Abstract 1695: Continuity of Epicardial Activation during Ventricular Fibrillation in the Isolated Swine Heart
During ventricular fibrillation (VF), electrical activation waves are fragmented and the heart cannot contract in synchrony. It has been proposed that VF waves emanate from stable periodic sources (often called “mother rotors”). In a previous study, we used new panoramic optical mapping technology to image VF wavefronts from nearly the entire epicardial surface of 6 isolated swine hearts. With this system, epicardial wavefronts can be continuously tracked without leaving the field of view. We found that VF in this preparation was not driven by rotors visible on the epicardium, but could not exclude the presence of stable driving rotors hidden within the ventricular walls. In the present study, we use graph theoretic analysis of these data to show that in all 17 VF episodes we analyzed, epicardial wavefronts could be traced through successive fragmentation and collision events from the beginning to the end of the mapped interval (4 s of VF beginning ~20 s after induction). The set of wavefronts that were so related (called the dominant component) consisted of 92% +/− 1% of all epicardial wavefronts. The presence of a dominant component shows that epicardial activation proceeds without interruption for the entire mapped interval. Thus, epicardial reentrant pathways are sufficient to maintain continuous epicardial activation and wavefront infusion from sources not visible on the epicardium is not strictly necessary for VF maintenance. The wavefronts participating in epicardial reentry were not confined to a compact region; rather, they activated the entire epicardium. These data suggest that VF in this experimental model is not driven by localized driving sources. This implies that new anti-VF treatments designed to target local driving sources may be less effective than more global interventions.