Heart rate asymmetry by Poincare plots of RR intervals

The Poincare plot is a widely used method for visualizing and calculating heart rate variability and for investigating the oscillatory nature of heart action. We show that the Poincare plot produced using physiological data for FIR intervals is asymmetric. This suggests that the processes of heart rate acceleration (shortening of consecutive FIR intervals) and deceleration (prolongation of successive RR intervals) might be asymmetric. To investigate this phenomenon, we define descriptors quantifying the heart rate asymmetry and present the results of a study involving 5-min ECG recordings of 50 healthy subjects in which, despite of the shortness of the recordings, the asymmetry is clearly visible.