320 Clinical usefulness of cardiac MRI for making the definitive diagnosis of myocarditis in children

Abstract

We sought to evaluate the clinical usefulness of cardiac MRI for making the definitive diagnosis of acute myocarditis in children. Twenty-three children (age 12 years, range 1 -15 years) were hospitalized in our institution for suspected acute myocarditis. The following examinations were performed : ECG, cardiac enzymes including troponin, chest x-ray, transthoracic echocardiography, and cardiac MRI. Cardiac MRI were performed with a 1.5T machine using the following sequences : SSFP, T2-weighted black blood, perfusion, and myocardial delayed enhancement. Diagnosis of acute myocarditis was based on MRI: normal perfusion but presence of subepicardial hypersignal on the T2-weighted and SSFP sequences associated with an enhancement late after peripheral injection of gadolinium. The following diagnosis were found: acute myocarditis (n=12), primitive dilated myocardiopathy (n=8), normal heart (n=3). Among the 12 cases of acute myocarditis on MRI, 9 patients presented with recent symptoms (< 7 days), increased troponin enzymes (0.21-54 μg/ml), and ECG abnormalities. There were focal abnormalities in left ventricle contraction on echocardiography in 5 patients. The 3 other patients with abnormal MRI presented with symptoms that dated more than 7 days. In these cases, tropinin enzymes, ECG and transthoracic echocardiography were normal. Biological examinations and coronary CT angiography were normal in the 11 patients (8 patients with a dilated cardiomyopathy and 3 patients with normal heart) who did not presented with myocarditis on MRI. Focal subepicardial hypersignal on cardiac MRI associated increased troponin enzymes allowed to make the definitive diagnosis of acute myocarditis in children who presented with symptoms that dated less than 7 days.