Researchers are another step closer to bringing heart patients a temporary "smart" pacemaker that simply dissolves once it's no longer needed.
Pacemakers are devices that are implanted to help control certain abnormal heart rhythms, by sending electrical pulses to the heart muscle. They are normally permanent, but in some cases patients only need temporary heart pacing for a matter of days.
Last year, researchers at Northwestern University reported initial success in developing an alternative to the temporary pacemakers used today: a wireless, "dissolving" pacemaker made of materials that biodegrade over a few weeks.
At that point, the focus was on the pacemaker itself, said researcher John Rogers, who is leading the development of the technology.
The pacemaker is a thin, flexible device composed of an encapsulating layer that contains electrodes. The bottom of each electrode is exposed and adheres to the heart's surface.
Now the researchers have added components that allow the pacemaker to be self-contained: a network of thin, wireless sensors and a control unit worn on the skin. They work together to monitor the heart's electrical activity and other body processes, such as breathing rate, and control the heart's pacing.
The system is also designed to pick up problems like a pacemaker malfunction, then alert the patient. Meanwhile, all of this vital information can be streamed to a smart device, allowing doctors to check on patients remotely.
That's in contrast to the way temporary heart pacing works today, Rogers explained.
Traditional permanent pacemakers consist of a battery-powered pulse generator that is implanted under the skin of the chest and connected to the heart via wires called leads.
When patients need heart pacing for only a short time, doctors use an external pulse generator, rather than implanting one. But patients still need electrodes sewn onto the heart, equipped with leads that exit the chest and connect to the generator.
That system works well, Rogers said, but there are small risks — such as a lead becoming dislodged or causing an infection. Plus, it keeps patients tethered to hospital equipment.
The wireless system could allow them to move around, and perhaps recover at home, according to Rogers.
"We envision a future where patients are released earlier from the hospital," he said.
Much works remains first, however. The technology has so far been tested in animals and on human heart tissue in the lab — not yet in patients.
This latest step in its development, described May 26 in the journal Science, offers "proof of concept," said Dr. Jim Cheung, a cardiologist at Weill Cornell Medicine in New York City.
"This is very interesting, creative work," said Cheung, who also chairs the American College of Cardiology's electrophysiology section leadership council.
He noted that it is a "niche" group of patients who need temporary pacing. A typical scenario would be after a heart procedure that leaves a patient with a slowed-down heartbeat for a short time.
Another example, Cheung said, would be patients who need to have a permanent pacemaker removed due to an infection. Temporary pacing can be used as a "bridge" until the infection clears and a new permanent device can be implanted.
The Northwestern researchers pointed to another scenario: Newborns who require surgery because they were born with a hole in the wall that separates the heart's upper chambers. Those babies need temporary pacing after the procedure.
Cheung said it's conceivable that the new technology could allow patients who need temporary pacing to be mobile or even go home sooner. He also pointed to the bigger picture: The basic premise of this technology — a wireless, smart system that detects issues within specific tissue and applies treatment — could have a range of medical uses.
Rogers said that is, indeed, the broader goal.
The pacemaker's dissolving feature would negate the need to remove anything from patients' bodies afterward. If that idea sounds concerning, Rogers said the device is made from substances found in vitamin pills -- like small amounts of iron, magnesium and silicon -- and can be safely broken down in the body.
"There isn't anything exotic in this," he said.