Relationship Between Coronary Microvascular Dysfunction and Improvement of Left Ventricular Systolic Function in Patients With Heart Failure With Reduced Ejection Fraction Caused by Non-ischemic Etiology

Inclusion Criteria: * a) Subject must be at least 19 years of age. b) Subject with symptoms or signs of HF (NYHA ≥2 dyspnea) and reduced ejection fraction (LVEF ≤ 40%) c) Subject who clinically need coronary angiography d) Subject who can voluntarily sign informed consent form Exclusion Criteria: * a) Subject with significant coronary artery stenosis on coronary angiography (diameter stenosis ≥90% or 50-90% with fractional flow reserve \[FFR\] ≤0.80) b) Subject scheduled for cardiac replacement therapy (heart transplantation or left ventricular assisted device \[LVAD\] implantation) c) HF due to restrictive cardiomyopathy, active myocarditis, or constrictive pericarditis d) Significant valvular heart disease requiring surgery e) Subject who have non-cardiac co-morbid conditions with life expectancy \<1 year