By Amy Norton
Pacemakers are electronic devices implanted to regulate your heartbeat -- usually because of a condition that slows your heart's normal rate. Traditional pacemakers have two parts: a battery-powered pulse generator implanted under the collarbone, and insulated wires that connect it to your heart.
Because those batteries eventually wear down, pacemakers have to be replaced every five to 12 years. So, some scientists have been working an alternative: battery-free pacemakers that in theory would never have to be replaced.
The "most promising" approach right now is to harness the energy of the heartbeat to power the pacemaker, said researcher and study author Bin Yang.
One problem with the experimental devices developed so far has been their rigid structure, which limits their power.
So, Yang and his team designed a tactic that includes a pacemaker "chip" and an "energy harvester." The harvester is made of a flexible plastic frame bound to so-called piezoelectric layers -- which generate energy when they are bent.
The researchers implanted the devices into pigs and found that, in fact, the motion of the heart was enough to bend the harvester's frame and churn out energy at the level of a battery-powered pacemaker.
"The energy harvester can generate sustainable electricity for the pacemaker chip," said Yang, of Shanghai Jiao Tong University in Shanghai, China.
That is, however, only a very early step, he stressed.
"There are still many foundational issues with this approach," Yang said. For one, the technology currently exists in separate parts -- the energy harvester, the pacemaker chip and wires. They need to be integrated into one device, according to Yang.
Beyond that, he said, further animal research will be needed to see how stable the integrated device remains over time. Lastly, animal research does not always pan out in humans.
The ultimate hope, Yang said, is to develop a pacemaker that requires one-time surgery -- and less risk of surgical complications such as infections and bleeding.
Dr. Dhanunjaya Lakkireddy is chair-elect of the American College of Cardiology's electrophysiology section leadership council.
The concept of a battery-free pacemaker is not new, said Lakkireddy, who is also medical director of the Kansas City Heart Rhythm Institute. Back in the 1970s, some manufacturers came out with plutonium-powered pacemakers.
Lakkireddy, who was not involved with the study, said the new findings are interesting -- and a long-lasting battery-free pacemaker would have certain advantages.
However, he said, there are also several potential "downsides."
For one, current pacemakers allow doctors to monitor patients remotely -- a function that uses up energy, Lakkireddy explained. The technology described in this study may not be capable of that.
And in recent years, Lakkireddy said, the field has been moving toward tiny, wireless pacemakers that are implanted via catheter instead of chest incision. The goal of that technology -- which is still under study, but used for some patients -- is to avoid the risks associated with pacemaker wires and conventional surgery.
To fit into the wave of the future, Lakkireddy said, any battery-free technology would need to work in a wireless structure.
There are also some bigger-picture issues, according to Lakkireddy.
One, he said, is that medical devices are continually evolving and improving. So, a lifetime pacemaker that is never replaced would not necessarily be the best thing for patients.
And then there's the practical "business side," Lakkireddy pointed out: Would manufacturers have any incentive to make pacemakers that need no replacement?
The findings were published online Feb. 20 in the American Chemical Society journal ACS Nano.