Quantification of Myocardial Extracellular Volume Fraction with Cardiac MR Imaging in Thalassemia Major

Published Online:https://doi.org/10.1148/radiol.2015150341

Patients with myocardial iron overload have increased myocardial extracellular volume, as assessed noninvasively with cardiac MR imaging.

Purpose

To quantify myocardial extracellular volume (ECV) by using cardiac magnetic resonance (MR) imaging in thalassemia major and to investigate the relationship between ECV and myocardial iron overload.

Materials and Methods

With institutional review board approval and informed consent, 30 patients with thalassemia major (mean age ± standard deviation, 34.6 years ± 9.5) and 10 healthy control subjects (mean age, 31.5 years ± 4.4) were prospectively recruited (clinicaltrials.gov identification number NCT02090699). Nineteen patients (63.3%) had prior myocardial iron overload (defined as midseptal T2* < 20 msec on any prior cardiac MR images). Cardiac MR imaging at 1.5 T included cine steady-state free precession for ventricular function, T2* for myocardial iron quantification, and unenhanced and contrast material–enhanced T1 mapping. ECV was calculated with input of the patient’s hematocrit level. Peak systolic global longitudinal strain by means of speckle tracking was assessed with same-day transthoracic echocardiography. Statistical analysis included use of the two-sample t test, Fisher exact test, and Spearman correlation.

Results

Unenhanced T1 values were significantly lower in patients with prior myocardial iron overload than in control subjects (850.3 ± 115.1 vs 1006.3 ± 35.4, P < .001) and correlated strongly with T2* values (r = 0.874, P < .001). Patients with prior myocardial iron overload had higher ECV than did patients without iron overload (31.3% ± 2.8 vs 28.2% ± 3.4, P = .030) and healthy control subjects (27.0% ± 3.1, P = .003). There was no difference in ECV between patients without iron overload and control subjects (P = .647). ECV correlated with lowest historical T2* (r = −0.469, P = .010) but did not correlate significantly with left ventricular ejection fraction (r = −0.216, P = .252) or global longitudinal strain (r = −0.164, P = .423).

Conclusion

ECV is significantly increased in thalassemia major and is associated with myocardial iron overload. These abnormalities may potentially reflect diffuse interstitial myocardial fibrosis.

© RSNA, 2015

Online supplemental material is available for this article.

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Article History

Received February 11, 2015; revision requested April 14; revision received July 14; accepted August 6; final version accepted September 30.
Published online: Dec 10 2015
Published in print: June 2016