Effects of short-term levothyroxine therapy on myocardial injuries in patients with severe overt hypothyroidism: Evidence from a cardiac MRI Study.

<bold>Purpose: </bold>To investigate using magnetic resonance imaging (MRI) myocardial injuries and cardiac function in patients with newly diagnosed severe primary overt hypothyroidism (HT) before and after achieving euthyroidism by short-term levothyroxine treatment. Levothyroxine treatment improves cardiovascular performance and ventricular remodeling in patients with HT, but diffuse myocardial injuries induced by HT are difficult to detect clinically.<bold>Materials and Methods: </bold>Myocardial longitudinal relaxation time (T1 ) mapping using the modified Look-Locker inversion-recovery (MOLLI) sequences at 3.0T was performed before and after euthyroidism was achieved by levothyroxine treatment in 24 patients with Hashimoto's thyroiditis, and compared to 17 healthy controls. Subjects underwent measurements of T1 values and left ventricular stroke volume (SV), ejection fraction (EF), cardiac index (CI), and peak filling rate (PFR). Cardiac data were expressed as an index, as per body surface area, except for heart rate and EF.<bold>Results: </bold>Patients with untreated HT exhibited significantly longer native myocardial T1 values (all P < 0.05) accompanied by reduced SV (30.7 ± 5.6 vs. 34.9 ± 6.8 mL/m2 , P < 0.05), CI (2.1 ± 0.4 vs. 2.4 ± 0.4 L/min/m2 , P < 0.05), and PFR (3.5 ± 0.9 vs. 4.2 ± 1.1 EDV/s, P < 0.05) compared to healthy controls at baseline. Achieving euthyroidism resulted in a significant decrease in T1 values and improved SV, CI, and PFR values (all P < 0.05) in the patients with HT. Negative correlations of the T1 values with free triiodothyronine (r = -0.55, P < 0.001) and PFR (r = -0.46, P = 0.0016) were observed.<bold>Conclusion: </bold>We suggest that the negative effect induced by severe overt HT on the cardiovascular system can be significantly improved by restoring euthyroidism with short-term levothyroxine therapy.<bold>Level Of Evidence: </bold>1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:897-904. [ABSTRACT FROM AUTHOR]