Objectives: The aim of our study was to assess the effect of long-term right ventricular (RV) volume overload on repolarization. The reason was a frequent observation of prolonged QTc intervals in children prior to atrial septal defect (ASD) closure.
Methods: QRS, QTc and JTc intervals were measured manually from leads II and V5 of standard ECGs in 45 children with an isolated ASD a day before and at least 6 months after the ASD closure. Each QTc was compared to gender and age matched normal values. RV dimensions were obtained from echocardiographic M-mode images.
Results: The prevalence of prolonged QTc decreased from 22.2 to 2.2 % after surgery (p= 0,007). Individual QTc intervals shortened significantly (Table) whereas QRS duration did not change. There was a highly significant correlation between the change in QTc and JTc intervals (R=0.741, p<0.001). RV dimensions did not correlate with QTc values. Inter- and intra-observer coefficient of variation for QTc measurements was 2.53 and 1.45 %, resp.
| QTc ms |
Prior to surgery | After surgery | P value |
| Lead II mean (SD) | 418 (25) | 380 (25) | <0.001 |
| Lead V5 mean (SD) | 412 (26) | 378 (25) | <0.001 |
Conclusions: Prolonged QTc intervals occur frequently in children with hemodynamically relevant ASD and may not reflect an inborn channelopathy but rather a reversible effect of myocyte stretch on ion channel function. Such mechano-electrical feedback might participate in arrhythmogenesis in patients with more complex heart defects and significant residual RV volume overload
(Supported by MHCZ-DRO, University Hospital Motol, Prague, Czech Republic 00064203).