SPATIAL AND TEMPORAL ORGANIZATION DURING CARDIAC FIBRILLATION

Cardiac fibrillation (spontaneous, asynchronous contractions of cardia c muscle fibres) is the leading cause of death in the industrialized w orld(1), yet it is not dear how it occurs. It has been debated whether or not fibrillation is a random phenomenon. There is some determinism during fibrillation(2,3), perhaps resulting from rotating waves of el ectrical activity(4-6). Here we present a new algorithm that markedly reduces the amount of data required to depict the complex spatiotempor al patterns of fibrillation. We use a potentiometric dye(7) and video imaging(8,9) to record the dynamics of transmembrane potentials at man y sites during fibrillation. Transmembrane signals at each site exhibi t a strong periodic component centred near 8 Hz. This periodicity is s een as an attractor in two-dimensional-phase space and each site can b e represented by its phase around the attractor, Spatial phase maps at each instant reveal the 'sources' of fibrillation in the form of topo logical defects, or phase singularities(10), at a few sites. Using our method of identifying phase singularities, we can elucidate the mecha nisms for the formation and termination of these singularities, and re present an episode of fibrillation by locating singularities. Our resu lts indicate an unprecedented amount of temporal and spatial organizat ion during cardiac fibrillation.