Quantification of Myocardial Extracellular Volume Fraction with Cardiac MR Imaging in Thalassemia Major
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Kate Hanneman1, Elsie T Nguyen1, Paaladinesh Thavendiranathan1
1Department of Medical Imaging (K.H., E.T.N., P.T., I.Y.Y., M.S.S., B.J.W.) and Division of Cardiology (P.T.), Peter Munk Cardiac Centre, University Health Network, University of Toronto, 585 University Ave, NCSB-1C557, Toronto, ON, Canada M5G 2N2; Division of Hematology, Department of Medicine, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada (R.W.); Siemens AG Healthcare, Erlangen, Germany (A.G.); Department of Corporate Research, Siemens Corporation, Princeton, NJ (M.P.J.); and Division of Pathology, Department of Laboratory Medicine and Pathobiology, University Health Network, University of Toronto, Toronto, Ontario, Canada (J.B.).
Insights
Myocardial extracellular volume (ECV) is elevated in thalassemia major patients and linked to iron overload. This cardiac MRI finding may indicate interstitial fibrosis.
Area of Science:
- Cardiovascular Imaging
- Hematology
- Medical Physics
Background:
- Thalassemia major patients face risks of iron overload, particularly in the heart.
- Cardiac magnetic resonance (MR) imaging is crucial for monitoring iron levels and cardiac function.
Purpose of the Study:
- To quantify myocardial extracellular volume (ECV) using cardiac MR imaging in thalassemia major.
- To investigate the relationship between ECV and myocardial iron overload in these patients.
Main Methods:
- Prospective study of 30 thalassemia major patients and 10 healthy controls.
- Cardiac MR imaging (1.5 T) included T2* for iron, T1 mapping for ECV calculation, and cine imaging.
- Echocardiography assessed global longitudinal strain; statistical analysis used t-tests and Spearman correlation.
Main Results:
- Patients with prior myocardial iron overload had lower unenhanced T1 values and higher ECV compared to controls.
- ECV correlated with myocardial iron levels (lowest historical T2*), but not with ejection fraction or global longitudinal strain.
- No significant difference in ECV was observed between patients without iron overload and healthy controls.
Conclusions:
- Myocardial ECV is significantly increased in thalassemia major and associated with myocardial iron overload.
- Elevated ECV in thalassemia major may reflect diffuse interstitial myocardial fibrosis.
- Cardiac MR-derived ECV is a valuable metric for assessing cardiac involvement in thalassemia major.
Abstract:
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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