Taken from an entry in YouTube referring further to "The Virtual Heart" which contains additional information and resources, including movies from experiments.

From the description:
This is a simulation of the chaotic electrical activity during ventricular fibrillation. The multiple spiral waves drive the heart at a faster period than that of the normal sinus rhythm. This results in irregular activation of the ventricles and thereby prevents an effective mechanical contraction. Blood pressure instantaneously drops to zero, leading to death within minutes due to lack of cardiac output unless successful electrical defibrillation is performed.