Study of the impact of electrical heterogeneities in the right and left atrium on atrial fibrillation perpetuation

Introduction: Electrical heterogeneity in the atria has been consistently linked with the initiation and perpetuation of atrial fibrillation (AF). The present model-based study investigated the contribution of action potential duration (APD) heterogeneities in the left atrium (LA) and right atrium (RA) on the perpetuation of the reentrant activity during AF. Methods: A computer model with a geometry based on computed tomography of AF patients and a Courtemanche atrial cellular model was implemented. Self-terminated AF episodes were initiated via ramp pacing in a model with modified channel conductance, homogeneous tissue and 4:1 anisotropy ratio. Once AF was observed, random patchy heterogeneities with shorter APD were separately introduced in the LA and the RA. Percentage of heterogeneities was progressively increased from 20% to 80% of each atrium size (characteristic length scale of patches was 7.5mm). For each simulation, the following values were assessed: average AF duration, the number of sustained AF episodes (lasting more than 50s), number of wave-fronts (#WF) and AF cycle length (AFCL). The results were averaged across the atria surface over 130 simulations (26 AF initial conditions and 5 random localizations of heterogeneities). Results: For the model with no heterogeneities, #WF was 6.82±3.67, AFCL 278±52ms and the average AF duration 15.42±9s. For low percentage of heterogeneities there were no significant differences between RA, LA and the model with no heterogeneities. For high percentage of heterogeneities the results showed that a significant right-to-left atrial APD gradient was associated with more sustained AF episodes, longer duration, higher #WF and shorter AFCL compared to the left-to-right APD gradient (sustained AF episodes: 95% vs. 52%, p