[Diagnostic Values and Reliability of Cardiac Magnetic Resonance Tissue Tracking 2D and 3D Strain Assessments for Experimental Autoimmune Myocarditis in Rats].

OBJECTIVE: To determinethe diagnostic valuesand reliabilityof cardiac magnetic resonance tissue tracking (CMR-TT) derived two-dimensional(2D) and three-dimensional(3D) strains in assessing experimental autoimmunity myocarditis (EAM) in rats. METHODS: 20 Lewis rats were randomly divided into model and control groups. The animal model of autoimmune myocarditis was induced by injecting porcine cardiac myosin into the footpads of the rats.On day 35, all of the rats were examined using the 7.0T CMR cine scan. The cardiac function and global strain of the left ventricular of the rats were analyzed with specific cardiac post-processing. The rats were then sacrificed and myocardial samples were taken and stained with HE and Masson. The diagnostic values of the strain parameters were assessed by receiver operating characteristic (ROC) curves with the pathological results as diagnostic criteria.The reliability of the strain parameters were tested using interclass correlation coefficient (ICC), coefficients of variation (CV) and Bland-Altman. RESULTS: No abnormal pathological changes in myocardial cells were found in the control group. Myocarditis was successfully induced in all of the rats in the model group, showing myocardial fiber arrangement disorder, degeneration, necrosis, inflammatory cell infiltration and interstitial fibrosis. The ROC showed that 2D global strain parameters possessed higher diagnostic values than 3D strain parameters. The 2D had an area under the curve (AUC) of 0.96 in global circumferential strain (GCS), 0.95 in global radial strain (GRS), and 0.90 in global longitudinal strain (GLS), compared with 0.87 GCS, 0.85 GRS, and 0.77 GLS in the 3D, respectively.The reliability of the 2D strain parameters was high, except for inter-observer 2D GRS(ICC=0.893). The 3D strain parameters had lower reliability (ICCs:0.421-0.79) than the 2D strain parameters (ICCs:0.893-0.986). CONCLUSION: The diagnostic values of 2D strain parameters are higher than 3D strain parameters in diagnosing myocarditis.