Prevalence and prognostic implications of myocardial injury in patients with influenza

Aims: Influenza may cause myocardial injury and trigger acute cardiovascular events. The aim of this study was to investigate the prevalence and prognostic implications of elevated high-sensitivity cardiac troponin I (hs-cTnI) in patients with influenza. Methods and results: In this prospective cohort study, we consecutively enrolled patients with influenza-like illness from two emergency departments in Sweden during three seasons of influenza, 2017-20. Ongoing Influenza infection was diagnosed by polymerase chain reaction and blood samples were collected for later analysis of hs-cTnI. All patients were followed-up for a composite endpoint of major adverse cardiovascular events (MACE) including death, myocardial infarction, unstable angina, heart failure, atrial fibrillation, and stroke within 1 year. Of the 466 patients with influenza-like symptoms, 181 (39%) were positive for influenza. Fifty (28%) patients were hospitalized. High-sensitivity cTnI was elevated in 11 (6%) patients and 8 (4%) experienced MACE. In univariate analyses, MACE was associated with age [hazard ratio (HR): 1.14, 95% confidence interval (CI): 1.05-1.23], hypertension (HR 5.56, 95%CI: 1.12-27.53), estimated glomerular filtration rate (HR: 0.94, 95%CI: 0.91-0.97), and elevated hs-cTnI (HR: 18.29, 95%CI: 4.57-73.24), N-terminal prohormone of brain natriuretic peptide (HR: 14.21, 95%CI: 1.75-115.5), hs-CRP (HR: 1.01, 95%CI: 1.00-1.02), and white blood cell count (HR: 1.12, 95%CI: 1.01-1.25). In multivariate analysis, elevated hs-cTnI was independently associated with MACE (HR: 4.96, 95%CI: 1.10-22.41). Conclusion: The prevalence of elevated hs-cTnI is low in unselected patients with influenza. Elevated hs-cTnI was associated with poor prognosis. A limitation is that the estimated associations are uncertain due to few events.