Effect of age on QT variability

Heart rate variability is influenced significantly by age. Recent studies h ave shown the utility of QT variability to study temporal repolarization la bility, and increased QT variability is reportedly associated with sudden d eath. Because beat-to-beat QT interval variability appears to closely follo w heart rate variability, this study investigated the relationship between age and QT variability. We obtained QT variability measures in 34 adults (2 2-55 years of age) and 15 children (6-14 years of age) using a novel algori thm 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 als o significantly inversely correlated with age. QT(vi) (QT variability corre cted for mean QT interval over heart rate variability corrected for mean he art rate) was not significantly related to age in supine posture during spo ntaneous or controlled breathing, whereas there was a modest negative relat ionship in standing posture. These findings suggest that coherence between QT and heart rate time series appears to be modulated by cardiac vagal acti vity.