Validity of the software-hardware complex “Rytm” for measuring the RR intervals and heart rate variability at rest

Abstract

In order to perform the correct analysis of heart rate variability (HRV) by newly designed devices, it is necessary to confirm the sufficient level of accuracy in the registration of RR intervals. We have examined the accuracy of RR time series measurements by software-hardware complex “Rytm” (SHC “Rytm”) and validity of subsequently calculated HRV indexes at rest.The subjects were 20 healthy male adults20.0±0.27 years old. Recording of RR intervals was performed simultaneously with ECG recorder (CardioLab CE12), Polar RS800, and SHC “Rytm” during 5 minutes in the supine position at rest. HRV indexes were calculated by Kubios HRV 2.1. Intraclass correlation coefficients (ICC = 0,951–0,954), Bland–Altman limits of agreement (LoA = -22,89– 22,54 ms for SHC “Rytm” vs Polar) and paired t-test showed good agreement between all the devices in the measurements of RR intervals. No difference (P > 0.05) for HRV indexes, calculated from Polar RS800 and SHC “Rytm” data was found. There are some differences in HRV indexes, derived from the RR data of CardioLab CE12 and SHC “Rytm” (LF,% and pNN50) and also CardioLab CE12 and Polar RS800 (STD RR, RMSSD, pNN50, SD1, SD2). The results suggest that the SHC “Rytm” is able to capture series of RR intervals as reliable as those obtained by ECG and Polar RS800.We found good agreement between most of the HRV indexes based on data of SHC “Rytm” and medical electrocardiographic system.