Biochemical markers of cardiac dysfunction predict mortality in acute exacerbations of COPD

BACKGROUND: Retrospective studies suggest that plasma levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiac troponin T are often elevated in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) and are associated with increased mortality. These cardiac biomarkers were investigated in an unselected cohort of patients admitted to hospital with exacerbations of COPD. METHODS: Consecutive patients with physician-diagnosed COPD exacerbation but without clinical evidence of acute cardiac disease admitted to a public hospital over a 1 year period were studied prospectively. NT-proBNP and troponin T were measured on admission. The primary end point was all-cause mortality at 30 days. RESULTS: Elevated NT-proBNP (>220 pmol/l) was present in 65/244 patients (27.5%) and significantly predicted 30-day mortality (OR 9.0, 95% CI 3.1 to 26.2, p0.03 μg/l) was found in 40/241 patients (16.6%) and also predicted 30-day mortality (OR 6.3, 95% CI 2.4 to 16.5, p<0.001). These associations persisted after adjusting for other clinical and laboratory predictors of mortality (arterial CO(2) pressure (Paco(2)), body mass index and CURB65 score). NT-proBNP and troponin T levels appeared to have additive associations with mortality: 30-day mortality among patients with abnormalities of both NT-proBNP and troponin T was 15-fold higher than among patients with normal values. CONCLUSION: Elevated levels of NT-proBNP and troponin T are strong predictors of early mortality among patients admitted to hospital with acute exacerbations of COPD independently of other known prognostic indicators. The pathophysiological basis for this is unknown, but indicates that cardiac involvement in exacerbations of COPD may be an important determinant of prognosis.