Arrythmogenic right ventricular cardiomyopathy
Arrythmogenic right ventricular cardiomyopathy (ARVC) is an autosomal-dominant (incomplete penetrance) genetic heart disease of dogs characterized by ventricular arrhythmias, sudden death and fatty or fibrofatty replacement of right ventricular myocytes.
This disease, caused by a genetic defect in the Striatin gene on chromosome 17, primarily affects the Boxer breed but other breeds such as English Bulldog and Dalmatian have been reportedly affected.
Clinical characteristics of ARVC including monomorphic left bundle branch block ventricular arrhythmias, heart failure and sudden cardiac death.
Affected dogs are at high risk for sudden cardiac death but many can be asymptomatic or may have syncope and/or exercise intolerance, dyspneic and lethargy.
Although a tentative diagnosis can be established through thoracic radiographs, auscultations and elevated troponin 1 levels, diagnosis can be difficult and most cases necessitate 24-hour ambulatory electrocardiographic (Holter) monitoring and echocardiography.
ECGs usually show regular ventricular fibrillations, infrequent premature ventricular complexes and bundle branch block. As is characteristic of the inherited arrhythmias in this breed, the number of arrhythmias is negligible after 2 years of age.
Echocardiography and MRI studies usually confirm reduced right ventricular ejection velocities, even in asymptomatic dogs.
A definitive diagnosis can be established from histopathology analysis of affected heart muscle, which usually shows fatty or fibro-fatty replacement of myocardium beginning, particularly the right ventricle (known as the triangle of dysplasia). Both ventricles can be affected, but the right ventricle is always more severe affected.
Screening in asymptomatic breeding dogs can be performed through PCR-based genetic testing.
Most clinically affected dogs require antiarrhythmic treatment.
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