Inclusion Criteria:  Stable coronary artery disease scheduled for invasive treatment Age 18 - 80 years Planned treatment with ticagrelor or clopidogrel (according to European Cardiology Society guidelines)  Exclusion Criteria:  Hypersensitivity to ticagrelor or clopidogrel Active pathological bleeding History of intracranial haemorrhage Severe hepatic impairment Other contraindications to the use of ticagrelor or clopidogrel A need for oral anticoagulation therapy Concomitant therapy with a strong cytochrome P-450 3A inhibitor or inducer Untreated, clinically significant bradycardia or atrio-ventricular conduction disorders Patients requiring haemodialysis Clinically significant anemia and/or thrombocytopenia Pregnancy or breastfeeding Scheduled coronary artery bypass grafting (CABG) Any severe valvular heart disease requiring further interventional or surgical treatment Symptomatic bronchial asthma Chronic obstructive pulmonary disease (COPD) in stage C or D according to GOLD Carotid artery stenting, carotid endarterectomy in medical history NYHA IV heart failure patients Any mental disorder, that may influence on patient's compliance Any other, unmentioned here factor, which in the opinion of investigator may increase the risk of the procedures performed during the study