Relationship of Magnetic Resonance Imaging Estimation of Myocardial Iron to Left Ventricular Systolic and Diastolic Function in Thalassemia
Benedetta Leonardi, MD,
Renee Margossian, MD,
Steven D. Colan, MD, FACC,
Andrew J. Powell, MD, FACC*
Department of Cardiology, Children's Hospital Boston, and the Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
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Figure 1 Relationship Between EF and Myocardial T2*
Among 24 subjects with transfusion-dependent thalassemia, there were 47 paired echocardiograms and magnetic resonance imaging (MRI) examinations performed within 1 month of each other. Left ventricular ejection fraction (EF) was measured with both echocardiography and MRI. Myocardial T2*, a parameter that varies inversely with tissue iron concentration, was measured by MRI and T2* <20 ms indicates an elevated iron level. The figure shows the relationship between myocardial T2* and percent EF measured by MRI (A) and by echocardiogram (B). Note that all patients with a depressed EF (<50%) by either modality have evidence of elevated myocardial iron but that not all patients with elevated myocardial iron have a depressed EF.
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Figure 2 Receiver-Operating Characteristic Curve Analysis
A receiver operating characteristic curve analysis was used to explore the sensitivity and specificity of threshold values of myocardial T2* for left ventricular dysfunction. Using a T2* threshold value of 9 ms, sensitivity = 1 and specificity = 0.86 for a MRI EF <50% (A), sensitivity = 0.77 and specificity = 0.85 for a MRI EF <55% (B), sensitivity = 1 and specificity = 0.83 for echocardiographic EF <50% (C), and sensitivity = 0.71 and specificity = 0.84 for an echocardiographic EF <55% (D). Thus myocardial T2* had a strong relationship with EF and appears to be a promising approach for predicting the development of heart failure and for iron chelator dose adjustment. Abbreviations as in Figure 1.
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