I don't know about you, but I often find myself day dreaming about what future doctors might think of our current technology.
Sure, in this moment, most of us consider our tools quite nifty. And they are. Quadripolar LV pacing leads, wireless remote monitoring, and now, even pacemakers without leads are entering the market. When I started medicine, such things were not yet imagined. With the lens of the present, we look good.
But with a lens of the future, maybe it is not so much. Consider the pacemaker and its battery. Patients often ask: "Doc, what happens when the battery runs down?" And we reflexively answer, as if it were easy: "We just replace the generator." The problem with "gen changes" is that they carry significant risk,[1] often higher than an original implant.
But what if we never had to replace the generator? Now that would be something.
Adrian Zurbuchen
Enter Adrian Zurbuchen (University of Bern, Switzerland), who gave one of the most futuristic abstracts I have ever seen at a major medical conference. His PhD thesis, accepted as a featured presentation here at the European Society of Cardiology (ESC) 2014 Congress centered on the feasibility of a batteryless pacemaker.[2]
I sat down with the mountain-biking PhD student for coffee after his presentation, and he explained how it works. What follows involves a little engineering, but worry not, I don't know enough to make it painful.
The idea of the batteryless pacemaker is similar to the self-powered watch, which dates back to the 1770s. Swiss engineers designed an oscillator that moves an eccentric weight. Motion of the wrist moves the oscillator, which then transfers that energy to a spring. When the spring uncoils, energy transfers to a small generator.
As a moving object goes, the heart is perfect. It beats continually, 100 000 times daily. Zurbuchen and his group took a small device, which looks a lot like the back of a commercial watch, and sewed it onto a pig heart. In (hydraulic) power terms, the typical heartbeat generates about 1.4 W of energy per beat. The device extracts only 52 μW.
The net positive energy from the watch-mechanism is transferred to an electronics box (capacitor) and then sent back as a pacing stimulus to the pig's heart via epicardial leads. The videos he showed in the session were amazing. The device drives a pacemaker with energy extracted from the heart itself! And the pig heart rocked and rolled.
Of course, this is early. The pig's chest was open and the system is epicardial. You can't think about this technology in terms of weeks or months. Who would have thought a leadless pacemaker was possible? As electronics become smaller, it's a small leap to think a device like this could be placed transvenously in the endocardium.
We cardiologists often forget, at least I do, that many of the things we do, and get enormous credit for, began with young men like Adrian Zurbuchen. Engineers and engineering lie at the core of our interventions.
In yesterday's post, I mentioned the importance of teamwork in advancing patient care. Indeed, engineers are vital members of our team.
JMM
Video: A five-second clip of the prototype watchlike device
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WebMD, LLC
Cite this: The Self-Winding Pacemaker That Could . . . Seeing the Future of Batteryless Cardiac Devices - Medscape - Sep 01, 2014.
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