Depolarization, Repolarization Inhomogeneity and Late Potential after Surgical Repair of Tetralogy of Fallot

Kim, Soo Young; Hyun, Myung Chul; Lee, Sang Bum; Kim, Seung Tae; Lee, Jong Soo

Abstract

PURPOSE: After repair of tetralogy of Fallot(TOF), ventricular arrhythmia and sudden death remain as serious late complications which are due to right ventricular systolic and diastolic overloading, exposure to hypoxia and surgical scar. Among the various methods for predicting the risk of such complications, we evaluated signal average ECG(SAECG), QRS duration, QT and JT dispersion, cardiothoracic(CT) ratio, age at repair and follow-up duration.
METHODS
Patients were divided into 3 groups : repaired TOF patients(group 1, n=22), patients with complete right bundle branch block(CRBBB) after ventricular septal defect and/or atrial septal defect repair(group 2, n=16) and normal controls(group 3, n=13). There were no significant differences in mean age at presentation, mean age at repair, or at mean follow up among the 3 groups.
RESULTS
QRS duration was significantly prolonged in group 1 and 2(121+/-29ms, 119+/-17ms, respectively) compared to group 3(81+/-4ms)(P<0.01). In group 1, QRS duration showed significant positive correlations with age at repair(r=0.43, P<0.05) and follow-up duration(r=0.46, P<0.05). QT dispersion was significantly increased in group 1 and 2(88+/-38ms, 71+/-27ms, respectively) compared to group 3(37+/-20ms)(P<0.01). JT dispersion showed significant differences among groups, being 96+/-38ms in group 1, 68+/-25ms in group 2, 44+/-18ms in group 3(group 1 vs 2 : P<0.05, group 2 vs 3 : P<0.05, group 1 vs 3 : P<0.01). CT ratio was significantly increased in group 1(59+/-6%) compared to group 2 and 3(50+/-3%, 50+/-2%, respectively)(P<0.01). There were no significant differences in parameters of SAECG among the 3 groups.
CONCLUSION
We concluded that abnormality of JT dispersion, in repaired TOF pateints indicating inhomogeneity of repolarization, can be a cause of ventricular arrhythmia.