Intermediate coronary microvascular dysfunction: a case report highlighting challenges in diagnosis and management.

Background: Coronary microvascular dysfunction (CMD) is a heterogeneous and underappreciated clinical presentation of cardiac chest pain in the absence of obstructive epicardial coronary disease. While risk factors for CMD are not dissimilar from those that contribute to epicardial coronary disease (e.g. hypertension, diabetes, obesity, smoking, etc.), CMD requires additional therapy beyond addressing those risk factors. Case summary: A 46-year-old woman presented with cardiac chest pain and non-ST elevation myocardial infarction. Myocardial perfusion imaging demonstrated a large, moderate perfusion defect in the anterior myocardium. Left heart catheterization ruled out epicardial disease, and microvascular testing was intermediate. Nevertheless, her symptoms resolved completely with empiric medical management of presumed CMD. Discussion: Invasive ischaemic testing can facilitate a CMD diagnosis and offers more diagnostic specificity than non-invasive modalities. However, diagnostic thresholds remain debated and can be confounded by coronary anatomy and clinical profiles, posing challenges to accurately diagnosing CMD. A high index of suspicion and a low threshold for empiric treatment may be beneficial in alleviating symptoms.