What is degenerative valve disease?

Degenerative valve disease (DVD) is an age-related condition that typically affects middle aged and older small and medium sized dogs. Breeds such as the Cavalier King Charles Spaniel appear to be particularly affected. Other names for the condition include myxomatous mitral valve disease or valvular endocardiosis.

As you may guess from the name, DVD is a condition that affects the valves within the heart. In healthy animals, these valves function to keep blood flowing in one direction. In dogs with DVD, one or more of these valves will thicken. This thickening can prevent the valves from closing properly, causing them to leak. Over time, this leak may lead to enlargement of the chambers of the heart on either side of the leaky valve. If the leak is large enough, the heart may become overwhelmed, leading to a backup of fluid known as congestive heart failure.

The most commonly affected valve is the mitral valve. This valve separates the left atrium from the left ventricle. Normally, the left side of the heart fills with blood from the lungs and sends that blood to the rest of the body. Animals with a large leak across their mitral valve may therefore see fluid back up into their lungs (left sided congestive heart failure). This can lead to clinical signs such as exercise intolerance, trouble breathing, or worsening cough. In the uncommon cases where the tricuspid valve on the right side of the heart is particularly affected, this fluid will first build up in the belly, leading to a bloated appearance (right sided congestive heart failure).

Not every dog with DVD progresses into congestive heart failure. Many dogs with this disease will lead a completely normal life. There are some options for managing these dogs before they develop clinical signs that may help to prolong the progression of disease.

What is dilated cardiomyopathy?

Dilated cardiomyopathy (DCM) is a primary disease of the heart muscle. It most often affects large breed dogs including Doberman Pinschers, Boxers, and Great Danes. Dogs with DCM have an enlarged heart with weakened muscle, meaning it cannot pump blood effectively. Like dogs with DVD, dogs with DCM may eventually be unable to pump the normal amount of blood to the body, resulting in either left or right sided heart failure. Dogs with DCM are also at an increased risk for developing clinically significant arrhythmias (abnormal heart rhythms).

Certain abnormalities can lead to changes in the heart that mimic DCM, including low blood taurine levels, certain arrhythmias, hypothyroidism, and certain infectious / inflammatory diseases.

How are these diseases diagnosed?

Your vet may suspect these diseases in your pet based on their breed, clinical signs, and physical exam findings such as a heart murmur or arrhythmia. They may then do other tests such as X-rays of the chest to investigate if your pet has evidence of heart enlargement or heart failure. Often, a reasonable diagnosis can be made based on your pet’s breed and these findings alone.

However, while X-rays are particularly useful when looking for evidence of heart failure, they also represent the heart as a shadow and are unable to give specific information about the heart’s size and function. The best test for this information is an echocardiogram (ultrasound of the heart). This information can be used along with other diagnostics to determine things such as your pet’s risk for anesthesia or if they may benefit from other treatments.

Other diagnostics used may include an electrocardiogram (ECG) to evaluate your pet’s heart rhythm as well as things like a blood pressure. While these rarely help diagnose the specific nature of your pet’s disease, they can help to guide treatment.

How are these conditions treated?

Both DVD and DCM are often treated similarly. Specific treatments include:

• Diuretic medications such as furosemide to treat heart failure. These medications will cause your pet to urinate more and drink more water. These help to eliminate excess fluid that has built up in the body.

• Vetmedin (pimobendan) to help improve the heart’s pumping ability. This medication is often prescribed in asymptomatic animals to potentially help prolong the time until clinical signs are seen.

• ACE-inhibitors and spironolactone to help offset some of the abnormal hormonal systems that start up in patients with heart failure and to help reduce remodeling in the heart.

• Anti-arrhythmic medications to help treat abnormal heart rhythms.

• Physical removal of fluid from the chest or abdomen. Some dogs with right-sided heart failure will develop fluid surrounding their lungs or within their abdomen. This fluid can be manually removed if needed. Typically diuretics are also used to help limit this fluid from building back up.