Extensive and balanced reduction of myocardial blood flow in patients with suspected obstructive coronary artery disease: 15O-water PET study

PET myocardial perfusion imaging: Trends, challenges, and opportunities

Various non-invasive images are used in clinical practice for the diagnosis and prognostication of chronic coronary syndromes. Notably, quantitative myocardial perfusion imaging (MPI) through positron emission tomography (PET) has seen significant technical advancements and a substantial increase in its use over the past two decades. This progress has generated an unprecedented wealth of clinical information, which, when properly applied, can diagnose and fine-tune the management of patients with different types of ischemic syndromes. This state-of-art review focuses on quantitative PET MPI, its integration into clinical practice, and how it holds up at the eyes of modern cardiac imaging and revascularization clinical trials, along with future perspectives.

Usefulness of dynamic perfusion SPECT with quantitative assessment of myocardial perfusion reserve for the detection of myocardial ischaemia in patients with presumed new left bundle branch block

Aims

The aim of this retrospective study was to evaluate the ability of dynamic SPECT with quantitative analysis of myocardial blood flow (MBF) and myocardial flow reserve (MFR) for the detection of coronary artery disease (CAD) in patients with presumed new left bundle branch block (LBBB).

Methods and results

We evaluated the dynamic SPECT results from 174 consecutive patients with LBBB without a history of CAD from a single center. MBF was assessed at rest and during regadenoson (400 μg). Normal MFR was defined as ≥ 2.1. Left ventricular function and segmental perfusion were assessed from conventional gated SPECT. SPECT abnormalities were found in 17/174 (10%) patients including a reversible SPECT defect in 4 patients (2.3%), a fixed defect in 12 patients (7%), and both in 1 patient. Global left ventricular function was normal despite a significant impairment of septal wall motion. Stress and rest MBF was decreased in the septum and the inferior wall compared with other walls (P < 0.0001), resulting in similar MFR. A reduced MFR was associated with a fixed defect (P = 0.04). Only 18 patients (10%) presented with a decreased MFR. They were more often referred to subsequent coronary angiography (8/18, 44%) compared with patients with a normal MFR (9/156, 6%, χ2 = 27.382, P < 0.0001). However, significant coronary lesions were finally found in only 4/174 patients (2%).

Conclusion

Although a decreased MFR was associated with a fixed defect on conventional perfusion imaging, the low rate of CAD finally demonstrated in this study questions the relevance of routine screening for CAD in patients with presumed new LBBB.

Quantitative Perfusion Imaging with Total-Body PET

Recently, PET systems with a long axial field of view have become the current state of the art. Total-body PET scanners enable unique possibilities for scientific research and clinical diagnostics, but this new technology also raises numerous challenges. A key advantage of total-body imaging is that having all the organs in the field of view allows studying biologic interaction of all organs simultaneously. One of the new, promising imaging techniques is total-body quantitative perfusion imaging. Currently, 15O-labeled water provides a feasible option for quantitation of tissue perfusion at the total-body level. This review summarizes the status of the methodology and the analysis and provides examples of preliminary findings on applications of quantitative parametric perfusion images for research and clinical work. We also describe the opportunities and challenges arising from moving from single-organ studies to modeling of a multisystem approach with total-body PET, and we discuss future directions for total-body imaging.

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

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.