Methods. We prospectively evaluated electrocardiography (ECG) parameter of QTc interval in 50 β-thalassemia major patients aged 10-18 years. All participants had a 12-lead ECG evaluation, echocardiogram and cardiac MRI T2* examination within three months (average 15 days). They were categorized as cardiac iron overload (MRI T2* <20 millisecond) and non-cardiac iron overload (MRI T2* >20 millisecond).
Results. Of the 50 patients, the male to female ratio was 1.08:1 and the mean age was 13.7 ± 2.43 years. All participants showed normal systolic and diastolic function using conventional echocardiography. The mean QTc interval was significantly different between cardiac iron overload group (464.44 ± 20.35 ms) and noncardiac iron overload group (431.09 ± 32.29) (p= 0.001). Diagnostic study of QTc interval resulted in AUC 0.8 (p= 0.002). Calculated sensitivity and specificity of QTc interval were 0.88 and 0.73 respectively, with cut-off point of 449 ms.
Conclusion. Cardiac iron overload is associated with QTc prolongation in adolescents. QTc interval of 449 ms could be considered as a cut-off point of cardiac iron overload.
Keywords : adolescent, β- thalassemia major, cardiac MRI T2*, QTc interval