Objective: To assess the alterations of gastric mucosa, its pathomorphological and functional characteristics in patients with complete erosions suffering from chronic heart failure II-III NYHA functional class. Materials and Methods: 185 patients with complete erosions comprised the main group, while the control group consisted of 183 patients with incomplete erosions of the stomach. Patients in both groups had chronic heart failure II-III NYHA functional class. All patients underwent esophagogastroduodenoscopy with white light imaging (WLI), narrow-band imaging (NBI), and ZOOM modes, as well as biopsy sampling followed by pathomorphological examination, determination of Helicobacter pylori presence, and endoscopic pH-metry. The diagnosis of chronic heart failure was established based on anamnestic data and the results of instrumental and functional diagnostic methods, including electrocardiography (ECG), echocardiography, Holter monitoring of ECG, stress echocardiography, and coronary angiography. Results: The study utilized the classification of gastric erosive lesions by K. Toljamo (2012), according to which in the main group, mature erosions subtype Ia were detected in 83.8% of cases, while immature extensive erosions subtype Ib were found in 16.2%. In combination with haemorrhagic erosions (type III), complete erosions were detected in 12.6% of cases, while with incomplete erosions of type II, they were found in 11.4%. The combination of complete erosions with erosive prepyloric changes (type IV) was identified in 8.7%. In the control group, gastric erosive lesions were mainly represented by type III (41%) and type IV (38.8%). Based on the analysis of endoscopic changes in the gastric mucosa using WLI, NBI, and ZOOM modes, the most characteristic visual changes were identified for each type and subtype of erosive gastric mucosa alterations. In patients with chronic heart failure II-III NYHA functional class, gastritis was noted in 75.1% of cases in the main group and in 58.5% in the control group. Helicobacter pylori infection of weak degree was determined in 40.5% in the main group and 37.7% in the control group. Evaluation of endoscopic pH-metry showed predominantly hypochlorhydria in both groups - 70.8% in the main group and 48.6% in the control group. Conclusion: By comparing the macroscopic features of various gastric erosive lesions in WLI, NBI, and ZOOM modes according to the classification by K. Toljamo (2012), the most characteristic signs for each type and subtype were identified. High prevalence of gastritis was established among patients with chronic heart failure II-III NYHA functional class.