Predictive value of cardiac magnetic resonance-derived parameters on the improvement of left ventricular function in patients with acute viral myocarditis

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Objective: To evaluate the predictive value of cardiac magnetic resonance (CMR)-derived parameters on the improvement of left ventricular function in patients with acute viral myocarditis. Methods: Forty patients, who referred for acute viral myocarditis in our hospital from September 2011 to September 2015, were prospectively enrolled in this study.All patients were examined by CMR during hospitalization for acute viral myocarditis (baseline) and after 12 months.The CMR sequences include: two dimension steady state free precession, 2D SSFP; triple inversion recovery, triple IR; early gadolinium enhancement; phase sensitive inversion recovery turbo field echo, PSIR TFE. Results: Thirty out of 40 patients with susceptive acute viral myocarditis met the CMR criteria of acute viral myocarditis (Lake Louise Criteria) (LL+ ) and the other 10 patients did not meet the diagnostic criteria (LL-). Left ventricular ejection fraction (LVEF) values were significantly lower in LL+ group than in LL- group at baseline and at 12 months after discharge (P<0.01 or 0.05, respectively). The baseline left ventricular end-systolic volume index (LVESVI) was significantly higher in LL+ group than in LL- group (P<0.05) and was similar between the groups at 12 months follow up.Left ventricular end-diastolic volume index (LVEDVI )was similar between the two groups at baseline and at 12 months follow up.LVEF was significantly higher during 12 months follow up compared to baseline in LL+ group and remained unchanged in LL- group during the two time points.LVESVI and LVEDVI remained unchanged at baseline and during 12 months follow up both in LL+ and LL- groups (P>0.05). Results showed that LL+ , edema ratio (ER) positive and global relative enhancement (gRE) positive were associated with significant increase of LVEF at 12 months follow up.However, LL-, ER negative, gRE negative, late gadolinium enhancement(LGE) negative and LGE positive linked with unchanged LVEF at 12 months follow up (P>0.05). Patients were further divided into LVEF increase (ΔLVEF≥5%) group and non LVEF increase group (ΔLVEF<5%), the results of Chi-square test showed that LL+ and ER positive were related to the improvement of LVEF (P<0.05), while gRE and LGE were not associated with improvement of cardiac function (P>0.05). Multiple linear regression analysis, using ER, gRE and LGE as independent variables and LVEF as dependent variables, showed that the presence of myocardial edema was the strongest independent predictor of an increase in LVEF at follow up (full model: non-standardized coefficient 0.445, P=0.043; reduced model: non-standardized coefficient 0.442, P=0.12). Conclusion: Cardiac magnetic resonance imaging monitoring is valuable to observe the cardiac function and morphology changes in patients with acute viral myocarditis, and myocardial edema imaging is the most powerful parameter to predict the improvement of LVEF in this patient cohort.