Sensitivity of temporal heart rate variability in Poincare plot to changes in parasympathetic nervous system activity

Background: A novel descriptor (Complex Correlation Measure (CCM)) for measuring the variability in the temporal structure of Poincare plot has been developed to characterize or distinguish between Poincare plots with similar shapes. Methods: This study was designed to assess the changes in temporal structure of the Poincare plot using CCM during atropine infusion, 70 degrees head-up tilt and scopolamine administration in healthy human subjects. CCM quantifies the point-to-point variation of the signal rather than gross description of the Poincare plot. The physiological relevance of CCM was demonstrated by comparing the changes in CCM values with autonomic perturbation during all phases of the experiment. The sensitivities of short term variability (SD1), long term variability (SD2) and variability in temporal structure (CCM) were analyzed by changing the temporal structure by shuffling the sequences of points of the Poincare plot. Surrogate analysis was used to show CCM as a measure of changes in temporal structure rather than random noise and sensitivity of CCM with changes in parasympathetic activity. Results: CCM was found to be most sensitive to changes in temporal structure of the Poincare plot as compared to SD1 and SD2. The values of all descriptors decreased with decrease in parasympathetic activity during atropine infusion and 70 degrees head-up tilt phase. In contrast, values of all descriptors increased with increase in parasympathetic activity during scopolamine administration. Conclusions: The concordant reduction and enhancement in CCM values with parasympathetic activity indicates that the temporal variability of Poincare plot is modulated by the parasympathetic activity which correlates with changes in CCM values. CCM is more sensitive than SD1 and SD2 to changes of parasympathetic activity.