Positional ventricular tachycardia in left ventricular assist device: a new frontier in ventricular tachycardia ablation.

progressive endo-epicardial dissociation, transforming the atria into an electrical double layer of dissociated waves that constantly ‘feed’ each other. Figure 1 gives a diagrammatic presentation of the double layer hypothesis. In Figure 1A and B, a rotor is compared with an epicardial breakthrough. Whereas a rotor at best can maintain itself, endo-epicardial breakthroughs act as multiplication sites of fibrillation waves. Figure 1C illustrates how endo-epicardial (and epi-endocardial) breakthroughs can perpetuate AF. We calculated that in patients with long-standing AF, endo-epicardial breakthroughs can generate .400 fibrillation waves per second. Also in the present study of Lee et al., . 35% of the fibrillation waves arose from a focal point on the epicardium, distributed over the entire atrial surface. Simultaneous endo-epicardial mapping is required to answer the question of whether long-standing persistent AF is due to a rotor or to endo-epicardial dissociation.