SUNDAY, Nov. 4 (HealthDay News) -- Implantable pacemakers have been around for more than 50 years, but they've always had one drawback: batteries that need to be replaced. Now, there are early signs that a device that gains power from the patient's own heartbeat might change all that.

The "energy harvester" device uses magnets plus vibrations from within the chest cavity to create energy sufficient to power a pacemaker, its developers report.

Right now, replacing a worn-out pacemaker battery requires surgery that must happen about every seven years. That means that "if the patient starts with a pacemaker at age 2, which is not uncommon, then we are talking about 10 ... surgeries throughout their life," noted co-researcher David Inman, chair of the department of aerospace engineering at the University of Michigan, in Ann Arbor.

So, the advent of a battery-free pacemaker "would be a huge savings in terms of either reducing the number of operations, or completely eliminating them," he said. "It would also be a huge saving in terms of medical costs."

Details on the research are set to be presented Sunday at the annual meeting of the American Heart Association in Los Angeles.

According to Inman, the energy-harvesting device is the brainchild of co-researcher M. Amin Karami, a postdoctoral researcher working with Inman at the university. The tiny device is about half the size of a conventional pacemaker battery and utilizes piezoelectricity -- an electrical charge that's generated from motion -- plus a small magnetic field.

"These two effects together take the natural vibrations inside the chest cavity, which are caused by the heart beating, and change it into electricity which then runs the pacemaker," Inman explained.

He stressed that the research remains at an early stage. Estimates of the power available to the device once implanted in a patient are based on 20-year-old data on the vibratory energy inside the human chest, as well as newer data on energy generated by pig and goat hearts.

According to Inman, the next step is to obtain up-to-date measurements of heartbeat energy from patients undergoing heart surgeries. Inman expects those measurements to be carried out within the next four to five months.

After that, he said, "one of the major medical device manufacturers has to say 'OK, we want to make this a product.'" The prototype harvester he and Karami developed has worked as predicted, generating more than 10 times the amount of energy required to run a pacemaker, he added.

Another expert said the device shows promise, but there are still questions about how it operates in the ling run.

"The advent of a self-charging pacemaker would be revolutionary," agreed Dr. Neil Sanghvi, an electrophysiologist at Lenox Hill Hospital in New York City.

He noted that while the risks involved in replacing a pacemaker's battery are "typically low," in about 1 percent of cases post-replacement infection occurs, often requiring surgical removal of the pacemaker and long hospital stays. "A renewable self-contained source of energy for pacemaker function would allow us to prevent these rare but serious complications," Sanghvi said.

He also cited "several concerns," however. Since the harvester relies on magnets, it would require "thorough testing to confirm that outside sources of electromagnetic interference do not result in device malfunction," according to Sanghvi. Most importantly, "the technology needs to demonstrate reliable and persistent power generation over years of use without seeing a significant decline in power generation," he said.

Karami and Inman said that common appliances such as cellphones or microwave ovens should not affect the energy harvester's performance. And they added that it is possible the technology might also be able to power other cardiac devices, such as implanted defibrillators.

Still, Inman cautioned that all of that is years away, and much more work needs to be done -- including testing self-powered pacemakers in animals and then humans.

But the response from the medical community has been encouraging, he said. "We wrote this little academic article in Biophysics Letters[on the device]," he said, "and the phones started ringing off the hook."

Experts note that findings presented at medical meetings are typically considered preliminary until published in a peer-reviewed journal.

More information

Find out more about pacemakers at the U.S. National Heart, Lung, and Blood Institute.