Subvalvular Aortic Stenosis in Dogs

Most dogs affected by subvalvular aortic stenosis are born with the condition as it can be genetic.  While your dog may not be diagnosed with this condition as a puppy, that does not mean he is disease free.  He can develop the condition as he ages at any time.  Symptoms can vary from moderate, such as lethargy or a heart murmur, to something as severe as sudden death.  Subvalvular aortic stenosis is the most common form of aortic stenosis in dogs.  Treatment of this condition can be with supportive therapies and supplemental medications. Another treatment option is surgery but this can be extremely risky.  The good news is, many dogs do not need treatment at all and have a fair to good prognosis.

Subvalvular aortic stenosis is a narrowing of a region your dog’s aorta within his heart.  It is a very serious condition and veterinary attention should be sought out.

Symptoms may include but are not limited to:

• Lethargy
• Syncope (fainting, loss of consciousness)
• Exercise intolerance 
• Systolic heart murmur
• Weak femoral pulse 
• Sudden death 

Types

Subvalvular aortic stenosis is also known as subaortic stenosis; it is when there is a narrowing below the aortic valve.  Aortic stenosis in general interferes with the normal emptying of the left ventricular area of the heart.  Subvalvular aortic stenosis is the most common form of aortic stenosis in dogs.

Subvalvular aortic stenosis is caused by a ridge or ring of fibrous tissue or by fibrous nodules within the left ventricular outflow tract located just below the aortic valve.  It is most commonly seen in Boxers, Rottweilers, German Shepherds, Newfoundlands, and Golden Retrievers.  It can be a congenital condition, meaning the animal was born with it, or it can develop as he ages.

The severity of this condition depends on the severity of the stenosis, also known as narrowing.  In more severe cases, the overall output of the left ventricle may be decreased, especially during exercise.  A narrowing of the valves can even lead to a possible blockage or life-threatening arrhythmia.  

An electrocardiogram may be able to show the left ventricular enlargement.  Doppler echocardiography can also confirm the aortic stenosis if present.  The velocity of the systolic blood flow determines the severity of the stenosis.  An ultrasound may also be utilized during the diagnostic process.  It can show the different chambers of the heart and offer a live feed of the heart pumping.  It can allow the veterinarian to see where the flow of blood is altered and by how much.  

There are other diagnostic imagings your veterinarian may recommend, however you may have to go to a specialist for it.  In veterinary medicine, there are cardiologists available that may be better equipped to handle your dog’s case.

Treatment for subvalvular aortic stenosis can be by medical management or by surgical correction.  If you chose medical management, your veterinarian will prescribe medications including a beta-blocker which can potentially decrease myocardial oxygen demand and reduce ventricular wall stress.  If your dog develops an arrhythmia, an antiarrhythmic medication will be prescribed as well.  You may need to have checkups with your veterinarian more frequently than you would another pet, but it would be in your dog’s best interest.

If you want surgical intervention, one option is a balloon valvuloplasty.  This is a short term fix but not consistent as a long term fix.  The other surgical option is open resection.  This is a very expensive surgery and very few facilities are set up to perform this type of surgery.  It is also very risky with a high morbidity/mortality rate.

There are also herbal medication, homeopathic remedies, and Chinese holistic medications you can look into in addition to western medicine.  This would require you to go to a holistic veterinarian who is practiced in the field, but it can be an extremely beneficial option for your dog.  In some cases, you may even utilize a combination of western medicine and holistic medicine for the best treatment plan for him.

Some animals show no symptoms of this condition.  Ones who are mildly affected typically do not even need treatment.  Prognosis in these animals can range from fair to good.  For those with a more serious condition, prognosis declines and can become guarded to poor.  It is highly recommended animals with this condition are not bred as it is genetic.