Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

By Michael Luethy, DVM, DACVIM (Cardiology)

ARVC or boxer cardiomyopathy is an adult onset muscle disease that may lead to sudden death due to ventricular arrhythmias or to CHF secondary to deterioration in muscle function. While the disease is adult onset, it is known to be an inherited abnormality in the boxer breed. Recent work by Dr. Kate Meurs has indicated that a genetic deletion in the gene coding for the striatin protein is responsible for the development of the disease in some boxers. Other genetic mutations are also likely present in some affected individuals of the breed. The average age of onset for ventricular arrhythmias in affected dogs is 6 years, but this is highly variable among individuals. Boxers that develop ventricular arrhythmias at less than 3 years of age are likely suffering from a problem other than ARVC, such as post-viral myocarditis. Screening boxers with 24-hour ambulatory ECG recordings annually beginning at 3 years of age is recommended. Individuals with ventricular ectopic pairs, runs of ventricular tachycardia, or R on T are considered candidates for antiarrhythmic therapy. Sotalol (1 to 2 mg/kg BID) is typically the first line drug for treating arrhythmias associated with ARVC with mexiletine (4 to 8 mg/kg TID) plus metoprolol (0.5 to 1 mg/kg BID) a good second option. Amiodarone may be effective in controlling resistant ventricular arrhythmias, but has too high an incidence of complications to consider it a first line drug.

A small percentage of boxers will develop myocardial rather than, or in addition to, ventricular arrhythmias. These patients will present with CHF signs typical of dilated cardiomyopathy and treatment recommendations are consistent with those for other breeds with dilated cardiomyopathy. All boxers diagnosed with ventricular arrhythmias due to ARVC should receive a screening echocardiogram to evaluate ventricular myocardial function.

Genetic testing is available for the striatin deletion with current recommendations being that heterozygously affected, asymptomatic individuals be bred with unaffected individuals and homozygously affected individuals be eliminated from a breeding program. A disease that is clinically similar to ARVC is also seen in the English bulldog.

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