Ventricular fibrillation (VF) is a rapidly lethal cardiac arrhythmia and one of the leading causes of sudden death in many industrialized nations. VF appears at random, but is produced by a spatially extended excitable system. We generated VF-like "pseudo-ECG" signals from a numerical caricature of cardiac tissue of 100 × 100 × 50 elements. The VF-like "pseudo-ECG" signals represent the propagation and break-up of an excitation scroll wave under FitzHugh-Nagumo dynamics. We use surrogate data and correlation dimension techniques to show that the dynamics observed in these computational simulations is consistent with the evolution of spontaneous VF in humans. Furthermore, we apply a novel adaptation of the traditional first return map technique to show that scroll wave break-up may be represented by a characteristic structural transition in the first return plot. The patterns and features identified by the first return mapping technique are found to be independent of the observation function and location. These methods offer insight into the evolution of VF and hint at potential new methods for diagnosis and analysis of this rapidly lethal condition.