Boxer Cardiomyopathy (AVCP): A Threat to the Boxer Breed
Cardiomyopathy refers generally to failure of the heart muscle. Boxers are one of several breeds with a higher chance of contracting cardiomyopathy—specifically one type of cardiomyopathy. It’s called Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) and, although seen in other breeds as well, it’s often called Boxer cardiomyopathy. ARVC is characterized by a fatty infiltrate of the right ventricular muscle. It’s a hereditary condition that generally produces no indication of disease until adulthood.
Symptoms of ARVC in Boxers
There are three clinical forms of ARVC:
- The concealed form, which may have no clinical signs at all. (Dogs appear totally healthy but ECG/Holter evaluation shows arrhythmias.)
- The overt form; dogs with this form show clinical signs including collapse, weakness, and/or fainting.
- Myocardial failure and resultant heart failure. Signs include syncope and fainting (Heart rates can be as high as 300 beats per minute. Since it takes 6–8 seconds of no blood flow to the brain to result in unconsciousness, the tachycardia must last for that long for the dog to lose consciousness.)
ARVC can lead to congestive heart failure and sudden death depending on the form and stage.
Detection of ARVC in Boxers
Because many affected dogs are without symptoms, we really don’t know how common the disease is. Abnormal cardiac rates and rhythms can occur in dogs not affected. When listening to the heart, it is not uncommon to hear occasional extra or absent beats in any dog. These abnormalities do not necessarily indicate cardiomyopathy in any breed or ARVC in a boxer. The diagnosis must then be based on a combination of factors including:
- A family history of ARVC
- Presence of ventricular arrhythmias (abnormal heart rhythm)
- History of syncope (fainting)
- Exercise intolerance
The diagnosis can be confirmed by excessive numbers of abnormal beats over a 24 hr period. While a regular ECG is able to detect these beats, it only evaluates beats over a short period of time. A device about the size of a deck of cards, called a Holter monitor, can be can be used to monitor the heart for longer1.
Genetic testing is available but while a positive genetic test confirms the presence of the disease, a negative test does not rule it out. There are two known genetic mutations resulting in ARVC in Boxers, so the absence of one may have no predictive value. Additionally, it is likely other mutations will be