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Hospitalized patients with influenza showed significant left and right ventricular dysfunction, comparable to findings in patients with COVID-19 infection.

Influenza infection has been associated with multiple cardiovascular complications. In new research from the FluHeart study published in Influenza and Other Respiratory Viruses, investigators examined the effects of influenza infection on cardiac function in hospitalized patients.

The FluHeart study was a prospective cohort study of hospitalized patients with laboratory-confirmed influenza infection at 2 hospitals in Copenhagen during the 2021-2022 influenza season. For the study, Kristoffer Grundtvig Skaaru, MD, and colleagues used echocardiography to assess cardiac function in patients matched 1:1:1 for age, sex, and heart failure status with control participants from the general population and patients hospitalized with COVID-19.

This interim analysis included 108 patients (36 patients with influenza, 36 control participants, and 36 patients with COVID-19). Mean age was 72±18 years, and 58% of study participants were men. Median time from admission to echocardiography was 1 day (interquartile intervals [IQI]: 1:1) for patients with influenza.

Among the patients, a majority (75%) exhibited any left ventricular (LV) dysfunction, whereas any right ventricular dysfunction (RV) was less frequent (20%). In addition, biochemical assessments showed levels of myocardial injury and acute heart failure similar to the occurrence of RV dysfunction. N-terminal pro-brain natriuretic peptide levels were elevated (≥300 pg/mL) in 61.5% of patients, and 19.2% of patients exhibited myocardial injury with elevated high-sensitivity troponin I levels.

Both LV and RV function were significantly worse for patients with influenza versus matched control participants. LV dysfunction was 10.2 (IQI, 8.4; 14.1) for patients with influenza versus 8.8 (IQI: 6.6; 11.1; P=0.026) for control participants, but no difference was observed regarding the systolic measurements for LV ejection fraction and global longitudinal strain. Of the investigated RV function parameters, tricuspid annular plane systolic excursion was significantly lower in patients with influenza compared with matched control participants (2.1 cm; IQI, 1.8; 2.3 vs 2.4 cm; IQI, 2.2; 2.7; P=0.001).

When examining cardiac parameters, the researchers observed no differences in LV function, RV function, or cardiac biomarker levels between patients with influenza and patients with COVID-19. Also, echocardiographic measures did not differ considerably between these cohorts.

In conclusion, the authors said, “In this interim analysis of the FluHeart study, a substantial prevalence of both LV and RV dysfunction was observed among hospitalized influenza patients. Notably, RV and LV function measures were significantly worse in these patients than matched controls. The level of impairment resembled that observed in hospitalized COVID-19 patients.”