Linear and non-linear analysis of the surface electrocardiogram during human ventricular fibrillation shows evidence of order in the underlying mechanism

Ventricular fibrillation (VF) is a poorly understood yet potentially lethal cardiac arrhythmia. The electrocardiogram (ECG) time series of VF is inves tigated by comparison of the linear and non-linear features of VF time seri es and surrogates in which internal correlations have been destroyed. From 40 ECG time series of human VF and 40 surrogate time series, three quantiti es are evaluated: the percentage of the linear time-frequency distribution (TFD) exceeding a threshold, the non-linear coarse-grained correlation dime nsion (D-cg), and the percentage of diagonal lines in the nonlinear recurre nce plot longer than 10 elements (D-10) It is found that the mean (SD) perc ent threshold TFD and D-cg are higher for the surrogates (6.7% (1.3) and 5. 3 (0.6)) than the VF time series (5.6% (0.7) and 3.8(0.9)), whereas the mea n D-10 is higher for the VF time series (49% (13)) than the surrogates (32% (7)). All of these differences are significant (p < 0.0001) and indicate g reater order in the VF time series than in the surrogates. It is therefore shown that both linear and non-linear signal analysis demonstrate order in the ECG time series of VF.