Capacidade discriminativa do teste de degrau de 6 minutos na identificação da baixa capacidade funcional em pacientes com insuficiência cardíaca

Abstract

Introduction: Cardiovascular diseases (CVD) are the leading cause of death and disability- adjusted life years (DALYs) worldwide. In Brazil, heart failure (HF) stands out for the significant increase in hospitalizations and deaths, especially among the elderly. This condition reduces the functional capacity of patients, negatively impacting their quality of life. Assessment of physical fitness is essential for clinical management, and the 6-minute step test (6MST) is a practical alternative to the traditional 6-minute walk test (6MWT), especially in contexts with structural limitations. However, its applicability in HF still requires further investigation. Objective: To identify the cutoff point in the 6MST that is related to preserved functional exercise capacity in patients with heart failure. Methods: Cross-sectional, observational, and quantitative study, carried out between October 2022 and May 2024 at the Cardiology Outpatient Clinic of Hospital Universitário Walter Cantídio (UFC). A total of 112 adult patients diagnosed with HF (HFrEF, HFpEF, or HFmrEF) were included, excluding those with contraindications to physical exertion or limiting comorbidities. Participants underwent clinical evaluation, NYHA functional classification, 6-minute walk test (6MWT), quadriceps muscle strength assessment with a dynamometer, and 6-minute step test (6MST). Sociodemographic, anthropometric, and clinical variables were collected. Statistical analysis involved normality tests (Shapiro-Wilk), Pearson and Spearman correlations, ROC curve, and multiple linear regression, considering a significance level of p<0.05. The study was approved by the Human Research Ethics Committee, under opinion No. 6,066,757. Results: The total sample consisted of 112 participants, predominantly elderly women, overweight, preserved ejection fraction, and NYHA functional class I or II. In the 6MWT, patients walked, on average, 76.2% of the predicted distance, and in the 6MST, 67.5% of the expected steps (p<0.0001). Approximately 82.1% walked more than 300 meters in the 6MWT, indicating good functional capacity. The 6MST showed a moderate correlation with the 6MWT (r=0.689; p<0.001) and a weak to moderate correlation with quadriceps strength. In the regression analysis, advanced age, female gender, lower muscle strength and reduced ejection fraction were associated with worse performance in the 6MST. The ROC curve identified the cutoff point of 77 steps in the 6MST as indicative of preserved functional capacity, with a specificity of 90% and sensitivity of 78%. Conclusion: The 6MST proved to be an effective and accessible tool for functional assessment in patients with HF, showing good correlation with traditional tests and clinical parameters. Its application can optimize the planning of cardiovascular rehabilitation programs and expand access to functional assessment in different care contexts.