Open AccessVariability of the Interlead Synchronization of the T Wave: Beat‐to‐Beat ECG Analyses
Author(s) -
Lund Birgit,
Lund Kaspar,
Christiansen Evald Høj,
Pedersen Anders Kirstein
Publication year - 1998
Publication title -
annals of noninvasive electrocardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.494
H-Index - 48
eISSN - 1542-474X
pISSN - 1082-720X
DOI - 10.1111/j.1542-474x.1998.tb00037.x
Subject(s) - beat (acoustics) , medicine , standard deviation , reproducibility , physics , population , acoustics , statistics , cardiology , audiology , mathematics , environmental health
Background The mean intraobserver (two measurements) and interobserver (two observers) errors of dispersion of QT‐end (QTe‐d), corrected for heart rate, are 12 ms and 15 ms, respectively. One possible contribution to the low reproducibility is beat‐to‐beat variations, so we developed a surrogate of these variations, called the variability of the interlead synchronization of T waves (VST). Methods VST can be calculated for any pair of digitized leads, by cross‐correlation of the T wave and a substep alignment procedure that increases the precision from 0.5–0.2 ms. The precision of VST is relatively good (≠ 0.4 ms), because it bypasses the uncertain measurement of QT intervals. Conclusion The method was applied to Frank orthogonal leads of a small population of subjects (n = 9) with no cardiac history. The mean magnitudes and standard deviations (SD) of the magnitude of VST were in the range (mean ± SD) of 0.37 ± 0.28 to 2.93 ± 2.11 ms. This confirms the existence of a subject‐specific lower physical limit for the precision of QTe‐d in normal subjects. The results indicate that QTe‐d should be measured as a mean value of several beats if measured on the raw signal. This should, however, be verified by measurement of VST on larger populations. The results also indicate that optimal alignment of T waves requires the waves to be aligned individually, lead by lead. Notice, however, that if the mean beat is used for measurement of QTe‐d, then the alignment must be the same for all leads in each beat.