Commonly characterized by an irregular heartbeat, arrthymogenic right ventricular cardiomyopathy (ARVC) is a genetic disease in boxer dogs. Our Long Island veterinary specialists discuss other symptoms of this disease, treatment options and more.
What is cardiomyopathy (ventricular arrhythmia) in Boxers?
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic disease that appears in adult Boxer dogs. Also referred to as Boxer Cardiomyopathy, this disease rarely affects other breeds. With ARVC, normal heart muscle is replaced with fibrous, fatty tissue. This leads to electrical instability in the heart muscle and heart arrhythmias (irregular heart rhythm), which can seriously affect the heart and cause a dog to faint, collapse or even die suddenly.
The specific arrhythmia related to this disease is called ventricular premature complies (VPC). These early abnormal heartbeats originate from the heart muscle instead of the specialized conduction tissue in the heart, where normal heart beats originate. If VPCs occur sequentially, an arrhythmia called ventricular tachycardia occurs and can cause symptoms.
The condition generally develops in middle-aged (5 to 7 years old) dogs. The arrhythmia can often (but not always) be detected during a physical examination in dogs that are affected.
What causes cardiomyopathy in Boxers?
Up to 40% of Boxers have a genetic mutation in an important heart gene (striatin) with a characteristic called "incomplete penetrance", which means that even if a dog has the mutation it may not penetrate and result in the disease developing.
A DNA test can determine whether your dog has the mutation. Even if your dog is negative, it does not mean that heart disease or an arrhythmia will never develop; just as there are many genetic causes for the disease in people, this could also be true in Boxers.
How often do Boxers experience cardiomyopathy?
ARVC disease is very common in Boxers. In one study, 50% of Boxers were positive for the gene that causes ARVC.
What are symptoms of cardiomyopathy in Boxers?
For Boxers with cardiomyopathy, symptoms can be very serious and may vary. Clinical signs of ARVC can include:
- Accumulation of fluid in the abdomen
- Rapid breathing
- Irregular heartbeat (which a veterinarian may notice during a routine exam
- Exercise intolerance
- Fainting (syncope)'
- Collapse (especially during or after exercise)
- Sudden death
How is cardiomyopathy in Boxers diagnosed?
Unfortunately, ARVC is difficult to diagnose for a few reasons, but primarily because dogs may be asymptomatic between arrhythmias. The disease can also mimic other cardiac diseases such as dilated cardiomyopathy. Another challenge is that sudden death may be the first and only clinical symptom.
Our board-certified veterinary cardiologist at Atlantic Coast New York Veterinary Specialists is trained to diagnose cardiovascular diseases in pets. We offer state-of-the-art cardiology services, diagnostics and procedures for the assessment of heart conditions in cats and dogs at our two locations in Long Island.
Your veterinary cardiologist will need a thorough history of your pet's health leading up to the onset of symptoms, including any information you may have about your dog's family background.
The following tests and tools to test for and diagnose arrhythmias and ARVC in your Boxer:
- Histopathology (post-mortem)
- Blood tests
- Genetic screening
- Echocardiography (to rule out any other cardiac disease)
- 24-hours ambulatory ECG Holter monitoring (worn by the dog to record heart rhythm for a few days)
Unfortunately, histopathology, which is conducted post-mortem, is still widely accepted as the best method of diagnosing the disease.
A thoracic radiograph (chest X-ray) may help to determine whether there is enlargement of the heart or other evidence of heart failure.
How is cardiomyopathy in Boxers treated?
Your veterinarian will want to try to normalize the heartbeat as one of the first priorities of treatment.
Generally, treatment consists of antiarrhythmic agents (medications) unless there is evidence of congestive heart failure or other problems with the heart.
Some dogs seem to show improvement with the use of l-carnitine, a supplement used to increase levels of carnitine, which stimulates fatty-acid oxidation and is essential to a fully-functioning body.
If the disease is causing congestive heart failure, your veterinary cardiologist will likely recommend starting treatment right away.
If they suspect cardiac disease, a heart monitor may be placed on your dog to determine the complexity and severity of the arrhythmia. This will also provide a baseline for comparison once treatment has started.
If a dog is not displaying symptoms, the decision to begin treatment is based on the number of abnormal rhythms detected in a 24-hour period. Because antiarrhythmic agents have side effects such as anorexia or gastrointestinal issues, the decision to treat is on a case-by-case basis.
Your veterinary cardiologist may recommend an implantable cardioverter defibrillator (ICD) as a supplementary treatment option, which has become common in human medicine.
What is the prognosis of Boxers with cardiomyopathy?
While treatment with antiarrhythmic agents will decrease the number of episodes in which Boxers collapse, there is no evidence that it impacts long-term survival.
For Boxers with cardiomyopathy, life expectancy can be difficult to predict as dogs with this disease are always at risk of sudden death. Dogs that have systolic dysfunction (a condition in which the heart contracts and blood is forced into areas where it can cause harm — do not do as well.
Despite progress in veterinary medicine, dogs with ARVC are unfortunately still at risk of sudden death and prognosis may be poor. Some dogs can be asymptomatic and live for years, often with but occasionally without antiarrhythmic medication.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.