By Ankur Banerjee

(Reuters Health) – When people with heart failure are hospitalized, having influenza is tied to greater odds of respiratory and kidney complications and a higher chance they won’t survive to be discharged, a U.S. study suggests.

Using a national database, the researchers looked at more than 8 million heart failure-associated hospitalizations and identified 54,585 patients who had flu at the time. They compared this group to a similar group of heart failure patients hospitalized without flu.

The rate of acute kidney injury was 30.3 percent in patients with flu, compared to 28.7 percent in patients without influenza. Similarly, acute respiratory failure developed in 36.9 percent of the influenza group compared to 23.1 percent in the other group.

And 6.2 percent of patients with flu died in the hospital, compared to 5.4 percent of patients without flu, researchers reported in the medical journal JACC: Heart Failure.

Heart failure patients with influenza stayed longer in the hospital; half of them stayed longer than 5.9 days, while half of the patients without flu were discharged within 5.2 days.

Study co-author Dr. Ankur Kalra from the Cleveland Clinic in Ohio told Reuters Health that outcomes were the same no matter where the patients were hospitalized, calling it an eye-opener.

“One would tend to imagine that care delivered at a tertiary care medical center may be superior than community hospitals and that was not the case here,” Kalra said by phone.

Influenza is responsible for significant morbidity and mortality, and patients with heart failure are especially susceptible to complications, the authors wrote in their report.

They point out that although vaccination against the flu may reduce heart failure-associated morbidity and mortality, vaccination rates are low in the U.S., with less than half of all adults getting vaccinated during the 2016-17 influenza season.

The study’s results emphasize the need for increased efforts to boost vaccination rates and develop vaccines that provide more thorough protection, the authors argue.

An editorial published with the study says the results make it clear that the contribution of influenza to illness and death among heart failure patients “is neither negligible nor neglectable.”

In their editorial, Orly Vardeny of the VA Health Care System in Minneapolis, Minnesota and Dr. Scott Solomon of the Brigham and Women’s Hospital in Boston agree that although vaccination remains the best way to reduce the added risk conferred by influenza, the strikingly low vaccination rates of some of the most vulnerable patients represent both a significant public health challenge and a substantial opportunity.

The study’s limitations include the possibility that some of the database records may have been incomplete or incorrect, as well as the fact that researchers weren’t able to assess the severity of patients’ heart failure or the influence of vaccination status on outcomes.

Still, the authors say, their findings have important implications for patients and doctors and highlights the need for heightened efforts to prevent influenza infection in this high-risk cohort.

SOURCE: JACC: Heart Failure, online January 3, 2019.