Association of Contemporary Sensitive Troponin I Levels at Baseline and Change at 1 Year With Long-Term Coronary Events Following Myocardial Infarction or Unstable Angina : Results From the LIPID Study (Long-Term Intervention With Pravastatin in Ischaemic Disease)

Abstract

Objectives This study sought to assess whether baseline and change in contemporary sensitive troponin I (TnI) levels predicts coronary heart disease (CHD) death and myocardial infarction (MI), and to determine the effects of pravastatin on TnI levels. Background The role of troponins in predicting long-term outcomes in patients with stable CHD is not clearly defined. Methods The LIPID (Long-Term Intervention With Pravastatin in Ischaemic Disease) study randomized patients with cholesterol levels of 155 to 271 mg/dl 3 to 36 months after MI or unstable angina to placebo or pravastatin 40 mg per day. TnI levels were measured at baseline and after 1 year in 7,863 patients. Median follow-up was 6 years. Change in TnI was defined as moving up or down 1 tertile or ≥50% change. Results Baseline TnI tertiles were <0.006 ng/ml, 0.006 to <0.018 ng/ml, and ≥0.018 ng/ml. TnI levels were related to CHD death and MI after adjustment for 23 risk factors and treatment (≥0.018 ng/ml vs. <0.006 ng/ml hazard ratio [HR]: 1.64; 95% CI: 1.41 to 1.90; p < 0.001). TnI levels increased in 23.0%, were unchanged in 51.3%, and decreased in 25.7% of patients. Pravastatin decreased TnI levels by 0.003 ng/ml versus placebo (p = 0.002). In landmark analyses, increases in TnI levels were associated with increased numbers of CHD death and MI (HR: 1.31; 95% CI: 1.06 to 1.62) and decreases with decreased risk (HR: 0.90; 95% CI: 0.74 to 1.09; overall p = 0.01). Data were similar with 50% change criteria. Net reclassification improvement by adding TnI to the baseline model for CHD death and MI was 4.8% (p = 0.01). Conclusions Baseline TnI levels and change at 1 year are independent predictors of CHD death and MI. TnI levels are strong predictors of risk, and change modifies risk.