Long-term impact of myocardial inflammation on quantitative myocardial perfusion-a descriptive PET/MR myocarditis study

Eur J Nucl Med Mol Imaging. 2023 Oct;50(12):3609-3618. doi: 10.1007/s00259-023-06314-0. Epub 2023 Jul 1.

Abstract

Purpose: Whether myocardial inflammation causes long-term sequelae potentially affecting myocardial blood flow (MBF) is unknown. We aimed 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 (2.71 mL*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 a myocardial scar but without a corresponding LGE.

Conclusion: 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. CMR = cardiac magnetic resonance; PET = positron emission tomography; LGE = late gadolinium enhancement.

Keywords: Cardiac magnetic resonance; Inflammation; Myocardial blood flow; Myocarditis; Perfusion; Positron emission tomography.

MeSH terms

  • Ammonia
  • Cicatrix / diagnostic imaging
  • Contrast Media
  • Coronary Artery Disease*
  • Coronary Circulation / physiology
  • Gadolinium
  • Humans
  • Inflammation / diagnostic imaging
  • Magnetic Resonance Imaging
  • Myocardial Perfusion Imaging* / methods
  • Myocarditis* / diagnostic imaging
  • Nitrogen Radioisotopes
  • Perfusion
  • Positron-Emission Tomography
  • Radiopharmaceuticals

Substances

  • Nitrogen-13
  • Nitrogen Radioisotopes
  • Ammonia
  • Contrast Media
  • Gadolinium
  • Radiopharmaceuticals