Anatomical and functional assessment of coronary artery disease in patients with stable angina: Which is the gold standard?

Abstract

Stable coronary artery disease (sCAD) is a clinical condition encompassing diverse evolutionary phases of CAD, excluding acute coronary syndromes and its incidence varies in parallel with observed international differences in CAD mortality, being generally more prevalent in middle-aged women than in men, probably due to higher incidence of microvascular disease in female patients. As mortality rate sank in the latest years thanks to recent advantages in diagnostic procedures and therapies, a prompt and reliable diagnosis is highly desirable. Additionally, the ideal diagnostic procedure should also be preferably noninvasive and provide prognostic information. In fact, the prognostic assessment is a crucial part of the management of patients with sCAD, able to identify patients who may have an improvement in outcome with more aggressive intervention, including revascularization. As a matter of fact, various factors can act alone or in combination to cause a clinical evident sCAD, including plaque-related narrowing of epicardial arteries, focal or diffuse spasm of coronary arteries, microvascular dysfunction, and ischaemic cardiomyopathy with impaired left ventricular (LV) dysfunction. As such, a comprehensive anatomical and functional assessment is expected to yield highest accuracy in the workup of patients with sCAD. This topic has been addressed by Akil et al. in this issue of the Journal of Nuclear Cardiology, wherein the authors aimed at comparing two procedures able to provide a functional assessment of CAD (i.e., cardiac magnetic resonance-CMR and positron emission tomography-PET) and an invasive technique for the anatomical evaluation of epicardial vessels (i.e., coronary angiography-CA, eventually with fractional flow reserve-FFR assessment) for the evaluation of the significance of coronary stenosis prior to transcutaneous or surgical revascularization. The authors evaluated 41 Patients with suspected or known sCAD, who sequentially underwent a myocardial perfusion PET with N-ammonia, CMR, and invasive CA. Of note, FFR was assessed only in a fraction of vessels (17 of 141, 12.1%). Noticeably, the authors used PET-derived absolute quantification of myocardial flow reserve (MFR) as standard of reference, thus reporting suboptimal diagnostic performance both for CMR (sensitivity 27 to 47%, specificity 75 to 96%) and for CA (39 to 76% sensitivity and 54 to 83% specificity). These values are considerably lower than those reported in the literature. A meta-analysis by Jaarsma et al. including a total of 166 articles (17,901 patients) demonstrated a very good diagnostic accuracy for CMR (pooled sensitivity 88%, specificity 76%), similar to that of PET (89% and 81%, respectively). The contention may relate in the largely different patient population (n = 41 vs 17,901) as well as in that in the present study only patients with sCAD were included. But the choice of a different standard of reference represents a key factor in this regard. The use of PET-derived absolute myocardial flow quantification (MFQ) as gold standard is fascinating and Reprint requests: Federico Caobelli, MD, FEBNM, Clinic of Radiology and Nuclear Medicine, University Hospital Basel, University of Basel, Petersgraben 4, 4031 Basel, Switzerland; [email protected] J Nucl Cardiol 2020;;27:2360–4. 1071-3581/$34.00 Copyright 2019 American Society of Nuclear Cardiology.