Microvascular Angina (Angina With no Obstructive Coronary Artery Disease [ANOCA]) By Ranya N Sweis, MD, MS, Northwestern University Feinberg School of Medicine; Arif Jivan, MD, PhD, Northwestern University Feinberg School of Medicine Reviewed / Revised Jun 2022 | Modified Sep 2022 View Patient Education Microvascular angina (previously known as syndrome X) is cardiac microvascular dysfunction or constriction causing angina in patients with normal epicardial coronary arteries on angiography.