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 source(s): Swiss Science Foundation (SNSF). Background Whether myocardial inflammation causes long-term sequelae potentially affecting blood flow (MBF) is unknown. Objectives To assess the effect on quantitative MBF parameters, as assessed by 13N-ammonia positron emission tomography perfusion imaging (PET-MPI) late after myocarditis. Methods Fifty patients with a history myocarditis underwent cardiac magnetic resonance (CMR) at diagnosis and PET/MR follow-up least 6 months later. Segmental MBF, reserve (MFR), washout were obtained from PET, segments reduced retention, resembling scar, recorded. Based CMR, classified remote (n=469), healed (inflammation baseline but no gadolinium enhancement [LGE] follow-up, n=118), scarred (LGE n=72). Additionally, apparently scar PET discordant (n=18). Results Compared to segments, showed higher stress (2.71mL*min-1*g-1 [IQR 2.18–3.08] vs. 2.20 mL*min-1*g-1 [1.75–2.68], p<0.0001), MFR (3.78 [2.83–4.79] 3.36 [2.60–4.03], p<0.0001) (rest 0.24/min [0.18–0.31] 0.53/min [0.40–0.67] 0.22/min [0.16–0.27] 0.46/min [0.32–0.63], p = 0.010 0.021, respectively). While did not differ regarding MFR, was ∼30% (p<0.014). Finally, 10 (20%) diagnosed PET-MPI presenting without corresponding LGE. Conclusions In myocarditis, measurements remain altered in areas initially affected inflammation.