[Analysis of frequency-dependence of ventricular repolarisation by the Holter method in young adults. Influence of the autonomic nervous system on the rate-dependence of QT].
Adaptation of ventricular repolarization duration to heart rate provides additional information to the static duration of QT interval.


METHODS
QT/RR relation and his slope were determined using 24-hour ECG recordings from 17 young male normal volunteers (mean age: 22 +/- 3 years). In order to determine the influence of the autonomic nervous system on the rate-dependence of QT, the authors compared the slopes obtained from recordings during the day and the night. Then, the respective rate-dependences of the entire QT interval (QTe) and its initial subdivision (QTa) and their correlations with parameters of heart rate variability were studied.


RESULTS
the QTa/RR and QTe/RR relations were constantly linear, with very significant regression coefficients. The daytime QTa/RR and QTe/RR slopes were significantly steeper than the nighttime ones (0.138 +/- 0.035 vs 0.108 +/- 0.040, p < 0.05 for QTe/RR, 0.160 +/- 0.069 vs 0. 108 +/- 0.055, p < 0.01 for QTa/RR). The early part of QT showed a stronger rate-dependence than the global QT, but only at daytime (0.160 +/- 0.069 vs 0.138 +/- 0.035, p < 0.05). No correlation was found between rate dependences and heart rate variability parameters.


CONCLUSIONS
the authors demonstrate, from ambulatory ECG recordings, the influence of the autonomic nervous system on the rate-dependence of ventricular repolarization in normal young adults, and a difference in rate-dependence between the entire QT interval and its initial part QTa, due to differences in autonomic nervous system tone. This heterogeneity should be taken to account in the study of pathological changes or drugs effects on ventricular repolarization.
Catuli
D
D
Hôpital Necker, Paris.
Maison-Blanche
P
P
Fayn
J
J
Rubel
P
P
Larroque
P
P
Vacheron
A
A
Coumel
P
P
D000293:Adolescent; D001145:Arrhythmias, Cardiac / Q000175:diagnosis; D001341:Autonomic Nervous System / Q000502:physiology*; D002940:Circadian Rhythm; D015716:Electrocardiography, Ambulatory / Q000706:statistics & numerical data; D006329:Heart Conduction System / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012815:Signal Processing, Computer-Assisted; D012984:Software; D016276:Ventricular Function / Q000502:physiology