Alternans and the onset of ventricular fibrillation

Ventricular fibrillation (VF) remains a major cause of death in the industr ialized world. Alternans (a period-doubling bifurcation of cardiac electric al activity) have recently been causally linked to the progression from ven tricular tachycardia (VT) to VF, a more spatiotemporally disorganized elect rical activity. In this paper, we show how alternans and thus VT degenerate to chaos via multiple, specific dynamical routes, largely associated with spatial components of VF dynamics, explaining failures of many recently pro posed antiarrhythmic drugs. Identification of dynamical mechanisms for the onset of VF should lead to the design of future experiments and consequentl y to more effective antiarrhythmic drugs.