Spatial and temporal organization in ventricular fibrillation

Ventricular fibrillation (VF) is the leading heart rhythm alteration that r esults in sudden cardiac death, yet the detailed mechanisms of the arrhythm ia remain elusive. Fibrillation has been defined as "turbulent" cardiac ele ctrical activity, which conjures up the idea of totally random and disorgan ized activation of the ventricles. I review theoretical concepts and recent ly published results based on a newly developed algorithm, "two-dimensional phase mapping," which demonstrates that VF is not random and may be analyz ed quantitatively. The approach is based on video imaging of voltage-sensit ive dye fluorescence to record transmembrane potential simultaneously from 20,000 sites on the epicardial surface of rabbit and sheep ventricles. Duri ng VF, activity shows a strong periodic component centered near similar to 500 beats/min. Phase maps reveal that VF depends on the organization of ele ctrical waves around a small number of "phase singularities" that have rela tively short lifespans and form as a result of interactions of wavefronts w ith obstacles in their paths. Overall, the evidence demonstrates that there is a high degree of temporal and spatial organization in cardiac fibrillat ion. The results may pave the way for a better understanding of the mechani sms of VF in normal, as well as in diseased, hearts. (Trends Cardiovasc Med 1999;9:119-127). (C) 1999, Elsevier Science Inc.