1350330 - An Inflamed Call for an Update in the Arrhythmogenic Cardiomyopathy CMR Criteria and Scanning Protocols

An 18-year-old woman with no past medical history was admitted following an aborted ventricular fibrillation-cardiac arrest with two shocks. She had no family history of cardiomyopathy, sudden or premature death. The patient was healthy and undertaking regular exercise before this episode, therefore a cardiovascular magnetic resonance (CMR) was performed on day three of admission.

Diagnostic Techniques and Their Most Important Findings:

The exam was performed on a 3 Tesla scanner.

Balanced-Steady State Free Precession (b-SSFP) cine sequences demonstrated an upper-normal left ventricular (LV) size with a moderately reduced systolic function [LV ejection fraction (EF) = 47%] associated with hypokinesia of the mid inferolateral and apical lateral segments. Chemical shift artefact was noted in the mid inferolateral segment and in the LV apex (Panel A-B).

The right ventricle (RV) was not dilated; however, the global systolic function was mildly impaired (RVEF=40%) with hypokinetic areas in the RV outflow tract and the RV apex. Chemical shift artefact was founded in the tricuspid valve annulus and the RV apex. (Panel A).

Turbo Spin Echo (TSE) sequences weighted in T2 performed in short axis and long axis views revealed an increase myocardial intensity in the lateral wall (Panel C). Consistently, the T2 mapping sequences demonstrated increased myocardial T2 values in the basal-mid-apical lateral, anterior and septal segments (Panel D).

On the late gadolinium enhancement (LGE), there was extensive LV subepicardial myocardial in the basal-mid-apical lateral segments migrating to intra-myocardial enhancement in the basal-mid anterior and septal segments, and apical inferior segments (“ring-like” appearance LGE) (Panel E). The native T1 myocardial values were globally increased on 3T (1477±118 ms) with the highest values in the mid-inferolateral and mid-anterolateral segments (Panel F).

Learning Points from this Case:

In this case, the presence of biventricular dysfunction, subepicardial fibrosis and myocardial oedema pose a diagnostic challenge between acute myocarditis and hot phase Arrhythmogenic Cardiomyopathy (AC). Although the 2018 Updated Lake Louise Criteria for acute myocarditis are fulfilled, the presence of chemical shift artefact suggesting fat infiltration favour the diagnosis of AC. Nevertheless, its definite diagnosis requires correlation with genetic screening for pathological desmosome mutations and/or endomyocardial biopsy for immune-histology characterisation.
The role of inflammation in AC is unresolved; the ability to assess inflammation non-invasively by CMR may aid in the diagnosis and sudden cardiac death risk stratification. This case is a call for an update in the AC CMR scanning protocols and diagnostic criteria to include a more comprehensive assessment of the disease's pathophysiology.