Myocardial iron loading in transfusion-dependent thalassemia and sickle cell disease

Authors
John C. Wood, Michael Tyszka, Susan Carson, Marvin D. Nelson, and Thomas D. Coates

Journal
Blood, 2004, Vol. 103 pp 1934-1936

Background
Cardiac T2* (magnetic resonance imaging relaxation parameter) is abnormally low in approximately 40% of adults with thalassemia major (TM), suggesting myocardial iron deposition, but it is unknown at what age this occurs. To address this question, we measured cardiac T2* and function in 19 young patients (aged 7-26 years) with TM as well as 17 patients receiving long-term transfusions for sickle cell anemia (SCA) matched for age, sex, and liver iron content. 

Results and Discussion

Cardiac T2* was normal in all of the SCA patients, but was low (high iron) in 8 of 19 TM patients. Abnormal T2* was observed only in the TM patients receiving transfusions for 13 years or longer and was correlated with ferritin but not liver iron levels. Cardiac dysfunction was present in 3 of the 8 patients with low T2* scores. Cardiac T2* changes have a long latency relative to liver iron accumulation. Total transfustional burden is a significant independent risk factor for cardiac T2* and may partially account for differences observed between patients with SCA and TM.

Methodology

• Inclusion criteria:
  • Diagnosis of either SCA or TM 
  • More than 8 blood transfusions annually for at least three years 
  • Pretransfusion hemoglobin level of 95 g/L 
  • Informed consent
• Patients were considered to have cardiac dysfunction if they required cardiac medication, had an ejection fraction of less then 60%, or had persistent arrhythmias.
• Data was collected from 5 consecutive monthly visits prior to the MRI
• Data was analyzed using unpaired Student t and Fischer exact tests.

Results

Abnormal T2* scores (< 25 ms) were observed in patients who had been transfused and chelated for 13 years or longer (8 of 19 patients), suggesting myocardial iron loading.



Cardiac dysfunction was present in 3 of the 8 patients with low T2* scores. 

Conclusions

Abnormal T2* scores are correlated with transfusion duration as well as increased risk of cardiac symptoms. Further study is needed to determine if T2* has a predictive capability. 

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