SUB-AORTIC STENOSIS (SAS) - A HEART BREAKING
By: Robin Camken -
Berner-Garde Foundation SAS Information Rep
(article reproduced with
permission of the author)
I began collecting information on sub-aortic
stenosis (SAS) when a friend's Bernese Mountain Dog puppy was diagnosed with
this condition in January 1997. Through casual conversations with breeders
and owners, I soon discovered that SAS is more common in Bernese than many
people are aware.
Ontario Veterinary College (OVC) Cardiology homepage lists the following
breeds as predisposed for Aortic Stenosis:
- G. Shepherd
- Golden Retriever
- Bull Terriers
- Bouvier de Flanders
In addition, Bernese are listed as an
affected breed under sub-aortic stenosis in Dr. George Padgett book
"Control of Canine Genetic Diseases". (1)
SAS is a proven inherited condition; however,
a commonly accepted mode of inheritance has not been determined for all breeds (2).
Studies indicate that it is either an autosomal dominant trait with variable
penetrance (2) or a
polygenic trait (1);
in either case, the mode of inheritance is complex, making it difficult to
predict patterns of genetic transmission. By eliminating all SAS affected
dogs from the breeding pool, we will have a chance of keeping this disease from
spreading within the Bernese population.
There is enough evidence of SAS in Bernese
Mountain Dogs to warrant routinely screening our breeding animals for heart
problems. The symptoms of SAS can be very subtle and the correct performance of
cardiac evaluation by board certified veterinary cardiologist is crucial for
determining whether or not a dog is affected. Diagnosis of SAS is almost an art.
In spite of available technology, without the proper expertise to evaluate heart
function, an affected dog can be called "clear" (4).
(Some cardiologists have recommended that evaluation of breeding animals for SAS
be performed at 1, 2, 4, and 6 years of age, due to the late onset of some of
the murmurs associated with the defect (3).)
The author of the following Q&A's,
Dr. Linda Lehmkuhl, conducted research at Ohio State University Veterinary
Teaching Hospital from 1997 to 2000 on - - - - - - - - - - - - - - - - - - - - -
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EVERYTHING YOU WANTED TO KNOW ABOUT SUBVALVULAR AORTIC
STENOSIS (SAS) BUT WERE AFRAID TO ASK
Prepared by: Linda B. Lehmkuhl,
(reproduced with permission of the author)
What is SAS?
Subvalvular aortic stenosis, also referred to
as subaortic stenosis or SAS, is a common heart defect in dogs, especially
The heart anatomically is divided into 4
chambers separated by 4 valves. The 4 heart valves ensure that blood only flows
in one direction through the heart. The aortic valve separates the main pumping
chamber (left ventricle) from the aorta, a large blood vessel that carries blood
from the heart to the body. In dogs with SAS, there is added tissue below the
aortic valve (hence "subaortic"). This abnormal tissue creates an
obstruction ("stenosis" is the scientific term) that the heart has to
overcome to pump blood to the body. This stenosis makes the heart work harder
than normal. A heart murmur is created by blood being pumped across the stenosis
into the aorta.
What happens to dogs with SAS?
SAS comes in many grades of severity. We
subdivide them into mild, moderate, and severe. Dogs with mild disease usually
lead a normal life without complications. Dogs with severe disease may die
suddenly or develop exercise intolerance, fainting, rear limb weakness, or fluid
in the lungs (heart failure). Heart failure can cause coughing, rapid breathing,
or shortness of breath. The course of dogs with moderate disease is hard to
predict. All dogs with SAS are predisposed to heart valve infections (endocarditis).
How do dogs "get" SAS?
SAS is transmitted genetically. This has been
studied in the
How is SAS diagnosed?
SAS is suspected based on a combination of
physical examination findings including a heart murmur heard over the aortic
valve. In dogs with a murmur, definitive diagnosis and assessment of severity
requires echocardiography with Doppler. Echocardiography allows visualization of
the 4 heart chambers and valves and the anatomy of the subaortic area. Doppler
allows estimation of the pressure created in the heart by the obstruction. The
degree of pressure elevation correlates with the disease severity. Some dogs
with very mild disease are hard to distinguish from normal dogs even with
this technology. Radiographs of the heart and an electrocardiogram (ECG)
are important in the evaluation of dogs with moderate to severe SAS but are
usually normal in dogs with mild disease.
What should be done if my dog has mild disease?
These dogs should not be bred so castration
or spaying is recommended. Due to the risk for heart valve infections,
prophylactic antibiotics should be prescribed by a veterinarian for any
potential bacteria exposure (dentals, skin infections, minor cuts or abrasions).
Can a dog with severe disease be treated?
Therapeutic options are limited. Surgery can
be performed at some Universities, but it is expensive. Balloon catheter
dilation can also be performed at some referral centers. This procedure involves
passing a catheter with a balloon on the end down an artery in the neck.
The balloon is centered across the stenosis and then inflated to open up the
stenosis. This procedure helps to decrease the obstruction in some dogs. Medical
therapy may be prescribed to try and decrease the work load of the heart
(beta-blockers) or treat signs of heart failure once they develop.
How can I decrease the risk of transmitting this defect?
First, have all breeding animals listened to
at maturity by a veterinarian. If no murmur is present, these adults do not have
clinical SAS. Second, have all litters listened to carefully. Timing of
this exam is tricky; the older the puppy is at the time of examination, the
better. Age is important because the defect is progressive early in life such
that a murmur will be easier to detect in a
16 week puppy than an 8 week old puppy. Also, young puppies can have innocent murmurs (murmurs not caused by a heart defect). Innocent murmurs go away by 16 weeks of age. Innocent murmurs are difficult to differentiate from mild SAS. We recommend pups be at least 8 weeks old for screening; 12 weeks old is better, and 16 weeks old is ideal. If a pup is to be used for breeding, auscultation should be repeated as a mature adult (over 1 year of age). If pups with SAS are detected, have the sire and dam examined, and do not repeat the breeding.
Are there undetectable carriers of SAS?
Yes. A dog with no murmur may be a carrier of
SAS. These dogs are not detectable at this time. Hopefully, future studies will
identify a genetic marker that will lead to a rapid, noninvasive blood screening
test for this defect and aid us in eliminating this heart breaking problem from
so many wonderful breeds.
1. Control of Canine Genetic
Diseases, George A. Padgett, DVM 1998; Appendix 2, Heart
and Vascular Disease, page 226 para 18.
2. Canine Congenital Aortic
Stenosis: A review of the literature and commentary. Michael R.
O'Grady, David L. Holmberg, Craig W. Miller, Joanne R. Cockshutt, Can Vet J Volume 30;
3. SAS - What it is, and Why
Breeder Should be Concerned. Article by Denise Mankin, DVM;
4. SAS (Sub-Aortic
Stenosis). The ARC Health Committee Report by Dr.
Susan Reis, from The Rottweiler Quarterly second quarter; 1996.