BEAT-TO-BEAT MEASUREMENT AND ANALYSIS OF THE R-T INTERVAL IN 24-H ECGHOLTER 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 H olter system was increased by a specific interpolating filter, and the precision and accuracy of two T-wave fiducial point (T-wave maximum: T(m), T-wave end: T(e)) detection algorithms were compared. The result s of the validation tests show better performance of the T(m) measurem ent procedure in the presence of high noise levels. The overall proces s for the beat-to-beat R-T interval measurement was then tested on ECG Holter recordings collected during free and controlled respiration. F inally, the R-T(m) and the corresponding R-R intervals were measured o n 24 h ECG recordings of healthy subjects and the spectral analysis wa s applied to the constructed series. Both R-R and R-T(m) spectra show two main frequency components (low-frequency approximately 0.1 Hz, hig h-frequency approximately 0.25 Hz) changing in their power ratios cont inuously throughout the 24 h period. The method described seems to pro vide a dynamic index of the sympatho-vagal balance at the ventricle th at can be useful for a deeper understanding of ventricular repolarisat ion duration variability.