Concomitant influenza infection associated with worse in-hospital outcomes in heart failure patients

Rates of in-hospital mortality, acute respiratory failure with and without mechanical ventilation, and acute kidney injury with and without dialysis were significantly higher in patients admitted with heart failure and influenza infection compared to admissions for heart failure alone.


Patients hospitalized with heart failure and influenza may be at higher risk for death and comorbidity than those without influenza, a recent study indicates.

Researchers used 2013-2014 data from the National Inpatient Sample database to determine the additional risk associated with influenza infection in patients hospitalized for heart failure. Adult patients with heart failure who were admitted to the hospital with and without concomitant influenza infection were propensity-score matched using age, race, sex, and comorbid conditions. The study's primary outcome was in-hospital mortality, while secondary outcomes included in-hospital complications, length of stay, and average hospital costs. The study results were published Jan. 3 by JACC: Heart Failure.

Among 8,189,119 all-cause hospitalizations in patients with heart failure, 54,590 (0.67%) involved concomitant infection with influenza. Patients with influenza were older (mean age, 73±14 years vs. 72±13 years; P=0.001) and were more likely to be women (54.5% vs. 50.9%; P=0.001) and to be white (72.5% vs. 71.5%; P=0.03) than patients without influenza. Patients with influenza had higher rates of in-hospital mortality (6.2% vs. 5.4%; odds ratio [OR], 1.15; P=0.02), acute respiratory failure (36.9% vs. 23.1%; OR, 1.95; P<0.001), acute respiratory failure requiring mechanical ventilation (18.2% vs. 11.3%; OR, 1.75; P<0.001), acute kidney injury (30.3% vs. 28.7%; OR, 1.08; P=0.01), and acute kidney injury requiring dialysis (2.4% vs. 1.8%; OR, 1.37; P=0.001). Mean length of stay was longer in patients with influenza (5.9 days vs. 5.2 days; P<0.001), but average hospital costs were similar to those in patients without influenza ($12,137 vs. $12,003; P=0.40).

The authors acknowledged that their study involved only hospital inpatients, that influenza diagnosis could not be verified, and that type, duration, and severity of heart failure could not be determined, among other limitations. However, they concluded that in-hospital mortality and clinical outcomes appear to be worse in patients with heart failure and influenza infection. They called for increased emphasis on increasing influenza vaccination rates and developing vaccines that provide better protection.

An accompanying editorial noted that the influenza season evaluated in the study involved a particularly virulent influenza strain and said that an investigation of influenza and heart failure during other seasons and within the influenza season by month would have been helpful. The authors also pointed out that the flu vaccine does not always offer robust protection in patients with heart failure and that the optimal vaccine formulation in this population is not yet clear. However, the editorial authors said that the study's results clearly show that the contribution of influenza to morbidity and mortality in patients with heart failure is significant and should be addressed.

“Despite a growing armamentarium for treating patients with heart failure, traditional therapies cannot modify this increased risk,” the editorialists wrote. “Although vaccination remains the best way to reduce the added risk conferred by influenza, the strikingly low vaccination rates of some of our most vulnerable patients represent both a significant public health challenge and a substantial opportunity.”

In other cardiology news, the FDA recently released a warning about increased risk for ruptures or tears in the aorta in certain patients who use fluoroquinolones, based on an agency review. The estimated background risk of aortic aneurysm ranges from nine aortic aneurysm events per 100,000 people per year in the general population to 300 aortic aneurysm events per 100,000 people per year in individuals at the highest risk.

Fluoroquinolones should not be used in patients at increased risk (e.g., those with a history of blockages or aneurysms of the aorta or other blood vessels, those with hypertension, and the elderly) unless there are no other treatment options available, the FDA said. A new warning about this risk will be added to the prescribing information and patient medication guide for all fluoroquinolones.