Heart failure among patients admitted with Influenza. The influenza subtypes, seasonality and mortality: A case series

Respiratory infections like influenza infections have been found to increase the risk of coronary artery disease and precipitate cardiac failure. However, Indian data is lacking. A retrospective observational study was done to describe patients with influenza infection who had concomitant heart failure (HF) requiring admission over 5 years (January 2013-December 2017). A total of 93 influenza cases were hospitalised during this time, of which 14 (15%) also had features of HF. Among them, the types of influenza infection were AH1N1 (6,43%), BH1N1 (4,29%), AH3N2 (3,21%) with one patient having both strains. Two-thirds of the HF were new onset (10, 71%), whereas rest were due to acute worsening of pre-existing HF (4, 29%). Ten (64.3%) of the patients had HF with reduced ejection fraction (HFrEF). The average hospital stay was 10 days with 2 (14%) deaths. The peak of influenza in August and September preceded the peak admission for HF. A total of 15% of influenza admissions have concomitant HF. They are predominantly due to influenza A H1N1 (43%), influenza A H3N2 (21%) and influenza B (29%). Only 7% had preceding influenza vaccination. Influenza during August and September appears to precede the peak of HF admissions which happen in October and November. Overall mortality was 14%