The influence of QRS width on the outcome of heart rate variability

Analysis of heart rate variability (HRV) is used to assess autonomic control of the heart. Many technical aspects may influence the outcome of the HRV analysis. One of these aspects is the accuracy of onset QRS detection. Inconsistent determination of QRS onset may result in artificial variations, especially in patients with wide QRS complexes. The purpose of the present study was to investigate the effect of QRS width on the outcome of HRV analysis. After manual correction of the onset of QRS: HRV variables averaged over 24 hours showed changes up to 10% in patients with wide QRS complexes. However, comparing single 5 minute segments before and after manual correction of onset QRS, much larger differences were observed. Especially variables reflecting beat to beat changes (time as well as frequency domain) showed substantial differences. The average effect of manual QRS onset correction in single 5 minute segments proved to be 5.3% for rMSSD, 5.2% for high frequency power (0.15-0.40 Hz) and 1.3% for low frequency power (0.04-0.15 Hz). We conclude that accurate detection of QRS onset plays an important role in the outcome of HRV analysis, especially in the analysis of short segments and patients with wide QRS complexes.