Characterizing the Inflammatory Tissue Response to Acute Myocardial Infarction by Clinical Multimodality Noninvasive Imaging

Abstract

Background-Myocardial infarction (MI) triggers a systemic inflammatory response which determines subsequent healing.Experimentally, cardiac positron emission tomography and magnetic resonance imaging have been used successfully to obtain mechanistic insights. We explored the translational potential in patients early after MI. Methods and Results-Positron emission tomography/computed tomography and cardiac magnetic resonance were performed in 15 patients <7 days after first MI. Cardiac magnetic resonance showed regional transmural late gadolinium enhancement and edema exceeding the area of late gadolinium enhancement. Using F-18 deoxyglucose with heparin pretreatment, metabolic rate of glucose (MRGlc)

Imaging Systemic Inflammation in Patients With Acute Myocardial Infarction

“…Although the study did not directly correlate PET signal with infarct macrophage burden, preclinical studies in mice provide this correlation. 13 The PET data obtained by Wollenweber et al 10 harmonize with 2 recent molecular MRI studies. Alam et al 14 and Yilmaz et al 15 used iron oxide nanoparticles, which are avidly taken up by macrophages, 16 to image patients with acute MI.…”

“…Noninvasive imaging, in particular clinical molecular imaging, is poised to accelerate translation of basic research, demonstrated by 2 recent studies published in Circulation: Cardiovascular Imaging. 9,10 Both studies rely on 18 F-fluorodeoxyglucose ( 18 F-FDG), a positron emission tomography (PET) tracer that is in clinical use for cancer staging. The 18 F isotope-labeled imaging agent uses glucose transporters for uptake into cells with high glucose metabolism.…”

“…However, preclinical studies in mice after coronary ligation suggested that suppression of myocardial 18 F-FDG uptake allows correlation of PET signal with myeloid cell numbers in the infarct. 12,13 Translating this strategy from mice to humans, Wollenweber et al, 10 in this issue of Circulation: …”

“…The studies by Kim et al 9 and Wollenweber et al 10 provide an exciting glimpse into the transformative power of molecular imaging. The data are clearly preliminary because the studies lack rigorous validation in humans.…”

Imaging of Post-Infarct Inflammation

“…2,13 A consequential next step after initial proof of principle is to demonstrate that the FDG-derived inflammation signal early after AMI has predictive value for the occurrence of subsequent adverse remodeling and that this novel diagnostic approach provides information beyond current standard diagnostic parameters, such as infarct size, left ventricular geometry and function, and blood markers of myocardial damage or systemic inflammation. Only the proof of such an incremental value will support the clinical usefulness of inflammationtargeted imaging for guidance of novel inflammation-targeted therapy and for use as an early end point to monitor effectiveness.…”