SUBVALVULAR AORTIC STENOSIS (S.A.S.)


NORMAL HUMAN HEART	AORTIC STENOSIS narrowing below valve, thickening of heart muscle

S.A.S. refers to Subvalvular Aortic Stenosis, one of the more common heart malformations in dogs. In a mild form, there are a few nodes just under the aorta, barely affecting the flow of blood, and the quality of life for the dog remains optimistic. In a severe form there is a fibrous wreath surrounding the vessel partially blocking the flow of blood. This causes undo stress on the heart pushing the blood through a narrower opening, and on the constricted blood vessel itself. Dogs will experience chronic fatigue and at it's most extreme, sudden death.

It is genetically inherited although it's difficult to test for. There are no blood or DNA tests to easily identify it. Carriers are discovered as they grow and begin to manifest symptoms. Unlike most genetic problems, it is at times undetectable by any known means until the pup is several weeks old.

In genetic terms the mode of inheritance is complex and much is still not understood. In Newfoundland dogs it is being studied as an autosomal dominant trait with variable expressivity or as a polygenic trait. It means that only one parent has to have it, and all of their offspring have a possibility of being affected to various degrees. A recent study using Golden Retrievers and Newfoundlands, has suggested that it is inherited as a dominant gene with incomplete penetrance and variable expression. This means that a percentage of the pups will be affected to various degrees.

One of the first ways to detect a problem is to have a Vet screen the heart, listening for a heart murmur, associated to heart problems. If there is no murmur detected by 6-8 weeks old, the pup is considered free of heart problems. If a murmur is present, then the pup should be examined more extensively.

A pup can have an `innocent heart murmur', which means the pup will have a mild murmur until about 12-14 weeks old and then it will disappear. Afterwards, they also can be considered clear of heart problems and fit to breed, unless there is a family history of S.A.S. If the murmur continues beyond 14 weeks it is advised that more extensive testing is done - echocardiography or cardiac catheterization and angiocardiography. Murmurs can occur without any heart ailment, although it is advised that these dogs not be used as breeding dogs. As well, there is a small percentage of S.A.S. carriers who go undetected as they have no murmur.

Pups with moderate to severe S.A.S. can be diagnosed as young as 6-8 weeks. Depending on the severity, the overt symptoms will be exercise intolerance, fainting, heart failure or sudden death. S.A.S. is a progressive disease. The heart has to work harder and it's muscle, the wall of the heart, gets thicker over time which causes more problems with it's ability to beat regularly and to pump blood. It will cause them to become fatigued easily and perhaps faint. When the heart muscle is very thick the heart rhythm becomes very irregular, cardiac arrhythmia, and the heart can stop.

References

• SAS - What it is, and Why Breeder Should be Concerned

by Denise Mankin, DVM, 1996

http://www.europa.com/~dshecklr/SAS.html

• Sub-aortic Stenosis (SAS) - A Heart Breaking Problem

Best Beau BMD Health Info Links,

Sub-aortic Stenosis

http://www.bestbeau.ca/SAS.htm

• Subaortic Stenosis

University of Pennsylvania Veterinary Medicine,

Department of Clinical Studies, Cardiology

http://www.vet.upenn.edu/departments/csp/cardiology/brochures/Subaortic%20stenosis.pdf