Arrhythmogenic substrate in young patients with repaired tetralogy of Fallot: Role of an abnormal ventricular repolarization

Ventricular repolarization analysis has been shown to be effective in the i dentification of electrical myocardial instability leading to ventricular a rrhythmias. The aim of the present study was to examine ventricular repolar ization time indexes, in terms of both absolute measures and dispersion acr oss the myocardium, in young patients with repaired tetralogy of Fallot (41 pts; 28M/13F, age 11.7+/-3.6 years), assessing, furthermore, the possible influence of known negative prognostic factors relative to the surgical ope ration and residual haemodynamic abnormalities. The data of the study group were compared with those of 33 aged-matched asymptomatic control subjects (22M/11F, age 11.7+/-2.3 years). Ventricular depolarisation, as expressed b y QRS duration, resulted significantly longer in total Fallot group than in the Control group (P<0.0001). Particularly, patients operated through a ri ght ventricular approach showed higher values of QRS interval (P<0.0001) th an those operated through a combined transatrial-transpulmonary approach. A ll the patients operated on for tetralogy of Fallot exhibit, with respect t o control subjects, an inhomogeneous prolongation of ventricular repolariza tion across the myocardium, as showed by the significant increase in the ab solute indexes of ventricular repolarization, JTc (P<0.001), QT (P<0.0001) and QTc (P<0.0001) with a concomitant prolongation of the indexes of disper sion of ventricular recovery time, QTcD (P<0.0001), JTcD (P<0.0001), 'adjus ted' QTcD (P<0.001) and Tp-Te interval (P<0.0001). A temporal and regional variation in the ventricular repolarization across the myocardium in patien ts with repaired tetralogy of Fallot, could create the pathophysiological s ubstrate for an increased cardiac electrical instability. The presence of n egative prognostic factors, relative to the surgical intervention or residu al haemodynamic abnormalities, even if not influencing the arrhythmic subst rate, invariably present, could determine 'trigger' conditions essential fo r the development of ventricular arrhythmias. (C) 1999 Elsevier Science Ire land Ltd. All rights reserved.