Myocardial involvement characteristics by cardiac MR imaging in patients with polymyositis and dermatomyositis.

OBJECTIVE: Myocardial involvement is frequently observed in PM and DM but typically remains subclinical. This study aimed to investigate characteristics of myocardial involvement and compare differences between patients with PM and DM by cardiac MR (CMR) imaging. METHODS: From March 2017 to December 2019, a total of 17 PM and 27 DM patients were enrolled in this retrospective study. In all patients, clinical assessment and CMR examination were performed. CMR parameters, including left ventricular (LV) morphologic and functional parameters, and CMR tissue characterization imaging parameters, such as native T1, T2, extracellular volume (ECV) and late gadolinium enhancement, were analysed. RESULTS: In patients in both PM and DM groups, elevated global native T1 and ECV values were observed. Global ECV values were higher in the PM group when compared with the DM group (33.24 ± 2.97% vs 30.36 ± 4.20%; P = 0.039). Furthermore, patients in the PM and DM groups showed a different positive segment distribution of late gadolinium enhancement, native T1 and ECV, whereas the number of positive segments in PM patients was greater compared with that in DM patients. No significant differences in LV morphological and functional parameters were observed between patients in PM and DM groups, and most were in normal range. CONCLUSION: CMR tissue characterization imaging could detect early myocardial involvement in PM and DM patients without overt LV dysfunction. Furthermore, characteristics of myocardial involvement were different between PM and DM patients with more serious myocardial involvement seen in PM patients.