Your dog’s heart: mitral valve disease

Your dog’s heart may become diseased as he gets older. Of the 10% of dogs who suffer from heart ailments, 80% are diagnosed with mitral valve disease.

This article is intended to help pet parents whose pets have been diagnosed with mitral valve disease so that you understand everything you need to know about this condition. Always feel free to call us should you have additional questions.

Your dog’s heart: what is mitral valve disease?

Your dog’s heart has 4 chambers; 2 upper chambers and 2 lower chambers. The 2 upper chambers are called the Atriums (left and right) and the lower chambers are the ventricles (left and right). The valves are the ‘doors’ between the atriums and the ventricles, and they open and close to let blood through the heart in one direction only. In mitral valve disease, the affected valve is situated between the left atrium and the left ventricle.

Your dog’s heart: the causes

When we talk about mitral valve disease, it is usually a scenario where the mitral valve becomes thickened and irregular over time, and eventually becomes ‘leaky’. Instead of closing properly when the heart pumps blood forward (i.e., from the left atrium, to the left ventricle, and up through the aorta), it only closes partially or not at all. This means that some of the blood accidentally gets pushed backwards and the heart has to pump a little harder and a little faster to work against this constant backflow. This condition is known as mitral valve insufficiency (MVI) and is usually associated with a heart murmur (the sound we hear with our stethoscopes when there is abnormal flow through the heart).

How common is mitral valve disease?

Approximately 10 % of dogs will develop some form of heart disease in their lifetime, of which 80% is diagnosed as mitral valve disease. This condition is more common in middle-aged to older small dog breeds like Maltese poodles and Dachshunds.

Symptoms of mitral valve disease

The earliest symptom of mitral valve disease is detecting a murmur when listening to the heart with a stethoscope. At this point you as the pet’s owner may not have noticed that there is anything wrong with your dog’s heart as it is able to compensate for the problem, and will go about its life as normal. As the disease worsens, you may starting seeing that your pet tires more quickly during exercise. The heart is struggling to to keep up. Eventually, it gets too tired to keep up, and the blood flow starts backing up, causing congestive heart failure. Now you may notice coughing (initially at night), a cough that may result in gagging or bringing up white foam.

From the time your veterinarian diagnoses a heart murmur, it may be a few months to several years until actual heart failure occurs. Just because there is a murmur does not mean that your pet is in heart failure. The good news is that this condition is treatable.

What should I do when I start seeing these symptoms in my pet?

The best thing that you can do for your dog’s heart as an owner is take your dog to your vet for a thorough clinical exam.  There are a number of tests that may be done after a thorough examination.  Chest X-rays are advised to determine the size and shape of the heart and to check if any fluid is building up in the lung. There are certain blood tests that can be performed to see if there is significant heart damage. Further diagnostic tests like ultrasound of the heart (echocardiogram) or an ECG (electrocardiogram) may also be used to get even more information about the state of the disease.  These tests will help determine the extent of the heart failure and pinpoint the exact location of the problems.

What are the treatment options?

The severity of symptoms as well as the test results (such as chest X-rays) will determine what treatment and medication is necessary. There are several options; the aim of the medication is to help the heart pump (regain its strength), reduce the heart’s work load and reduce fluid build-up in the lung.  As every dog is unique, medication must be tailor made. Medication is life-long, and adjustments made be needed as time goes by. If left untreated, pets can deteriorate quickly and will ultimately die of heart failure.

Living with a pet with heart disease

Pets that have mitral valve disease and that respond well to treatment can live years after diagnosis. Early diagnosis and treatment are important to ensure maximum lifespan. Pets may die from unrelated illness and not always due to the heart condition, but this all depends on the progression and severity of the symptoms at the time of diagnosis.

Many pets can still continue to enjoy an active and fulfilling life. Exercise is good and should be encouraged. They can walk, play, and do their favourite activities. If some tiredness or fainting is noticed, exercise should  should be moderated.  Running for long periods of time is not advised, as this can place excessive strain on the heart.

It is particularly important to address any pre-existing obesity, or weight gain that may occur over time as  dogs that are overweight and have heart disease live shorter lives.

Article by Drs Morné de Wet and Tiaan Visser, Cottage Vet Clinic




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