Cell repolarization variability modulates atrial fibrillation dynamics in 3D virtual human atria

Intersubject variability in cardiac electrophysiology might determine the patient-specific proneness to suffer and/or sustain arrhythmia episodes, such as atrial fibrillation (AF). However, its potential influence on arrhythmogenesis is not well understood. In this study, we compare AF activity in virtual 3D human atria models with notable differences in cellular repolarization dynamics, in order to investigate mechanisms of intersubject variability. Physiological populations of models representing myocytes of patients with chronic AF were obtained and divided into sub-populations depending on the action potential duration (APD) measured at 90%, 50% and 20% repolarization. Each sub-population was used to build a model of the human atria. Analysis of calculated pseudo-electrograms showed the dominant frequency was in general higher for the short APD than for the long APD sub-populations. Organisation indices presented similar values for both APD₉₀ sub-populations, whereas they were higher for the short APD₅₀ and APD₂₀ sub-populations, respectively. Regularity indices were lower for the short APD sub-populations. In conclusion, our results indicate that patients with long atrial APD could be associated with slow but very regular fibrillatory patterns, whereas short APDs may entail high frequency reentrant rotors and larger organisation.