Characterization of patterned irregularity in locally interacting, spatially extended systems: Ventricular fibrillation

The re-entrant ventricular arrhythmias of monomorphic ventricular tachycard ia and fibrillation are produced by abnormal spatio-temporal patterns of pr opagation in the ventricular myocardium. These behaviors can be described b y solutions of reaction-diffusion equation excitable medium models. The dir ect comparison of such solutions with existing experimental observations is virtually impossible as there are too many factors to be taken into accoun t, including not only the complicated dynamics of the re-entrant waves of e xcitation in the tissue, but also the way the appearance of these waves on the surface is modified by the inhomogeneity, anisotropy and three-dimensio nal nature of heart tissue. One way of indirect comparison is to compare ch aracteristics of the complexity of the model and the real data, that are in variant under these modifications of the signal. Karhunen-Loeve decompositi on is a standard tool for evaluating the complexity of multidimensional sig nals. A comparison of the separate and conjoint complexities of the signals on the opposite sides of the preparation can be considered as an indicator how much three-dimensional effects are essential in the preparation behavi or. (C) 2001 American Institute of Physics.