Myocarditis-Related Heart Failure Is Associated With Worse Inpatient Outcomes

Introduction Heart failure (HF) is one of the leading causes of hospitalizations among elderly adults, accounting for high rates of morbidity and mortality in the United States. Myocarditis is a less common etiology of HF, and its outcomes are less well understood. In this study, we assessed outcomes in patients admitted with myocarditis-associated HF (MAHF) using a national database. Methods We used the Nationwide Readmissions Database (NRD) from 2016-2019, extracting adult patients with a primary diagnosis of HF who were admitted between January and November of each year studied. We excluded patients with missing data on event time or length of stay. Survey procedures were applied to accommodate for sampling design. Adjusted odds of readmission were calculated using logistic regression controlling for demographic variables and comorbidities. Propensity scores as covariates were used in survey-weighted models to estimate population average treatment effect on the treated (ATT). We used SAS 9.4 for data exploration and analysis. Results We included 4,454,272 HF-related weighted admissions for which 4,605 patients (0.1%) had a concurrent diagnosis of myocarditis. Overall, patients with MAHF, compared to HF patients without myocarditis (HFWM), were younger (mean age 53 years vs. 71 years, p <0.001) with fewer women (45% vs. 48%) respectively. Patients with MAHF had more inpatient complications including cardiac arrest, cardiogenic shock, and use of mechanical circulatory support (p <0.001) despite having fewer comorbidities such as DM, HTN, renal failure, and COPD (see Figure 1). Subsequently, patients with MAHF had longer mean lengths of stay (9.2 days vs. 5.8 days, p <0.001). In-hospital mortality during index admission was significantly higher in MAHF at 3.9% compared to 2.8% for HFWM (p < 0.001). The main predictor of inpatient mortality was the presence of myocarditis (see Figure 2) adjusting for age, gender, socioeconomic status, hospital location, and Elixhauser mortality index. Conclusion Myocarditis-related HF is associated with increased inpatient mortality, resource utilization, and prolonged hospitalization.