Global longitudinal strain by CMR improves prognostic stratification in acute myocarditis presenting with normal LVEF

Prognostic stratification of acute myocarditis (AM) presenting with normal left ventricular ejection fraction (LVEF) relies mostly on late gadolinium enhancement (LGE) characterization. Left ventricular peak global longitudinal strain (LV-GLS) measured by feature tracking analysis might improve prognostication of AM presenting with normal LVEF.

Data of patients undergoing cardiac magnetic resonance (CMR) for clinically suspected AM in seven European Centres (2013-2020) were retrospectively analysed. Patients with AM confirmed by CMR and LVEF ≥50% were included. LGE was visually characterized: localized versus. non-localized, subepicardial versus midwall. LV-GLS was measured by dedicated software. The primary outcome was the first occurrence of an adverse cardiovascular event (ACE) including cardiac death, life-threatening arrhythmias, development of heart failure or of LVEF <50%.

Of 389 screened patients, 256 (66%) fulfilled inclusion criteria: median age 36 years, 71% males, median LVEF 60%, median LV-GLS -17.3%. CMR was performed at 4 days from hospitalization. At 27 months, 24 (9%) patients experienced ≥1 ACE (71% developed LVEF <50%). Compared to the others, they had lower median LV-GLS values (-13.9% vs. -17.5%, p = .001). At Kaplan-Meier analysis, impaired LV-GLS (both considered as > -20% or quartiles), non-localized and midwall LGE were associated with ACEs. Patients with LV-GLS ≤-20% did not experience ACEs. LV-GLS remained associated with ACEs after adjustment for non-localized and midwall LGE.

In AM presenting with LVEF ≥50%, LV-GLS provides independent prognostic value over LGE characterization, improving risk stratification and representing a rationale for further studies of therapy in this cohort.