Patients undergoing PCI and IVUS pullback for the target vessel will be enrolled in a prospective study. Before PCI and at 24 month follow up fasting blood will be collected for glucose, HbA1c, insulin, C peptide, lipid profile assessment and the homeostasis model assessment of insulin resistance (HOMA-IR) calculation. Patients' baseline demographic characteristics, medical history, and procedural data will be collected during the index hospitalization and at 24 month follow up. Patients will be divided in groups according to HbA1c - control group (HbA1c<5.7) and prediabetic patients (HbA1c 5.7-6.4). PCI will be performed in accordance with the guidelines. After successful treatment of the culprit lesion IVUS will be done. Following PCI and IVUS patients with prediabetes will be randomly assigned in groups either receiving metformin at a dose of 2000 mg once daily plus standard lifestyle recommendations or standard lifestyle recommendations only. Intravascular ultrasound analysis will be repeated 24 months after the initial PCI.