Role of CMR feature-tracking derived left ventricular strain in predicting myocardial iron overload and assessing myocardial contractile dysfunction in patients with thalassemia major.

OBJECTIVE

Myocardial iron overload (MIO) in thalassemia major (TM) may cause subclinical left ventricular (LV) dysfunction which manifests with abnormal strain parameters before a decrease in ejection fraction (EF). Early detection of MIO using cardiovascular magnetic resonance (CMR)-T2* is vital. Our aim was to assess if CMR feature-tracking (FT) strain correlates with T2*, and whether it can identify early contractile dysfunction in patients with MIO but normal EF.

METHODS

One hundred and four consecutive TM patients with LVEF > 55% on echocardiography were prospectively enrolled. Those fulfilling the inclusion criteria underwent CMR, with T2* being the gold standard for detecting MIO. Group 1 included patients without significant MIO (T2* > 20 ms) and group 2 with significant MIO (T2* < 20 ms).

RESULTS

Eighty-six patients (mean age, 17.32 years, 59 males) underwent CMR. There were 68 (79.1%) patients in group 1 and 18 (20.9%) in group 2. Fourteen patients (16.3%) had mild-moderate MIO, and four (4.6%) had severe MIO. Patients in group 2 had significantly lower global radial strain (GRS). Global longitudinal strain (GLS) and global circumferential strain (GCS) did not correlate with T2*. T1 mapping values were significantly lower in patients with T2* < 10 ms than those with T2* of 10-20 ms; however, FT-strain values were not significantly different between these two groups.

CONCLUSION

CMR-derived GRS, but not GLS and GCS, correlated with CMR T2*. GRS is significantly decreased in TM patients with MIO and normal EF when compared with those without. FT-strain may be a useful adjunct to CMR T2* and maybe an early marker of myocardial dysfunction in TM.

KEY POINTS: • A global radial strain of < 29.3 derived from cardiac MRI could predict significant myocardial iron overload in patients with thalassemia, with a sensitivity of 76.5% and specificity of 66.7%. • Patients with any myocardial iron overload have significantly lower GRS, compared to those without, suggesting the ability of CMR strain to identify subtle myocardial contractile disturbances. • T1 and T2 mapping values are significantly lower in those with severe myocardial iron than those with mild-moderate iron, suggesting a potential role of T1 and T2 mapping in grading myocardial iron.