Outcomes of Acute Myocardial Infarction in Patients with Influenza and Other Viral Respiratory Infections

Background: Acute influenza infection can trigger acute myocardial infarction, however, outcome of patients with acute myocardial infarction during influenza infection is largely unknown. Methods: Patients ≥ 18 years old with ST-elevation and non-ST-elevation myocardial infarction during January 2013-December 2014 were identified using the National Inpatient Sample. The clinical outcomes were compared among patients who had no respiratory infection to the ones with influenza and other viral respiratory infections using propensity score-matched analysis. Results: Of 1,884,985 admissions for acute myocardial infarction, acute influenza and other viral infections were diagnosed in 9,885 and 11,485 patients, respectively, accounting for 1.1% of patients. Acute myocardial infarction patients with concomitant influenza infection had a worse outcome than those with acute myocardial infarction alone, in terms of in-hospital case fatality rate, development of shock, acute respiratory failure, acute kidney injury, and higher rate of blood transfusion after propensity scores. The length of stay is also significantly longer in influenza patients with acute myocardial infarction, compared with patients with acute myocardial infarction alone. However, patients who developed acute myocardial infarction during other viral respiratory infection have a higher rate of acute respiratory failure but overall lower mortality rate, and are less likely to develop shock or require blood transfusion after propensity match. Despite presenting with acute myocardial infarction, less than one-fourth of patients with concomitant influenza infection underwent coronary angiography, but more than half (51.4%) required revascularization. Conclusion: Influenza infection is associated with worse outcomes in acute myocardial infarction patients, and patients were less likely to receive further evaluation with invasive coronary angiography.