Despite extensive work over decades characterizing the physiology of the coronary circulation, there remain many barriers to obtaining a diagnosis of coronary microvascular dysfunction (CMD), even as the prevalence of the condition has be documented to be as high as 81 % of patients with and without epicardial coronary artery disease (CAD) [ ]. Some of the resistance is now historical, with angina and positive stress tests in the absence of epicardial obstruction having been termed “Syndrome X" before “microvascular angina” and most recently angina with no obstructive coronary artery disease (ANOCA). Some of the inattention undoubtedly derived from sexist attitudes towards a condition with a high female predominance of 56–82 % [ ] and atypical presentations, with many female patients even now being dismissed as having noncardiac chest pain or anxiety. Some of the barriers have been technical, with the Doppler coronary guidewire providing poor quality signals in 14 % of patients before it recently became unavailable, while thermodilution techniques have a higher variability of measurement and poorer correlation to [ 15 O]H 2 O PET [ ]. Varying diagnostic criteria, protocols, and definitions of normal and abnormal values of coronary flow reserve (CFR) have not helped. Finally, the absence of specific and effective treatments for CMD contributes to therapeutic and diagnostic nihilism in some circles, although the CorMicA trial [ ] definitively showed that specific diagnosis and treatment directed at CMD or vasospasm was effective in reducing angina in patients with ANOCA.