Mitral Valve Disease in Cavaliers

Mitral valve disease is the most common form of heart disease that affects adult dogs. This degenerative condition causes the heart’s mitral valve to leak, eventually leading to heart failure.

Unfortunately, mitral valve disease is 20 times more prevalent in Cavalier King Charles Spaniels than other breeds, and is the leading cause of death for Cavaliers all around the world.

So what causes mitral valve disease in Cavalier King Charles Spaniels, what are the symptoms to keep an eye out for, and what does treatment involve? Keep reading to find out.

In its early stages, mitral valve disease produces few noticeable symptoms. The earliest symptom of the condition is usually a heart murmur (heard with a stethoscope), which is a result of blood being regurgitated back through the mitral valve and into the left atrium. In most cases, no other symptoms are seen at this stage.

However, as the valve continues to deteriorate, the heart is no longer able to function at full capacity. This reduced efficiency leads to several symptoms, such as:

• Exercise intolerance
• Breathing difficulties
• A cough
• Lethargy
• Loss of appetite
• Fainting

Over time, congestive heart failure develops. However, the time between the appearance of a murmur and congestive heart failure could potentially be years.

In order to understand how mitral valve disease affects dogs, we first need to take a closer look at how the heart works.

There are four chambers in a dog’s heart. The two upper chambers are known as atria (the singular term is atrium) and the two lower chambers are called ventricles. Valves sit between each of these chambers to ensure that blood flows through the heart in one direction, and the mitral valve is located between the left atrium and the left ventricle.

Mitral valve disease occurs when this valve degenerates over time. This means the mitral valve doesn’t seal properly, resulting in blood flowing backwards (often referred to as being “regurgitated”) into the atrium. And as the valve continues to deteriorate, it can lead to heart failure.

Mitral valve disease is also known by a variety of other names, including endocardiosis, chronic mitral valve insufficiency, and chronic valvular disease.

Mitral valve disease is a hereditary condition that is classed as being polygenetic, which means it can be caused by more than one gene. The disease commonly affects older dogs, and small breeds are more prone to suffering from the condition than their larger counterparts.

However, mitral valve disease is especially prevalent in Cavalier King Charles Spaniels. In fact, it’s 20 times more common in Cavaliers than in other breeds.

Cavaliers are predisposed to this serious condition, and it’s the leading cause of death for the breed around the world. Statistics show that the condition affects more than half of all Cavalier King Charles Spaniels by the time they reach 5 years of age, and more than 90% of Cavaliers over the age of 10. 

In contrast, mitral valve disease is considered an old-age condition only in most other breeds, and will only affect roughly 10% of dogs during their lifetime.

The first stage in diagnosing mitral valve disease in Cavalier King Charles Spaniels is to take your dog to the vet for a physical examination. Your vet will listen to your pet’s heart with a stethoscope (auscultation) and will run further tests if a murmur is heard.

An ultrasound examination (echocardiogram) and electrocardiogram (ECG) can be used to determine how well the heart is functioning. They may also order chest X-rays to check whether the heart is enlarged and if there is any fluid in the lungs. This will allow your vet to assess how far the disease has progressed and decide on the best course of treatment.

The treatment of mitral valve disease typically involves the use of drugs and lifestyle changes to help increase the heart’s efficiency. Medication can include ACE inhibitors to lower blood pressure, diuretics to remove excess fluid, and beta-blockers to lower blood pressure and lower heart rate. Restricting your dog’s sodium intake and exercise levels can also play a part.

These treatments all focus on managing the symptoms of mitral valve disease rather than treating the condition itself. However, they can still delay the onset of heart failure for years and ensure that your dog lives a long and happy life.

A 2016 study showed that administering Pimobendan (a positive inotrope that increases myocardial contractility) to dogs with preclinical mitral valve disease can delay the onset of symptoms by up to 15 months, ensuring a significant impact on a dog's quality of life. As the disease advances and dogs become resistant to diuretic therapy, switching from furosemide to torsemide (a different type of diuretic) can also improve a dog's quality of life for months.

While malfunctioning heart valves can be surgically replaced in people, similar operations in pets have had historically low success rates. However, a team led by Dr Masami Uechi, director of the JASMINE Veterinary Car­diovascular Medical Center in Japan, developed an open-heart surgery technique to repair the valve with a claimed success rate of 90%.

Though surgical repair is becoming an increasingly successful option, it currently involves open heart surgery, the cost of which is beyond the reach of many pet parents. It's hoped that a minimally invasive and more affordable surgical option will be made available in coming years.

As research continues into the causes of mitral valve disease in Cavalier King Charles Spaniels, prevention centers on responsible breeding practices. The American Cavalier King Charles Spaniel Club requires its members to screen their breeding stock for the disease and recommends that this is done annually. 

And while owners can’t prevent the condition, it’s a good idea to take your Cavalier to the veterinarian for regular check-ups. This will ensure that any heart murmur is detected early and can be carefully monitored, allowing you to devise the best course of treatment as the disease continues to progress.

Mitral valve disease can be expensive to treat. If you suspect your dog is at risk of mitral valve disease, start searching for pet insurance today. Wag!’s pet insurance comparison tool lets you compare plans from leading companies like PetPlan and Embrace. Find the “pawfect” plan for your pet in just a few clicks!