The Role of Positron Emission Tomography in Advancing the Understanding of the Pathogenesis of Heart and Vascular Diseases

Abstract

Cardiovascular disease remains the leading cause of morbidity and mortality worldwide. For developing new therapies, a better understanding of the underlying pathology is required. Historically, such insights have been primarily derived from pathological studies. In the 21st century, thanks to the advent of cardiovascular positron emission tomography (PET), which depicts the presence and activity of pathophysiological processes, it is now feasible to assess disease activity in vivo. By targeting distinct biological pathways, PET elucidates the activity of the processes which drive disease progression, adverse outcomes or, on the contrary, those that can be considered as a healing response. Given the insights provided by PET, this non-invasive imaging technology lends itself to the development of new therapies, providing a hope for the emergence of strategies that could have a profound impact on patient outcomes. In this narrative review, we discuss recent advances in cardiovascular PET imaging which have greatly advanced our understanding of atherosclerosis, ischemia, infection, adverse myocardial remodeling and degenerative valvular heart disease.

Keywords: 18F-sodium fluoride; coronary artery disease; infective endocarditis; myocardial viability; positron emission tomography.

Figure 1

Schematic representation of the basic principles governing PET. A positive-beta decay: interaction of positron with electron followed by an annihilation process with the release of two 511 keV gamma photons detected by the PET scanner detector ring.

Figure 2

Myocardial viability imaging: Mismatch pattern, viable hibernated myocardium. (A) Myocardial perfusion imaging with MIBI-Tc^99m SPECT: heart scans showing lack of tracer uptake in the apical region and apical segments of the anterior wall (left anterior descending coronary artery territory). (B) ¹⁸FDG viability PET. ¹⁸FDG uptake is visible in the area of the perfusion deficit, ruling out scarring and confirming viability in this region.

Figure 3

Myocardial viability imaging: Match pattern, non-viable scarring. (A) Myocardial perfusion imaging with MIBI-Tc^99m SPECT: heart scans showing lack of tracer uptake in the apical region of the left ventricle (LAD territory). (B) ¹⁸FDG viability PET. ¹⁸FDG uptake is absent in the area of the perfusion defect, confirming myocardial scarring in this region.

Figure 4

Infective Endocarditis in a patient with a cardiac device-related infective endocarditis. Axial scans at the level of the pacing leads: Infection focus in the right atrial leads. (A) Fused ¹⁸FDG PET and CT with tracer uptake in right atrium. (B) ¹⁸FDG PET attenuation-corrected scan. (C) ¹⁸FDG PET attenuation non-corrected scan showing uptake presence matching attenuation-corrected scan.

Figure 5

Imaging of atherosclerotic disease activity. ¹⁸F-sodium fluoride coronary PET imaging for imaging the coronary microcalcification activity (CMA) and risk stratification in patients with established coronary artery disease. Reprinted from JACC, Vol 75, Issue 24, Kwiecinski et al., Coronary 18F-sodium fluoride uptake predicts outcomes in patients with coronary artery disease, Pages 3061–3074, 2020, with permissions from Elsevier [98].