Cardiac iron monitoring by MRI T2* is essential for people with transfusion-dependent thalassemia
In patients with transfusion-related iron overload, the two key target organs for iron accumulation are the heart and liver. Although the liver is the major site of iron storage, the smaller amount of iron that goes to the heart can have more serious clinical consequences, including arrhythmias, cardiac failure, and death.
Since serum ferritin and liver iron are not strong predictors of the level of iron deposition in the heart, cardiac iron content should be directly evaluated on a regular basis in patients with transfusion-dependent thalassemia syndromes, in order to determine the risk of iron-related cardiac damage and monitor the effectiveness of the patient’s current chelation regimen in removing excess iron from the heart. [SOC guidelines 2012; Pennell 2013 AHA guidelines]
Magnetic resonance imaging (MRI) is currently the preferred method for assessing iron levels in the heart, as it is non-invasive, widely available, and able to measure iron load in a reliable and quantitative manner. The recommended MRI sequence for measuring cardiac iron is T2*, which is inversely correlated with iron content, i.e., the lower the value, the higher the iron level. [SOC guidelines 2012; Pennell 2013 AHA guidelines]
Cardiac T2* values 20 milliseconds (ms) or lower indicate clinically significant levels of cardiac iron loading. [SOC guidelines 2012; Pennell 2013 AHA guidelines]
Assessment of cardiac iron by MRI T2* should start early in the patient’s life, ideally around age 6 to 10. If an older patient has never previously been evaluated using cardiac MRI, he or she should undergo a baseline scan as soon as possible to help determine his or her risk profile and define the optimal strategy for chelation therapy. [Pennell 2013 AHA guidelines]
The recommended frequency of ongoing cardiac MRI monitoring will depend on the patient’s degree of cardiac iron overload: [Pennell 2013 AHA guidelines]
- If a patient’s initial scan(s) show(s) heart iron in the normal range, (above 20 ms), follow-up scans should be performed approximately annually thereafter.
- Scans should be completed more frequently – every 6 months – in patients at higher cardiac risk due to elevated cardiac iron content (T2* under 10 ms), poor treatment compliance, or reduced left ventricular ejection fraction.
The cardiac T2* sequence can be run on most MRI machines currently in use, provided that the appropriate software has been installed. To find the center nearest you that offers cardiac T2*, enter your address and/or ZIP code into the interactive map.