Rytkin E, et al. - This research strived to inspect the effect of CYP2C19 and ABCB1 gene polymorphisms and CYP3A4 isoenzyme activity on stent implantation complications, among patients with an acute coronary syndrome (ACS) who underwent percutaneous coronary intervention (PCI). No evidence was yielded with regard to the presence of CYP2C19*2, CYP2C19*17, and ABCB1 3435 polymorphisms possibly jeopardizing the safety of stent implantation in patients with an ACS. Patients with low CYP3A4 isoenzyme activity could present with an increased risk of stent thrombosis.