Beyond ejection fraction: myocardial strain as a predictor of symptomatic recurrence in myocarditis

Introduction and aim Predicting long-term outcomes in myocarditis remains challenging using only Left Ventricular Ejection Fraction (LVEF). Global Longitudinal Strain (GLS) may detect subtle mechanical dysfunction even when LVEF is preserved. We aimed to evaluate the prognostic value of GLS in patients with confirmed myocarditis, specifically focusing on those with "apparently normal" LVEF. Methods We analyzed a cohort of patients with confirmed myocarditis from the prospective Pre-MYO registry (76 centers, Spain). GLS was classified as: Normal (<-18%), Borderline (-16% to -18%), and Abnormal (>-16%). Participants were categorized into: 1) Normal LVEF with normal GLS, 2) Normal LVEF with abnormal/borderline GLS, and 3) Reduced LVEF. Clinical characteristics, discharge treatments, and 1-year outcomes were compared. The primary endpoint was 1-year MACE (a composite of cardiovascular death, heart failure hospitalization, and life-threatening arrhythmias). Secondary endpoints included symptom recurrence. Results The study included 143 patients (mean age 47.1±19.2 years; 64.3% male). Significant baseline differences were observed: patients with normal LVEF but abnormal/borderline GLS were significantly younger (34.6±18.2 years) and more frequently male (83.3%) compared to those with reduced LVEF (51.0±17.4 years; 57.0% male) (p<0.001 and p=0.021, respectively). Pericarditis was notably more prevalent in the normal LVEF/abnormal strain group (44.4%) compared to the normal strain (8.3%) and reduced LVEF (9.6%) groups (p=0.027) (Table 1). Management at discharge reflected these phenotypes: patients with abnormal strain and preserved LVEF received more intensive anti-inflammatory therapy, specifically NSAIDs (52.6% vs. 32.0% in normal strain; p=0.013) and colchicine (52.6% vs. 36.0%; p=0.005). At 1-year follow-up, while MACE rates were low (p=0.298), a significant difference was observed in recurrent chest pain, which was highest in the normal LVEF/abnormal GLS group (43.8%) compared to those with normal GLS (33.3%) and, remarkably, those with reduced LVEF (15.7%) (p=0.015) (Figure 1). Total symptom recurrence followed a similar but non-significant trend (43.8% vs. 24.7% in reduced LVEF; p=0.194). Conclusions In confirmed myocarditis, abnormal myocardial strain despite preserved LVEF identifies a specific phenotype characterized by a higher inflammatory-pericarditic component and a significantly increased risk of recurrent chest pain. Myocardial strain provides incremental prognostic value over LVEF for predicting the long-term symptomatic course, suggesting its utility in guiding more personalized anti-inflammatory strategies.Table 1.Myocarditis outcomes by LVEF and GLSFigure 1.MACE and complications