Abstract
Although a number of studies have investigated the prognostic significance of exercise variables, they have focused only on short-term prognosis in relatively severe heart failure. This study was carried out to determine whether the indices obtained during cardiopulmonary exercise testing have prognostic significance during a 10-year follow-up in mild to moderate heart failure. Three hundred and sixty-four consecutive patients with cardiac disease performed 4 min of 20-W warm-up, followed by a symptom-limited incremental exercise test on a cycle ergometer. In addition to the measurements of peak oxygen uptake (VO2) and gas exchange (anaerobic) threshold, the time constant of VO2 kinetics during the onset of warm-up exercise was calculated using a single exponential equation. Data on mortality were available for follow-up in 260 patients. After 3, 331±610 days of follow-up, 29 cardiovascular-related deaths occurred. The time constant of VO2 in the nonsurvivors was 76.7±43.3s and was significantly prolonged compared with that of survivors (55.3±30.6s, p=0.001). Peak VO2 and gas exchange threshold were both significantly lower in nonsurvivors than in survivors. Kaplan-Meier survival curves for 10 years of follow-up demonstrated a survival rate of 89.0% for patients with a normal VO2 time constant (<80s) and 71.7% for those with a longer time constant (≥80s), showing a significant difference in survival (p=0.0028). Respiratory gas parameters obtained during exercise testing, particularly the time constant of VO2 kinetics, were found to be useful for predicting long-term prognosis in patients with chronic heart failure. These results suggest that cardiopulmonary exercise testing could be more applicable in ambulatory patients with minimal symptoms or minimal functional impairment.
