Predictive value of CMR criteria for LV functional improvement in patients with acute myocarditis

We assessed the value of cardiovascular magnetic resonance (CMR) criteria ('Lake Louise Criteria') for predicting left ventricular (LV) functional improvement in patients with acute myocarditis.

We studied 37 patients who referred for acute myocarditis during clinically acute myocarditis and after a 12-month follow-up. CMR sequences sensitive for oedema, hyperaemia, and irreversible injury were applied. Global and regional oedema were defined using published quantitative signal intensity (SI) cut-off values (area with an SI of >2 SD above visually normal myocardium). LV function was analysed using six long-axis views, with an increase of at least 5% of left ventricular ejection fraction considered as improvement. Out of a total of 37 patients, 29 met the CMR Lake Louise criteria (LL+) and eight did not (LL-). Baseline and 12-month ejection fraction (EF) were significantly lower in LL+ (53.2 ± 8 vs. 62.2 ± 5, P = 0.007 and 58.9 ± 4 vs. 62.9 ± 5, P = 0.045, respectively). At follow-up, EF increased in LL+ but remained unchanged within normal limits in LL- groups (delta EF: 5.7 ± 9.8 vs. 0.7 ± 2.0). The presence of global or regional myocardial oedema was strongly associated with an increase of EF ≥5%. In a multivariate analysis, the presence of global and/or regional oedema on admission was the only independent predictor of an increase of EF (P = 0.046).

In patients with clinically suspected acute myocarditis, the presence of positive CMR criteria is associated with LV function recovery. Myocardial oedema as defined by CMR was the strongest parameter, indicating that the observed increase of EF may be due to the recovery of reversibly injured (oedematous) myocardium.