ST elevation or depression in subendocardial ischemia?
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.
Potse
Mark
M
Res. Center, Hosp. du Sacre-Coeur de Montreal, Que. mark@potse.nl
LeBlanc
A-Robert
AR
Cardinal
René
R
Vinet
Alain
A
D004699:Endocardium / Q000503:physiopathology*; D006321:Heart / Q000033:anatomy & histology / Q000503:physiopathology*; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D017202:Myocardial Ischemia / Q000503:physiopathology*; D032383:Myocytes, Cardiac / Q000502:physiology