Comparison of Endothelial Dysfunction (BMS vs SES) in the Same Patient With Multiple Coronary Artery Lesions

Inclusion Criteria: * stable angina pectoris * at least two significant angiographic stenoses in different native coronary vessels or in the same vessel but two different ramifications with similar diameter * non-surgical patients Exclusion Criteria: * acute coronary syndromes * myocardial infarction within 3 months from event * clinical or angiographic coronary vasospasm * coronary angiographic findings of a fresh thrombus in the initial angiography (filling defect proximal to or involving the stenosis) * coronary anatomy unsuitable for for intracoronary acetylcholine testing (left main coronary artery disease \>30%, surgical three vessel disease or other anatomical considerations that make it unsafe to perform intracoronary studies) * progression of lesions or development of de novo lesions in nontarget lesions or vessels on follow-up angiography * patients with a vessel diameter \< 2,50 mm and length lesions \<10 and \>30 mm. * patients with vessel diameter difference (SES vs BMS) \>0,5mm and length difference of the stenosis \>50% * lesions treated with balloon injury \<10 mm or \>50 mm in length * severe left ventricular (LV) systolic dysfunction * bifurcation/ostial * presence of an unhealed dissection identified by intravascular ultrasound (IVUS) performed at the end of the study. * angiographic restenosis in follow-up angiography * patients with severe risk factors for endothelial dysfunction: severe renal failure, life expectancy less than 1 year, uncontrolled diabetes, uncontrolled hypertension (systolic blood pressure \>180mmHg), currently smoking, uncontrolled hypercholesterolemia (total cholesterol \>240mg/dl) * any contraindication/nontolerance to the use of aspirin, heparin and/or clopidogrel * lack of consent to participate