Subaortic Stenosis (SAS) In Your Puppy

Aortic / Subaortic Valvular Stenosis: AS/SAS

 

Ron Hines DVM PhD ..........................................

 

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Subaortic Stenosis is the second most common inherited heart disease in dogs. It is a heartbreaking discovery for every owner of a new puppy. And it is usually your veterinarian who has to break the news.

SAS is most common in large pure-bred dogs. We see it most often in German Shepherds, Great Danes, Boxers, Newfoundlands, Rottweilers, Golden Retrievers, German Short-haired pointers, Bull Terriers, Bouvier de Flanders and Bernese Mountain Dogs.

Subaortic stenosis or SAS is a complex genetic problem. Puppies that suffer from SAS inherited a gene-combination from one or both of their parents that caused their heart to develop abnormally. Because several genes are interacting to cause SAS in ways we do not understand, we can not predict which matings will produce puppies with this condition.

When Is SAS Usually Discovered?

If you are like most people dealing with SAS, a heart murmur was picked up by your veterinarian when the puppy was receiving its puppy shots. If the pet's heart was not examined at that time, it is usually the unexpected death of the puppy that makes this disease suspect.

Not all puppies with this condition have heart murmurs . Not all of them have developed a heart murmur by the time they received their last puppy vaccinations. Sometimes the murmurs come and go. And sometimes these juvenile heart murmurs are not signs of SAS. Heart murmurs that have no apparent cause are called innocent murmurs. They can leave as mysteriously as they appeared.

What Is The Problem In My Puppy's Heart?

In subaoritic stenosis the puppy is born with an abnormally narrow passage way leading from the heart to the aorta. I marked it as the "NARROWED AREA" in the picture at the top of this page vs the "NORMAL AREA" in the inset. The narrowing is due to muscular and fibrous tissue that keep growing longer than they should. When a puppy with SAS is first born, the heart is only slightly abnormal in this area. The tissue in this subaortic area can remain only slightly abnormal - or it can continue to grow until it prevents blood from passing through the narrowed channel. The more restricted blood becomes as it moves through this bottleneck, the louder the heart murmur and the more serious the problem. Very mild case require no treatment - severe stricture becomes a life-endangering problem. The length of time this narrowing continues also varies from case to case.

When you take a puppy to the vet for his first vaccinations, the veterinarian should listen to the puppy's heart. In a puppy with SAS, there will usually be a heart murmur over chest near the left base of the heart. This is how most cases of SAS are first diagnosed. Not every puppy with a heart murmur has SAS. The murmur of the most common heart defect of puppies, Patent Ductus Arteriosus (PDA), usually has a different sound - like a washing machine.

Puppies often outgrow heart murmurs without our really knowing what caused them in the first place. Only some complicated tests, performed by a veterinary cardiologist, can tell which murmur is important. But if your puppy still has a murmur when it is 6 months old, SAS or PDA become likely.

When a puppy has a significant degree of SAS, its heart has to work harder to force the blood through the narrow area just below the aortic valve. With time, the heart muscles get thicker due to the extra effort. As the walls thicken, the full heart holds less and less blood and needs more and more oxygen. Eventually, the heart begins to fail. Unlike older dogs with Congestive Heart Failure (CHF), SAS puppies often die suddenly when clots form in the heart muscle or its electrical system fails.

What Signs Will I See In My Puppy?

Most often, you will see no signs at all in your puppy. But as time goes by and the puppy's heart muscles thicken, problems in the electrical system of the heart can cause fainting or unexpected sudden death.

What Tests Will My Veterinarian Perform?

To decide how serious a heart murmur really is, your pet needs to have echocardiography (doppler ultrasound) performed by a veterinarian trained in interpreting the results. An x-ray and an EKG will also be required to see how much damage has already occurred.

What Are The Treatment Choices I Have?

Medications:

The most popular drugs used to treat SAS are known as beta blockers (ß-blockers). The most commonly used ones are Propranolol (Inderal) and atenolol (Tenormin). Beta blockers reduce heart rate, help control abnormal heart rhythm and reduce blood pressure. They are proven in their ability to extend the lives of dogs with SAS.

Surgery:

Open heart surgery to correct this problem in dogs has not been as successful as one might hope. Dogs that have had the surgery, live about as long as dogs that just receive medicine.

Balloon Valvuloplasty:

This technique is similar to balloon angioplasties that are done to dilate blocked coronary arteries in people. A catheter is threaded into the heart and a balloon is expanded in the narrowed area of the heart. So far, this technique has not led to increased life span.

How Long Will My Puppy Live?

That is very difficult to predict. They younger the puppy is when the problem is first noticed, and the louder the heart murmur, the bleaker the outlook. Most dogs with the typical signs of SAS do not live over 3 years without medication.

A cardiac work-up at a regional veterinary center that includes all the diagnostic tests, might give you more insight. But all pets with this condition can die suddenly - and often do.

What Can Be Done To Prevent SAS?

Matings that have produced puppies with Subaortic Stenosis should not be repeated. Bitches that have produced two such puppies with different studs should not be bred. Parent dogs should be examined by a board certified veterinary cardiologist or veterinary internist who has advanced training in congenital heart disease and be OFA-certified to be free of detectable heart defects.

Because some dogs that carry genes involved in SAS will be missed using the most current diagnostic tests - OFA or any other certification of a puppy's parents is not an absolute guarantee that the disease can not occur. Just like in people, a clean bill of health from a cardiologist is not a guarantee that one's heart will not fail unexpectedly.