Model Interpretation of Pathological Body Surface QRST Integral Maps Related to Action Potential Heterogeneity

According to theoretical and clinical considerations the risk of re-entry type malignant arrhythmia can be predicted by body surface QRST integral maps. Our aim was to understand better the intracardiac processes causing noninvasively measurable action potential (AP) heterogeneity. For this task we used a computer model of human cardiac ventricles with modifiable AP patterns to investigate the process on source level. To estimate the relevant potential maps on the body surface, we used a realistically shaped piecewise homogeneous torso model. The level of AP heterogeneity was quantified by the non-dipolarity index (NDI) of the QRST integral maps, calculated beat-to-beat. We found that the source level origin of extreme NDIs was in the apical region of the heart, due to significantly diminished or reversed transmural action potential gradients or myocardial necrosis.