Sub-Aortic stenosis (SAS) is a type of heart disease that is
usually fatal. It is very different than what is termed a
heart murmur. It sometimes shows up on a standard veterinary
examination with a stethoscope when the dog is a puppy, and
sometimes is not diagnosed until much later (well over a
year of age). A Doppler EKG is the usual diagnostic tool
used to pin point SAS. It is a progressive disease,
untreatable and inoperable in dogs. Although surgery has
been attempted at several veterinary schools, the results
have been unsatisfactory.
Sub-Aortic Stenosis, also known as sub-valvular aortic
stenosis, is a polygenic dominant disease, although some of
the data is equivocal regarding whether it is incomplete
penetrance or modifying factors. Data on a study of
Newfoundlands clearly showed that the disease was dominant,
most probably polygenic, and uncertain what the other
factors were.
Currently, research is being done on a significant
incidence in Bouviers, where the pedigrees indicate that it
is polygenic dominant.
The carrier modes, although "somewhat" similar between
polygenic-dominant and recessive--in that a series of genes
(multiple individual alleles in recessive, multiple single
dominant loci in polygenic dominant) are required--is
different in polygenic dominant inheritance in that one set
of genes gets transmitted as carrier or affected genes, and
the other may get transmitted as clear (whereas in
recessive, both are carriers if bred to a clear, or are
affected if bred to another affected or carrier).
In polygenic dominant, if one of the parents of the
litter were not individually affected (which is possible in
a sub-clinical affected status), the BOTH of the lines are
probably carriers. The disease shows up when you have a
combination of the critical genes loci brought in from both
sides of the lines, where if the lines were separated, the
disease would not be expressed. That is one of the unique
factors of polygenic dominant expression.....you need a
series of gene loci ALL to be there for the disease to be
expressed.
References to read: Ettinger, Veterinary Internal
Medicine, SECTION VIII, Chapter 74, "The Cardiovascular
System/Congenital Heart Disease"; R.L. Pyle & D.F.
Patterson, et.al., American Heart Journal, Sept 1976, Vol
92, No 3, pp. 324-334).
(Source: David J. Sheckler, DVM, Saratoga, CA)
