Myocardial Involvement Is Just as Common in Patients Hospitalised for Influenza as in Those Hospitalised for Covid-19: Insights From the GEMINI Initiative

BACKGROUND: The possibility of myocardial involvement is well recognised with Covid-19 infection but less so with influenza. We designed this study to explore the frequency of elevated biomarkers and new clinical cardiac diagnoses in patients hospitalised with influenza or Covid-19. METHODS: This was a retrospective cohort study of all adults hospitalised from April 2015 to March 2023 with either influenza or Covid-19 in 29 hospitals in Ontario. We used multivariable regression with generalised estimating equations to compare troponin and natriuretic peptide levels and new cardiac diagnoses during the index hospitalisations. RESULTS: The 25,200 patients with Covid-19 were younger (67 vs 72 years) and more likely to be men (56% vs 47%), and fewer had prior cardiovascular disease (7% vs 13%) than the 8569 patients with influenza (all P < 0.001). Although more likely to have their troponin (84.2% vs 78.7%; P < 0.001) or natriuretic peptides (21.6% vs 12.7%; P < 0.001) measured, patients with Covid-19 were not more likely to have elevated levels compared with influenza patients: 42.7% vs 39.8% for troponin (adjusted risk ratio [aRR] 1.07, 95% CI 0.99-1.15), and 72.3% vs 81.7% for natriuretic peptides (aRR 0.93, 95% CI 0.87-0.99). The frequency of new clinical diagnoses of heart failure (2.4% vs, 2.6%, aRR 1.18, 95% CI 0.79-1.77) or new atrial fibrillation (3.4% vs 5.2%, aRR 0.89, 95% CI 0.79-1.77) did not differ between those with Covid-19 or influenza. CONCLUSIONS: The frequencies of elevated troponins (two-fifths) and natriuretic peptides (three-fourths) were similar in patients hospitalised with influenza and Covid-19 who had biomarkers measured, but the frequencies of clinically recognised diagnoses were low.