Risk Factors, Trends, and Financial Impact for 30-Day Unplanned Readmissions in Patients Admitted With Myocarditis and COVID-19: Insights From the Healthcare Cost and Utilization Project (HCUP) Nationwide Readmission Database.

Background: The coronavirus disease 2019 (COVID-19) outbreak was first documented in Wuhan, China, in December 2019. Myocarditis, an inflammatory condition characterized by swelling and thickening of the heart muscle, has been linked to severe COVID-19 cases, contributing to worse clinical outcomes. The SARS-CoV-2 virus enters human cells through angiotensin-converting enzyme 2 (ACE2), and myocardial involvement can result from direct viral invasion, hyperinflammation, and immune-mediated damage. The exact prevalence of myocarditis among COVID-19 patients remains uncertain due to initial diagnostic limitations.

Objective: This study aims to evaluate the risk factors, trends, financial impact, and preventive strategies related to 30-day unplanned hospital readmission in patients diagnosed with both myocarditis and COVID-19.

Methodology: A retrospective analysis was conducted using a nationwide hospital database from 2020. Patients diagnosed with both myocarditis and COVID-19 were identified based on standardized diagnostic coding criteria. Confounding factors were addressed using multivariable logistic regression to adjust for demographics, comorbidities, and hospital characteristics.

Results: After applying inclusion and exclusion criteria, 28,726 patients were included, with 4,896 (17.04%) experiencing hospital readmission within 30 days. Compared to national readmission rates for other cardiovascular conditions, this rate is notably high. The median patient age was 67 years (interquartile range {IQR}: 56-78, p < 0.001). Women accounted for 38.1% of readmitted patients. Medicare was the primary insurer for 60.9% of the total cohort and 61.9% of those readmitted (p < 0.001). The median cost of the initial hospitalization was estimated at USD 56,480.37 (IQR: USD 56,433.13-56,930.00), highlighting the financial burden of these readmissions. Among readmitted patients, the median length of stay was seven days (IQR: 6-7 days). Multivariable logistic regression identified heart failure (adjusted odds ratio {AOR} 2.14, 95% confidence interval {CI}: 1.91-2.41, p < 0.001), chronic kidney disease (AOR 1.87, 95% CI: 1.63-2.14, p < 0.001), and diabetes mellitus (AOR 1.56, 95% CI: 1.38-1.76, p < 0.001) as the most significant comorbidities associated with readmission.

Conclusion: Our study found that the readmission rate of patients with COVID-19 and myocarditis was highest between days 7 and 14, with 42.3% of readmissions occurring in this period. This emphasizes the need for close post-discharge monitoring and timely follow-up appointments to reduce adverse outcomes. Additionally, patients with comorbidities such as heart failure, chronic kidney disease, and diabetes mellitus had a significantly higher risk of readmission, necessitating targeted management strategies. The substantial financial burden of readmissions underscores the need for healthcare system interventions to optimize post-discharge care.