IJCS | Volume 32, Nº2, March/April 2019

141 Morais and Rassi Six-minute walk test in heart failure Int J Cardiovasc Sci. 2019;32(2)134-142 Original Article In hierarchical analysis, clinical and physical functional factors showed a greater impact on 6MWD; in contrast, sociodemographic and emotional factors showed little effect. These findings differ from previous studies showing that emotional factors, especially depression, were associated with poor functional capacity and shorter 6MWD. 21,22,24 These discrepancies may be related to characteristics of the study population, including age, severity of HF, comorbidities such as COPD and asthma, as well as use of walking aids (not observed in our population). This study had some limitations – the outcome measures accounted for less than half of the variance of the 6MWD, and other factors that contributed for 63% of the variance need further investigation. It is possible that physiological factors, including renal function and B-type natriuretic peptide (BNP), contribute to these differences. These factors have been frequently reported as predictive factors of the 6MWD and were not evaluated in our study. In addition, most of our patients were NYHA class I and II and in most of them had Chagas’ heart disease. The possibility that the inclusion of patients with worse functional status could lead to different results cannot be ruled out. Lack of homogeneity of the samples in the studies made it difficult to compare the results. Performance of the second 6MWT and the size of the hallway were not standardized among the studies either. In most studies, only one test was performed, and a hallway shorter than 30 meters was used in the tests. Repeated administration may influence the 6MWD, which is known as the learning effect. 31 Also, themeasurement of the HGS considered for analysis is not standardized; in this study, we decided to consider the mean of three measurements, rather than the highest measurement, since this is the most common method described in the literature. Sex and age are expected to influence the 6MWD, regardless of the presence of HF. 25 Nevertheless, both pulmonary function anddyspnea onADLs aremodifiable variables that may be altered inHF. In addition, we found a bivariate correlation of the 6MWD with Borg scale, Charlson comorbidity index, MIP, MEP and HGS. These findings indicate that a careful and systematic approach by a multidisciplinary team is crucial for better outcome and impact on functional capacity of HF patients. Most patients had a sedentary lifestyle in our study. However, although active subjects covered a longer distance during the 6MWT, it was not statistically different (despite a trend) than that in sedentary subjects. Regular physical activity has well documented beneficial effects on peripheral muscle function, pulmonary function, exercise tolerance and quality of life, and hence is important in patients with HF. 32,33 Determinants of functional capacity are multifactorial, dependi ng on demograph i c , soc i oeconomi c , physiological, cultural and psychosocial factors. 34,35 Therefore, predictive factors may differ between cultural and sociodemographic profiles. Also, in the present study, most patients had Chagas’ heart disease, as the study was conducted in an endemic region of Chagas disease in Brazil. This is different from the studies cited throughout this article. Conclusion Four variables were identified as determinants of a shorter 6MWD in patients with chronic HF – severe dyspnea on ADLs (mMRC), female sex, older age, and lower FVC. Other variables, not explored in the present study, explain 63% of the variance in the 6MWD, indicating the multidimensionality of functional capacity in chronic HF patients. Author contributions Conception and design of the research: Morais ER, Rassi S. Acquisition of data: Morais ER. Analysis and interpretation of the data: Morais ER, Rassi S. Statistical analysis: Morais ER, Rassi S. Writing of the manuscript: Morais ER, Rassi S. Critical revision of the manuscript for intellectual content: Morais ER, Rassi S. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding There were no external funding sources for this study. Study Association This article is part of the thesis of Doctoral submitted by Elizabeth Rodrigues de Morais, from Universidade Federal de Goiás. Ethics approval and consent to participate This study was approved by the Ethics Committee of the General Hospital of the Federal University of