Mathematical modeling from ion channel to ECG
Proc. 28th IEEE-EMBS Annual International Conference, pages 3899-3902 New York City, USA, August/September 2006.
A more comprehensive version of this paper was published in Heart Rhythm, 2007. In this more recent paper we discuss also the role of geometric factors: more extensive ischemic zones make overlying ST depression more likely. The limiting case is global subendocardial ischemia. As we have shown at the ICE 2007 conference, this would lead to a typical "stress-test ECG".
ST-segment depression in epicardial electrograms can be a reciprocal effect of remote myocardial ischemia (MI), and can also be due to local partial-thickness or subendocardial MI. Experimental studies have shown either ST elevation or depression in leads overlying a subendocardial ischemic region. Those reporting elevation have shown depression over the lateral borders of the ischemia. Simulation studies with anisotropic models have explained the ST-elevation results. Presently, while experimentalists may have difficulty understanding the ST elevation, most model studies fail to explain ST depression in overlying leads during partial-thickness ischemia. We have simulated partial-thickness ischemia in a 3-dimensional model of the human heart. Our results show that the conductivity of the intracavitary blood, geometry of the ischemic region, and bidomain anisotropy ratios can all have a decisive influence on the sign of the ST deviation. We hypothesize that ST depression in leads overlying an ischemic zone is due to subendocardial ischemia in tissue where a redistribution of gap junctions has taken place.
Computations were performed on computers of the Réseau québécois de calcul de haute performance (RQCHP). This work was was supported by grants from FRSQ, Québec, to the Groupe de recherche en simulation et technologie biomédical (GRSTB), and the Research Center of Sacré- Coeur hospital, Université de Montréal.
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