Dynamics of Ventricular Fibrillation: A Model and Experimental Study

Wiggers initially described that after electrical induction of ventricular fibrillation (VF) the rhythm so induced progresses in complexity [14]. Previously Witkowski et al. [15] have described two distinct phases of perfused VF. The acute form was characterized by relatively well organized activity and was observed in the first few minutes after induction. The chronic form developed after this initial reentry and was more disorganized in nature. In this paper we describe computer simulations carried out using a complex three-dimensional model of cardiac tissue. Depending on the time constant of the dynamics of the calcium current, activity ranged from organized scroll waves, to highly disorganized chaotic activity in which it was possible to identify up to 10 different vortex filaments which continually drifted and split. The model data was compared to experimental measurements via the maximum cross-correlation function described previously by Witkowski et al. [15]. We found that the max cross-correlation function for a single scroll wave ranged between 0.6 and 0.9, and is similar to what was experimentally observed from optical transmembrane potential mapping during early VF. For the highly disorganized activity the maximum cross-correlation function was in the range of 0.2, which similarly was in same range reported experimentally for fully developed VF.