Subaortic Stenosis in Dogs

Subaortic stenosis is a congenital heart disease that commonly affects large breeds of dogs. It's caused by an hereditary malformation of the left ventricle of the heart. Dogs with this condition are predisposed to heart problems; without treatment, they can experience significantly shortened lives. Read on to learn more about diagnosing and treating this canine heart disease.

Subaortic Stenosis

Subaortic stenosis is a defect in your dog's heart, that is usually present at birth. A normal, healthy dog heart has two chambers on the right and two chambers on the left. The uppermost chambers are known as the atriums, while the lower chambers are known as the ventricles. 

Oxygenated blood from the lungs enters the left chambers of the heart, where it is pumped out through the rest of the body. De-oxygenated blood that has already passed through the body enters the chambers on the right side of the heart, and is pumped into the lungs to be reloaded with oxygen.

If your dog has subaortic stenosis, his left ventricle will have problems pumping blood back out to the body through the aorta. The ventricle will be abnormally narrow at the point where it joins the aorta, so that your dog's heart will have to pump excessively hard to move oxygenated blood back into the body. This can cause a heart murmur, which is usually the first symptom of subaortic stenosis in dogs.

Subaortic stenosis has a genetic component, and certain breeds are therefore more vulnerable. These breeds include the golden retriever, Rottweiler, Newfoundland and Great Dane.

Diagnosing Subaortic Stenosis in Dogs

Many puppies have what's called an "innocent" heart murmur before the age of six months. This type of murmur is normal and disappears on its own, without longterm ill effects, at the age of six months. Puppies that still have a heart murmur after six months of age may have subaortic stenosis, especially if the murmur is on the left side of the heart. X-rays and ultrasounds can help confirm the diagnosis.

Treating Subaortic Stenosis in Dogs

Dogs with subaortic stenosis need treatment to enjoy normal lifespans and a normal quality of life. Beta blocker medications can be administered to help normalized your dog's heartbeat and relieve some of the symptoms of subaortic stenosis, such as exercise intolerance and fainting. These drugs can help your dog live more than twice as long as he would without treatment of any kind.

Surgery is another option for treating subaortic stenosis in dogs. Open-heart surgery can help widen the left ventricle opening. It won't completely relieve your dog's symptoms or cure his condition, but it can drastically lengthen his life.

Balloon valvuloplasty can help minimize narrowing of the ventricle opening, by inserting a catheter with a balloon attached. The balloon is inflated during surgery to widen the ventricle opening. Surgical procedures, however, aren't considered terribly more effective than administering drugs, and may be most beneficial for dogs that have been diagnosed later in life.