Cardiac response and N-terminal-pro-brain natriuretic peptide kinetics during exercise in patients with COPD.

BACKGROUND COPD increases the risk of cardiovascular problems. Dyspnea on exertion can be associated with COPD or heart failure or both. N-terminal-pro-brain natriuretic peptide (NT-pro-BNP) is a marker of cardiac dysfunction, and exercise testing can identify subtle heart abnormalities. OBJECTIVE To determine whether cardiac dysfunction adds to the mechanism of dyspnea caused primarily by impaired lung function in patients with mild to moderate COPD. METHODS With 19 COPD patients and 10 healthy control subjects we measured physiologic variables and collected venous blood samples before and during incremental and constant-work-rate exercise, and measured NT-pro-BNP. RESULTS Peak oxygen uptake and constant-work exercise time were significantly lower in the COPD group than in the control group (16 ± 4 mL/min/kg vs 19 ± 6 mL/min/kg, P = .04, and 7.8 ± 6.5 min vs 14.8 ± 7.3 min, P = .02). Between the groups there were no significant differences in anaerobic threshold, oxygen pulse (oxygen uptake divided by heart rate), or heart-rate reserve (difference between predicted and measured maximum heart rate). Both at rest and during constant-work exercise, NT-pro-BNP was not significantly higher in the COPD group than in the control group. In the COPD patients there was no significant correlation between constant-work exercise time and NT-pro-BNP at rest or during exercise. CONCLUSIONS Heart failure did not contribute to exercise intolerance in patients with mild to moderate COPD.