Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) in a Boxer

ABSTRAST: A 3-year-old boxer bitch was evaluated for syncope and exercise intolerance. Physical examination revealed tachypnea, tachyarrhythmia and pulse deficit. Echocardiography demonstrated right atrial dilatation, thinning and hypokinesis of the right ventricular wall and normal contractility of the left ventricle. Three months after the first onset of clinical symptoms, the dog developed signs of congestive right heart failure despite treatment, and euthanasia was performed because of refractory ascites. The diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC) was reached based of the clinical evolution of rapid progressive right ventricular heart failure and the particular form of isolated right atrial and right ventricular alterations without any echographic abnormalities of the pulmonic and tricuspid valves. Definitive confirmation was made by necropsy. In contrast to boxer type dilated cardiomyopathy (BDCM), dilatation occurred primary on the right atrium and ventricle and the right ventricular wall was thinner in subtricuspidal, apical and infundibular locations, similar to the "triangle of dysplasia" of human patient with ARVC. Histological lesions showed myocyte atrophy and replacement with adipose and fibrous tissue extended from the epicardium toward the endocardium in the right ventricle (RV) and right atrium (RA). In contrast to BDCM, where the lesions are multifocal, they take here the form of waves, with a large base against the epicardium and a spike towards the endocardium, known as lesions with a wave-front pattern, which are typical of ARVC. This report with supraventricular arrhythmias and echographic location in the RA and RV supports the hypothesis that ARVC is a progressive disease which may also have left ventricular free wall involvement if the patient lives long enough.