Features of the Heart Electric Field In Children With Long QT Syndrome

Abstract

Anomalies in the ventricular repolarization process in patients (pts) with congenital long QT syndrome (LQTS) were discussed repeatedly but in no way - anomalies in their ventricular depolarization process. to estimate the features of body surface potential distributions QRS complex and ST-T interval in children with LQTS of different types. body surface potential mapping (BSPM) was carried out in 27 children with congenital LQTS (age - 12,7±3,4; 15 girls, 12 boys). The family history, course of disease, results of clinical tests and genetic analysis (in 15 cases) were the reasons for determining the type of LQTS. 15 pts were attributed to LQT1, 9 pts to LQT2, 1 pt to LQT3, LQT5 and LQT7 accordingly. Cardiag System (Czech Republic) with simultaneous ECG registration in 80 unipolar chest leads was used for BSM at rest. Isopotential and isointegral maps of the QRS complex, ST-T interval and QRST were observed. 5 of 15 pts (33%) with LQT1 revealed accessory negative extrema in the potential distributions during ventricular depolarization (in the middle of ventricular septum and anterior wall of LV projections). The potential distributions during ventricular repolarization in pts with LQT1 had no features. 4 of 9 pts (44%) with LQT2 revealed the wide zone of negative depolarization potentials on the anterior chest surface extending through the anterior wall of RV, top and middle of ventricular septum, whole of anterior wall of LV. 8 of 9 pts (88%) with LQT2 had the extensive zone of negative repolarization potentials on the right and middle chest surface extending to the left up to V6. Pts with LQT3 and LQT5 had no visual features of body surface maps in comparison with normal distributions. The distribution of heart electric field in pt with LQT7 was changed significantly as at de- as at repolarization. The maps of the QRS complex had an extensive negative zone on the anterior chest surface similarly to LQT2, the maps of the ST-T interval presented an extensive negative zone on the back and left chest. Our results testify to the presence of anomalies of both depolarization and repolarization processes in the heart of child with congenital LQTS. Body surface potential distributions in QRS complex and ST-T interval reveal characteristic features of the different localization in children with LQTS1 and LQTS2.