Cardiac biomarkers and long-term outcomes of exacerbations of COPD: a long-term follow-up of two cohorts

BACKGROUND: COPD patients often have cardiac comorbidities. Cardiac involvement at the time of a COPD exacerbation is associated with a high short-term mortality, but whether this influences long-term outcomes is unknown. We explored whether biomarkers of cardiac dysfunction at the time of a COPD exacerbation predict long-term outcomes. METHODS: Two prospective cohorts of patients admitted to Waikato Hospital for exacerbations of COPD were recruited during 2006–2007 and 2012–2013. N-terminal pro-B-type natriuretic peptide (NT-proBNP) and troponin T were measured on admission and were used to indicate cardiac stretch and myocardial injury, respectively. 5-year survival after discharge and subsequent admissions for cardiac disease and COPD exacerbations were analysed using Kaplan–Meier and Cox proportional hazards tests. RESULTS: The overall 5-year mortality was 61%. Patients with high NT-proBNP on admission had higher mortality than those with normal cardiac biomarkers (adjusted hazard ratio (aHR) 1.76, 95% CI 1.18–2.62). High NT-proBNP was also associated with a higher risk of future cardiac admissions (aHR 1.75, 95% CI 1.2–2.55). Troponin T levels were not associated with long-term survival (aHR 0.86, 95% CI 0.40–1.83) or future cardiac admissions (aHR 0.74, 95% CI 0.34–1.57). Neither biomarker predicted future COPD exacerbations. CONCLUSION: The long-term prognosis following a hospitalisation for an exacerbation of COPD is poor with less than half of patients surviving for 5 years. Elevated NT-proBNP at the time of a COPD exacerbation is associated with higher long-term mortality and a greater likelihood of future cardiac admissions, but not future COPD exacerbations.