In early stages of ARVC, diagnosis is difficult due to the absence of echocardiographic changes and day-to-day arrhythmia variability. A definitive diagnosis requires histopathologic identification of transmural fibrofatty replacement of the right ventricle. Reduction of immunofluorescent signal for the desmosomal protein plakoglobin has been reported in ARVC-affected humans and boxers. Reduction in plakoglobin signal within endomyocardial biopsy samples (EMBs) may help diagnose ARVC.

EMBs were obtained with owner consent from 48 dogs: 42 with advanced cardiac disease and six asymptomatic boxers (>5 years) with mild to moderate ventricular arrhythmia (VA) burden. Investigators were blinded to breed and clinical signs of the dogs. ARVC was diagnosed from EMBs by histopathology (MT) in 5 dogs. Of these, 3 had clinical signs consistent with ARVC (2 Boxers, 1 English Bulldog). Two were asymptomatic boxers with a moderate VA burden. Confocal microscopy was performed (EMO) to detect immunoreactive signal for plakoglobin in EMBs. Samples were prepared with antibodies recognizing cadherin (intercalated disc marker) and plakoglobin.

Forty-two samples were positive for cadherin signal and 6 were non-diagnostic. Plakoglobin signal was reduced in 4 samples: 2 Boxers and 1 English Bulldog with clinical signs and histopathologic diagnoses of ARVC. The fourth sample was from a mongrel diagnosed with myocarditis. Plakoglobin signal was present in all 6 asymptomatic Boxers, including those with a histopathologic diagnosis of ARVC.

These results suggest that reduced plakoglobin signal in EMBs may help to differentiate ARVC from other myocardial diseases in dogs, specifically when clinical signs of disease are present.

Disclosures

No disclosures to report.