Analysis and diagnosis of polycoherence based ECG signal for non-linearity detection

This method gives a new algorithm to detect nonlinearities in ECG signals and to determine the order of non-linearity. The ECG bispectrum is analysed and the bicoherence index is calculated to identify non-linearity. The diagonal slice of the polycoherence index of any order,calculated using the diagonal slice of the polyspectrum of the same order and the power spectrum, is proposed as an estimator. The possibility of higher-order non-linearities in ECG signals is investigated using these slices. Physiological and pathological cases have been studied. The polyspectrum and polycoherence slices indicate the presence of higher-order phase-coupled harmonics, in the physiological cases, which is attributed to higher order non-linearities. Differences between physiological and pathological cases are assessed and a decrease in the non-linearity order could be correlated with pathological conditions.