Endothelial Function-guided Therapy Compared to Usual Care in Patients With NOCAD

Inclusion Criteria: * Subjects with chest pain and non-obstructive coronary artery disease documented by coronary angiography with 20-70% luminal diameter stenosis that does not justify coronary revascularization * Stable subjects without evidence of prior MI/CABG/PTCA. * Age 20 to 79 years * Ability to understand the study procedures and provide written informed consent * Willingness and ability to comply with the study and its scheduled visits and study procedures Exclusion Criteria: * Age below 20 over 79 years * Subjects with documented MI, PTCA or CABG * Unstable angina * Any lesion \> 20% luminal narrowing in the left main coronary artery * Congestive heart failure, NYHA class II - IV * Severe renal dysfunction, defined as an estimated glomerular filtration rate (eGFR calculated by MDRD) \< 20 mL/min/1.73m2 at screening * Uncontrolled hyperthyroidism or hypothyroidism as defined by thyroid stimulating hormone (TSH) , 1.0 time the lower limit of normal (LLN) or \> 1.5 times the upper limit of normal (ULN), respectively, at screening * Symptomatic peripheral artery disease * History of drug or alcohol abuse * Active liver disease or hepatic dysfunction, defined as aspartate aminotransferase (AST) or alanine aminotransferase (ALT) 2 times the ULN as determined by local laboratory analysis at screening * Prior CVA or TIA * Malignancy (except non-melanoma skin cancers, cervical in-situ carcinoma, breast ductal carcinoma in situ or stage 1 prostate carcinoma) with life expectancy of \< 3 years * Any planned surgery within 3 months after randomization * Recipient of any major organ transplant (e.g., heart, lung, liver, bone marrow) * Severe, concomitant non-cardiovascular disease that is expected to reduce life expectancy to less than 3 years * Known, concerning active infection or major hematologic, renal, metabolic, gastrointestinal or endocrine dysfunction in the judgment of the investigator * Currently enrolled in another investigational device or drug study, or less than 30 days since ending another investigational device or drug study(s), or receiving other investigational agent(s). Special clearance can be obtained from the Steering Committee for subjects enrolled in studies not conflicting with this protocol * History or evidence of any other clinically significant disorder, condition or disease other than those outlined above that, in the opinion of the investigator may compromise the ability of the subject to give written informed consent, would pose a risk to the subject safety, or interfere with the study evaluation, procedures or completion * Deformities of the digits of the upper extremities, which preclude adequate signal acquisition * Subjects under the effect of short-acting NTG (3 hours washout period) * Patient suffering from a medical condition prohibiting blood flow occlusion in both arms