"MetCool ACS"- Metformin "Cooling" Effect on Metformin-naive Patients Treated With PCI Because of Acute Coronary Syndrome

Inclusion Criteria: * Age \>18 years * ACS, according to the current definition of the European Society of Cardiology, treated with percutaneous coronary intervention with drug eluting stent implantation * Occupation and place of residence not causing difficulties in participating in control visits * Uncomplicated course of the disease (ACS) as assessed by the treating physician * Negative history of diabetes * Not taking any hypoglycaemic drugs prior to hospitalization immediately or within the last 6 months * HbA1c\< 6,5% (assessment during hospitalization) * Written consent to participate in the study Exclusion Criteria: * Significant valve disease confirmed by ECHO * Previous CABG * NYHA IV during hospitalization * Chronic kidney disease with GFR \<60 ml / min / 1.73 m2 according to MDRD * ALT three times above normal according to laboratory criteria * Serious co-morbidities and estimated survival less than 2.5 years, as assessed by the treating physician * Known gastrointestinal disease that may potentially be responsible for the intolerance to metformin (e.g. inflammatory bowel disease, gastro-oesophageal reflux disease) * Known potential difficulties in cooperation with patients (dementia, mental disorders, distance from the place of residence, if considered potentially problematic, alcoholism) * Hypersensitivity to metformin * Pregnancy and breastfeeding * Patient participation in another clinical trial