Flu infection ups hospitalization, deaths in patients with heart failure

Seasonal influenza can increase the risk of morbidity and mortality in patients with heart failure (HF), according to a study.

A team of investigators obtained data on weekly number of deaths and hospitalizations among HF patients in Denmark and weekly estimates of flu circulation as determined by the number of positive flu samples analysed at Danish hospitals.

The investigators used a time series linear regression model to correlate the data and to estimate the annual excess number of deaths and hospitalizations attributable to influenza circulation among HF patients in Denmark. This model also included data on weekly mean temperature and restricted cubic spline terms to account for seasonality and trends over time.

Data from 2010 to 2018 were available, covering eight flu seasons with an annual mean of 25,180 samples tested for flu at Danish hospitals.

In a mean of 70,570 HF patients yearly, flu activity correlated with an annual excess of 250 all-cause deaths (95 percent confidence interval [CI], 144‒489), representing 2.6 percent of all all-cause deaths (95 percent CI, 1.5‒5.1) in this population.

Influenza also resulted in an annual excess of 115 cardiovascular deaths (95 percent CI, 62‒244), representing 2.9 percent of all cardiovascular deaths (95 percent CI, 1.5‒6.1). In addition, flu activity correlated with an annual excess of 251 hospitalizations for pneumonia or influenza (95 percent CI, 107‒533), which corresponded to 5.0 percent of all hospitalizations.

“[O]ur study suggests that approximately 2.6 percent of all deaths and 5.0 percent of all hospitalizations with influenza or pneumonia may be attributed to influenza in patients with HF,” the investigators said.