This disease causes your dog’s heart to work too hard.
The aortic valve is the gateway between the heart's main chamber and the main artery that pushes blood out to the rest of the body.
Aortic stenosis is the name for a particularly narrow aortic valve, and it is something your dog is born with — although you may never know they have the problem until it becomes severe. When the aortic valve is narrow, the heart must work harder to pump blood through it. Aortic stenosis is found most often in large-breed dogs, but any breed or mix can be affected.
As a bottom chamber of the heart, your dog’s left ventricle is the biggest and strongest chamber of the heart. When the heart contracts, it pushes oxygenated blood out through this valve to the rest of the body. In a dog with aortic stenosis, the left ventricle must push harder to force a normal amount of blood through the narrow valve. Over time, this can cause problems, even leading to heart failure or death.
Many dogs do not show obvious signs of aortic stenosis, but they may have a heart murmur, which is usually identified the first time they visit a veterinarian. If the disease becomes severe, the dog may exhibit:
- Exercise intolerance
- Difficulty breathing
- Sudden death
Puppies can sometimes have a heart murmur that will go away as the puppy ages. Your veterinarian will take notes describing the murmur that they hear and follow up at each exam when your pup comes back for vaccine boosters. If the murmur goes away, all is well. If your new pup has aortic stenosis, the murmur will not improve and may worsen.
Types of aortic stenosis
There are three types of aortic stenosis, based on where the defect occurs.
- Subaortic stenosis is when the narrowing is just beneath the aortic valve. This is by far the most common type in dogs, and one of the most common heart conditions in dogs overall.
- Valvular aortic stenosis is when the narrowing is in the valve itself.
- Supravalvular aortic stenosis is when the narrowing is just above the aortic valve.
All these can then be classified as mild, moderate or severe, which will impact treatment and prognosis.
“If they have mild stenosis then their life span is usually unaffected, with a normal life span compared to the general canine population,” says Kornreich. “Dogs with moderate-to-severe stenosis definitely have a worsening prognosis with the degree of severity. Dogs with severe stenosis have a poor long-term prognosis.”
Getting a diagnosis
If your veterinarian hears a suspicious heart murmur during an exam, they will recommend some tests to find out if your dog does have aortic stenosis.
Chest X-rays are an easy place to start, but the heart will usually look normal in mild cases or early in the disease process. Some physical changes may be visible in more severe cases. An electrocardiogram also will probably be normal in mild cases, but will show some abnormalities in more severe ones.
An echocardiogram (or “echo”) is an ultrasound of the heart. This is the best way to check for aortic stenosis because the veterinarian can see the aortic valve and measure the velocity of blood flow across it. An echo can distinguish between mild, moderate and severe cases. This test is non-invasive and doesn’t require anesthesia, but you will need to visit a specialist.
Bloodwork may be run as well, particularly if your dog has a more severe case and may need to start on medications.
Mild cases of aortic stenosis usually do not require treatment. Your veterinarian will listen to your dog’s heart during every exam and track any changes in the severity of the murmur.
Moderate-to-severe cases usually require treatment. There is no cure, so the goal is to manage any symptoms and slow progression.
“Usually, these patients are treated with lifestyle modification, avoiding severe exertion,” says Kornreich. “In many cases, we use beta blockers to decrease the force of contraction of the heart.”
Atenolol is the most commonly used beta blocker.
If the dog is showing signs of congestive heart failure, additional medications will likely be added to address those issues. “In some cases, we may end up treating with other antiarrhythmics,” says Kornreich. These medications will need to be continued for the rest of your dog’s life.
Exercise restriction is often recommended. Intense play and hard exercise require the heart to beat harder, which puts extra strain on your dog’s already overworked heart. If your dog has experienced episodes of fainting or collapse during exercise, limiting their activity will likely be part of their treatment plan. Dogs with moderate-to-severe aortic stenosis could experience sudden death if they are too active.
You can keep your dog moving — just stick to low-impact activities that don’t get them panting hard. Walks are usually fine, and obedience and trick training will work your dog’s mind. Avoid hard running, such as chasing or fetching, and discourage crazy or rough play.
Surgical procedures have been attempted to correct aortic stenosis, with mixed results. The most promising technique is called “cutting balloon valvuloplasty.”
A tiny balloon with little blades is inserted into the carotid artery and guided into the heart to the location of the restriction, and once in place, the balloon is inflated so that the blades can score the inside of the narrowed region. A second balloon is then inserted and inflated to dilate the vessel to a normal width. Dogs who undergo cutting balloon valvuloplasty for subaortic stenosis may have better exercise tolerance and less strain on their left ventricle after the procedure, but results overall have not been good.
“Initially, it looked promising, but more recent studies have shown that these dogs often re-stenose over time,” says Kornreich. “This procedure has not been shown to improve lifespan in dogs with subaortic stenosis. We don't routinely recommend it at Cornell, except for extreme cases in which there is no other option, and owners understand its risks and limitations.”
The problem is that the cutting balloon valvuloplasty does not provide a permanent solution. It may not be initially successful, and in those cases in which it is, most dogs regress back to where they were within a year or two. There is also the potential for damage to the aortic valve. Going through the procedure does not seem to extend overall survival time, and of course, it comes with the typical risks of going under anesthesia and the introduction of catheters into the cardiovascular system.
For most dogs with subaortic stenosis, the risk of this procedure is presumed to be greater than its potential benefit at this time.
There is no cure for aortic stenosis, but you can help your dog’s heart by limiting hard exercise. Medications may be needed in severe cases. Dogs with mild cases can live normal, happy lives without any symptoms.
This article has been reprinted with permission from the Cornell University College of Veterinary Medicine’s DogWatch newsletter, published by Belvoir Media Group. When you become a member of the Riney Canine Health Center, you will receive a free subscription to DogWatch.