Determinants of Exercise Intolerance in Elderly Heart Failure Patients With Preserved Ejection Fraction

ObjectivesThe purpose of this study was to determine the mechanisms responsible for reduced aerobic capacity (peak Vo2) in patients with heart failure with preserved ejection fraction (HFPEF).BackgroundHFPEF is the predominant form of heart failure in older persons. Exercise intolerance is the primary symptom among patients with HFPEF and a major determinant of reduced quality of life. In contrast to patients with heart failure and reduced ejection fraction, the mechanism of exercise intolerance in HFPEF is less well understood.MethodsLeft ventricular volumes (2-dimensional echocardiography), cardiac output, Vo2, and calculated arterial-venous oxygen content difference (A-Vo2 Diff) were measured at rest and during incremental, exhaustive upright cycle exercise in 48 HFPEF patients (age 69 ± 6 years) and 25 healthy age-matched controls.ResultsIn HFPEF patients compared with healthy controls, Vo2 was reduced at peak exercise (14.3 ± 0.5 ml·kg·min−1 vs. 20.4 ± 0.6 ml·kg·min−1; p < 0.0001) and was associated with a reduced peak cardiac output (6.3 ± 0.2 l·min−1 vs. 7.6 ± 0.2 l·min−1; p < 0.0001) and A-Vo2 Diff (17 ± 0.4 ml·dl−1 vs. 19 ± 0.4 ml·dl−1, p < 0.0007). The strongest independent predictor of peak Vo2 was the change in A-Vo2 Diff from rest to peak exercise (A-Vo2 Diff reserve) for both HFPEF patients (partial correlate, 0.58; standardized β coefficient, 0.66; p = 0.0002) and healthy controls (partial correlate, 0.61; standardized β coefficient, 0.41; p = 0.005).ConclusionsBoth reduced cardiac output and A-Vo2 Diff contribute significantly to the severe exercise intolerance in elderly HFPEF patients. The finding that A-Vo2 Diff reserve is an independent predictor of peak Vo2 suggests that peripheral, noncardiac factors are important contributors to exercise intolerance in these patients.