Arrythmogenic right ventricular cardiomyopathy in an english bulldog

26-10-2018

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a primary heart muscle disease mainly affecting Boxers, although it has also been reported in other breeds with a familial predisposition, such as the English bulldog or the American Staffordshire. ARVC, characterized by a progressive replacement of cardiac muscle cells by fatty or fibrous tissue, is a hereditary disease that occurs in adult dogs, with an incidence that increases with age. Its clinical presentation can range from asymptomatic arrhythmias to congestive heart failure, syncope or even sudden death.

An 8-year-old female English bulldog was brought to our hospital following 7 days of exercise intolerance and weakness, which had progressively worsened. Physical examination revealed pale mucous membranes, capillary refill time >2", weak and asynchronous heart action, with heart rates ranging from 128-220 bpm, without a murmur at auscultation. Respiratory frequency measured 44 rpm and pulmonary auscultation was within normal limits. The dog’s body condition score was 7/9 and PAS 120 mmHg.

  • Electrocardiogram showed sustained ventricular tachycardia (VT) with left bundle branch block morphology and a 68° electrical axis, which was positive in lead I and with a notched R wave, consistent with a VT of the free wall of the right ventricle (RV). (Fig. 1). 
  • Radiological examination showed a cardiomegaly with increased sternal contact in the laterolateral view. (Fig. 2). Cardiomegaly in the ventrodorsal view.
  • Echocardiograph revealed dilatation of the atrium and right ventricle (Figs. 4 and 5) with a more marked dilatation in the RV outflow tract, with an aneurysmal morphology, appearing more convex and with hyperkinesia of the RV free wall. (Fig. 6).
  • Blood analysis was within normal limits, except for an increase in troponin I (0.41 ng/ml, ref range <0.06 ng/ml). The abdominal ultrasound study was normal.

Clinical diagnosis was consistent with ARVC complicated by sustained ventricular tachycardia (VT) of the right ventricular outflow tract (RVOT). Although an electrophysiological study of the affected area was required to confirm the mechanism and exact location of the arrhythmia, the presence of the aneurysmal area in the RVOT and the configuration of the QRS suggested a tachycardia of the RVOT.

Hospital treatment was begun with intravenous lidocaine, which produced a good response in the first 24-48 hours. Subsequently, Sotalol, treatment the patient was later discharged with, was added orally. A partial response to the therapy was observed, with a slight improvement in heart rate and rhythm, in spite of a worsening clinical picture. As a result, we added mexiletine, which showed a good clinical response within a few hours. The ECG shows a nonsustained monomorphic ventricular tachycardia, which reverted to a base sinus rhythm with isolated ventricular complexes. The Holter study, performed 15 days post treatment, showed a reduction in heart rate variability, with less than 1000 ventricular premature complex (VPC) with left bundle branch block axis morphology, with ventricular bigeminism complexes and some episodes of sustained monomorphic ventricular tachycardia, with heart rates up to 160 bpm. Antiarrhythmic treatment decreased the frequency and complexity of arrhythmia and episodes of collapse. 

Prognosis of this condition is difficult to establish. With mediation and clinical controls, which help to reduce the occurrence of congestive heart failure, progressive increase in cardiac size and myocardial dysfunction, many affected dogs can live a long life. 


Fig. 1: ECG in 6 leads. Ventricular tachycardia with left bundle branch block morphology. Speed 50 mm/sec and amplitude 10 mm/5mv.

Fig. 2 : Laterolateral view, in which a cardiomegaly is observed with increased sternal contact. 

Fig. 3: Ventro-dorsal view also shows cardiomegaly. 

Fig. 4: Echocardiography. Right parasternal longitudinal views, showing dilation of the atrium and right ventricle. 

Fig. 5: Echocardiography. Apical four-chamber view of left side, showing dilation of the atrium and right ventricle. 

Fig. 6: Echocardiography. Cross-sectional view of the right parasternal where aneurysmal zone is observed in the right ventricular outflow tract.