Dispersion of repolarization and beta-thalassemia major: the prognostic role of QT and JT dispersion for identifying the high-risk patients for sudden death.

BACKGROUND: Patients with beta-thalassemia major (β-TM) are at increased risk for sudden cardiac death (SCD). Heterogeneity of ventricular repolarization is considered to provide an electrophysiological substrate for malignant arrhythmias. QT dispersion (QTc-D) and JT dispersion (JTc-D) are electrocardiographic parameters indicative of heterogeneity of ventricular repolarization. The aim of our study was to evaluate the heterogeneity of ventricular repolarization in patients with beta-thalassemia and to test the hypothesis that an abnormal QTc and JTc dispersion may predict SCD in this population.
MATERIALS AND METHODS: The study involved 51 patients with β-TM (age 33.9±8.4; 33M) and 51 healthy subjects used as controls, matched for age, gender, and body mass index (BMI). Among the β-TM group, 14 patients with β-TM (age 27±6.64; 11M) died from SCD during follow-up. For each patient, QTD and JTD intervals were calculated.
RESULTS: Compared to the healthy control group, β-TM group presented increased values of the QTc-D (65.36±33.95 vs. 37, 62±17.65; P<0.003) and JTc-D (74.64±33.27 vs. 40.32±12.45; P<0.001). In the β-TM sudden death group, QTc-D and JTc-D were significantly greater than in survived β-TM group (92.70±44.24 vs. 56.14±23.80, P=0.0001; 101.54±47.93 vs. 64.47±17.90, P=0.0001). A cutoff value of 70ms for QTc-D had a sensitivity and specificity of 77% in identifying patients at risk for SCD. A cutoff value of 100ms for JTc-D had a sensitivity of 65% and a specificity of 94% in identifying this category of patients.
CONCLUSION: β-TM is associated with significant changes in heterogeneity of ventricular repolarization. QTc and JTc dispersion are useful markers of risk of SCD in patients with β-TM.