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

• Published in: European heart journal cardiovascular imaging Vol. 24; no. Supplement_1
• Main Authors: Buechel, R, Ciancone, D, Bakula, A, Schmidt, G A, Patriki, D, Benz, D C, Giannopoulos, A A, Kaufmann, P A
• Format: Journal Article
• Language: English
• Published: 19-06-2023
• ISSN: 2047-2404; 2047-2412
• DOI: 10.1093/ehjci/jead119.025

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<0.0001), MFR (3.78 [2.83–4.79] vs. 3.36 [2.60–4.03], p<0.0001) and washout (rest 0.24/min [0.18–0.31] and stress 0.53/min [0.40–0.67] vs. 0.22/min [0.16–0.27] and 0.46/min [0.32–0.63], p = 0.010 and p = 0.021, respectively). While PET discordant segments did not differ from healed segments regarding MBF and MFR, washout was higher by ∼30% (p<0.014). Finally, 10 (20%) patients were diagnosed by PET-MPI as presenting with myocardial scar but without corresponding LGE.
Conclusions
In patients with a history of myocarditis, quantitative measurements of myocardial perfusion as obtained from PET-MPI remain altered in areas initially affected by inflammation.