Outcomes and risk factors associated with mortality in patients suffering from fulminant myocarditis: Results from an international pragmatic cohort study

Background: Fulminant myocarditis (FM) is a complex clinical syndrome characterized by acute myocardial inflammation and subsequent cardiogenic shock. Data on long-term outcomes, risk factors associated with mortality, and targeted treatment options is limited.

Methods: This comprehensive retrospective analysis was conducted at 26 European tertiary centers and included all adult patients admitted for FM between January 2012 and November 2022. According to histopathologic findings, patients were categorized as lymphocytic (LM), eosinophilic (EM), necrotizing eosinophilic (NEM), and giant-cell myocarditis (GCM) for the main analyses. Primary outcomes were in-hospital and 1-year mortality. Multivariable logistic regression models were used to analyze the association of prespecified risk factors with mortality. Estimated associations are reported as odds ratios, generalized marginal effects, and adjusted prediction plots.

Results: 271 patients (median age 43 years, 57.9% male) were included in the analysis, of whom 146 fulfilled histopathologic criteria of LM (n=99), EM (n=18), NEM (n=3), or GCM (n=26). In the remaining 125 cases endomyocardial biopsy was inconclusive (n=48) or not performed (n=77). While there were no significant differences in cardiac arrest rate, admission Simplified Acute Physiology Score (SAPS) II, ventricular function, initial pH, and liver and kidney function parameters between histopathologic subgroups, the use of immunosuppressive medications and need for organ replacement varied. In the overall population, in-hospital and 1-year mortality were 31.4% and 33.6%, respectively. The highest mortality rates were observed among patients with GCM (50.0% and 53.8%, respectively). Patients who survived to discharge had an excellent functional outcome and long-term recovery of ventricular function. In total, 17 patients, including those who underwent high-urgency transplantation, received a heart transplant until last follow-up. Higher age, lower pH, and histopathologic diagnosis of GCM were independently associated with in-hospital and 1-year mortality.

Conclusion: Patients with FM are at high risk of early death, but long-term prognosis is excellent among hospital survivors. Age, pH, and histopathological diagnosis of GCM may be useful parameters for risk assessment in clinical practice