FM is a severe inflammatory syndrome that often presents with cardiogenic shock, yet long-term outcomes remain poorly defined. A multicenter retrospective study published in the European Heart Journal, assessed 271 adults admitted with FM across 26 European tertiary centers between 2012 and 2022 to clarify prognosis and risk factors.

The cohort had a median age of 43 years (IQR 33–55), and 58% were male. Endomyocardial biopsy identified 146 patients with lymphocytic (n=99), eosinophilic (n=18), necrotizing eosinophilic (n=3), or giant-cell myocarditis (n=26). The remaining 125 had inconclusive or no biopsy findings.

Overall in-hospital mortality reached 31%, with 1-year mortality at 34%. Giant-cell myocarditis was associated with the highest risk (54%) compared with 25–33% in other histologic subtypes (P=0.04). Seventeen patients (6%) underwent heart transplantation. Survivors had excellent functional outcomes with recovery of ventricular function.

Independent predictors of mortality included older age, lower admission pH, and giant-cell histology. While FM carries a high early fatality rate, long-term prognosis is favorable for patients who survive to discharge, highligting the importance of early recognition and risk stratification.