168 Chapter 8 INTRODUCTION Angina with non-obstructive coronary arteries (ANOCA) is an entity of chronic coronary syndrome (CCS) in which angina is caused by a mismatch between myocardial oxygen demand and oxygen supply. ANOCA impacts almost half of the patients undergoing coronary angiography for suspected ischemic heart disease.1 Abnormal vasomotor responses affect the coronary circulation in ANOCA, distinguishing vasospastic angina (VSA) defined as an enhanced vasoconstriction and/or coronary microvascular dysfunction (CMD) characterized by an impaired vasodilation.2 Coronary function testing (CFT) is widely considered the benchmark procedure for comprehensive assessment of ANOCA, using acetylcholine to evaluate VSA and adenosine to evaluate vasodilation during hyperemia.2 Current guidelines also suggest non-invasive evaluation of ANOCA.2, 3 Recommended modalities include stress echocardiography, positron emission tomography (PET), and cardiac magnetic resonance (CMR) imaging to investigate myocardial perfusion.1 CMR offers several specific benefits, including a high contrast-to-noise ratio, excellent safety profile, no ionizing radiation, and avoidance of iodinated contrast exposure, making it a well-suited modality for the detailed assessment of myocardial viability and function.4 Stress perfusion CMR, utilizing visual assessment of first-pass contrast-enhanced imaging, is a well-established non-invasive method for detecting myocardial ischemia through identifying perfusion defects.3, 5 However, visual assessment is subjective and heavily relies on observer’s expertise, as it depends on identifying perfusion defects based from signal variations within the imaged myocardial section.6 In ANOCA, assumed to be a generalized disease affecting all myocardial tissue, especially in CMD, much of the imaged section may appear normal despite being hypoperfused7, potentially leading to false-negative findings in ANOCA patients. Fully automated quantitative perfusion (QP) CMR is a promising tool for absolute quantification of myocardial blood flow (MBF, ml/g/min)8, enabling the derivation of the myocardial perfusion reserve (MPR).9 MPR, reflecting capillary perfusion capacity, is calculated as the stress-to-rest MBF ratio. During CFT, perfusion is typically only characterized in the left anterior descending (LAD)10, while QP CMR provides MBF and MPR across various coronary territories. Despite its potential, only few reports have discussed fully automated QP CMR in ANOCA patients, with validation limited to PET and in patients with stable angina.9, 11 Therefore, this study aims to assess QP’s efficacy in detecting ANOCA, diagnosed via CFT, in comparison to healthy controls.
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