Rottweilers are a breed which has a high incidence of an abnormal
heart sound, or murmur, caused by Subaortic stenosis (SAS). When you
use an ordinary garden hose (without a nozzle) the water flows out
quietly; when you cover part of the hose with your finger, it causes
a disruption of the water flow and a lot of noise. If the heart is
working normally, there are few sounds (except the pumping sound) but
if something causes a disruption of the blood flow, a murmur occurs.
A narrowing of the heart, a stenosis, just below the aortic valve,
results in an abnormal sound, the murmur.
SAS is the second most common congenital heart defect in the dog, and
the Rottweiler has a higher occurrence than most other breeds. It is
a clue to a veterinarian that there is something wrong. This
condition is heritable and should be addressed, with the following
information in mind. Heart murmurs are graded on a scale of 1 to 6,
with one being very mild and six being very serious Murmurs can exist
due to a large number of heart problems ( infection, trauma, anemia,
etc.) and some murmurs are innocent, meaning that no cardiac
pathology exists. Discussions with Dr. M. O'Grady, Dipl. ACVIM (
Cardiology ) at the Ontario Veterinary College and Dr. D. Brummer
Dipl. ACVIM, of the Orchard Park Veterinary Medical Center, as well
as the article by Dr.W.A. Brown, Dipl. ACVIM ( Cardiology ) in the
Third Quarter of the 1997 MRC Newsletter, entitled " Canine
Subvalvular Aortic Stenosis " provided me with the following
information. Mild heart murmurs in puppies less than 20 weeks of age
are to be noted only and are not an immediate cause for concern. Some
of these will be innocent, some may be a result of a minor problem,
and some of these can and do disappear with age. A serious murmur in
a young pup is definitely significant and a murmur which persists
past 20 weeks of age should then become a cause for concern. The
health status of the puppy and the advice of the veterinarian may
warrant investigative procedures in order to give a prognosis.
Auscultation of the heart (with a stethescope) in an adult dog over
the correct area of the chest could lead to a presumptive diagnosis
of SAS, if a murmur were present. The problem with SAS is that a dog
can be a carrier and never be diagnosed even with the current
available veterinary techniques. " Distinguishing murmurs caused
by mild SAS from functional (innocent ) murmurs can be dificult and
sometimes impossible, " ( Dr. Brown ) If a dog has SAS, it may
be detected on auscultation, on echocardiography,on Doppler or on a
post-mortem by a qualified pathologist. However, it can be a very
difficult ante-mortem (alive) diagnosis.
The carrier state means that the dog itself is normal, but can
produce the defect in its offspring (genes). Until genetic markers
are available for this problem, we are unable to identify carriers
prior to breeding. " Innocent murmurs are most common in young
growing dogs.The prevalence of innocent murmurs in the adult dog
population is unknown. " ( Dr. Brown ) If a murmur is heard on
auscultation, and warrants further investigation, it is then
appropriate to seek the services of a specialist in cardiology. It is
at this point that sophisticated diagnostic procedures will be recommended.
Echocardiography is like an ultrasound of the heart and allows the
cardiologist to see if the anatomy and function of the heart are
normal. " A two-dimensional echocardiogram study ( without
Doppler, the ultimate in cardiovascular testing ) is not sufficiently
sensitive to exclude a diagnosis of mild SAS" ( Dr. Brown ) It
is therefore suggested that a cardiac examination for the
determination of mild SAS include two dimensional, m-mode and Doppler
studies.( Suffice it to say that this is a very detailed study of a
dogs' heart. ) The results of the cardiac examination can be; a)
Negative on auscultation ...means that a murmur is not present at
rest and therefore most dogs will be free of SAS. ( may still be a
carrier ) b) Positive on auscultation...means that a murmur is
present which may be innocent or a sign of congenital heart disease.
As innocent murmurs are generally mild, those dogs with a murmur of
Grade 3 or more will likely have congenital heart disease 1) Positive
on echocardiogram...is a definite diagnosis of SAS 2) Negative on
echocardiogram... the murmur may be innocent or mild SAS may be
present Dr, Brown : " Presently we lack the ability to reliably
identify all carriers or mildly affected dogs with SAS. Until
molecular markers or some other highly specific test is developed it
will be impossible to eliminate these dogs from the breeding pool. "
The OFA has established a Congenital Heart Registry whose guidelines
were established by veterinary cardiologists. A dog at 12 months of
age, which auscultates normally is considered to be free of
congenital heart disease Upon confirmation of this, the OFA will
issue a certificate. Although the OFA prefers the expertise of a
cardiologist ( to perform the auscultation), a letter from any
veterinarian is acceptable. This is in contrast to a CERF
certificate, which is performed only by veterinary ophthamologists. (
A veterinary cardiologist has endured extra years of training, and
has acquired a degree, Diplomate of the American College of
Veterinary Internal Medicine, Cardiology or ACVIM (cardiology),
whereas an ophthamologist has acquired the degree, American College
of Veterinary Ophthamologists, ACVO, both are prestigious academic
titles). A cardiologist, is more likely to auscultate a murmur than a
regular veterinarian. The Congenital Heart Registry certificiate
states the age of evaluation and one of the letters "C" for
cardiologist, "S" for specialist, an ACVIM with an interest
in another field ( i.e. neurology ) or "P" for private practitioner.
Now, what does all this imply? I would suggest that any negative
response to a mild heart murmur in a dog less than 20 weeks of age is
premature and unfounded. If an adult dog of merit is found to have a
murmur, it should be investigated by a cardiologist as to the exact
diagnosis and consequential impact on the breed. If a veterinary
report for cardiac evaluation is presented for review to a breeder,
it should be carefully examined as it may state that "SAS is not
ruled out by this exam". I have seen such a statement on a
cardiac evaluation form from a veterinarian who is an ACVIM certified
cardiologist. This statement is a result of the difficulty in
diagnosing SAS, as previously discussed..
If you currently breed rottweilers, you can produce SAS no matter
what you have done to try to prevent this problem. ( i.e. two
phenotypically normal "carriers" bred together. ) If
puppies have mild SAS, do they have to be euthanized? Absolutely not!
Many will lead a normal life. A dog may fail a cardiac evaluation
under one veterinarian but pass under another and still be advertised
as "cardiac clear", I've seen it done. One of our two stud
dogs, Jack, prior to us including him in our breeding program, was
given a thorough veterinary examination, including clinical
examination, auscultation, blood work, fecal, heartworm, thyroid and
sperm evaluation at the Veterinary Teaching Hospital at Michigan
State University. We would not have considered him as a stud dog for
our kennel, if he had clinical evidence of SAS, and yet I have no
heart certificate for him. He has had no problems to my knowledge, in
his numerous breedings, except for one case in which I have received
no concrete evidence of substantiated cardiologist examination after
the age of 5 months !!! As well, Draviet, our other stud dog, has
been auscultated by myself and by at least two of my Associates, is
free of any audible heart murmur and yet I have no heart certificate
for him. Should I obtain one? If a phenotypically OFA "good"
male is breed to a phenotypically OFA "good" female and
two pups are dysplastic out of ten, should the parents of these
offspring be neutered or is this an acceptable rate of occurrence?
What if all the pups had excellent stable temperaments, a definite
aim and priority in our breed. Similarly, if two phenotypically
normal heart dogs are bred, and the same results occur as to SAS,
what do you do? I believe that it should be our aim to decrease the
occurrence of SAS by eliminating dogs with heart murmurs ( SAS ) from
the breeding program. I worry that in some cases the decision may be
premature, i.e. before 5 months of age, such that puppies which may
have a great deal to add to the breed are placed in a non-breeding
environment. If in doubt it would be prudent to seek the best
veterinary advice available to the owner/breeder i.e. seek the advice
of a specialist in cardiology who has all the sophisticated equipment
to accurately diagnose the problem.
Dr. P.K. St. John DVM
