Detection of nonlinearity in temporal patterns of ventricular premature beats

The occurrence of ventricular premature beats (VPBs) is a common ventricular arrhythmia. However, relatively little is known about the temporal pattern of VPB generation. In this study the authors evaluated the temporal pattern of VPB generation by measurement of Lyapunov exponents. Twenty subjects were identified as having more than 3000 VPB´s per day. For each patient the authors generated a time series consisting of number of VPBs in each minute of ECG data. They checked for the presence of nonlinearity in these time series using the surrogate data method and found that thirteen of the patients had a significant Lyapunov exponent. VPBs might be generated by chaotic dynamical mechanism in the eleven patients who had a significant positive Lyapunov exponent.