Genotypic groups as risk factors for cardiac magnetic resonance abnormalities and complications in thalassemia major: a large, multicentre study.

Background: The causes and effects of genotypic heterogeneity in beta-thalassemia major (β-TM) have not been fully investigated. The aim of this multicentre study was to determine whether different genotype groups could predict the development of cardiovascular magnetic resonance abnormalities and cardiac complications.
Materials and Methods: We considered 708 β-TM patients (373 females, age 30.05±9.47 years) consecutively enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) network. Data were collected from birth to the first cardiac magnetic resonance scan. Myocardial iron overload was assessed using a T2* technique. Biventricular function was quantified by cine images. Macroscopic myocardial fibrosis was evaluated by a late gadolinium enhancement technique.
Results: Three groups of patients were identified: β ⁺ homozygotes (n=158), β ⁺ /β° heterozygotes (n=298) and β° homozygotes (n=252). Compared to β ⁺ homozygotes, the other two groups showed a significantly higher risk of myocardial iron overload and left ventricular dysfunction. We recorded 90 (13.0%) cardiac events: 46 episodes of heart failures, 38 arrhythmias (33 supraventricular, 3 ventricular and 2 hypokinetic) and 6 cases of pulmonary hypertensions. β° homozygotes showed a significantly higher risk than β ⁺ homozygotes of arrhythmias and cardiac complications considered globally.
Discussion: Different genotype groups predicted the development of myocardial iron overload, left ventricular dysfunction, arrhythmias and cardiac complications in β-TM patients. These data support the importance of genotype knowledge in the management of β-TM patients.