ELECTROCARDIOGRAPHIC MARKERS OF LATE SUDDEN-DEATH RISK IN POSTOPERATIVE TETRALOGY OF FALLOT CHILDREN

Following surgery for tetralogy of Fallot (TOF), children may develop late onset ventricular arrhythmias. Many patients have both depolariza tion and repolarization abnormalities, including right bundle branch b lock (RBBB) and QT prolongation. The goal of this study was to improve prospective risk-assessment screening for late onset sudden death. Re sting ECG markers including QRS duration, QTc, JTc, and interlead QT a nd JT dispersion were statistically analyzed to identify those patient s at risk for ventricular arrhythmias and sudden cardiac death, To det ermine predictive markers for future development of arrhythmia, we exa mined 101 resting ECGs in patients (age 12 +/- 6 years) with postopera tive TOF and RBBB, 14 of whom developed late ventricular tachycardia ( VT) or sudden death. These ECGs were also compared with an additional control group of 1000 age-and gender-matched normal ECGs. The mean QRS (+/- SD) in the VT group was 0.18 +/- 0.02 seconds versus 0.14 +/- 0. 02 seconds in the non-VT group (P < 0.01). QTc and JTc in the VT group was 0.53 +/- 0.05 seconds and 0.33 +/- 0.03 seconds compared with 0.5 0 +/- 0.03 seconds and 0.32 +/- 0.03 seconds in the non-VT group (P = NS). There was no increase in QT dispersion among TOF patients with VT or sudden death compared with control patients or TOF patients withou t VT, although JT dispersion was more common in the TOF groups. A prol onged QRS duration in postoperative TOF with RBBB is more predictive t han QTc, JTc, or dispersion indexes for identifying vulnerability to v entricular arrhythmias in this population, while retaining high specif icity, The combination of both QRS prolongation and increased JT dispe rsion had very good positive and negative predictive values, These res ults suggest that arrhythmogenesis in children following TOF surgery m ight involve depolarization in addition to repolarization abnormalitie s. Prospective identification of high-risk children may be accomplishe d using these ECG criteria.