Early cardiac involvement in patients with hyperthyroidism identified by multiparametric cardiovascular magnetic resonance imaging

Background: Hyperthyroidism is reportedly associated with increased cardiovascular risk and heart failure. However, a definite association between hyperthyroidism and cardiomyopathy has not been reported. This study aimed to analyze alterations in myocardial tissue characteristics and strain, and to fill the knowledge gap about identifying early cardiac involvement in patients with hyperthyroidism. Methods: In this single center retrospective study, forty-one patients in the hyperthyroid state with a clinically indicated cardiac magnetic resonance (CMR) (and thus: 1≥ marker of cardiac involvement cardiac symptoms, electrocardiograph abnormalities or elevated cardiac biomarkers) and thirty-one healthy controls underwent CMR imaging. Results : The myocardial native T1 value was significantly higher in the hyperthyroidism group compared with the control group (1301.8 ± 38.5 vs. 1270.0 ± 19.6 ms; P＜0.001). The left ventricular T2 value, global myocardial strain, myocardial mass, and ejection fraction (LVEF) was similar in hyperthyroidism and control patients. In the hyperthyroidism group, ECV fraction was significantly correlated with free triiodothyronine (FT3) levels (r=0.498, p=0.002) and total triiodothyronine (TT3) levels (r=0.408, p=0.012). Native T1 values＞1284 ms could distinguish patients with hyperthyroidism from healthy controls, with a sensitivity of 78% and a specificity of 80.6%. Conclusions: Hyperthyroidism with normal myocardial strain exhibits increased native T1 value and ECV fraction, indicative of myocardial extracellular interstitial expansion, which is associated with serum triiodothyronine levels. T1 mapping may be an early marker of myocardial involvement in patients with hyperthyroidism.