A new approach to the analysis of numeric series of 100 R–R intervals duration in studying heart rate dynamics

Abstract

The aim of the investigation was to assess a new approach to the analysis of variations in 100 successive R‒R intervals duration in determining heart rate dynamics variants during an orthostatic test. Materials and Methods. Electrocardiogram was recorded and duration of 100 R‒R intervals following each other was measured during an orthostatic test in 74 healthy children aged 12.8±0.16 years, 34 of which were training to play football during 1.5‒2 years. While processing numeric series of 100 R‒R intervals we were the first to apply color coding of each value, including those corresponding to the “true” heart rate (THR) parameter. For this purpose, having divided the region of R‒R interval values from 0.35 to 1.25 into i spaces by 0.15 s, each interval value depending on its belonging to i, as well as R‒R intervals corresponding to THR, were marked by a certain color. A THR parameter was determined by a known empirical equation (118.1‒0.57a) beats per minute, where a is age in years. Evaluating the whole set of parameters: mode (Mo, s) — the most frequently occurring R‒R interval duration; mode amplitude (AMo) — a number of Mo value repetitions — some of which were used in cardiointervalography for the first time (a total quantity of i spaces, in which R‒R interval variations occurred — it; the quantity of transitions from one space i to another — Nabs; R‒R duration corresponding to THR). Results. The approach developed made it possible to present clearly the change of the heart rate in time, to assess quantitatively the heart rate dynamics in time and determine the variants of its alteration in the orthostatic test. Their set in healthy children with a high level of physical activity has been found to be similar, though the ratio of diverse variants is different: in changing over to orthostasis cases of a weak influence of the vegetative nervous system on the heart rate occur more often in the young football players than in children with a lower physical load. Conclusion. Application of color coding of the R‒R intervals succession and assessment of the suggested set of parameters for heart rate variability investigation make it possible to present clearly heart rate dynamics and evaluate activity intensity of various parts of the vegetative nervous system without conversion of the numeric series of R‒R interval succession to the analog form. The software for automated processing of the investigated data, created on the basis of the algorithm suggested by us, provides the opportunity to assess a vegetative control of the heart rate in various groups under investigation.