For patients with heart failure, the pacemaker can be a lifesaving device. But for all of the benefits, the existing models also come with some concerning drawbacks.
The tiny wires that provided electrical shock and kept heart rhythm normal might need to be removed from veins and reset. Infection could set in around the device, requiring the whole system to be replaced.
But a new adaptation of the pacemaker has helped mitigate those risks while maintaining the device’s vital functions.
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The Medtronic Micra is the world’s smallest pacemaker, measuring about 7 percent of traditional devices. Without the wires used in most pacemakers, the Micra is implanted directly into the heart.
Franciscan Health Indianapolis was the first hospital in Indiana to use the compact pacemaker on a patient. Dr. Robert Kinn, electrophysiologist at Franciscan Health Heart Center and Indiana Heart Physicians, helped explain what makes the device so important.
Normal heart function
“The way the heart works is, there is an upper chamber that has your God-given pacemaker, and you have your lower chamber that pushes blood out of the heart. In between, you have an electrical bridge. You get an upper chamber impulse then a lower chamber impulse,” Kinn said.
The existing solution
“Most pacemakers that get put in in the U.S. are what’s called ‘duel-chamber pacemakers.’ There’s an electrode in the upper chamber and an electrode in the lower chamber, and it tries to restore that normal electrical system because that has failed,” Kinn said. “The traditional pacemaker has electrodes that go through a vein, usually under the collarbone, and go down through that vein to the heart. The electrodes come out of the vein and attach to a half-dollar sized generator under the skin that has the battery and computer technology that tells it when to pace and what to do.”
“Anything under the skin, such as the generator, is at increased risk of becoming infected,” Kinn said. “When pacemakers get infected, everything has to come out. There’s no way to sterilize synthetic material under the skin.” Also, over time, the veins around the heart can close off with the leads in them, Kinn said.
Solving the problem
“The Micra is a little capsule that goes directly into the heart, sending electrical charges without any wires. It has little grappling hooks on the end. You deliver this capsule to the lower chamber of the heart through a hollow tube, and push it into these crevices so the hooks catch. It paces the bottom chamber on its own, without electrodes,” Kinn said.
Not for everyone
Because the device is placed directly in the heart, it can currently only be used in the lower chamber of the heart. “Maybe only about 10 percent of people need a one-chamber pacemaker right now. Right now, they don’t have a way to pace the upper chamber with one of these capsules,” Kinn said.