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.