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Influenza Outcomes in Heart Failure Patients
Study Questions:
What is the impact of acute influenza infection on outcomes in patients with heart failure (HF) admitted for any cause?
Methods:
The authors queried the National Inpatient Sample database—a US national database of all payers that includes approximately 94% of discharges—for all adults with heart failure (HF) with or without a concomitant influenza infection admitted for any cause. They performed a 1:1 propensity score matching using age, race, sex, discharge weights, insurance status, hospital characteristics, and comorbidities to identify a control sample without influenza. The primary outcome examined was in-hospital mortality. Other outcomes included incidence of acute kidney injury, respiratory failure, the use of mechanical circulatory support, length of stay, and average hospital costs.
Results:
Of 8,189,119 hospitalizations in patients with HF, the authors identified 54,590 inpatients (0.67% of the total sample) with concomitant influenza infection. In the propensity-matched population, patients with influenza had higher inpatient mortality (6.2% vs. 5.4%), acute respiratory failure (36.9% vs. 23.1%), acute kidney injury (30.3 vs. 28.7%), and longer length of stay (5.9 vs. 5.2 days). The use of mechanical circulatory support and average hospital costs were similar. Results were unchanged when accounting for the month of admission.
Conclusions:
Influenza infection was an independent predictor of adverse in-hospital clinical outcomes in patients with HF admitted for any cause.
Perspective:
This study extends what has been previously known on the impact of influenza on outcomes in patients with acute coronary syndromes to that of HF patients, and emphasizes the importance of influenza vaccination, which has repeatedly been shown to be associated with improved outcomes in high-risk populations. Interestingly, there was no increase in the use of mechanical circulatory support, or in the average hospital costs. The drivers of poor outcomes secondary to influenza thus may not be specific to exacerbating HF. It would have been interesting to examine the subgroup of patients admitted for acute chronic HF exacerbation and concomitant influenza—rather than the entire population of patients in whom HF is coded as a comorbidity—to better understand the impact of influenza on HF.
Clinical Topics: Heart Failure and Cardiomyopathies, Prevention, Acute Heart Failure
Keywords: Acute Kidney Injury, Comorbidity, Heart Failure, Hospital Costs, Hospital Mortality, Influenza, Human, Insurance Coverage, Length of Stay, Outcome Assessment, Health Care, Respiratory Insufficiency, Vaccination
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