Increased QT variability in young asymptomatic patients with beta-thalassemia major

Despite recent progress in iron chelation therapy, sudden cardiac death due to malignant ventricular arrhythmias remains a vexing, clinical problem in patients with beta-thalassemia major (TM). In this study we assessed whether the major indices of QT variability, emerging tools for risk stratification of sudden cardiac death, differ in young asymptomatic patients with TM and healthy persons.

Thirty patients with TM and 30 healthy control subjects underwent a 5-min electrocardiography recording to calculate the following variables: QT variance (QT(v)), QT(v) normalized for mean QT (QTVN) and QT variability index (QTVI). All subjects also underwent a two-dimensional and Doppler echocardiography study and magnetic resonance imaging (MRI) to determine cardiac and hepatic T2* values.

No differences were observed in clinical and conventional echo-Doppler findings in healthy control subjects and patients with TM whereas QT(v), QTVN and QTVI values were significantly higher in patients than those in controls (QT(v), P < 0.001; QTVN, P < 0.05 and QTVI, P < 0.001) and cardiac T2* and hepatic MRI T2* values were significantly lower in patients with TM (P < 0.001). The indices of temporal QT variability correlated significantly with MRI data.

Young asymptomatic patients with TM have increased cardiac repolarization variability as assessed by QT variability indices, probably due to cardiac iron deposition. These easily assessed, non-invasive markers could be used to identify increased myocardial repolarization lability early in asymptomatic patients with TM.