Comparison of heart rate variability parameters calculated by two different commercial analysis systems

The heart rate variability parameters in the time and frequency domain are compared between two commercial Holter systems (Oxford Excel II ver7.1, and Marquette Laser S ver002A). A total of 35 recordings were analyzed by both systems. In the time domain, the standard deviation of the normal RR intervals (SDNN), the mean of the 5 minute standard deviations for the normal RR intervals (SDNNi), the standard deviation of the 5 minute average for the RR intervals (SDANNi), the root mean square of differences in successive RR intervals (rMSSD), and the percentage of intervals that are at least 50 msec different from the previous one (pNN50) were measured. The total power and the low and high frequency power were estimated by spectral analysis. All time and frequency domain parameters were closely correlated (p<0.001), however InHFP and rMSSD were significantly higher when analyzed by the Oxford system. These differences should be considered when results obtained by different systems are compared.