Aim. To analyze prevalence of heart failure (HF), clinical and demographic characteristics, health care utilization, and outcomes according to the used International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) codes in regional integrated electronic health record database in Saint Petersburg.Material and methods. The retrospective analysis of the Saint Petersburg regional integrated electronic health record database for 2019 was performed. At least one of the following ICD-10 codes has been considered as HF case: I50.x (standard coding) and/or I11.0, I13.0, I13.2, I25.5, I42.0, I42.9, I09.9, I43.0, I43.1, I43.2, I43.8, I42.5, I42.6, I42.7, I42.8 (extended coding).Results. A total of 64070 adult patients with HF had medical encounters in 2019, 34,5% of whom were identified using standard coding, 65,5% — using extended coding. The combination of codes was observed in 9,9% of cases. HF prevalence/mortality was 1,4%/6,8% in general, as well as 0,49%/15,7% and 0,93%/2,1% with standard and extended coding, respectively. HF patients had high healthcare utilization with the mean number of 14 encounters per patient per year. Actually, 24% of patients had more than 20 both inpatient and outpatient encounters and 54% of patients — at least 1 all-cause hospitalization during the year. Encounters of patients with HF accounted for 4,3% of all visits, 6,5% of all hospitalizations, 4,1% of all outpatient visits and 9,7% of all emergency contacts during the year. Patients identified by the standard coding compared with the extended coding had older age and higher incidence of comorbidities, as well as greater hospitalization and death rates, but lower number of outpatient visits.Conclusion. The prevalence of HF among the adult population of Saint. Petersburg in 2019 was 1,4%. HF was characterized by a high health care utilization and mortality rate reaching 15,7 % per year. The use of different approaches to coding presumably could help to identify different groups of patients with HF, which requires the adaptation of healthcare models and an active monitoring system to reduce the risk of adverse events.