Background. The latest electrical activation site (LEAS) of the left ventricle is considered the optimal target for lead placement in cardiac resynchronization therapy (CRT). However, the location of the LEAS shows pronounced inter- patient variability, making individualized electrical mapping necessary. Non invasive electrocardiographic imaging (ECGI) is an attractive tool for this purpose. However, ECGI has limited accuracy in determining local activation times. This fact makes direct identification of the LEAS based on activation mapping unreliable. Nevertheless, during the final stage of ventricular depolarization, a pronounced and well demarcated maximum of positive electrical potential is consistently observed within the LEAS. This reproducible electrophysiological phenomenon may serve as an alternative marker for identifying the latest activation site.
Aims: (1) to provide a theoretical explanation for the above electrophysiological phenomenon and (2) to validate the accuracy of LEAS localization by ECGI using this electrical potential-based approach.
Methods. Ventricular depolarization was simulated in six personalized CT derived heart–torso models of patients with non ischemic cardiomyopathy, resulting in 18 activation scenarios with different focal origins. A bidomain model with the TNNP 2006 cellular model implemented in the Oxford Chaste software was used. In total, 224 unipolar body surface ECGs with added Gaussian noise were generated, and inverse reconstruction of cardiac surface potentials was performed using the Amycard (EP Solutions SA) system software.
Results. The appearance of positive electrical potential in LEAS can be qualitatively explained using the double layer myocardial activation model derived from the bidomain framework. The positive electrical (extracellular) potential closely corresponded to the true LEAS, with a center-to-center distance of 2.3 ± 2.1 mm. ECGI based reconstruction localized the LEAS with a mean error of 7.8 ± 5.5 mm.
Conclusion. A potential-based ECGI approach enables non invasive localization of the LEAS with acceptable accuracy and may support optimization of CRT lead placement.