CMR in diagnosis of Arrhythmogenic cardiomyopathy
As the diagnostic criteria evolved and studies over the decades have
uncovered more about the various phenotypic expression of ARVC, CMR
imaging has emerged as the noninvasive gold standard for ARVC workup. It
provides a useful tool to evaluate morphology, function, and tissue
characteristics. It can highlight myocardial fibrosis, fatty replacement
or identify wall motion abnormalities with high accuracy. The most
recent 2020 International diagnostic criteria of arrhythmogenic
cardiomyopathy relies on CMR to characterize the phenotype and aid with
the exclusion of other diagnoses. The new criterion adds the minor
criterion for the diagnosis of biventricular or left dominant variants
with the demonstration of LV systolic dysfunction.18,19
Late gadolinium enhancement (LGE) of the myocardium is often used to
assess myocardial fibrosis but has a limited role in the current
diagnostic criteria of ARVC. LGE is nonspecific and the differential
diagnosis can include sarcoidosis, myocarditis, amyloidosis, or dilated
cardiomyopathy.20 Furthermore, LGE is less useful in
classic ARVC where the thin RV wall makes the technique less useful, in
comparison to LDAC where LGE has been reported in up to 61% of cases
presenting in a circumferential, mid-myocardial pattern extending to the
right side of the septum.21 Of note the
circumferential or mid-myocardial fibrosis pattern is seen in only left
dominant/biventricular ARVC. Autopsy studies of ARVC patients have
demonstrated fibro-fatty infiltration predominantly on the epicardial
surface leading to the understanding that the disease starts in the
epicardium with progression toward the endocardium. LV systolic
dysfunction can become more severe in advanced stages as there is
progression of transmural involvement. Our patient’s second CMR study
reflected early yet significant changes with normal cavitary size/wall
thickness but mild-moderate hypokinesis of the mid to apical lateral
wall. Furthermore, he had predominately epicardial fibrosis in a
relatively circumferential pattern of the lateral wall with mid
myocardial fibrosis involving the septal walls.