PET Imaging of Post-infarct Myocardial Inflammation

Abstract

Purpose of review: To examine the use of positron emission tomography (PET) for imaging post-infarct myocardial inflammation and repair.

Recent findings: Dysregulated immune responses after myocardial infarction are associated with adverse cardiac remodelling and an increased likelihood of ischaemic heart failure. PET imaging utilising novel tracers can be applied to visualise different components of the post-infarction inflammatory and repair processes. This approach could offer unique pathophysiological insights that could prove useful for the identification and risk-stratification of individuals who would ultimately benefit most from emerging immune-modulating therapies. PET imaging could also bridge the clinical translational gap as a surrogate measure of drug efficacy in early-stage clinical trials in patients with myocardial infarction. The use of hybrid PET/MR imaging, in particular, offers the additional advantage of simultaneous in vivo molecular imaging and detailed assessment of myocardial function, viability and tissue characterisation. Further research is needed to realise the true clinical translational value of PET imaging after myocardial infarction.

Keywords: Heart failure; Inflammation; Molecular imaging; Myocardial infarction; Non-invasive imaging; PET.

Fig. 1

PET imaging of inflammation and related processes after myocardial infarction. Left panels: tracers for imaging inflammatory cells. Top A ⁶⁸Ga-DOTATATE (SST₂) PET-CT image demonstrating residual inflammation (arrow) in B partially viable myocardium with subendocardial infarct (dashed arrow), bordering full thickness scarring (asterisk) confirmed by late gadolinium enhancement magnetic resonance imaging, 4 years after a left anterior descending artery MI. (Reproduced from: J Am Coll Cardiol. 2019;73:2489–91; doi: 10.1016/j.jacc.2019.02.052; Creative Commons user license https://creativecommons.org/licenses/by/4.0/) [34]. Bottom An apical myocardial infarct (arrows), visualised using contrast-enhanced multishot inversion recovery turbo field echo cardiac MRI (C), ⁶⁸Ga-pentixafor (CXCR4) PET (D) and fused PET-CT (E). (Reprinted from JACC Cardiovasc Imaging. 2015;8:1466–8, with permission from Elsevier) [35]. Right panels: tracers for imaging post-infarct myocardial processes related to inflammation. Top ¹⁸F-Fluciclatide (angiogenesis) PET-CT (F) and MRI images (G) of an antero-septal infarct. (Reproduced from: Heart. 2016;103:607–15; doi: 10.1136/heartjnl-2016-310115; Creative Commons user license https://creativecommons.org/licenses/by/4.0/) [•]. Bottom ⁶⁸Ga-FAPI (fibrosis) imaging. In this patient with thyroid cancer, whole-body PET-CT imaging reveals ⁶⁸Ga-FAPI uptake in the left ventricle as shown on the PET (H) and fused PET-CT (I) images. (Reproduced from: J Nucl Cardiol. 2020;1–10; doi: 10.1007/s12350-020-02307-w; Creative Commons user license https://creativecommons.org/licenses/by/4.0/) [37]