Myocardial iron load measured by cardiac magnetic resonance imaging to evaluate cardiac systolic function in thalassemia.

Background: The assessment of cardiac iron overload in thalassemia major has been considered as an important predictive factor of heart injury. The magnetic resonance imaging (MRI)-derived relaxation time parameter (T2*) varies inversely with iron level, and elevated myocardial iron levels by T2* are associated with depressed left ventricular (LV) ejection fraction (EF). We compared echocardiographic (ECHO) indices of systolic function to myocardial T2* in these patients.

Methods: A cross-sectional database review identified 200 consecutive patients with thalassemia who underwent both ECHO and MRI T2* assessment.

Results: There was a negative correlation between T2* measurement and ECHO EF (r = -0.389, P < 0.001). Using a cutoff value of 50% for differentiating LV normal and abnormal function by ECHO, T2* MRI had a sensitivity of 57.1%, a specificity of 89.9%, and an accuracy of 86.5% for predicting LV dysfunction. Receiver operating characteristic analysis showed that cardiac iron measurement had an acceptable value for discriminating normal and abnormal LV function (area under the curve = 0.769, 95% confidence interval: 0.653-0.885). With respect to the relationship between serum ferritin level and cardiac iron value, the level of serum ferritin was positively correlated with the level of cardiac iron load (r = 0.257, P < 0.001).

Conclusion: Myocardial iron load assessed by MRI T2* is associated with deterioration of the LV function assessed by ECHO with a high specificity and moderate sensitivity. It is important to identify the thalassemic patients with a risk of iron overloaded cardiomyopathy and heart failure.