Diabetes increases the risk of heart failure in myocarditis: a propensity-matched nationwide database analysis

BACKGROUND AND AIMS: The impact of diabetes on non-atherosclerotic cardiac disease has not been studied extensively. We aimed to assess the in-hospital and long-term effects of diabetes in patients hospitalized for myocarditis. METHODS: The Nationwide Readmissions Database (2016-2020) was used to identify adults hospitalized with a primary diagnosis of myocarditis. Patients were stratified by the presence of diabetes, and those discharged alive were followed for a calendar year. The primary outcome was in-hospital mortality. Secondary outcomes included in-hospital ventricular fibrillation, ventricular tachycardia, acute renal failure, cardiogenic shock, heart failure, and one-year all-cause readmission, readmission for heart failure, and mortality. Multivariable logistic and Cox regression models were applied, and propensity score matching was performed as a sensitivity analysis. RESULTS: Among 8826 adults with myocarditis, 951 (11%) had diabetes. Compared with patients without diabetes, those with diabetes were older, had a higher prevalence of comorbidities, and showed an increased adjusted risk of in-hospital acute renal failure [aOR = 1.74 (95% CI: 1.42-2.12)], heart failure [aOR = 1.62 (95% CI: 1.37-1.91)], cardiogenic shock [aOR = 1.36 (95% CI: 1.04-1.78)], but not of mortality, ventricular fibrillation, and ventricular tachycardia. In one year, diabetes was not associated with higher adjusted risks of all-cause readmission or mortality [aHR = 0.81 (95% CI: 0.41-1.60) and aHR = 0.81 (95% CI: 0.68-0.97), respectively]. However, it was associated with a higher risk of readmission for heart failure [aHR = 1.16 (95% CI: 1.02-1.31)]. These associations remained consistent in propensity score-matched analyses. CONCLUSION: Diabetes independently increases the risk of in-hospital and one-year heart failure in patients with myocarditis.