Inclusion Criteria:  Age 20 to 80 Typical/atypical chest pain or ischemic symptoms including dyspnea No significant coronary artery stenosis (>50% stenosis) in coronary angiography or computed tomography Left ventricular ejection fraction ≥50%  Exclusion Criteria:  More than 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 Patients with difficulty in performing exercise load evaluation (treadmill, bicycle ergometer) Atrial fibrillation Atrioventricular block with more than second degrees, symptomatic bradycardia, cryo-node failure syndrome, Wolff-Parkinson-White (WPW) patients