[Role of cardiac magnetic resonance imaging in myocarditis patients with biopsy negative: a retrospective case series study].

Objective: To analyze the cardiac magnetic resonance (CMR) imaging feature of clinically diagnosed myocarditis patients with negative endocardial biopsy (EMB) results, and to further demonstrate the diagnostic value of CMR in these patients. Methods: This was a retrospective case series study. Fourteen patients, who were clinically diagnosed as myocarditis according to 2013 European Society of Cardiology (ESC) clinical diagnostic criteria for myocarditis, but with negative EMB results, were enrolled. All patients underwent CMR examinations. The morphological, functional and histological changes of the heart were assessed based on black blood sequence, cine sequence, T2W-STIR sequence and contrast agent late gadolinium enhancement,(LGE). Results: There were 10 males and 4 females in this cohort, the age was (25.6±13.2) years. The interval between symptom onset and CMR was 21 (13, 60) days, and the interval between symptom onset and EMB was 19 (9, 40) days. There were 13 patients with abnormal CMR results including myocardial oedema, fibrosis, decreased ejection fraction, pericardial effusion or increased cardiac chamber dimension. Nine out of 14 patients had CMR morphological and/or functional abnormalities, including 1 case of left atrium enlargement, 1 case of left ventricle enlargement, 3 cases of right ventricle enlargement, 4 cases of increased left ventricular end diastolic volume index. Left ventricular ejection fraction was 3 mm was detected in 3 cases. Of the 14 patients, 11 had histological changes, of which 6 had T2 ratio≥2. Among the 10 patients (10/14) with positive LGE, the most common patterns were subepicardial LGE of the lateral wall and/or midwall LGE of the septum (n=9); 2 cases showed extensively subendocardial LGE of the left ventricular wall. No LGE involved in the right ventricular wall in the whole cohort. Conclusion: CMR plays a complementary role in the diagnosis of myocarditis in clinically diagnosed myocarditis patients with negative EMB findings.