Arrythmogenic right ventricular cardiomyopathy

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Gross specimen illustrating cardiomegaly associated with ARVC[1]
Cross-sectional MRI from a Boxer with ARVC (left) compared to a normal dog, showing bright, high-intensity signal in RV infundibulum[2]

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[1].

This disease, caused by a genetic defect in the Striatin gene on chromosome 17[3], primarily affects the Boxer breed but other breeds such as English Bulldog[4] 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[5].

Although a tentative diagnosis can be established through thoracic radiographs, auscultations and elevated troponin 1 levels[6], diagnosis can be difficult and most cases necessitate 24-hour ambulatory electrocardiographic (Holter) monitoring and echocardiography[7].

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[8].

Echocardiography and MRI studies usually confirm reduced right ventricular ejection velocities, even in asymptomatic dogs[9].

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)[10]. Both ventricles can be affected, but the right ventricle is always more severe affected[11].

Screening in asymptomatic breeding dogs can be performed through PCR-based genetic testing[12].

A differential diagnosis would include nemaline myopathy, other cardiomyopathies, congestive heart failure and infections with Dirofilaria spp.

Most clinically affected dogs require antiarrhythmic treatment.

References

  1. 1.0 1.1 Oxford EM et al (2007) Molecular composition of the intercalated disc in a spontaneous canine animal model of arrhythmogenic right ventricular dysplasia/cardiomyopathy. Heart Rhythm 4(9):1196-1205
  2. Basso C et al (2004) Arrhythmogenic right ventricular cardiomyopathy causing sudden cardiac death in boxer dogs: a new animal model of human disease. Circulation 109(9):1180-1185
  3. Meurs KM et al (2011) Genome-wide association identifies a deletion in the 3' untranslated region of striatin in a canine model of arrhythmogenic right ventricular cardiomyopathy. Hum Genet 128(3):315-324
  4. Santilli RA et al (2009) Outflow tract segmental arrhythmogenic right ventricular cardiomyopathy in an English Bulldog. J Vet Cardiol 11(1):47-51
  5. Basso C et al (2004) Arrhythmogenic right ventricular cardiomyopathy causing sudden cardiac death in boxer dogs: a new animal model of human disease. Circulation 109:1180–1185
  6. LaVecchio D et al (2009) Serum cardiac troponin I concentration in retired racing greyhounds. J Vet Intern Med 23(1):87-90
  7. Scansen BA et al (2009) Temporal variability of ventricular arrhythmias in Boxer dogs with arrhythmogenic right ventricular cardiomyopathy. J Vet Intern Med 23(5):1020-1024
  8. Moïse NS et al (1997) Age dependence of the development of ventricular arrhythmias in a canine model of sudden cardiac death. Cardiovasc Res 34:483–492
  9. Baumwart RD et al (2009) Magnetic resonance imaging of right ventricular morphology and function in boxer dogs with arrhythmogenic right ventricular cardiomyopathy. J Vet Intern Med 23(2):271-274
  10. Corrado D et al (1997) Spectrum of clinicopathologic manifestations of arrhythmogenic right ventricular cardiomyopathy/dysplasia: a multicenter study. J Am Coll Cardiol 30:1512–1520
  11. Nakao S et al (2011) Pathological features of arrhythmogenic right ventricular cardiomyopathy in middle-aged dogs. J Vet Med Sci 73(8):1031-1036
  12. Hariu CD & Carpenter DH (2010) Arrhythmogenic right ventricular cardiomyopathy in boxers. Compend Contin Educ Vet 32(12):E1-E7