Myocardial Transmural Electrical Disruption Affects Electrogram Pattern

Myocardial structural remodeling leads to atrial fibrillation (AF). Interstitial collagen deposits remodel myocardium, causing disruption of electrical propagation between the endocardial and the epicardial layers, and affecting propagation within layers as well. How these changes manifest on the electrogram (EGM) is unclear. Here we investigate the consequences of epicardium- endocardium electrical dissociation on EGMs. Left atrial patient-specific bilayer computational models were constructed using MRI from AF patients (n = 11). Interstitial collagen was incorporated as microstructural discontinuities within layers and causing transmural dissociation in the high-fibrosis areas. The models where the fibrosis was not included were considered as controls. Changes in the unipolar EGM characteristics were computed. A propagation delay was observed between both layers. No monotonic linear relationship between control and fibrotic EGMs was found. With the collagen deposits, amplitude decreases and increased fractionation on EGMs were significant. EGM area also tended to become smaller, and duration and waveform asymmetry were affected. In conclusion, measurements of EGM morphology can be used together with clinical imaging data to distinguish between different substrate modifications, and better select ablation targets.