5035Comparative assessment of diagnostic algorithms of myocardial inflammation by endomyocardial biopsy and tissue mapping by CMR against high-sensitive troponin in viral myocarditis

Abstract Background Myocarditis is defined by inflammatory involvement of the myocardium, either histologically by evidence of myocardial necrosis and cellular infiltration on endomyocardial biopsy (EMB), or non-invasively by presence of myocardial oedema using tissue mapping with cardiovascular magnetic resonance (CMR). Objective: to undertake intra-individual comparisons of EMB vs. CMR diagnostic algorithms of myocardial inflammation, as well as against an independent gold-standard of myocardial injury, high-sensitive troponin (hs-TropT). Methods Prospective multicentre study of consecutive patients (n=109) with clinical diagnosis of myocarditis. EMBs were analysed by 2 reference centres using the ESC diagnostic and their local algorithms. The CMR criteria used sequence-specific cut-offs for native T1 and T2 (standard deviation, SD); myocardial inflammation T1 ≥2SD, T2 ≥2SD and no inflammation: T1 and T2<2SD, with subcategories for acute/high-grade: T1 ≥5SD, T2 ≥2SD; chronic/low-grade: T1 ≥2SD, T2 ≥2SD; healed: T1 <2SD, T2 <2SD but myocardial impairment and non-inflammatory cardiomyopathy: T1 ≥2SD, T2 <2SD. Results The agreement between ESC criteria and CMR criteria (AUC: 0.56, p=0.381) was poor. There was a significant agreement between myocardial injury (hs-TropT ≥13.9 ng/L) and CMR criteria (AUC: 0.84, p<0.001), but not ESC algorithm. hs-TropT levels had significant associations with native T1 and T2 (r=0.37 and 0.35, p<0.001), but not with immunohistochemical inflammatory markers. Viral presence was similarly proportioned between inflammatory/non-inflammatory subjects, irrespective of the algorithm. AUC of CMR and EMB versus hs-TroponinT Conclusions Poor agreement between CMR and EMB-based diagnostic algorithms suggests non-overlapping definitions of myocardial inflammatory involvement. Excellent agreement between CMR algorithm and hs-TropT reiterates its high sensitivity for inflammatory myocardial injury. Acknowledgement/Funding 1. National Institute for Health Research (NIHR) Biomedical Research Centre 2. German Centre for Cardiovascular Research (DZHK)