Do cardiac biomarkers predict long-term outcomes from exacerbations of COPD?

Abstract

Background: A study of patients hospitalised for COPD exacerbations found that high N-terminal pro-B-type natriuretic peptide (NT-proBNP) and troponin T levels were associated with higher 30-day mortality but not mortality between 30 days and 1 year (Chang et al. Thorax 2011;66:764-768). Aim: To study the associations between NT-proBNP and troponin T levels in COPD exacerbations and long-term outcomes in this cohort. Methods: 247 consecutive patients admitted with COPD exacerbations were followed up for 5 years for all-cause mortality and readmissions for COPD exacerbations and cardiac disease (heart failure / acute coronary syndromes). We analysed median survival and time to first readmission in patients with high NT-proBNP (>220pmol/L) and troponin T (>0.03mcg/L) levels. Associations between cardiac biomarkers and mortality were analysed using logistic regression adjusting for potential confounders including the severity of exacerbation. Results: Mortality at 30 days was 9% (n=21), 26% at 1 year (n=64) and 64% at 5 years (n=158). Patients with high NT-proBNP and troponin T had shorter survival than patients with normal biomarkers (median 11 vs 41 months, HR 2.48 (95%CI 1.54-3.99)), but this difference was due to a higher 30-day mortality. Cardiac biomarker levels at the time of the exacerbation did not predict subsequent mortality at 5 years and were not associated with time to readmission for either COPD or cardiac disease. Conclusion: In patients hospitalised for COPD exacerbations, abnormal cardiac biomarker levels are associated with higher early-mortality but not with long-term outcomes. Cardiac dysfunction in this setting is likely an acute event caused by the exacerbation rather than a chronic phenomenon.