Coronary no-reflow phenomenon (CNR) is a complication of primary percutaneous coronary intervention (PCI). According to different reports, CNR occurs in 10 to 60 % of cases. Despite the long history of studying this phenomenon many issues remain unsolved. This article presents a clinical case of electrocardiographically confirmed ST-segment elevation myocardial infarction. In this case, the CNR phenomenon occurred during PCI and was associated with heart rhythm disorders, left ventricular (LV) cavity dilatation with a decrease in LV contractility, and formation of intracavitary thrombus. The patient asked for medical care late, which could influence the development of CNR. This case demonstrates the clinical significance, diagnostic characteristics, and successful drug correction of the no-reflow phenomenon.