Heart (Aortic) Valve Narrowing in Dogs

Your dog’s heart (just like ours) is just like a pump. Blood is taken in on one side where it is pushed into the lungs to replace the carbon dioxide with oxygen. Carbon dioxide is the waste product from the metabolism process in your dog’s body. The oxygenated blood goes into the other side of the heart where the heart pushes the oxygenated blood through the rest of the body. With aortic stenosis, your dog can look and act just like any other healthy dog and show no symptoms at all, but can collapse without warning. Because the aortic valve is so narrow, an obstruction of the blood flow can develop, causing the heart to work harder to pump the blood. This leads to a decreased flow of blood to the body, which can cause abnormal heart rhythms and fluid build-up in the tissues surrounding the heart. This can be mild, moderate, or severe. If your dog’s aortic stenosis is moderate or severe, the heart has to work much harder, and it can cause your dog to faint, have trouble breathing, and can even cause sudden death.Many times, aortic stenosis is found during a routine examination because the symptoms are so mild at first. Taking your dog to the veterinarian on a regular basis can help find illnesses such as aortic stenosis so you can start treatment before the problem gets worse.

Narrowing of the heart (aortic) valve in dogs (aortic stenosis) is a serious condition that is usually genetic. Large breed dogs, such as the Boxer, German Shepherd, Rottweiler, Golden Retriever, and Newfoundland are the most susceptible. Aortic stenosis is the second most common heart defect in dogs and causes muscle fibers in the left ventricle to become thicker to form a ring of fibrous tissue, making the aortic valve more narrow.

The aortic valve is responsible for pushing the oxygenated blood from your dog’s heart into the rest of the body, and if it is not working properly, your dog’s symptoms can range from non-existent to sudden death. Most often, this condition will be discovered during a checkup with the veterinarian rather than because of symptoms you have noticed. However, the most commonly reported symptoms are:

• Collapse
• Difficulty breathing
• Exercise intolerance 
• Fainting, and in extreme cases
• Fatigue
• Poor growth
• Sluggishness
• Sudden death
• Weakness

 Types

• Mild aortic stenosis pressure occurs when your dog’s heart rate is less than 50 mm Hg and may show no signs of illness
• Moderate aortic stenosis is when your dog’s pressure is between 50 mmHg and 80 mmHg; at this point, your dog will show mild to moderate symptoms such as fatigue with exercise, weakness, and poor growth
• Severe aortic stenosis occurs when your dog’s pressure is over 80 mmHg and has several serious symptoms, such as fainting, heart failure, and can even be fatal

The cause of aortic stenosis is a congenital (birth defect) of the genes in the phosphatidylinositol-binding clathrin assembly protein (PICALM). This is the same gene responsible for Alzheimer’s syndrome in humans. Some of the most common breeds of dogs known to be susceptible to aortic stenosis are:

• Bouvier des Flanders
• Boxer
• English Bulldog
• German Shepherd
• German Shorthair Pointer
• Great Dane
• Golden Retriever
• Newfoundland
• Rottweiler
• Samoyed

To diagnose aortic stenosis, the veterinarian will first perform a complete physical examination of your dog, including heart rate, respirations, breath sounds, blood pressure, body temperature, height, weight, and reflexes. The results of these tests will give your veterinarian a clearer idea of the immediate health of your dog so he can do the rest of the workup, such as laboratory tests and imaging. The tests done will include a complete blood count (CBC), blood gases, chemistry panel, and urinalysis.

Next, chest x-rays will be performed to check for built up fluid in the lungs. An electrocardiogram (ECG) may also be done to look at the electrical activity of the heart and check for arrhythmias. The ECG is a painless procedure done with an ultrasound machine just like they do with pregnant women. This allows your veterinarian to see the inside of the heart to assess the blood flow patterns, heart valves, speed, amount of blockage, and severity of disorder (mild, moderate, or severe) and other details of the heart’s status and functioning ability.  

electrocardiography. In cases where a dog faints frequently or shows other signs of possible heart rhythm problems, the veterinarian may monitor heart activity over a full day. Other tests, such as a Doppler ECG may be the best diagnostic tool to detect even mild cases of aortic stenosis. The Doppler uses the same technique as the normal ECG but uses Doppler waves rather than ultrasound.

Treatment is usually only necessary for moderate or severe stenosis, because mild usually shows no symptoms, and does not affect your dog’s quality of life or life span. Moderate and severe stenosis needs treatment to enable your dog to live a good quality of life although his lifespan will be shorter.

One of the choices of treatment is surgery to correct the aortic stenosis, depending on where, and how bad it is. The surgery is not recommended unless other treatments have failed (catheter-based) because this procedure is only somewhat successful and can be risky. Other treatments, such as medication (atenolol) have been known to be effective and are not dangerous at all.

The prognosis for dogs with congestive heart failure due to aortic valve stenosis is not good. However, those dogs with mild stenosis usually do not require treatment. The average dog with stenosis can live a long, healthy life without even knowing it is there and can be expected to have a normal life span. The prognosis for animals with clinical signs of congestive heart failure is poor but mildly affected animals may remain free of clinical signs.