Functional Capacity in Heart Failure. Comparison of Methods for Assessment and Their Relation to Other Indexes of Heart Failure. The V-HeFT VA Cooperative Studies Group

Background: Left ventricular (LV) dysfunction plays a primary role in the pathogenesis of congestive heart failure and correlates with prognosis, but a strong quantitative relation between exercise performance and indexes of LV function has not been demonstrated. We examined the relation between LV ejection fraction at rest, oxygen consumption at peak exercise (VO2), patient and physician assessments of clinical severity, and other clinical attributes in 804 patients with moderate heart failure.

Methods And Results: Ejection fraction correlated weakly with VO2, and mean ejection fraction was related to severity of symptoms. There was a statistical association between the patient's self-assessed quality of life questionnaire score and the physician-assigned New York Heart Association (NYHA) functional class; NYHA class was statistically associated with exercise performance. To identify other factors that might influence exercise capacity, comparisons of clinical attributes were made between patients grouped by VO2 within each stratum of LV function. Exercise performance was inversely related to plasma norepinephrine levels within the ejection fraction < 25% stratum. The percentage of patients reaching their anaerobic threshold was not different between groups, yet the peak heart rate increased with VO2 within all strata. Elevated venous pressure and cardiomegaly were inversely related to exercise performance.

Conclusions: Clinical scales based on physician and patient assessment of symptoms were statistically associated with exercise capacity but do not accurately predict individual exercise performance. The strong association of heart rate response to exercise performance suggests that the variability of the chronotropic response to exercise contributes to differences in exercise capacity among patients with a similar degree of LV dysfunction.