The relationship between heart and liver iron in thalassemia: a quantitative analysis using MRI

Abstract

Objective To quantify the heart and liver iron overload in thalassemia patients and discuss the relationship of iron deposition between them,and to evaluate the accuracy of using hepatic iron concentration ＞ 15 mg/g dry tissue as an index to predict heart iron deposition as used in clinical practice.Methods One hundred and three transfusion-dependent patients with thalassemia,who were older than 5 years,underwent MRI heart and liver measurement to obtain T2 * values.The Spearman rank correlation was employed to analyze the relationship between cardiac T2 * and liver T2 * values.By using liver T2 * =0.96 ms as standard setting,patients were divided into two groups,and the differences of cardiac T2 * values between the two groups were compared by Wilcoxon rank sum test.Then by using cardiac T2 * =10,20 ms as standard setting,patients were divided into 3 groups,and the differences of liver T2 * values among the 3 groups were compared by Wilcoxon rank sum test.The ROC curves were drawn to predict the possibility of using hepatic iron concentration ＞ 15 mg/g dry tissue as an index of cardiac iron deposition.Results The cardiac and liver T2 * values of the 103 thalassemia patients showed low correlation(r =0.453,P =0.000).With the liver T2 * value reduced,the cardiac T2* value did not decline proportionally.The cardiac T2 * value range and median of 25 patients' group whose liver T2 * ＜ 0.96 ms were 4.70 to 41.70 ms and 12.10 ms,respectively.The cardiac T2 * value range and the median of 78 patients' group whose liver T2 * ＞ 0.96 ms were 4.80 to 51.10 ms and 26.10 ms,respectively.There was statistically significant difference between those of the two groups(Z =-3.566,P =0.000).The liver T2 * value range and the median of 20 patients'group whose cardiac T2 * ＜ 10 ms was 0.68 to 3.83 ms and 1.06 ms,respectively.The liver T2 * value range and the median of 58 patients' group whose cardiac T2 * ≥20 ms were 0.74 to 14.80 ms and 1.76 ms,respectively.There was statistical difference between those of the two groups(Z =-3.553,P =0.000).The liver T2 * value range and the median of 25 patients' group with cardiac 10 ms≤T2 * ＜20 ms were 0.69 to 13.59 ms and 0.99 ms,respectively.The values were significantly different from that of T2* ≥20 ms group(Z =-3.951,P =0.000).The liver T2 * values of cardiac T2* ＜ 10 ms group was not statistically different from that of 10 ms≤T2* ＜20 ms group(Z =-0.046,P =0.964).To predict cardiac iron deposition with the index of hepatic iron concentration ＞ 15 mg/g dry tissue,the area under the ROC curve was 0.771.The sensibility was 42.2％,the specificity was 89.7％.Conclusions There is low correlation between heart and liver iron level in thalassemia patients with long-term transfusions.Patients with hepatic iron concentration ＞ 15 mg/g dry tissue have a higher incidence of heart iron deposition,but the accuracy of using hepatic iron concentration as an index to predict myocardial iron deposition is low to moderate. Key words: Thalassemia; Magnetic resonance imaging; Comparative study