Tag Archives: atrial fibrillation

Norbert Weiner

In the Cambridge Mass of the early 60’s the name Norbert Weiner was spoken in hushed tones. Widely regarded as a genius tutti the assembled genii of Cambridge, that was all I knew about him aside from the fact that he got a bachelor’s degree in math from Tufts at age 14. As a high school student I tried to read Cybernetics, a widely respected book he wrote in 1948, and found it incomprehensible.

Surprisingly, his name never came up again in any undergraduate math courses, graduate chemistry and physics courses, extensive readings on programming and computation (until now).

From PNAS vol. 114 pp. 1281 – 1286 ’17 –“In their seminal theoretical work, Norbert Wiener and Arturo Rosenblueth showed in 1946 that the self-sustained activity in the cardiac muscle can be associated with an excitation wave rotating around an obstacle. This mechanism has since been very successfully applied to the understanding of the generation and control of malignant electrical activity in the heart. It is also well known that self-sustained excitation waves, called spirals, can exist in homogeneous excitable media. It has been demonstrated that spirals rotating within a homogeneous medium or anchored at an obstacle are generically expected for any excitable medium.”

That sounds a lot like atrial fibrillation, a serious risk factor for strokes, and something I dealt with all the time as a neurologist. Any theoretical input about what to do for it would be welcome.

A technique has been developed to cure the arrhythmia. Here it is. “Recently, an atrial defibrillation procedure was clinically introduced that locates the spiral core region by detecting the phase-change point trajectories of the electrophysiological wave field and then, by ablating that region, restores sinus rhythm.” The technique is now widely used, and one university hospital (Ohio State) says that they are doing over 600 per year.

“This is clearly at odds with the Wiener–Rosenblueth mechanism because a further destruction of the tissue near the spiral core should not improve the situation.” It’s worse than that because the summary says “In the case of a functionally determined core, an ablation procedure should even further stabilize the rotating wave”

So theory was happily (for the patients) ignored. Theorists never give up and the paper goes on to propose a mechanism explaining why the Ohio State procedure should work. Here’s what they say.

“Here, we show theoretically that fundamentally in any excitable medium a region with a propagation velocity faster than its surrounding can act as a nucleation center for reentry and can anchor an induced spiral wave. Our findings demonstrate a mechanistic underpinning for the recently developed ablation procedure.”

It certainly has the ring of post hoc propter hoc about it.