In-Hospital Outcomes of Acute Myocarditis in Adults With Systemic Inflammatory Disease: A Perspective on the Nationally Representative Sample Within the United States

Background Systemic inflammatory diseases (SID) are associated with adverse cardiovascular (CV) events due to the derangement in innate immunity. Understanding the association with acute myocarditis (AMC) is crucial for preemptive management strategies and improving patient outcomes. Methods We identified and compared adults (>18 years) with SID versus non-SID who were hospitalized with AMC using a large, nationally representative inpatient database from 2016 to 2021 and standardized diagnostic codes. Six SIDs were selected based on the distribution of human leukocyte antigens (HLA). The risks of all-cause mortality and major adverse cardiac and cerebrovascular events (ischemic stroke, cardiac arrest, acute heart failure (AHF), ventricular arrhythmia (VA), complete atrioventricular block, acute myocardial infarction (AMI)) and use of circulatory support were assessed in adult AMC admissions with and without SID after adjusting for confounders. SID was divided into six cohorts: systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), psoriasis (PS), inflammatory bowel disease (IBD), Hashimoto's thyroiditis, and multiple sclerosis (MS) subgroups. Results Overall, there were 34,540 adult admissions to AMC. Prevalence of AMC in non-SID 96% (34,540/35,865). The mean age of non-SID was similar across the four cohorts, but relatively older in RA and MS (60.8 and 59.5 years, respectively). The cohorts also had a higher proportion of females in the PS and IBD cohorts. Hypertension, peripheral vascular disease, and smoking were more frequently seen in the SID-AMC cohort. At the same time, obesity was more regularly seen in RA and MS, diabetes mellitus (DM) was more commonly seen in SLE and MS, and hyperlipidemia was more frequent with SLE, RA, PS, and MS. The RA-AMC cohort had significantly higher adjusted odds of using mechanical circulatory support (adjusted odds ratio (aOR) 2.8, CI 1.22-6.55, p = 0.015) after adjusting for sex, dyslipidemia, DM, and chronic kidney disease (CKD). However, odds outcomes of acute, VA, mortality, and major adverse cardiovascular events were not statistically significant. Conclusions The RA-AMC cohort is 280% more likely to require mechanical circulatory support during hospitalization for AMC, suggesting worse AHF and cardiogenic shock outcomes. Prospective studies would be necessary to further examine the cardiovascular outcomes in this cohort.