Hubmed Page: Reentry in heterogeneous cardiac tissue described by the Luo-Rudy ventricular action potential model (with abstract)
The primary focus of this article is the effect of a gradient of action potential duration (APD) on spiral wave dynamics. The authors ran several simulations of a spiral wave using the Luo-Rudy I ionic model, and tracked the drift of the spiral wave’s phase singularity with respect to a gradient of APD. As the abstract says, spiral wave drift was in the direction of longer rotation period (analogous to longer APD, in this case), which is right in line with what should be expected. Higher-frequency rotation should push the spiral wave center (phase singularity) away, regardless of the phenomenon underlying that higher frequency. The article is a medium-length read at six pages. While it seems somewhat redundant, in that every test yielded approximately the same results, this leant strong support to the conclusions of the paper — no caveats or qualifications were necessary. The conclusions of this article are important to the study of arrhythmias in regional disease, where gradients of electrophysiological disease exist along the borders between normal and diseased tissues.
The paper does not, unfortunately, delve into the details of why high-frequency rotation pushes away low-frequency rotation. A similar phenomenon was explained to me this past fall by Dr.Valentin Krinski with regard to two interacting spiral waves or periodic sources. I’m currently struggling to find the bridge — the relationship between different frequencies in different parts of the same spiral wave, and different frequencies in different spiral waves.

If you know why this is, kindly leave a comment. In the mean time I’ll be puzzling over it.

Hubmed Page: A Chilling Tale

This is an article about a clinical case of a man who went to an emergency room for diarrhea, and ended up having a heart attack. It goes on to analyze the odd ECG recordings he produced, describe how hypothermia was induced to minimize damage, and elucidate the origin of the problem. It’s a quick read at 3 pages, two of which consist primarily of ECG plots.

As a basic scientist who does mostly simulation work, I’m not very good at reading pathology from ECG readouts. However, I’m trying to read more clinical literature to become more familiar with the way cardiologists look at a heart’s electrophysiological function. This article points out a number of odd features of the subject’s ECG readout, and explains the sources of them. It’s a little over my head, but it should be valuable information as I try to learn more about this form of diagnosis.