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Wireless, battery-less pace maker for the heart
June 12, 2017, 11:13 am
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A new pacemaker that can be implanted directly into a patient’s heart without trailing wires or onboard batteries was revealed last week by researchers from Rice University in Texas and the Texas Heart Institute (THI).

The pacemaker, which was presented at the International Microwave Symposium in Honolulu, harvests energy wirelessly from microwave radio frequency radiation transmitted by an external battery pack.

Pacemakers use electrical signals to prompt the heart to keep a steady beat, but they have traditionally not been implanted directly into a patient's heart. Instead, they are located away from the heart, where surgeons can periodically replace their onboard batteries with minor surgery; their electrical signals are transmitted to the heart via wires called ‘leads’.

Some of the common problems with this arrangement are complications related to the leads, including bleeding and infection. The prototype wireless pacemaker reduces these risks by doing away with leads and onboard batteries that need to be changed. Moreover, these wirelessly powered microchips can be implanted directly to pace multiple points inside or outside the heart.

"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.

The chip at the system's heart is less than 4 millimeters 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.

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 successfully tested the device in a pig and demonstrated it could tune the animal's heart rate from 100 to 172 beats per minute; research on humans is still awaiting permissions.

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