Impact of myocardial inflammation on quantitative myocardial perfusion at long-term follow-up - a descriptive hybrid PET/MR myocarditis study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation (SNSF). Background Whether myocardial inflammation causes long-term sequelae potentially affecting myocardial blood flow (MBF) is unknown. Objectives To assess the effect of myocardial inflammation on quantitative MBF parameters, as assessed by 13N-ammonia positron emission tomography myocardial perfusion imaging (PET-MPI) late after myocarditis. Methods Fifty patients with a history of myocarditis underwent cardiac magnetic resonance (CMR) imaging at diagnosis and PET/MR imaging at follow-up at least 6 months later. Segmental MBF, myocardial flow reserve (MFR), and 13N-ammonia washout were obtained from PET, and segments with reduced 13N-ammonia retention, resembling scar, were recorded. Based on CMR, segments were classified as remote (n=469), healed (inflammation at baseline but no late gadolinium enhancement [LGE] at follow-up, n=118), and scarred (LGE at follow-up, n=72). Additionally, apparently healed segments but with scar at PET were classified as PET discordant (n=18). Results Compared to remote segments, healed segments showed higher stress MBF (2.71mL*min-1*g-1 [IQR 2.18–3.08] vs. 2.20 mL*min-1*g-1 [1.75–2.68], p