Beat-to-beat measurement and analysis of the R-T interval in 24 h ECG Holter recordings.

This study assesses the feasibility of beat-to-beat measurement of the R-T interval in Holter ECG recordings. The low sampling rate of the Holter system was increased by a specific interpolating filter, and the precision and accuracy of two T-wave fiducial point (T-wave maximum: Tm, T-wave end: Te) detection algorithms were compared. The results of the validation tests show better performance of the Tm measurement procedure in the presence of high noise levels. The overall process for the beat-to-beat R-T interval measurement was then tested on ECG Holter recordings collected during free and controlled respiration. Finally, the R-Tm and the corresponding R-R intervals were measured on 24 h ECG recordings of healthy subjects and the spectral analysis was applied to the constructed series. Both R-R and R-Tm spectra show two main frequency components (low-frequency approximately 0.1 Hz, high-frequency approximately 0.25 Hz) changing in their power ratios continuously throughout the 24 h period. The method described seems to provide a dynamic index of the sympatho-vagal balance at the ventricle that can be useful for a deeper understanding of ventricular repolarisation duration variability.