Predictive Value of Cardiac Magnetic Resonance Imaging-Derived Myocardial Strain for Poor Outcomes in Patients with Acute Myocarditis.

Objective: To evaluate the utility of cardiovascular magnetic resonance (CMR)-derived myocardial strain measurement for the prediction of poor outcomes in patients with acute myocarditis. Materials and Methods: We retrospectively analyzed data from 37 patients with acute myocarditis who underwent CMR. Left ventricular (LV) size, LV mass index, ejection fraction and presence of myocardial late gadolinium enhancement (LGE) were analyzed. LV circumferential strain (Ecc(SAX)), radial strain (Err(SAX)) from mid-ventricular level short-axis cine views and LV longitudinal strain (Ell(LV)), radial strain (Err(Lax)) measurements from 2-chamber long-axis views were obtained. In total, 31 of 37 patients (83.8%) underwent follow-up echocardiography. The primary outcome was major adverse cardiovascular event (MACE). Incomplete LV functional recovery was a secondary outcome. Results: During an average follow-up of 41 months, 11 of 37 patients (29.7%) experienced MACE. Multivariable Cox proportional hazard regression analysis, which included LV mass index, LV ejection fraction, the presence of LGE, Ecc(SAX), Err(SAX), Ell(LV), and Err(Lax) values, indicated that the presence of LGE (hazard ratio, 42.88; p = 0.014), together with ErrLax (hazard ratio, 0.77 per 1%, p = 0.004), was a significant predictor of MACE. Kaplan-Meier analysis demonstrated worse outcomes in patient with LGE and an Err(Lax) value <= 9.48%. Multivariable backward regression analysis revealed that Err(Lax) values were the only significant predictors of LV functional recovery (hazard ratio, 0.54 per 1%; p = 0.042). Conclusion: CMR-derived Err(Lax) values can predict poor outcomes, both MACE and incomplete LV functional recovery, in patients with acute myocarditis, while LGE is only a predictor of MACE.