Commonly affecting large breeds of dogs, subaortic stenosis is a congenital heart disease. It’s caused by a hereditary malformation of the left ventricle of the heart. Dogs with the condition are also predisposed to other heart problems and without treatment, will have a significantly shortened life span. As a hereditary condition, the subaortic stenosis is present in your dog at birth.
In a normal heart, there are two chambers on both the right and left side of his heart. The upper chambers are called atriums while the lower chambers are called ventricles. Oxygenated blood from the lungs enters the left chambers of the heart and is pumped through the rest of the body. De-oxygenated blood that has already passed through the body enters the chambers on the right side and is pumped into the lungs to be reloaded with oxygen and the process begins anew.
A dog with a subaortic stenosis, his left ventricle will have problems pumping the blood through his body. The ventricle will be abnormally narrowed at the point where it joins the aorta. Therefore, his heart will have to pump excessively to move the oxygenated blood through his system. This excessive strain can cause a heart murmur, which is usually the first symptom of a subaortic stenosis.
The breeds that are commonly afflicted by subaortic stenosis are Golden Retrievers, Rottweilers, Newfoundlands and Great Danes.
Don’t panic if you take your puppy to the vet and he tells you that your puppy has a heart murmur. Many puppies have what’s called an “innocent” heart murmur for their first six months of age. This murmur is normal and can disappear on its own without causing the dog any long-term ill effects around six months of age. If your puppy is older than six months and still has a heart murmur, especially if it appears on the left side of his heart. At this juncture, he may be diagnosed with a subaortic stenosis. X-rays and ultrasounds can then help to confirm the diagnosis.
Once your dog has received a diagnosis, he will require treatment to maintain his normal projected lifespan and a normal quality of life. Beta blocker medications will help to normalize your dog’s heartbeat and relieve some of the subaortic stenosis’ symptoms, such as exercise intolerance and fainting. These drugs alone will give your dog twice as long a life span he would have without any medical intervention.
Open-heart surgery is another option. This surgery will widen the opening of the left ventricle. The surgery won’t relieve all your dog’s symptoms nor cure his condition, but it will also dramtically lengthen your dog’s life.
Balloon valvuloplasty will minimize the narrowing of the ventricle opening. Balloon valvuloplasty involves inserting a catheter with a balloon attached. During surgery, the balloon is inflated to widen the ventricle’s opening.
Neither surgery is considered to be more effective than administering the beta blocker medications. However, either surgery may be the better option for your dog if he receives his diagnosis later in his life.