Newfoundland Health Information - SAS Study
Funded by the North
Central Newfoundland Club & The Ohio State University
The North Central Newfoundland Club Inc.
is pleased to announce that in partnership with The Ohio State University
College of Veterinary Medicine, it is funding a study comparing a
surgical procedure and drug therapy for treatment of SAS in Newfoundland
dogs.
What is SAS ? 1. What is
SAS?
Subvalvular aortic stenosis, also referred to as subaortic stenosis or SAS, is
a common heart defect in dogs, especially Newfoundlands, Golden Retrievers, Rottweilers,
and German Shepherds.
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.
2. 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).
3. How do dogs "get" SAS?
SAS is transmitted genetically. This has been studied in the Newfoundland breed;
the mode of inheritance in this breed is either autosomal dominant with
modifiers or polygenetic. Dogs with mild disease do not necessarily produce
dogs with only mild disease, ie a dog with mild disease may sire a litter
with severe disease. This defect develops very soon after birth (at approximately
3 weeks of age), and continues to worsen through maturity.
4. 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.
5. 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).
6. 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.
7. 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 breeding.
8. Are there undetectable carries
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.
Prepared by Linda B. Lehmkuhl,
DVM, DACVIM (Cardiology)
The Ohio State University
Veterinary Teaching Hospital
SAS Study Background
North Central Newfoundland Club to
Fund SAS Study This
study, "Comparison
of Balloon Valvuloplasty and Atenolol in the Treatment of
Subaortic Stenosis in Newfoundland Dogs" will be conducted
by Drs. Linda Lehmkuhl DVM, MSc and Kathym Meurs DVM, PhD
from the College of Veterinary Medicine staff. Funding for
the cost of the study, $19,886.00, will be contributed equally
by NCNC and the State of Ohio Canine Research Fund through
Ohio State Universtiy.
A group of from twelve to
twenty Newfoundlands with comparable severity of SAS will be
selected for this study. Comparable age and lack of complicating
medical conditions will also be determining factors. All will
have been diagnosed between twelve and twenty-six weeks of
age using Doppler echocardiography. These Newfs will then be
randomly assigned to one of two groups. The first will be put
on a daily program of medication (atenolol - 25mg twice per
day). Atenolol reduces the heart rate and work load on the
heart. The second group will undergo a surgical procedure known
as balloon valvuloplasty. In this procedure a catheter, with
an inflatable cuff, is introduced by way of the carotid artery
into the heart to the point of abnormal narrowing. The cuff
is then inflated in an effort to dilate the narrowed area.
Thorough examinations of
the study dogs, including physical exams, chest radiographs,
Doppler echocardiography, and Holter monitoring (continuous
24 hour electrocardiogram recording in the home environment)
will be performed at 6, 12, and 18 months.
While expensive, and not
without some risk, balloon valvuloplasty, if successful over
the long term, could be recomended for those dogs in which
a long and productive life is anticipated. Daily drug therapy,
with exercise restrictions, is less expenseive but requires
daily intervention by the owner.
Funds for this study became
available to NCNC because of the strong support we had, by
Newfoundland lovers, when hosting the 1995 NCA National Specialty.
Our membership felt strongly that a substantial portion of
that income should be returned to the betterment of the breed.
Towards that end a committee was established to make recommendations
to the membership. Research proposals were solicited from eight
Midwestern veterinary schools for studies addressing health
problems of concern to Newfoundland owners. After careful evaluation,
the decision was made to support this study since it appears
to have the potential to benefit the breed in treatment of
one of our most vexing problems within a relatively short period
of time. Although balloon valvuloplasty has been studied before,
to our knowledge this is the first study to directly compare
it to drug therapy over an extended period of time. We hope
future host clubs will consider similar support of Newfoundland
research.
1996. Prepared by
Bob Ohle
Treasurer
NCNC
SAS Study Updates
North Central Newfoundland Club
Funding SAS Study
December 18, 1998
We currently have finalized
patient enrollment with 24 patients (15 are Newfoundlands).
We were able to enroll 4 more patients than planned and still
stay within our budget. This is great as it will increase our
chance of detecting a difference in treatment effects if one
exists (i.e. increased dog number will increase our statistical
power). Also, this provides us a small cushion if any dogs
are lost to follow-up through drop out. We have 12 dogs on
each therapeutic arm of the trial (12 receiving beta blocker
and 12 having been ballooned), and we are very pleased with
the severity matching. Four dogs have died up to this point;
two dogs in each treatment arm. Nine of the surviving dogs
have passed their one year evaluation, and four of these have
reached their 2 year follow-up.
As an outgrowth of this
project, we have identified a very important feature of subaortic
stenosis in Newfoundlands that we are only now fully appreciating.
As part of our clinical study, numerous dogs were evaluated
serially to determine whether their disease would progress.
This was done because of our past experience that occasionally
a dog may have progression of their disease with growth. If
a dog with mild or moderate disease progressed to severe disease
then therapy would be indicated and they could be enrolled
in the clinical trial. This led us to the discovery that this
disease is often DRAMATICALLY progressive in the first year
of life in the Newfoundland. This has obvious importance to
our ability as veterinarians to prognosticate for an individual
dog as well as implications in our decisions to treat or not
treat affected dogs.
We looked at a total of
23 Newfoundlands (many of the ones on the clinical trial plus
a few others) that had pressure gradients determined more than
one time before the age of 12 months. The pressure gradient
is our best clinical indicator of severity. Dogs with mild
disease (<50 mm Hg) do great without therapy. Dogs with
severe disease (pressure gradient >100 mm Hg) die from their
disease. Dogs with moderate disease have a variable outcome.
Fifteen of these dogs had pressure gradients that progressed
more than 25 mm Hg, and 7 had less than a 25 mm Hg change in
their gradient. The change in pressure gradient in some dogs
was as high as 123 mm Hg and averaged 50 mm Hg for the group
of 23 dogs. These changes in gradient would definitely have
important clinical implications! We are preparing a scientific
abstract on this data for presentation at the American College
of Veterinary Medicine Forum this Spring in Chicago as we believe
this is a very important finding for the breed and we want
our colleagues to realize this occurs. As always, your group
will be acknowledged in this presentation.
Thanks for your continued
support as we strive to improve the understanding and treatment
of this devastating disease.
Sincerely,
Linda Lehmkuhl, DVM, MS, DACVIM
Assistant Professor
Department of Veterinary Clinical Sciences
The Ohio State University
SAS Study Updates
North Central Newfoundland Club
Funding SAS Study December 14,
1999
We are currently still
following the enrolled patients through the cardiology
service at OSU. We ended up staying with 22 patients enrolled
(we were going to do 20 initially but were able to do 2
more and stay in our budget. In last year's update it lists
24 patients but we were unable to severity match the last
two patients so we stayed at 22). Of the 22 patients enrolled,
14 are Newfoundlands. We have 11 dogs on each therapeutic
arm of the trial (11 receiving beta blocker and 11 having
been ballooned), and we are pleased with the severity matching.
Five dogs have died up to this point; three dogs on the
beta blocker arm and two dogs on the balloon dialtion arm.
Three of the surviving dogs are out over 3 years, 3 are
out over two years, and the remaining 11 are all out over
1 year. One of the dogs has been partially lost to follow-up
(this dog received it's one year follow-up visit, but then
was given to a family in New Hampshire by the original
owner). We will still be able to get a final outcome (survival
data) but will not be able to get additional clinical data
from this one dog.
We presented the abstract
detailed in the December 1998 update letter (abstract attached)
at the American College of Veterinary Internal Medicine
this past Spring and it was very well received as this
information is very important! Your group was acknowledged
on the poster presentation of this project.
In terms of future publications,
we have not finalized how we will divide this information
up for publication (as that depends a little on the results),
but most likely we will submit one paper on balloon dilation
versus beta blockers (once we have final outcomes (survival
times) on all enrolled patients; this could be a few years
away if the treatments are helping!!), one detailing the
progression of SAS in young Newfoundlands (as per abstract
presented at ACVIM in the spring of this year), and one
on Holter monitor (24 hour ambulatory ecg) results in dogs
with SAS of varying severity (we have well over 100 Holters
to date!).
Thanks for your continued
support.
Sincerely,
Linda Lehmkuhl, DVM, MS, DACVIM
Assistant Professor
Department of Veterinary Clinical Sciences
The Ohio State University
Journal of Veterinary
Internal Medicine
Volume 13, May/June 1999 RETROSPECTIVE EVALUATION
OF PRESSURE GRADIENT CHANGE IN YOUNG NEWFOUNDLAND DOGS
WITH SUB-VALVULAR AORTIC STENOSIS. LB Lehmkuhl, C
Cataldo, KM Meurs, TR Maxson, AW Spier, JC Bonagura.
College of Veterinary Medicine, The Ohio State University,
Columbus, OH.
Prognosis for dogs with
subvalvular aortic stenosis (SAS) varies with lesion severity.
Mild lesions may not compromise quality of life or longevity,
but moderate to severe lesions often lead to syncope, exertional
weakness, congestive heart failure, and sudden cardiac
death. Doppler-derived peak left ventricular to aortic
pressure gradient (PG) is the method most often used for
quantifying severity of SAS. Gradients are often categorized
as mild (PG <50 mmHg), moderate (PG > 50 and < 100
mmHg), or severe (PG > 100 mmHg). The purpose of this
study was to determine the change in PG in young Newfoundlands
with SAS.
Medical records from
all Newfoundlands with SAS evaluated between July 1988
and July 1998 were reviewed retrospectively to identify
untreated dogs examined by Doppler echocardiography at
least twice during the first year of life. Twenty-three
dogs (13 female, 10 male) were identified. Age at the initial
exam ranged from 2 to 7 mos (median = 4 mos), wile age
at the second exam ranged from 3 to 12 mos (median = 8
mos). The median PG increased from 56 mmHg (range, 25-210)
at the first exam to 117 mmHg (range, 32-263) at the second
exam. The median PG change from exam 1 to exam 2 was 48
mmHg ranging from a decrease of 60 mmHg to an increase
of 123 mmHg. The PG increased by >25 mmHg in 15 dogs,
decreased by >25 mmHg in 1 dog, and changed <25 mmHg
in 7 dogs. The increment in PG affected severity classification
in 16 (70%) of the dogs. Three dogs changed from mild to
moderate, 8 dogs from moderate to severe, and 5 dogs from
mild to severe.
This study documents
the progressive nature of SAS in some Newfoundlands during
the first year of life. The degree of disease progression
is sufficient in some dogs to affect prognosis and therapeutic
decisions.
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