Localization of intramural necrotic regions using electrocardiographic imaging

Recent studies have demonstrated that electrocardiographic imaging (ECGI) is a novel noninvasive modality for exploring the spread of electrical activation within the ventricular wall. In this study, our goal was to explore the ability of ECGI in reconstructing epicardial potentials and electrograms in the ventricles damaged by localized necroses (<2 cm2). An anatomical model of the human ventricular myocardium was used to simulate activation sequences initiated at 428 epicardial and endocardial pacing sites distributed over the right ventricular and left ventricular free walls. From these realistic sequences, we simulated extracardiac potentials at epicardial (202 sites) and torso surfaces (352 sites) using boundary element model of the human torso. ECGI in terms of the L-curve was applied to compute epicardial potentials and unipolar electrograms (202 sites). Inversely computed electrograms correlated well with those simulated by an anatomical model (r > 0.9 at 68% of sites). Specifically, ECGI accurately reconstructed the following features that have been observed during measurements on the exposed canine hearts: (a) an epicardial potential pattern with a central minimum and two maxima, with the minimum positioned above the pacing site; (b) a complete transient loss of one of the positive areas in the epicardial potential pattern when the necrosis was located subepicardially; and (c) a transient gap in the expanding positive areas of the epicardial potential pattern when the necrosis was located intramurally or subendocardially. Findings of our study indicate that ECGI provides detailed reconstruction of patterns of myocardial activation in the presence of localized necroses and may be useful in the assessment of arrhythmogenic substrate in the clinical setting.