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Aortic Stenosis in Dogs

My puppy was diagnosed with a heart murmur, and after some tests I was told he has a condition called “aortic stenosis.” I am trying to understand more about this condition.

normal-heartA dog’s heart has four chambers. The top chambers are called the atria and the bottom chambers are called the ventricles. Valves separate the atria from the ventricles on both sides of the heart. Valves also separate the right ventricle from the main artery to the lungs (the pulmonary artery) and the left ventricle from the aorta (the main artery to the body).

The word “stenosis” means “narrowing,” and aortic stenosis describes a narrowing along the aorta as it leads out of the heart. It is typically present at birth and worsens over the first year of life. Clinical signs of heart disease can occur at any age and depend upon the severity of the obstruction of blood flow out of the heart and into the aorta. The defect can occur above the valve, just inside the aorta, at the valve itself, or below the valve, closer to the heart itself. A heart ultrasound (or echocardiogram) is an important way to see what is happening with the heart and surrounding blood vessels.

 

Are there some breeds of dog that are more susceptible to aortic stenosis?

There are several dog breeds in which there are risk factors for aortic stenosis. These include:

 

What are the clinical signs associated with aortic stenosis?

The signs of aortic stenosis are related to the severity of the narrowing, and range from no signs at all, to congestive heart failure, fainting, or sudden death. A heart murmur may not be present in very young puppies, but then will develop over the first 6 months of life. Sometimes the murmur is dramatic enough that, by placing a hand against the chest wall, it is possible to feel a vibration caused by the turbulence of the blood flow. As heart failure progresses, the dog may develop rapid breathing or difficulty breathing, and will develop exercise intolerance. Even the pulses in the major arteries may be affected.

Most of the time, aortic stenosis is a developmental problem that is present at birth, although it can also occur secondary to infection of the lining of the heart (endocarditis). Endocarditis is more likely in dogs with a suppressed immune system, bacteria in the blood, a generalized infection, or abnormal blood flow through the heart.

 

Is there any treatment for aortic stenosis? 

Treatment focuses on managing the symptoms of congestive heart failure, irregular heartbeats, and fainting episodes. Activity may need to be restricted in order to prevent fainting or collapse.  In dogs who are severely affected, exertion can be fatal, so these are dogs who need extra supervision. A low-sodium diet may be in order. Your veterinarian can guide your feeding choices.

Theoretically, definitive treatment would require open-heart surgery with heart-lung bypass to repair or replace the valve, but the risks of this surgery for dogs with aortic stenosis currently outweigh the possible benefits. Dilating the narrowed aorta using an expandable balloon via heart catheterization may improve clinical signs in some dogs.

"Medical management treats
clinical signs but is not a cure."

Medical management treats clinical signs but is not a cure. There are several classes of medication from which your veterinarian may choose including beta blockers and calcium channel blockers.

Your veterinarian may recommend periodic monitoring. This could include electrocardiogram to evaluate the electrical activity in the heart, chest x-rays to assess changes in heart size and shape, and/or echocardiogram.

 

What is the long-term outlook?

A mildly affected dog may live a normal lifespan without treatment. Dogs with severe aortic stenosis usually develop congestive heart failure which limits life expectancy. Anaesthesia may be contraindicated.

Robin Downing, DVM, DAAPM, DACVSMR, CVPP, CRPP
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