Effect of age on QT variability

Heart rate variability is influenced significantly by age. Recent studies have shown the utility of QT variability to study temporal repolarization lability, and increased QT variability is reportedly associated with sudden death. Because beat-to-beat QT interval variability appears to closely follow heart rate variability, this study investigated the relationship between age and QT variability. We obtained QT variability measures in 34 adults (22-55 years of age) and 15 children (6-14 years of age) using a novel algorithm to compute beat-to-beat QT intervals. QT variability corrected for mean QT interval was significantly inversely correlated with age. Coherence in the band of 0 to 0.5 Hz and high-frequency coherence (0.15-0.5 Hz) were also significantly inversely correlated with age. QTvi (QT variability corrected for mean QT interval over heart rate variability corrected for mean heart rate) was not significantly related to age in supine posture during spontaneous or controlled breathing, whereas there was a modest negative relationship in standing posture. These findings suggest that coherence between QT and heart rate time series appears to be modulated by cardiac vagal activity.