In addition to NYHA functional class, more objective indices of functional capacity—such as peak oxygen uptake and the six minute walk test—also showed some relation to the quality of life. This contrasts with the report by Steptoe and colleagues,18 who found no univariate association between exercise capacity and quality of life in patients with mild to moderate congestive heart failure (predominantly in NYHA classes I and II); however, our present study included a broader spectrum of patients with congestive heart failure, with a large proportion in NYHA class III. Cardiopulmonary exercise testing and the six minute walk test represent different aspects of functional capacity, as only the latter—a submaximal exercise test—reflects the work load of daily activities.21 However, in accordance with the close relation between both these exercise tests,20 all SF-36 scales were related similarly to peak oxygen uptake and to the six minute walk test. In contrast, the left ventricular ejection fraction was not significantly correlated with any of the short form scales. Furthermore, there was no difference in health related quality of life in patients subgrouped according to their ejection fraction. This finding confirms the lack of relation between left ventricular ejection fraction and disease specific quality of life observed in other studies.32 33
The findings of our present study may also explain why β blocker treatment in congestive heart failure has no consistent effect on the quality of life, despite a pronounced improvement in left ventricular ejection fraction (for review, see Carson34), whereas the increase in peak oxygen uptake achieved by exercise training is associated with an improvement in quality of life.35
In general, the variance in the short form scales that can be explained by factors such as NYHA functional class, peak oxygen uptake, six minute walk test, left ventricular ejection fraction, age, and the duration of disease was small. Only the variance of physical functioning was determined to a considerable degree (51%) by NYHA functional class and the six minute