Angina with non-obstructive coronary arteries (ANOCA) predominates in women, believed to be due to (1) vasoreactivity, especially that of the microvasculature and (2) flow autoregulatory failure from restricted or expended microvascular vasodilatory reserve. As yet these classifications have not yielded a homogeneous grouping with predictable outcome to drug therapy. Most of these women have a structurally and functionally normal heart on imaging studies, which begs the question—could their angina be due to extracardiac factors? This chapter describes six women with tentative polycystic ovary syndrome (PCOS) background and angina. They appeared to share either in part or in total, features of left ventricular and coronary haemodynamics, which are potentially generalisable; a triad of (1) raised left ventricular end-diastolic pressure (LVEDP) and coronary resistance, (2) reduced or expended vasodilatory reserve, and (3) microvascular reactivity, which are consistent with the diagnosis of coronary microvascular dysfunction (CMD). However, what is usually regarded as isolated microvascular spasm to acetylcholine-provocation does not automatically translate to responsiveness to calcium channel blockers and nitrates. Thus, raising the prospect that the dramatic findings in the cardiac catheter laboratory, characterised by slowing of coronary flow, chest pain and ECG changes; though clearly pathological, counterintuitively may in fact not vasospastic in nature, but to a greater extent due to subendocardial extravascular compression of the microvasculature, which could be the hitherto underrecognised, but postulated underlying mechanism of ANOCA.