SIAM News Blog

An Appeal from a Heart Doctor to Mathematicians

By Michael Lloyd

In the 1950s, a power outage killed a young patient who underwent life-saving surgery, but needed a pacemaker to keep the heart beating during recovery. These pacemakers, as ridiculous as it may sound, needed to be plugged into the wall like a lamp, or vacuum cleaner. Dr. Lillehei, the surgeon of this patient, had had enough. He called up a young electrical engineer who had a modest workshop in a garage in Minnesota. The engineer recalled a schematic of a simple metronome circuit he saw in a magazine and created the first battery powered pacemaker. That engineer was Earl Bakken, who went on to create one of the largest medical device corporations in the world.

This is one of countless examples of a medical doctor, knowledgeable enough about things anatomic, physiologic, and pathologic, going outside the circle of white-coated colleagues to an engineer, a mechanic, a mathematician with a problem.

This graphic, taken from Alessie et al. 1977 shows the initial animal experiments of electrodes placed on atrial tissue (#1-6, discs) during fibrillation and the procession of wavefronts around varying anatomic barriers. High-resolution real-time mapping in beating human hearts could offer cardiologists a tool to help target areas that sustain atrial fibrillation.
As a cardiac electrophysiologist (and most certainly NOT a mathematician) I was invited to speak at the SIAM Conference on Computational Science and Engineering from a clinician’s perspective about the problem of atrial fibrillation. This seemingly chaotic beating of the top chambers of the heart is the most common rhythm disturbance (arrhythmia) that we encounter. Since a quivering heart chamber does not transport blood efficiently, the blood can stagnate in recesses of the atrium and form blood clots that can then dislodge and travel to other organs, most notably the brain, and cause permanent damage (such as, strokes). Doctors in my specialty spend much of their careers trying to fix this arrhythmia by applying radiofrequency through platinum-tipped catheters or delivering liquid nitrogen within balloons in the desperate hope of destroying enough atrial tissue so that the atrial fibrillation cannot persist.

The hard reality is that we're (ahem) not very good at it. Large-scale clinical trials show a success rate of about 60-70% with our best efforts. This comes at a substantial financial cost ($60,000) and a 3% chance of major complications. We simply need a more elegant understanding and treatment approach for this arrhythmia. The state of the art whereby killing so much atrial tissue that fibrillation (or any rhythm for that matter) could exist must come to an end.

There is hope in the form of rotor or focal impulse mapping, which uses basket like electrode catheters or high-density skin electrodes to map the wavefronts of meandering depolarizations that occur during atrial fibrillation and target very specific areas within the atrium that seem critical to sustain the arrhythmia. Nonetheless, despite promising initial clinical results, more recent data suggests this perhaps wouldn’t even qualify as a mediocre beta. Despite this, most of us believe there is something to this technology. Big companies are taking very big chances on rotor and focal impulse mapping of atrial fibrillation.

Last week, the title of my presentation used the term "gap." The most unfortunate "gap" is that we as clinicians don't share our clinical data enough with those capable of incorporating this data and enhancing models to better target rotor and focal impulse sources for atrial fibrillation. I am hopeful and grateful for the opportunity to narrow that gap and help treat the biggest problem for our patients.

Michael Lloyd is a clinical cardiac electrophysiologist at Emory University Hospital. He specializes in the treatment and research of cardiac arrhythmias.

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