Abstract
Atrial fibrillation (AF) is the most common atrial arrhythmia and affects more than 0.8 million Japanese. In the past decade, while several mechanisms (focal discharge and/or rotor, etc.) have been proposed to explain AF initiation and maintenance, AF mechanisms are still debated. We summarize recent high-resolution optical mapping studies in isolated sheep hearts, which have provided new insights into the dynamics and mechanisms of AF. First, we discuss results from experiments on AF induced by acute atrial stretch in the presence of adreno-cholinergic stimulation that revealed the presence of interplay between rotors and focal discharges. Next, we outline the results obtained from a persistent AF model (PtAF) induced by intermittent rapid atrial pacing. By using simultaneous optical mapping of epi- and endocardial activation patterns, we demonstrated that PtAF was maintained by 3-dimensional rotor, a.k.a scroll waves with I-shaped filaments anchored to junctions between thin and thick myocardium. Thus, these results clearly suggest that self-sustained rotors do exist in the atria and that such rotors are in fact the high frequency sources that determine the complex patterns of activation that characterizes AF.
