Endothelium-dependent Coronary Microvascular Dysfunction - A Diagnosis by Integrated Non-invasive Imaging.

Coronary microvascular dysfunction (CMD) is a common but often underdiagnosed cause of ischemia and angina in patients with angina and no obstructive coronary artery disease (ANOCA). The reliance on invasive testing contributes to delayed or missed diagnosis. Exercise-induced ST-segment abnormalities in ANOCA patients may serve as a non-invasive marker, particularly reflecting impaired endothelium-dependent vasodilation. We report the case of a middle-aged man undergoing a treadmill exercise test for competitive sports eligibility. The patient developed atypical chest pain with significant (>2 mm) down-sloping ST depression in precordial and inferior leads during exertion. Coronary computed tomography angiography revealed normal coronary arteries, raising suspicion for CMD. Further assessment with dipyridamole stress echocardiography demonstrated normal coronary flow velocity reserve (CFVR) in the left anterior descending artery = 3.2, indicating preserved endothelium-independent vasodilation. However, contrast myocardial perfusion imaging revealed patchy areas of delayed replenishment-indicative of CMD and suggestive of impaired endothelium-dependent function. Exercise-induced ST depression was reproducible during stress echocardiography. In patients with ANOCA, patchy perfusion abnormalities during vasodilator stress and preserved CFVR may reflect CMD due to endothelium-dependent dysfunction. Ecostress may offer valuable diagnostic insights and support early identification and management of CMD.