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.