The reproducibility and sensitivity of the 6-min walk test in elderly patients with chronic heart failure

Abstract

The 6-min walk test (6-MWT) is used to estimate functional capacity. However, in elderly patients with chronic heart failure (CHF): (i) 1 year reproducibility of the 6-MWT; (ii) sensitivity of the 6-MWT to self-perceived changes in symptoms of heart failure; and (iii) implications for patient numbers required for studies using the 6-MWT as an endpoint have not been described. One thousand and seventy-seven patients with CHF, aged>60, with NYHA Class > or =II were recruited. Heart failure symptom assessment was determined using a questionnaire related to aspects of physical function, and patients performed a baseline 6-MWT, with follow-up 1 year later. Seventy-four patients with unchanged symptoms had an unchanged 6-MWT distance, with an overall intraclass correlation coefficient of 0.80 (95% CI=0.69-0.87). Four hundred and twenty-three patients reported an improvement in symptoms during follow-up. There was a negative correlation (r=-0.55; P=0.0001) between Delta symptoms and Delta 6-MWT (i.e. a reduced 6-MWT distance is associated with reduced symptom severity at follow-up). Five hundred and sixteen patients reported worsening symptoms of heart failure, a moderate inverse correlation (r=-0.53; P=0.0001) was displayed between Delta symptoms and Delta 6-MWT. For all patients, irrespective of symptom status, a high inverse correlation (r=-0.75; P=0.0001) was evident. On the basis of the data for patients with unchanged symptoms, it is calculated that to detect an increase in 6-MWT of 50 m, with 90% power, a study size of approximately 120 is required. In elderly patients with CHF, the 6-MWT shows satisfactory agreement when repeated 1 year later. Change in 6-MWT distance is sensitive to change in self-perceived symptoms of heart failure.