Subaortic Stenosis in Dogs

A stenosis is the scientific term for a narrowing within an organ or structure that is tube-like, or a blood vessel. Another term for stenosis is “stricture”, such as when a smooth muscle contracts. A lesion is typically found that may cause the narrowing in stenosis. In aortic/subaortic stenosis, fibrous tissue has formed within the area of the left ventricle, which is just under the aortic valve. This tissue is like a ring, and it creates a thin and abnormally narrow canal for the blood to flow through. What happens is an obstruction forms, thus increasing the heart muscles’ workload. While increasing the workload of the organ, a smaller amount of blood comes from the heart. This causes a myriad of symptoms and can eventually cause cardiac failure.

The aorta is the body’s largest artery, and it is the primary carrier for the blood. When the aorta is abnormally narrow, often from birth, from the point of the left ventricle where it joins the heart, the dog’s health can be at risk. With different cases of this defect, the dog’s treatment can be from monitoring the condition to surgery to help repair the defect. 

This condition is predisposed in many dog breeds; it is typically found at birth. It can worsen as the dog gets older. It is very common in dogs of large breeds.

Subaortic stenosis is the narrowing of the outlet right underneath the aortic valve within the heart. This narrowing causes an increase in the workload of the heart, thus putting strain on the cardiovascular system.

If your dog has aortic/subaortic stenosis, he may have mild or severe symptoms, depending on his condition. Symptoms of this condition may include:

• Weakness
• Lethargy
• Difficulty breathing
• Fainting
• Resistance to exercise
• Collapse

Types

This condition is genetic and tends to occur in various dog breeds. The dog breeds affected are larger breeds. Types of breeds include:

• Boxer
• Golden Retriever
• Newfoundland
• German Shorthair Pointer
• Pointer
• Rottweiler
• Great Dane
• Samoyed
• Bouvier des Flanders
• English Bulldog

The causes of this condition are genetics and the predisposition in certain breeds. Specific causes include:

• Obstruction caused by narrowing of the area beneath aortic valve
• The heart is forced to work harder
• The heart’s health is compromised
• Less blood flow is a result

There are several tests your veterinarian will perform in order to diagnose this heart condition. Once you take your dog to the veterinarian, he will ask you questions pertaining to his symptoms and his lifestyle, as well as his overall health, age, and breed. Once your veterinarian has discussed specifics with you, he will begin by taking blood work, biochemistry profile, and urinalysis. Once he gets the results back, he will begin to focus on the heart and lungs to see what is causing your canine’s symptoms. 

The veterinarian may be able to hear a heart murmur when using a stethoscope, and an echocardiography to take a closer look at the inside of the heart. It is a very effective method of ultrasound that will show the valves, blood flow, the velocity of the blood flow, and other parts of the heart structure. Chest x-rays will show all signs and can check for the accumulation of fluid in the lungs. An electrocardiogram will be able to show the electrical impulses and activity of the heart and any arrhythmia. 

Your veterinarian will conduct any other testing he feels is necessary in order to rule out any other conditions. Your dog may be suffering from other health issues in addition to the subaortic stenosis which is causing similar symptoms. Your veterinarian will also need to test for other health issues before he prescribes any medications.

If your dog is diagnosed with subaortic stenosis, your veterinarian will explain to you his method of treatment. Treatment methods may include:

Medications

Your veterinarian will prescribe medications according to your dog’s diagnosis. Medications for subaortic stenosis include beta blockers such as atenolol, or other medications that can help reduce the workload of the heart.

Surgical Methods

In order to reduce the obstruction of your dog’s subaortic stenosis, your veterinarian may recommend surgery. Balloon catheterization has been performed with moderate success in dogs, which is where a soft catheter is inserted with a balloon at the tip. The balloon helps open the narrowed section to allow blood to flow more freely.

Cutting Balloon Angioplasty

This is a relatively new procedure in which vessel injury and stretch are significantly reduced. This is due to the fact that this method scores the vessel in a longitudinal fashion, and is minimally invasive. 

Monitoring

Your dog may have a mild case of subaortic stenosis in which the veterinarian will suggest monitoring and possible lifestyle changes. Minimizing exercise and getting plenty of rest may be all your dog needs for the time being. Your veterinarian may suggest other ways to help keep him calm and stable if he has a mild case.

Your veterinarian will explain your dog’s prognosis, as his condition may be mild, moderate, or severe. If your dog had a balloon catheterization or a cutting balloon angioplasty, your medical professional will relay specific instructions to you on how to properly care for him at home. 

Your veterinarian may suggest a type of physical therapy for your dog to help him continue to live a quality life; however, overexertion of any type needs to be avoided. Your therapist will show you the types of activities your dog can do without putting strain on his heart. He will also alert you to any symptoms you should watch for and let you know when you should take him to the veterinarian if specific symptoms do occur.

Since this condition is genetic, you should avoid breeding your dog. Although some dogs do live a long life with this condition, there are others who succumb to this disease rapidly. Your dog’s prognosis depends on your specific dog’s condition and overall health and well-being.