Mitral valve disease (MVD) — also referred to as degenerative mitral valve disease or endocardiosis — in dogs is a common cardiac condition that affects the heart’s mitral valve, which separates the left atrium from the left ventricle. When functioning normally, this valve allows blood to flow in one direction — from the atrium to the ventricle. MVD occurs when the mitral valve deteriorates and fails to function properly. As a result, blood leaks backward into the left atrium, leading to an increase in the heart’s workload and, over time, congestive heart failure.
Mitral valve disease in dogs typically progresses through several stages:
- Stage A: This stage is characterized by dogs at high risk for developing MVD but showing no detectable signs of the condition.
- Stage B: In this stage, dogs show evidence of heart changes due to MVD but do not display symptoms. Stage B is further divided into B1 — without heart enlargement — and B2 — with heart enlargement.
- Stage C: Dogs in this stage exhibit clear clinical signs of heart failure. Depending on the severity, hospitalization with supplemental oxygen may be necessary at this stage.
- Stage D: This is the most advanced stage of MVD. Despite treatment, dogs might suffer from severe symptoms of congestive heart failure. At this stage, managing the dog’s condition requires aggressive treatment strategies and intensive care, with the aim of improving their quality of life.
Here’s what you should know about the symptoms, causes, and treatments for the condition.
Symptoms of mitral valve disease (MVD) in dogs
The symptoms of mitral valve disease in dogs can vary widely, from asymptomatic in the early stages to more severe symptoms as the condition progresses. As such, early detection can be challenging without regular veterinary check-ups. Symptoms to watch for include:
- Coughing
- Difficulty breathing or increased respiratory effort
- Decreased tolerance to exercise
- Lethargy
- Loss of appetite
- Rapid breathing (tachypnea) or panting
- Fainting spells
- Weight loss
As the disease advances, signs of congestive heart failure, such as fluid accumulation in the abdomen — ascites — or lungs — pulmonary edema, may develop. A hallmark of the disease that veterinarians often detect during physical examinations is a heart murmur, which is a result of the turbulent blood flow through the compromised valve.
Causes of mitral valve disease (MVD) in dogs
Mitral valve disease is most commonly a disease of aging in dogs, with the valve gradually deteriorating over time. The exact cause of this degeneration is not entirely understood, but genetics appear to play a significant role.
Certain breeds predisposed to MVD include Cavalier King Charles Spaniels, Dachshunds, Poodles, Chihuahuas, and other small breeds, suggesting a hereditary component.
Studies indicate that by the age of 13, approximately 85% of small-breed dogs will develop degenerative mitral valve disease. However, endocardiosis or MVD is not exclusive to small breeds and can affect dogs of all sizes, particularly as they get older.
Beyond age and genetics, other factors thought to potentially contribute to the development of endocardiosis include poor dental health. This can lead to bacteria entering the bloodstream and affecting the heart valves, though the evidence is more anecdotal than conclusively proven. In some cases, underlying health conditions — such as high blood pressure, can contribute to the progression of MVD by putting additional strain on the heart.
To diagnose mitral valve disease, your vet will likely start with a thorough physical examination of your dog, paying special attention to any abnormal heart sounds, such as murmurs, through a stethoscope. From there, your vet will conduct further diagnostic tests such as chest X-rays, an echocardiogram — an ultrasound of the heart — or an electrocardiogram (ECG) to examine the condition of your dog’s heart and the severity of the mitral valve degeneration. These tests are non-invasive and crucial for a correct diagnosis, allowing for the best possible management of your pet’s condition. Additionally, your vet will recommend blood tests to assess the overall health of your dog and to rule out conditions other than endocardiosis.
Treatments for mitral valve disease (MVD) in dogs
While there is no cure for degenerative mitral valve disease currently, there are various treatment options available that can help manage the condition and improve your dog’s quality of life. The treatment strategy for MVD will depend on the stage of the disease and the specific symptoms your dog is experiencing.
- Medical management: In the early stages or mild cases of MVD, treatment may not be immediately necessary, but your veterinarian will likely recommend regular monitoring to track the progression of the disease. As symptoms develop or worsen, your vet may prescribe medications such as ACE inhibitors — benazepril and enalapril — or diuretics such as furosemide, and even pimobendan to reduce the workload on the heart, control blood pressure, and prevent fluid buildup.
- Lifestyle changes: Modifying your dog’s diet and exercise routine can also be beneficial. Diets low in sodium can help reduce fluid build-up. Furthermore, regular, moderate exercise can help maintain heart health. However, it’s crucial to tailor the exercise routine to your dog’s capacity, avoiding excessive exertion.
- Surgical intervention: For certain cases, especially in dogs not responding well to medical management, surgical options like mitral valve repair may be considered. This procedure is more commonly performed in humans and requires specialized veterinary surgical centers with the capability to conduct open-heart surgery on dogs. While promising, surgical intervention is not widely available and can be cost-prohibitive.
That said, early detection through regular veterinary check-ups is critical for managing MVD effectively. If you notice any symptoms or if your dog is a breed at a higher risk of developing endocardiosis, consult with your veterinarian promptly. MVD is a lifelong condition, but early and appropriate treatment can help manage the symptoms and potentially extend your pet’s quality of life.
