Sex Difference of Coronary Microvascular Dysfunction in Patients With Non-obstructive Coronary Artery Disease

Inclusion Criteria: * Typical/atypical chest pain or ischemic symptoms including dyspnea * No significant coronary artery stenosis (\<50% stenosis) in coronary angiography or computed tomography Exclusion Criteria: * ≥ Moderate valvular heart disease * Congenital heart disease * Chronic renal failure (estimated glomerular filtration rate \<30 ml/min/1.73m2) or end-stage renal failure undergoing hemodialysis or peritoneal dialysis * Asthma, chronic obstructive pulmonary disease and primary pulmonary hypertension * Receiving anticancer drugs * Vasculitis associated with autoimmune diseases * Atrioventricular block with more than second degrees, symptomatic bradycardia, cryo-node failure syndrome, Wolff-Parkinson-White (WPW) patients