Evolution of ventricular fibrillation revealed by first return plots

The authors examine computational simulations of the propagation of activation and break-lip of a scroll wave in a 100/spl times/100/spl times/50 army under Fitz-Hugh Nagumo dynamics. Calculating the temporal evolution of a spatial average in each of the x-, y-, and z-directions produces a "pseudo-ECG". The authors apply a combination of high-dimensional embedding, singular value decomposition and projection, to transform the data and extract a derived time series. The "inter-beat" intervals of this derived time series are used to compute first return plots, the temporal evolution of which shows characteristic time-dependent dynamics. This technique provides a pictorial representation of the scroll wave break-up. The authors show that the same characteristic pattern may be observed in episodes of VF recorded from human subjects. Furthermore, this characteristic evolution may be observed from each of three scalar "pseudo-ECG" time series derived from the three orthogonal directions in the same computational simulation. This technique offers a new approach to analyze and track the evolution of scroll wave break-up in ventricular fibrillation.