Epicardial Mapping of Longstanding Persistent Atrial Fibrillation

The electropathological alterations of the atria responsible for development of a substrate of persistent atrial fibrillation (AF) in humans are still unknown. In this chapter we evaluate a new mapping algorithm (wave-mapping) by comparing the spatiotemporal characteristics of the fibrillatory process in patients with normal sinus rhythm and long-standing persistent AF. In patients with structural heart disease, the electropathological substrate was determined by electrical dissociation between atrial muscle bundles (longitudinal dissociation) and a high incidence of endo-epicardial breakthroughs. Longitudinal dissociation was quantified by measuring the total length of lines of block per cm2 per AF cycle. These lines of block were predominantly oriented parallel to the major atrial muscle bundles. Endo-epicardial breakthroughs occurred over the entire atrial surface, both in the left and the right atrium. They are considered as an important source of "new" fibrillation waves, because they represent transmural junction sites and bifurcation points between fibrillation waves propagating in the dissociated endo- and epicardial layers of the atrial wall. We hypothesize that the high persistence of AF in patients with valvular disease is due to the existence of a double layer of fibrillation waves, resulting from electrical dissociation of the endo- and epicardial layers. In patients with structural heart disease, AF is maintained by a constant "ping-pong" of multiple fibrillation waves between the endo-and epicardial layers of the atrial wall. This edition first published 2013

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