Background Cardiac magnetic resonance feature tracking (CMR-FT) derived myocardial strain emerged as a promising technique for advanced myocardial characterization of the left and right ventricle (LV and RV) in the evaluation of suspected myocarditis. To date, there is a lack of data for biventricular strain analysis in chronic myocarditis compared to the endomyocardial biopsy proven gold-standard. 

Objectives To evaluate the diagnostic value of global and segmental CMR-FT-based LV and RV myocardial strain parameters in endomyocardial biopsy-proven chronic myocarditis.

Methods 403 patients with persistent symptoms (>30 days) suggestive of myocarditis were consecutively screened. All patients had to undergo endomyocardial biopsy and a 1.5 T CMR protocol including dedicated strain analysis. In detail, CMR-FT-derived myocardial strain analysis in radial, circumferential and longitudinal direction comprised peak strain, time to peak, peak systolic and peak diastolic strain rates, peak systolic and peak diastolic velocities. 

Results Endomyocardial biopsy revealed chronic lymphocytic myocarditis in 50 patients (median age, 49 ± 14 years; 32 men, 18 women).

LV ejection fraction (LVEF) was reduced (<50%) in 35 of 50 patients (70%) with chronic myocarditis. Specifically, LVEF was 39 ± 17 % in patients vs. 60 ± 4 % in controls, P < .001. For the detection of chronic myocarditis, biventricular radial (AUC_LV 0.96, P < .001; AUC_RV 0.91, P < .001) and circumferential (AUC_LV 0.97, P < .001; AUC_RV 0.81, P < .001) peak systolic strain rates yielded excellent diagnostic performances. RV radial peak systolic strain rate showed to be decreased even in patients with preserved LVEF (>50%) compared to controls (0.9 ± 0.6 s^-1 vs. 2.6 ± 0.5 s^-1), P < .001.

Conclusion Our study evaluated comprehensive global and segmental CMR-FT-derived strain parameters of the left and right ventricle in biopsy-proven chronic lymphocytic myocarditis and healthy controls. We identified the biventricular radial (AUC_LV 0.96 and AUC_RV 0.91) and circumferential (AUC_LV 0.97 and AUC_RV 0.81) peak systolic strain rates as most sensitive parameters in the detection of chronic myocarditis. Additionally, RV radial peak systolic strain rate has shown to be decreased even in patients with preserved LVEF compared to controls. Our results suggest a potential role of dedicated strain parameter analysis in the diagnosis of chronic lymphocytic myocarditis beside other CMR techniques of myocardial tissue characterization, which may improve non-invasive detection of these high-risk patients.