Worse In-Hospital Outcomes Among Patients With Heart Failure (HF) and Concomitant Influenza Infection.

Introduction:  A sizable proportion of heart failure (HF) admissions is precipitated by respiratory infections. Influenza has been linked to higher rates of HF hospitalizations and in-hospital morbidity and mortality.

Aim/objective:  We aim to describe the in-hospital outcomes of systolic HF vs. diastolic HF admissions with concomitant influenza infection in US hospitalizations from 2016 to 2017.  Materials and Methods: We queried the National Inpatient Sample (NIS) from 2016 to 2017 for discharge diagnosis for SHF and DHF and influenza per ICD-10 CM codes. Using binominal logistic regression analysis and adjusting for demographic and comorbid conditions, we compared the outcomes of SHF vs. DHF admissions with concomitant influenza as an independent risk factor for inpatient mortality, acute respiratory failure, ICU admission, assisted ventilation, as well as length of stay, and total hospital costs.

Results:  A total of 7,490,596 HF weighted admissions were analyzed, among which 0.9% had concomitant influenza infection. SHF and DHF admissions with influenza had higher mortality, ICU admission, ventilation assistance, and acute respiratory failure when compared to those without influenza. Among influenza admissions, those with SHF had higher mortality (6.6% vs. 5%, adjusted odds ratio - aOR 1.31, p<0.001) compared to DHF. While intensive care unit (ICU) admission (7.8% vs. 5.2%, aOR 1.30, p<0.001) and ventilation assistance rates (22.1% vs. 18.9%, aOR 1.15, p<0.001) were greater among SHF patients with influenza, acute respiratory failure was more common amongst diastolic HF with influenza (46.6% vs. 51.2%, aOR 0.86, p<0.001). Finally, SHF patients with concomitant influenza had higher inpatient costs ($82,788) when compared to diastolic HF patients ($66,373) and a longer in-hospital stay (7.29 days compared to 6.98 days in the diastolic HF group) p <0.001.

Conclusion:  Concomitant influenza infection in hospitalized patients with HF is associated with higher mortality, ICU admission, and the need for assisted ventilation, especially in those with SHF. A greater emphasis on vaccination against influenza may improve in-patient outcomes among HF patients.