Arrhythmogenic cardiomyopathy is one of the main causes of sudden cardiac death in the young and especially in athletes. Although initially described for the right ventricle, with left ventricle (LV) involvement only as a late manifestation, nowadays 3 patterns of the disease have been recognized, among which there is a "left dominant arrhythmogenic cardiomyopathy" (LDAC) pattern characterized by an early and predominant LV involvement. Our objective was to review the cardiac magnetic resonance (CMR) image characteristics of our patients diagnosed of LDAC with positive genetic tests and describe the main common findings.
We reviewed 30 patients that had been diagnosed of LDAC after performing a CMR study, in which genetic test results proved positive for different mutations associated with this disease. Patients with coexistent ischemic cardiomyopathy were excluded. The CMR characteristics to be analysed were late gadolinium enhancement (LGE), LV dilation and LV dysfunction.
The most common finding was a midwall and/or subepicardial almost diffuse LGE pattern (100%). 40% showed LV dilatation and 77 % had LV dysfunction (46% moderate and 13% severe). An additional feature detected on 87% of patients was an irregular epicardial contour on cine images, associated in most cases with myocardial thinning and LGE. In those with more prominent wall irregularities, adipose tissue was demonstrated on fat and non-fat saturated T1-weighted images. We correlated this finding with the subepicardial foci of fibrofatty infiltration found on histopathology samples.
LDAC is one of the recently recognized arrhythmogenic cardiomyopathy forms of presentation. It is characterized by a midwall-subepicardial diffuse enhancement pattern on late gadolinium images. Additionally, an irregular epicardial contour can be found, representing the fibrofatty infiltration characteristic of this disease. We have baptized this feature as the "rat-bite sign" after its resemblance to a piece of cheese that has been bitten by such an animal. We believe that, as well as calculating the LV volumes and function, or pointing out the presence of LGE, it is also important to take a closer look at the epicardial contour on cine MR images since this feature can lead us to such an important diagnosis.