Cardiac troponin I for prediction of clinical outcomes and cardiac function through 3-month follow-up after primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

Background Circulating levels of cardiac troponin I (cTnI) after ST-segment elevation myocardial infarction (STEMI) are associated with infarct size and chronic left ventricular dysfunction, but the relation to clinical end points and biochemical measures of global cardiac function remains less well defined. Methods One thousand sixty-six patients receiving primary percutaneous coronary intervention (PCI) in the PROTECTION AMI trial were studied in a post hoc analysis. Cardiac troponin I was measured at several time points during the index hospitalization, and patients were followed up for 3 months before reassessment including N-terminal pro-B-type natriuretic peptide (NT-proBNP) and left ventricular ejection fraction (LVEF) measurements. Results The median (quartile 1-3) cTnI levels were 0.4 (0.1-0.4) mu g/L at admission, 33.1 (12.8-72.1) mu g/L after 16 to 24 hours, and 9.1 (3.9-17.5) mu g/L after 70 to 80 hours. In adjusted models, all post-PCI single points, peak, and area under curve were found to be independently associated with clinical events, NT-proBNP >118 pmol/L, or LVEF <40% (P for all <.001). When cTnI was added to a baseline risk model for prediction of clinical events, the C statistic improved from 0.779 to 0.846 (16-24 hours) and 0.859 (70-80 hours). Quantified by integrated discrimination improvement, the addition of cTnI significantly augmented prediction ability (relative integrated discrimination improvement 44%-154%; P for all <=.001). Consistent improvements in discrimination of NT-proBNP >118 pmol/L and LVEF <40% were observed. Conclusions Cardiac troponin I measured after primary PCI for STEMI is independently associated with clinical outcomes and cardiac function through 3-month follow-up. These results suggest that cTnI levels are a useful risk stratification tool in STEMI patients.