Analysis of the ventricular fibrillation ECG with methods from nonlinear dynamics

Ventricular fibrillation (VF) ECGs (electrocardiograms) show rapid and irregular oscillations described by cardiologists as `chaotic´. To investigate whether the observed chaotic rhythm reflects a model of deterministic chaos, a dimensional analysis of four VF ECGs obtained from the American Heart Association Database has been carried out. The correlation dimension D calculated at embedding dimension equal to 20 gives values ranging from 7.7 to 9.5. Since D, as a function of the embedding dimension does not show a complete saturation, it turns out that low-dimensional models cannot account for the dynamics of the fibrillation ECG. A comparison between correlation dimensions obtained during VF and sinus rhythm (literature data range from 3.6 to 5.2) suggests a potential relevance of this new parameter in a comparative sense