Phase shift, coherence, BPV and HRV before and during self-terminating cardiac arrhythmia

The purpose of this work is to discuss the ability of wavelet analysis and cross-spectral algorithm to follow up the short-term cardiovascular function changes during cardiac arrhythmia. It was analyzed the (a) coherence between systolic blood pressure (SBP) and cardiac oscillations in low frequency (LF) and high frequency (HF) band; (b) fluctuations of phase; (c) heart rate variability (HRV) and blood pressure variability (BPV) as a LF power and HF power in frequency and time frequency domain. The analysis was performed on blood pressure and electrocardiogram signals from one rabbit anaesthetized, paralyzed and mechanically ventilated with self-terminating atrial and ventricular fibrillation after 7 minutes of cardiac arrhythmia. Arrhythmia was preceded by a) decreased coherence; b) increase in fluctuations of phase between signals; c) increased spectral energy associated with respiratory frequency in blood pressure signal; d) increased sympathetic outflow to the heart and e) decreased HRV. Cardiac arrhythmia was characterized mainly by increased LF power in blood pressure and cardiac signal. During self-termination of dysrhythmia a larger increased in total BPV and HRV was recorded. These results suggest that important information about both neuronal cardio-circulatory control and risk for spontaneous arrhythmia might be provided by combined analysis of frequency, phase, time-frequency analysis of blood pressure and cardiac oscillation.