Prevalence of influenza and other acute respiratory illnesses in patients with acute myocardial infarction in Bangladesh: a cross-sectional study

Background: Several studies imply that influenza and other respiratory illness could lead to acute myocardial infarction (AMI), but data from low-income countries are scarce. We investigated the prevalence of recent respiratory illnesses and confirmed influenza in AMI patients, while also exploring their relationship with infarction severity as defined by ST-elevation MI (STEMI) or high troponin levels. Methods: This cross-sectional study, held at a Dhaka tertiary hospital from May 2017 to October 2018, involved AMI inpatients. The study examined self-reported clinical respiratory illnesses (CRI) in the week before AMI onset and confirmed influenza using baseline qRT-PCR. Results: Of 744 patients, 11.3% reported a recent CRI, most prominently during the 2017 influenza season (35.7%). qRT-PCR testing found evidence of influenza in 1.5% of 546 patients, with all positives among STEMI cases. Frequencies of CRI were higher in patients with STEMI and in those with high troponin levels, although these associations were not statistically significant after adjusting for other variables. The risk of STEMI was significantly greater during influenza seasons in unadjusted analysis (RR: 1.09, 95% CI: 1.02- 1.18), however, this relationship was not significant in the adjusted analysis (aRR: 1.03, 95% CI: 0.91- 1.16). Conclusions: In Bangladesh, many AMI patients had a recent respiratory illness history, with some showing evidence of influenza. However, these illnesses showed no significant relationship to AMI severity. Further research is needed to understand these associations better and to investigate the potential benefits of infection control measures and influenza vaccinations in reducing AMI incidence.