A comparison of magnetic resonance imaging and cardiac biopsy in the evaluation of heart iron overload in patients with β-thalassemia major

Objectives: To apply magnetic resonance imaging (MRI) for the assessment of myocardial iron deposition in patients with beta-thalassemia and compare the results with cardiac biopsy data. Background: Myocardial iron accumulation is the main cause for cardiac complications in beta-thalassemia. Methods: Twenty-five consecutive thalassemic patients were studied using a 0.5-T (Tesla) system, ECG-gated, with echo time (TE) = 17-68 ms. T2 relaxation time of the interventricular septum was calculated assuming simple monoexponential decay. A heart T2 relaxation time value of 32 ms was used for the discrimination between high and low iron deposition. Heart biopsy was performed within a week after the MRI study. Patients with stainable iron in more than 50% of the myofibrils were graded as having severe iron deposition. A serum ferritin level below 2000 ng/mL was considered as an indication of successful chelation. Results: Seven of the 25 patients had heart biopsy indicative of low iron deposition (Group L) and the remaining 18 patients had heart biopsy indicative of high iron deposition (Group H). T2 relaxation time of the heart (T2H) was lower in Group H compared to Group L (31.5 +/- 3.9 (range: 28-40) ms vs. 35.7 +/- 3.7 (range: 29-40) ms, P = 0.026). The T2H was in agreement with heart biopsy in 86% of the patients in Group L and in 78% of the patients in Group H (overall agreement 80%). Similarly, serum ferritin levels were in agreement with heart biopsy in 28% and 88%, respectively (overall agreement 72%). In Group L, MRI was in better agreement with biopsy compared to serum ferritin (86% vs. 28%, P < 0.05). A receiver operating characteristic curve (ROC) analysis confirmed that a T2 relaxation time of 32 ms had the highest discriminating ability for the corresponding biopsy outcome. Conclusions: Heart T2 relaxation time appears in agreement with cardiac biopsy, both in high and low iron deposition, and may become a useful non-invasive index in beta-thalassemia.