Persistent fibrosis after acute myocarditis: missed opportunities for genetic evaluation
A Lobo, M C Almeida, I Neves, I Rodrigues, A Goncalves, N Ferreira, R Fontes-CarvalhoAbstract
Background
Acute myocarditis may be the first clinical manifestation of an inherited cardiomyopathy, particularly arrhythmogenic cardiomyopathy (ACM). Persistence of late gadolinium enhancement (LGE) on follow-up cardiac magnetic resonance (CMR) reflects irreversible myocardial injury and constitutes a recognized indication for genetic testing, together with recurrent myocarditis or a positive family history. However, the prevalence of such indications and their implementation in clinical practice remain unclear.
Aims
To determine the prevalence of objective indications for genetic testing in patients with acute myocarditis and to identify predictors of persistent extensive myocardial fibrosis on follow-up CMR.
Methods
We conducted a retrospective, single-centre study including consecutive patients admitted with CMR-confirmed acute myocarditis between 2017 and 2024 who underwent both baseline and follow-up CMR. Indication for genetic testing was defined by at least one of the following: (i) persistent extensive LGE involving ≥3 myocardial segments on follow-up CMR, (ii) recurrent myocarditis, or (iii) family history of cardiomyopathy. Quantitative segmental CMR analysis was performed to assess myocardial edema and fibrosis. Logistic regression was used to identify predictors of persistent extensive fibrosis.
Results
Sixty-three patients were included; the median interval between CMR examinations was 7 months (IQR 5–10). Persistent extensive LGE on follow-up CMR was present in 31 patients (49.2%), with a median of 3 affected segments (IQR 2–6). Overall, 38 patients (60.3%) fulfilled at least one criterion for genetic testing. Despite this high prevalence, only two patients underwent genetic evaluation; ACM—without an identified pathogenic variant—was confirmed in one case according to the 2024 European Task Force criteria. Among demographic, clinical, and laboratory variables, none predicted fibrosis persistence. The only independent predictor was the number of edema-involved segments on baseline CMR, with each additional segment approximately doubling the odds of persistent extensive LGE (p = 0.012).
Conclusions
More than half of patients with CMR-proven acute myocarditis meet established criteria for genetic testing, driven primarily by persistent extensive fibrosis. Baseline CMR edema burden is a strong predictor of fibrosis persistence, whereas clinical parameters are uninformative. These findings reveal a substantial gap between guideline-based recommendations and real-world practice and underscore the central role of quantitative CMR in identifying patients who warrant closer follow-up and genetic evaluation.