Optimal timing of follow-up cardiac magnetic resonance in patients with uncomplicated acute myocarditis

Background: Cardiac magnetic resonance (CMR) is central in the diagnosis and prognostic stratification of acute myocarditis (AM) but the timing of repeated CMR scans to assess edema resolution and late gadolinium enhancement (LGE) stabilization remain unclear. We assessed edema and LGE evolution over 12 months to identify the optimal timing of repeat CMR evaluation in AM. Methods and results: Thirty-three consecutive patients with AM underwent CMR at clinical presentation (CMR-1), after 3 months (CMR-2) and after 12-months (CMR-3). CMR included assessment of edema and LGE, left ventricular ejection fraction (LVEF) and left ventricular mass index (LVMi). After CMR-3 patients were followed-up every three-months by clinical evaluation, Holter-monitoring, and echocardiography. All patients had edema and LGE at CMR-1. At CMR-2 edema-positive segments (0.42 +/- 0.34 vs. 3.18 +/- 2.33, p < 0.005), LGE (4.98 +/- 4.56 vs. 9.60 +/- 8.58 g, and 4.22 +/- 3.97% vs 7.50 +/- 5.61%) and LVMi (69.82 +/- 11.83 vs 76.06 +/- 13.13 g/m(2)) (all p < 0.0001) significantly reduced, while LVEF (63.12 +/- 5.47% vs.61.15 +/- 6.87% p < 0.05) significantly improved, compared to CMR-1. At CMR-2 edema persisted in 7 patients (21%) but resolved at CMR-3 with no further changes of LVMi, LVEF and LGE. During follow-up (85 +/- 15 months), 5 (15%) patients showed persistent ventricular arrhythmias. Univariate predictors of arrhythmic persistence were LGE extension at CMR-2 and CMR-3 (both p < 0.05), but not at CMR-1 (p = 0.07). Conclusions: Most patients with uncomplicated AM show edema resolution with LGE stabilization after 3 months. Further CMR evaluations should be limited to patients with persisting edema at this time. LGE extent measured after edema resolution is associated with persistent ventricular arrhythmias.