44 Micra AV

For upgrading the world’s smallest pacemaker—without skipping a beat

Medtronic introduced a revolutionary pacemaker in 2016. The device was tiny enough to be inserted via catheter rather than scalpel, with no wired connection to heart muscles. But those advances came with limitations, making the Micra VR viable for only 15 percent of pacemaker candidates.

Improving on the device would require extraordinary collaboration, mixing health science, intricate algorithms and deft electrical engineering. Traditional pacemakers (and the original Micra) pick up on the electrical signals from the heart to time their signal and stimulate contractions. The first Micra could only pace the right ventricle: Its wireless electrical signal was too weak to reach the atria—and it had no way to sense when to send that signal.

“We did hours-long in-person consultations with physicians, and we also had data points from more than 500 physicians across the U.S., Europe and Asia to understand who the patients are for this technology and to try to understand their sensitivity to the technology’s performance,” says Leonardo Rapallini, vice president, R&D, cardiac rhythm management business, Medtronic, Minneapolis, Minnesota, USA.

The first stage of the solution was to design an accelerometer, which could pace the heart by sensing mechanical movements rather than electrical signals. They would need an algorithm to make it work reliably and a battery that could power the accelerometer for a decade. Oh, and they had to safely squeeze all that innovation into the tiny device.

The challenges included synchronizing the work and goals of varied teams. “The problem is that these things were happening in parallel, and so we could have had the algorithm, but if we couldn’t do it in a way that was energy efficient, we didn’t have a product,” Rapallini says.

In the early stages, the algorithms that met the health requirements quickly drained Micra AV’s battery power. An engineering team led by Julie Pronovici redesigned Micra AV’s circuitry to improve processing efficiency, plus added software to optimize the system. “This is by far the most innovative, most technically challenging product project I’ve ever been involved with in my 19 years at Medtronic,” Pronovici said.

In January, the U.S. Food and Drug Administration approved the Micra AV. Now 55 percent of pacemaker patients can use it and avoid many of the complications that arise from traditional pacemakers, such as infections, bleeding or problems with the wire that connects the device to the heart.

Medtronic also worked to limit the risks that accompany any breakthrough device, engaging in a carefully phased release, first to a limited number of physicians with the most expertise with Micra technology, then to a broader group of physicians two and a half months later. “We didn’t just open the doors,” Rapallini says. “This is completely novel.”