Asymmetric properties of long-term and total heart rate variability

We report on two new physiological phenomena: the long-term and total heart rate asymmetry, which describe a significantly larger contribution of heart rate accelerations to long-term and total heart rate variability. In addition to the existing pair of indices, $${\text {SD1}}_{\rm d}, {\text {SD1}}_{\rm a},$$ which are based on partitioning short-term variance, we introduce two other pairs of descriptors based on partitioning long-term ($${\text {SD2}}_{\rm d}, {\text {SD2}}_{\rm a}$$) and total ($$ {\text {SDNN}}_{\rm d}, {\text {SDNN}}_{\rm a}$$) heart rate variability. The new asymmetric descriptors are used to analyze RR intervals time series derived from the 30-min ECG recordings of 241 healthy subjects resting in supine position. It is shown that both new types of asymmetry are present in 76% of the subjects. The new phenomena reported here are real physiological findings rather than artifacts of the method since they vanish after data shuffling.