Ventricular Inhomogeneity and Beat-to-beat QT Interval Variability after Surgical Repair of Tetralogy of Fallot

Kim, Su Hyun; Yum, Myung Kul; Kim, Nam Su; Kim, Chang Ryul; Lee, Chul Burm; Noh, Chung Ill; Kim, Hee Soo

Abstract

PURPOSE: The object of this study is to determine whether QT interval variability in patients with postoperative tetralogy of Fallot increases.
METHODS
We enrolled 41 patients who had total correction of tetralogy of Fallot, and 31 healthy controls. They were 6-12 years old. Patients were divided into 2 groups : arrhythmia-positive patients(n=10) who had ventricular premature contractions more than 30/hour or who had couplets, and arrhythmia-negative patients(n=31). We selected the 10-minute arrhythmia-free portion of 24-hour ambulatory ECG recorded during sleep(1-3AM). We selected the 2nd beat of recordings for a template, then found the QT interval for each beat. The method was that T-wave shape best matches template T-wave under the time-stretch model. The mean heart rate and variance and mean QT interval and variance were computed and then a QT variability index(QTVI)-which represents the log ratio between QT interval variability and heart rate variability-was derived.
RESULTS
Postoperative tetralogy of Fallot patients with/without ventricular arrhythmia showed significantly increased QTVI compared with the control(-0.481+/-0.310/-0.661+/-0.376 vs -1.200+/-0.380, P<0.0001). There was a trend that QTVI in patients with ventricular arrhythmia increased more than in patients without ventricular arrhythmia, but there were no statistical significances.
CONCLUSION
QT interval variability increased in repaired tetralogy of Fallot patients with/without ventricular arrhythmia compared with the control. And this finding indicates that inhomogeneity of temporal ventricular repolarization exists in repaired tetralogy of Fallot patients.