T2* magnetic resonance and myocardial iron in thalassemia.

Magnetic resonance T2* values of the myocardium are directly related to tissue iron levels. Minor effects from myocardial oxygenation and fibrosis are overwhelmed by the highly dominant iron effect in clinically relevant levels of myocardial iron overload. Myocardial T2* values less than 20 ms indicate iron overload, and this is considered severe when T2* is less than 10 ms. Decreasing myocardial T2* levels are associated with systolic and diastolic ventricular dysfunction. Most recorded cases of heart failure in thalassemia to date have occurred in patients with very low T2* values (in the severe range). Exceptions to this have occurred in patients with other causes of heart failure such as concomitant congenital heart disease. In patients presenting with heart failure who undergo aggressive chelation with continuous intravenous deferoxamine, longitudinal studies show that myocardial T2* increases, and this is accompanied by increases in ejection fraction and relief of heart failure. In cross-sectional studies, the myocardial T2* and ejection fraction of patients on deferiprone was superior to that of patients on deferoxamine. Randomized controlled prospective trials comparing these two drugs for their action in clearing myocardial iron, as measured by myocardial T2*, are under way and should report in 2005/2006. These trials will clarify the role of different chelators in the management of myocardial iron overload and may be valuable in reducing the toll of death in thalassemia from heart failure.