1353851 - Recurrent Myocarditis and Early CMR Evidence of Arrhythmogenic Cardiomyopathy in a Pediatric Patient

Ten-year-old male with a history of myocarditis two years prior presented with acute chest pain and troponin elevation with a peak of 54 ng/mL. CMR met modified Lake Louise criteria for acute myocarditis. Extensive infectious work-up was unrevealing. He was discharged from the hospital after down trending troponin and resolution of pain. He presented two months later with another recurrence of chest pain and troponin leak. Repeat CMR revealed low normal RV systolic function and dyskinesis of the inferior RV wall raising concern for arrhythmogenic cardiomyopathy (ACM). Endomyocardial biopsy showed focal fibrosis and myocyte hypertrophic changes without lymphohistiocytic or eosinophilic infiltrate. Cardiomyopathy genetic panel resulted in three variants of uncertain significance that were not thought to be disease-causing. Follow-up CMR seven months after discharge demonstrated increase in the extent of RV septal and inferior wall fibrosis and fatty infiltration in the LV free wall with associated dyskinesis. The working diagnosis is a myocarditis-like cardiomyopathy with early findings of ACM.


Diagnostic Techniques and Their Most Important Findings:

CMR studies were performed on a 1.5T magnet. Pre and post-contrast T1 mapping as well as T2 mapping were performed in the short axis geometry. LGE imaging was performed in the short axis and 4-chamber geometries. Initial CMR (Figure 1) was notable for elevation in T2 relaxation times in the LV basilar inferolateral and apical anterior segments, consistent with edema. There was subepicardial LGE in the corresponding segments with calculated ECV 36-41%. Subsequent CMR showed low normal RV systolic function, EF 47%, and dyskinesis of the RV inferior wall. T2 relaxation times were only borderline elevated, though pre-contrast T1 relaxation times and ECV remained elevated in the basilar inferolateral segment consistent with fibrosis. LV LGE remained stable, and new subendocardial LGE was noted in the inferior and septal walls of the RV. Follow-up CMR (Figure 2) demonstrated new regions of hypokinesis of the mid and apical lateral LV wall with low normal LV systolic function, EF 55%. Cine SSFP imaging revealed macroscopic fatty infiltration in the mid and apical LV lateral wall, confirmed by decreased pre-contrast T1 relaxation times. The degree of LGE in the RV septal and inferior walls increased.


Learning Points from this Case:

Our pediatric patient with recurrent acute myocarditis has developed regional dyskinesis, extensive fibrosis of the RV myocardium, and fatty infiltration of the LV myocardium. Though not meeting major or minor CMR criteria, these findings raise concern for ACM. Most inheritable forms of ACM are caused by desmosome gene mutations, and variants in DSP, PKP2, and DSG2 have been associated with recurrent episodes of myocarditis which may precede diagnosis. Though genetic evaluation was unrevealing, our suspicion for an underlying cardiomyopathy remains high. Evaluation for desmosome mutations should be considered in children with recurrent myocarditis.