Left and right atrial feature tracking in acute myocarditis: A feasibility study

Purpose: The present study aims at evaluating the feasibility and reproducibility of cardiac magnetic resonance (CMR) feature tracking (FT) derived strain and strain rate (SR) parameters of the left and right atrium (LA, RA) in patients with acute myocarditis as well as their potential to detect diastolic dysfunction. In addition, the diagnostic value of LA and RA strain parameters in the setting of acute myocarditis is investigated. Methods: CMR cine data of 30 patients with CMR-positive acute myocarditis were retrospectively analyzed. 25 age- and gender-matched healthy individuals served as a control. Analysis of longitudinal strain and SR of both atria was performed in two long-axis views using a dedicated FT-software. LA and RA deformation was analyzed including reservoir function (total strain [ε_s], peak positive SR [SR_s]), conduit function (passive strain [ε_e], peak early negative SR [SR_e]) and booster pump function (active strain [ε_a], peak late negative SR [SR_a]). Intra- and inter-observer reproducibility was assessed for all strain and SR parameters using Bland-Altman analyses, intra-class correlation coefficients (ICCs) and coefficients of variation (CV). Results: FT analyses of both atria were feasible in all patients and controls. Reproducibility was good for reservoir and conduit function parameters and moderate for booster pump function parameters. Myocarditis patients demonstrated an impaired LA reservoir and conduit function when compared to healthy controls (LA ε_s: 32 ± 17 vs. 46 ± 13, p = 0.019; LA SR_s: 1.5 ± 0.5 vs. 1.8 ± 0.5, p = 0.117; LA SR_e: −1.3 ± 0.5 vs. −1.9 ± 0.5, p < 0.001), while LA booster pump function was preserved. In logistic regression and ROC-analyses, LA SR_e proved to be the best independent predictor of acute myocarditis (AUC 0.80), and using LA SR_e with a cut-off of −1.6 s⁻¹ resulted in a diagnostic sensitivity of 83% and a specificity of 80%. Changes in RA phasic function parameters showed a tendency to parallel those of the LA and showed no additional effect with respect to the diagnostic potential in acute myocarditis. Conclusions: Myocarditis patients exhibit an impaired atrial reservoir and conduit function, what might be indicative of ventricular diastolic dysfunction. LA SR_e was the best predictor for the presence of acute myocarditis in our study, pointing towards the discriminative power of atrial strain analysis in the CMR-based diagnosis of acute myocarditis.