Researchers have developed a battery-free pacemaker that can be implanted directly into a patient’s heart, an advance that could mitigate the need for follow-up surgery.
The wireless, battery-free pacemaker is being introduced this week by researchers from Rice University, Texas and colleagues at the Texas Heart Institute (THI) at IEEE’s International Microwave Symposium (IMS) in Honolulu.
Designed by the Rice lab of electrical and computer engineering professor Aydin Babakhani, the pacemaker is said to harvest energy wirelessly from radio frequency radiation transmitted by an external battery pack. In the prototype presented at IMS, the wireless power transmitter can be up to few centimetres away.
Pacemakers use electrical signals to prompt the heart to keep a steady beat, but they’ve traditionally not been implanted directly into a patient’s heart. Instead, they’re located away from the heart, where surgeons can periodically replace their onboard batteries with minor surgery.
The electrical signals are transmitted to the heart via wires called leads, which are linked with problems associated with this arrangement, including bleeding and infection. Babakhani said Rice’s prototype wireless pacemaker reduces these risks by doing away with leads.
He said other recently introduced leadless pacemakers also mitigate some of these complications, but their form factors limit them to a single heart chamber and they are unable to provide dual-chamber (biventricular) pacing. Battery-free, lead-less and wirelessly powered microchips can be implanted directly to pace multiple points inside or outside the heart, Babakhani said.
“This technology brings into sharp focus the remarkable possibility of achieving the ‘Triple Crown’ of treatment of both the most common and most lethal cardiac arrhythmias: external powering, wireless pacing and — far and away most importantly — cardiac defibrillation that is not only painless but is actually imperceptible to the patient,” said Dr Mehdi Razavi, director of clinical arrhythmia research and innovation at THI and an associate professor at Baylor College of Medicine, who collaborated with Babakhani on development and testing of the new pacemaker.
The chip at the system’s heart is less than 4mm wide and incorporates the receiving antenna, an AC-to-DC rectifier, a power management unit and a pacing activation signal. A capacitor and switch join the chip on a circuit board that is smaller than a dime. The chip receives power using microwaves in the 8 to 10 gigahertz electromagnetic frequency spectrum.
According to Rice University, the frequency of the pacing signals produced by the pacemaker can be adjusted by increasing or decreasing power transmitted to the receiving antenna, which stores it until it reaches a predetermined threshold. At that point, it releases the electrical charge to the heart and begins to fill again.
The team tested the device in a pig and demonstrated it could tune the animal’s heart rate from 100 to 172 beats per minute.
A short paper describing the device will be released at the conference. The paper’s authors are Babakhani and Yuxiang Sun of Rice; Brian Greet, David Burkland and Razavi of Baylor College of Medicine and THI; and Mathews John of THI.