Increased frequency of epicardial breakthroughs provides a mechanistic explanation for the high persistence of atrial fibrillation in patients with structural heart disease.
Focal fibrillation waves are due to epicardial breakthrough of waves propagating in deeper layers of the atrial wall. In patients with longstanding AF, the frequency of epicardial breakthroughs was 4 times higher than during acute AF. Because they provide a constant source of independent fibrillation waves originating over the entire epicardial surface, they offer an adequate explanation for the high persistence of AF in patients with structural heart disease.
Groot et al. (2010) studied this question.