Prognosis of myocarditis stratified by initial clinical presentation: Does "intermediate" risk still play a role?

Myocarditis is an inflammatory disease with diverse clinical presentations. It is known that low-risk patients have a good prognosis compared to high-risk patients. There are few data regarding the prognosis of intermediate-risk patients. This study aimed to analyze the long-term outcomes of patients with acute myocarditis with different risk profiles at presentation, focusing on the intermediate risk one.

A retrospective multicenter study was conducted, enrolling patients who met the diagnostic criteria for clinically suspected myocarditis with acute presentation. Patients were stratified into high, intermediate and low risk, according to the classification proposed by Sinagra and his team. Cardiovascular adverse events (AEs) were assessed after a median follow-up of 19 months. Echocardiographic and cardiac magnetic resonance (CMR) parameters predictive of adverse events have been reported.

We enrolled 127 patients (mean age 30 ± 13 years; 103 men, 24 women). High-risk patients had a higher frequency of adverse events (80 %) compared to other groups (16 %-16 %, p < 0.0001). An association was observed between the number of segments with late gadolinium enhancement (LGE) at baseline CMR and the occurrence of adverse events (p < 0.0037). The sum of segments with LGE was statistically correlated with lower left ventricular GLS (p < 0.009). The number of segments with LGE that most accurately identified the occurrence of adverse events was 2.5 [AUC 0.5; p = 0.24].

Our study confirms the higher incidence of AE in the high group; the prognosis of patients at intermediate risk is not very different from those at low risk. It can be hypothesized that the extent of LGE at baseline is the main predictor of adverse events in patients at intermediate risk.