C-Reactive Protein and Long-Term Risk of Death in Patients with Myocardial Infarction

Background and Aims The long-term prognostic value of standard C-reactive protein (CRP) in patients with myocardial infarction is unknown. Methods Using Danish nationwide registries, we identified patients with a first diagnosis of myocardial infarction from 2013 through 2020, who had a CRP measurement <=24 hours of index hospitalization. The primary outcome was death from any cause, and the secondary outcome was hospitalization or outpatient contact for new-onset heart failure. Absolute and relative risks for outcomes according to CRP quartiles at days 0-30 and 31-365 were calculated using multivariable Cox regression with average treatment effect modeling, adjusted for demographics and clinical features, including high-sensitivity troponin concentrations. Results A total of 29,035 patients with myocardial infarction were included. Median CRP was 4 mg/l, and quartile intervals were: quartile 1: <2.9 mg/l, quartile 2: 2.9 to <4 mg/l, quartile 3: 4 to <12 mg/l, and quartile 4: >=12 mg/l. At 0-30 days, 1,660 patients had died, and 1,861 died between days 31-365. The standardized absolute risk of death at both 0-30 and 31-365 days was lowest among patients in quartile 1 (0-30 days: 2.8%, 31-365 days: 4.1%) and highest among patients in quartile 4 (0-30 days: 9.7%, 31-365 days: 9.5%). The standardized relative risks of death increased in a stepwise fashion from quartile 2 to quartile 4 when using quartile 1 as the comparator. Similar findings were observed for heart failure. Conclusion Among patients with myocardial infarction, higher CRP concentrations were significantly associated with a higher risk of death and incident heart failure.