Acute Cardiovascular Events Associated With Influenza in Hospitalized Adults: A Cross-sectional Study

Background Influenza may contribute to the burden of acute cardiovascular events during annual influenza epidemics. Objective To examine acute cardiovascular events and determine risk factors for acute heart failure (aHF) and acute ischemic heart disease (aIHD) in adults with a hospitalization associated with laboratory-confirmed influenza. Design Cross-sectional study. Setting U.S. Influenza Hospitalization Surveillance Network during the 2010-to-2011 through 2017-to-2018 influenza seasons. Participants Adults hospitalized with laboratory-confirmed influenza and identified through influenza testing ordered by a practitioner. Measurements Acute cardiovascular events were ascertained using discharge codes from the International Classification of Diseases (ICD), Ninth Revision, Clinical Modification, and ICD, 10th Revision. Age, sex, race/ethnicity, tobacco use, chronic conditions, influenza vaccination, influenza antiviral medication, and influenza type or subtype were included as exposures in logistic regression models, and marginal adjusted risk ratios and 95% CIs were estimated to describe factors associated with aHF or aIHD. Results Among 89 999 adults with laboratory-confirmed influenza, 80 261 had complete medical record abstractions and available ICD codes (median age, 69 years [interquartile range, 54 to 81 years]) and 11.7% had an acute cardiovascular event. The most common such events (non-mutually exclusive) were aHF (6.2%) and aIHD (5.7%). Older age, tobacco use, underlying cardiovascular disease, diabetes, and renal disease were significantly associated with higher risk for aHF and aIHD in adults hospitalized with laboratory-confirmed influenza. Limitation Underdetection of cases was likely because influenza testing was based on practitioner orders. Acute cardiovascular events were identified by ICD discharge codes and may be subject to misclassification bias. Conclusion In this population-based study of adults hospitalized with influenza, almost 12% of patients had an acute cardiovascular event. Clinicians should ensure high rates of influenza vaccination, especially in those with underlying chronic conditions, to protect against acute cardiovascular events associated with influenza. Primary funding source Centers for Disease Control and Prevention.