What is degenerative mitral valve disease?
Degenerative mitral valve disease is known by other names such as chronic valve disease or even mitral endocardiosis. This disease is a consequence of the degeneration of the mitral valve located between the atrium and the left ventricle of the heart.
" The degeneration process causes the valve leaflets to become abnormally thick and take on a bumpy appearance. These degenerative changes to the valves and the structures that support them prevent them from forming a tight seal between the atrium and the ventricle when the heart contracts.The valve can then no longer prevent the backflow of blood to the atrium. This backward leakage of blood is called regurgitation and causes an abnormal sound called a heart murmur, which your veterinarian can detect with a simple stethoscope."
Note!
The mitral valve is not the only heart valve likely to be affected by a degenerative disease. In 30% to 35% of cases of degenerative valve disease, the tricuspid valve - separating the right chambers of the heart - may also be affected.
Which dogs are most at risk?
Degenerative mitral valve disease is the most common heart disease in dogs.
It most often affects small and medium-sized dogs weighing less than 15kg and dogs over 5 years old, with the exception of the Cavalier King Charles in whom the disease can develop much earlier, around 1 to 2 years old.
Other dog breeds are also at higher risk of developing chronic degenerative valve disease. This is the case of the Dachshund, the Bichon M altese, the Poodle, the Chihuahua, the English Cocker Spaniel, the American Cocker Spaniel, the Spitz, the Shih Tzu, the Whippet as well as the Yorkshire Terrier.
Males seem to be affected more often than females.
What causes degenerative mitral valve disease?
Degenerative mitral valve disease is a degenerative process associated with aging in dogs.
There is probably a genetic component within certain breeds, such as the Cavalier King Charles in which the hereditary transmission of the condition has been demonstrated. For other breeds, heredity is only strongly suspected.
What are the symptoms?
Dogs with chronic degenerative valvular disease can be completely asymptomatic at the start of their course.The only sign of the disease is then the heart murmur perceptible by your veterinarian, when he performs cardiac auscultation using his stethoscope.
But the blood reflux caused by the degeneration of the valves can lead to an enlargement of the heart chambers, causing the appearance of clinical signs that you may notice such as exercise intolerance, rapid and/or difficult breathing or coughing.
Pressure in the enlarged heart chambers causes congestive heart failure, which in severe cases can result in fluid leaking from blood vessels into the lungs (called pulmonary edema) and sometimes the stomach (ascites).
Clinical signs usually set in very slowly over a period of years, but can sometimes set in quite quickly.
How is degenerative mitral valve disease diagnosed?
Initially, the disease can be suspected during a routine consultation, when the veterinarian listens to your pet's heart using his stethoscope.
If the veterinarian then hears a heart murmur, he can then advise you to carry out additional examinations such as:
- a chest X-ray to assess the size of the heart and the condition of the lungs and blood vessels,
- an echocardiogram to determine the size of the heart chambers and the contractility of the ventricles,
- an ECG (electrocardiogram) to assess heart rhythm,
- a blood test for NT pro-BNP, a marker of heart failure.
What is the treatment for degenerative mitral valve disease?
Treatment for degenerative mitral valve disease depends on what stage of the condition your dog is at.
At stage A and B1 of the disease, that is to say when the dog has no symptoms (apart from a heart murmur at stage B1) and the examinations have shown no structural changes from his heart, no treatment is put in place.
At stage B2, when the dog has a mitral insufficiency heart murmur and an increase in the size of the heart chambers without other symptoms, most veterinarians recommend the implementation of a specific diet and the administration of ACE inhibitors.
At stages C and D, when the dog shows signs of moderate to severe heart failure respectively, he should receive medical treatment that may combine diuretics, positive inotropes and ACE inhibitors. more than one specific diet.
Following treatment instructions by the animal owner is essential to improve the lifespan and quality of life of dogs with mitral endocardiosis.
The drugs, which will need to be taken for life, help to reduce the severity of the clinical signs but the disease will continue to progress and the drugs will eventually not be as effective. Sometimes, new medications may be added or doses may be adjusted over the course of your pet's follow-up consultations.
Sometimes the dog's condition deteriorates rapidly and requires emergency hospitalization.
A surgical solution?
Valvular replacement surgeries have recently been successful but, in fact, this procedure is still little practiced in France. It should become more democratic in the coming years.