Myocardial Iron Overload (Siderosis)
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Author: Amit R. Patel
Published Date: 11/1/2017

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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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