Myocardial Iron Overload (Siderosis)
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Author: Amit R. Patel

Published Date: 11/1/2017

Indications and Purpose of the Scan:

  • The presence of myocardial iron overload is rare but without treatment can be associated with significant risk of death and heart failure.
  • CMR T2* imaging can be used to detect and quantify the burden of myocardial iron overload.
  • CMR T2* imaging can be used to risk stratify patients with known or suspected myocardial iron overload.
  • T2* relaxation times can be used to guide iron chelation therapy in patients with myocardial iron overload.

Description:

  • During a single, short, breath-hold, a series of images are acquired at increasing echo times (TE). 
  • The signal intensity of the mid-ventricular septum is determined for each of the images. The signal intensity is plotted against the echo time and the T2* relaxation time is calculated. This is typically done using special software.

Why CMR (specific advantages):

  • Myocardial iron overload can be very difficult to detect with commonly used tests such as serum ferritin levels, electrocardiography, or echocardiography. However, CMR T2* imaging is considered the reference standard for detecting and quantifying myocardial iron overload.
  • Abnormalities in CMR T2* can occur prior to the development of systolic or diastolic dysfunction.
  • CMR T2* imaging can be used to guide iron chelation therapy to prevent heart failure in patients with myocardial iron overload.

Evidence:

  • Leonardi et al. JACC Cardiovascular Imaging 2008. In transfusion dependent thalassemia, echocardiographic diastolic function parameters correlated poorly with EF and myocardial T2* and were thus not well-suited for risk stratification. 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.
  • Kirk et al. Circulation 2009. Cardiac T2* magnetic resonance identifies patients at high risk of heart failure and arrhythmia from myocardial siderosis in thalassemia major and is superior to serum ferritin and liver iron. Using cardiac T2* for the early identification and treatment of patients at risk is a logical means of reducing the high burden of cardiac mortality in myocardial siderosis. 
  • Modell et al. Journal of Cardiovascular Magnetic Resonance 2008. Since 1999, there has been a marked improvement in survival in thalassaemia major in the UK, which has been mainly driven by a reduction in deaths due to cardiac iron overload. The most likely causes for this include the introduction of T2* CMR to identify myocardial siderosis and appropriate intensification of iron chelation treatment, alongside other improvements in clinical care.

References:

  1. Modell B, Khan M, Darlison M, Westwood MA, Ingram D, Pennell DJ. Improved survival of thalassaemia major in the UK and relation to T2* cardiovascular magnetic resonance. Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance 2008;10:42.
  2. Anderson LJ, Holden S, Davis B et al. Cardiovascular T2-star (T2*) magnetic resonance for the early diagnosis of myocardial iron overload. European heart journal 2001;22:2171-9.
  3. Wood JC, Tyszka JM, Carson S, Nelson MD, Coates TD. Myocardial iron loading in transfusion-dependent thalassemia and sickle cell disease. Blood 2004;103:1934-6.
  4. Leonardi B, Margossian R, Colan SD, Powell AJ. Relationship of magnetic resonance imaging estimation of myocardial iron to left ventricular systolic and diastolic function in thalassemia. JACC Cardiovascular imaging 2008;1:572-8.
  5. Kirk P, Roughton M, Porter JB et al. Cardiac T2* magnetic resonance for prediction of cardiac complications in thalassemia major. Circulation 2009;120:1961-8.
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