit inside the small, screw-like anchors.

The device is essentially a magnet wrapped by electric wires. As the heart beats, the motion moves the wires over the magnetic, creating an electrical charge. The electricity travels up the lead to the pulse generator implanted near the collarbone. The energy can be used immediately to power the generator or it can be stored in a capacitor for use later.

"They are to be commended because this is an important issue," said Robert Biederman, associate professor of medicine at Drexel College of Medicine in Pittsburgh, PA, and director for cardiovascular magnetic resonance imaging.