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

Background Chronic obstructive pulmonary disease (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 proBNP (NT-proBNP) and troponin T were measured on admission and were used to indicate cardiac stretch and myocardial injury respectively. Five-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.