The effect of electrophysiological heterogeneities on scroll wave dynamics in three-dimensional cardiac tissue: Simulation study

The scroll wave dynamics were investigated in a 3D tissue which incorporated the electrophysiological heterogeneities of epi-, M-, and endo cell layers. The dynamic model for each cell layer was developed by properly modifying the Luo Rudy Phase 1 model according to experimental findings. The ‘spike and dome’ morphology of epi and M cell layers and the strong rate sensitivity of M cell restitution at long cycle length were reproduced successfully in this modified model. The three cell types were put into a slab of 3D tissue with varying proportion of M cell layers. The determining factor of scroll wave stability was the average cycle length of the system and the point at which the average cycle length crosses the M cell restitution curve. For the 3D tissue whose M cell proportion is small, the scroll wave rotates with a cycle length at which the slope of M cell restitution is greater than 1 thus promoting the breakup in the M cell region. However, when the M cell proportion is large enough, the scroll wave rotates with a slower cycle length at which the slope of M cell restitution is less than 1 and the scroll wave rotates without breakup. Thus, the M cells may play an important role in the stability of scroll wave dynamics and the stability of the scroll wave is decided by the restitution characteristics of the M cell.