EARLY Detection of Cardiac and Hepatic Iron Overload by T2* Magnetic Resonance in Very Young Patients with Thalassemia Major in Oman

Despite availability of iron chelation, iron-mediated cardiac toxicity remains the leading cause of death in thalassemia major patients. Although serum ferritin is widely used as a measure of iron overload, this has been challenged by recent magnetic resonance imaging (MRI) studies. Magnetic resonance using myocardial T2* is a highly sensitive, non-invasive and reproducible technique for detection of myocardial iron content.

Seventy-four children are on follow-up at the Pediatric Thalassemia Day Care Center, Sultan Qaboos University Hospital, Muscat, Oman. Twenty-seven patients above the age of 7 years underwent T2* MRI procedure, and 9 of these patients had a follow-up T2* MRI at an interval of 1 year. MRI T2* was introduced at our institution in 2007 but was performed only on patients over the age of 12 years as it was thought that younger children would be unable to comply with the requirements of the MRI examination. Initially, we found that many of our patients failed to complete the procedure for T2* MRI (28.5% failure rate) mainly because of their inability to either hold their breath in expiration or due to movement during the procedure. But after training by physiotherapy we were successful in completing the procedure in children as young as 7 years, with no failures without the use of general anesthesia, as has been practiced by some centers.

Previous reports reveal no detectable cardiac iron in patients with thalassemia major less than 9.5 years of age. But we have detected in our patients severe and mild cardiac iron overload at the age of 7.5 years and 9.5 years respectively. At the time of the initial T2*MRI, the patient with severe cardiac iron overload was on chelation with Desferrioxamine with sub-optimal compliance, with a ferritin of 2605 ng/ml and a T2* MRI cardiac value of 9.3 ms. Repeat T2* MRI after 18 months (despite extensive counseling and optimization of chelation) revealed a cardiac T2* value of 4.8 ms at a ferritin level of 2796 ng/ml revealing that cardiac siderosis worsened despite the fairly constant ferritin level and the patient was shifted to combination chelation therapy. Also 44.5 % of our patients have moderate to severe hepatic iron overload. All these children were on regular 3–4 weekly follow-up for transfusion therapy with serial monitoring of ferritin levels guiding the chelation therapy. Of these, 62.9% (n=17) are on Deferiprone monotherapy at a mean dose 85.7 mg/kg, 33.3 % (n=9) are on combination chelation therapy with Deferiprone and Desferrioxamine, mean dose 95.6 mg/kg and 36.6 mg/kg respectively, and 14.2% (n=1) on Deferasirox at a dose of 40 mg/kg. Our results revealed inadequate iron chelation in some of our patients, most probably due to sub-optimal compliance that was not detected by serial ferritin monitoring (mean =1309 ng/ml). Moreover there was a poor correlation of ferritin to cardiac T2* and hepatic T2* values.

With compliance to chelation therapy being a major issue in our patients, and failure of ferritin levels to predict the severity of cardiac and hepatic iron overload in some of the patients in a younger age group; we emphasize the importance of early and routine T2* MRI to detect organ iron overload for timely intervention with optimal iron chelation therapy in patients with thalassemia major.

No relevant conflicts of interest to declare.