Screening and recruitment
Participants were identified during routine clinical visits at each of the participating centers. Potential participants (i.e., patients with HFrEF and NYHA class II or III symptoms, aged at least 18 years, with the absence of exclusion criteria 1 to 7 as listed in the Eligibility section) underwent a screening phase, which consisted of the 6MWT. Participants who walked more than 450 m during the 6MWT (exclusion criterion 8) or those who failed to perform the 6MWT (exclusion criterion 9) were excluded.The total number of HFrEF patients evaluated for the absence of exclusion criteria 1 to 7 (i.e., the criteria that can be assessed based on electronic medical records and routine examination) was not collected during this study as it would not be sufficiently reliable. However, the number and characteristics of the patients who underwent the screening phase (i.e., the 6MWT) were recorded and will be reported.Following the screening phase, a physician or a research nurse explained the study in detail to all eligible patients. Those who agreed to participate were provided with an informed consent form, indicating their full understanding of the study and their protected rights for confidentiality and withdrawal from the study without giving a reason.