We propose a biophysical modelling approach to separately investigate the impact of right and left atrial (RA/LA) electrical heterogeneity on atrial fibrillation (AF) perpetuation. The baseline AF substrate was based on a 4:1 anisotropy ratio and uniform membrane properties. AF was initiated by a ramp-pacing protocol applied in the pulmonary veins region. Once AF was observed, random patchy heterogeneities in action potential duration (shorter duration inside the patches) were introduced in the cellular model for the subsequent simulation of AF. The effect of tissue heterogeneity on AF perpetuation was quantified by the duration of AF episodes (an AF episode lasting more than 50 s was considered as sustained). For high percentages of heterogeneities, the mean AF episode duration and the number of non-terminated AF episodes were significantly higher for the RA compared to the LA. This could be indicative of a very probable involvement of the RA substrate into the persistent AF process in this model. A direct link between the spatial localization of tissue heterogeneity and AF duration was also observed.