Patients with long QT syndrome exhibited a decreased correlation between the Q-aT and RR intervals compared to controls (median r 0.87 vs 0.93; P=0.001) and a steeper Q-aT/RR slope.
Case-Control (n=21)
Does the dynamic relationship between the Q-aT interval and heart rate differ between patients with long QT syndrome and control subjects during 24-hour Holter monitoring?
Patients with long QT syndrome exhibit abnormal T wave morphology that affects the Q-aT interval, resulting in a decreased correlation and steeper slope between Q-aT and RR intervals compared to healthy controls.
Absolute Event Rate: 0.87% vs 0.93%
p-value: p=0.001
The purpose of this study was to investigate the dynamic relationship between heart rate and the Q-aT interval (the interval from the Q wave to the T wave apex) in patients with long QT syndrome. The QT to heart rate relation is useful for evaluating abnormalities of the ventricular repolarization, but its clinical application to the long QT syndrome requires accurate computer aided measurement of the QT interval and the sampling of a large number of beats. Therefore, the Q-aT interval was used on the basis of some reports that the heart rate dependency of the QT interval was concentrated in the Q-aT interval. Recent advances in the computer technology have allowed analysis of the relationship between the Q-aT and RR intervals on Holter ECG recordings. However, in addition to a prolonged QT interval, most patients with long QT syndrome have bizarre and variable T waves and the influence of this T wave morphology on the Q-aT to heart rate relation has not been clarified. We investigated the dynamic relationship between the Q-aT interval and heart rate in 10 patients with long QT syndrome and 11 control subjects using our original computer algorithm for the analysis of 24-hour Holter ECG recordings. The patients showed morphological T wave changes associated with heart rate changes during Holter recordings and these affected the Q-aT interval. The patients showed the following characteristics in the relationship between the major T wave peak and the RR interval: (1) a modestly decreased correlation between Q-aT and RR than in the control subjects (a median r value of 0.87 vs 0.93; P = 0.001); and (2) a steeper Q-aT/RR slope than in controls (a median slope of 0.24 vs 0.16; P < 0.05). Abnormal and variable T wave morphology in the long QT patients was closely related to a modestly decreased correlation between Q-aT and RR than in the control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Emori et al. (Sun,) conducted a case-control in Long QT syndrome (n=21). Long QT syndrome vs. Control subjects was evaluated on Correlation between Q-aT and RR interval (r value) (p=0.001). Patients with long QT syndrome exhibited a decreased correlation between the Q-aT and RR intervals compared to controls (median r 0.87 vs 0.93; P=0.001) and a steeper Q-aT/RR slope.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: