DEPOLARIZATION-REPOLARIZATION INHOMOGENEITY AFTER REPAIR OF TETRALOGYOF FALLOT - THE SUBSTRATE FOR MALIGNANT VENTRICULAR-TACHYCARDIA

Background We have previously shown that QRS prolongation (greater tha n or equal to 180 ms) is a risk marker for sustained ventricular tachy cardia (VT) late after repair of tetralogy of Fallot (rTOF). We have n ow examined the dispersion of QT and its components QRS and JT, in an attempt to determine whether any association exists between these meas urements and the presence of VT in these patients. Methods and Results QRS duration and QT/QRS/JT dispersion were measured manually from sta ndard ECGs in 10 syncopal rTOF patients (21.4+/-4.6 years after repair ; group 1) with QRS greater than or equal to 180 ms and with documente d VT and were compared with 9 rTOF patients with QRS greater than or e qual to 180 ms and no VT (group 2), 40 rTOF patients with QRS <180 ms and no clinical arrhythmias (group 3), and 40 nontetralogy control sub jects (20 with right bundle-branch block [group 4] and 20 with normal ECG patterns [group 5]). Mean QT dispersion (62+/-36 ms) in the tetral ogy patients was greater than in the nontetralogy control subjects (34 +/-10 ms, P<.001). There were significant differences in all measured parameters between groups 1 and 3 and more importantly between groups 1 and 2. QRS dispersion in group 1 also correlated with QRS duration b ur not with JT dispersion. Conclusions Our data suggest that both depo larization and repolarization abnormalities are associated with VT aft er rTOF. Furthermore, increased QT, QRS, and JT dispersions, combined with a QRS greater than or equal to 180 ms, refine risk stratification for VT in these patients.