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Editor’s note: the
following is Dr. Theresa Garton’s account of the 1998 ABC Health Seminar. Parts of
this account have previously appeared on several of the Boxer e-mail lists. BU will
publish a transcription of the 1999 health seminars as soon as it becomes available to us.
Kudos to the ABC and the Boxer Health & Research Committee for this great service to
the breed!
THE 1998 ABC
HEALTH SEMINAR
Dr. Theresa Garton,
Health Committee Reporter
The 1998 ABC Health Seminar was a fact
filled program. Dr. Neil Harpster started off the seminar with data from his screening
clinic last year [1997]. He is a very kind man with impeccable credentials. His talk was
interesting, but perhaps not really geared toward the lay audience. Things to take away
from his part are that last year, he found a murmur in one puppy (eight months or
younger), and five murmurs in adult dogs. This is a total of six murmurs in 121 boxers. I
think that statistic is quite a relief, especially compared with some of the data from
England, but is still obviously a concern.
Dr. Harpster found no EKG abnormalities in
the eight months and younger group, but did find three in the eight months to 12 months
group. These three adolescents represented 16.7% of the adolescent group. The adult group
included 15 with EKG abnormalities, or 15% of the total.
This EKG data is particularly concerning
when you remember that EKG's only pick up a VERY small proportion of abnormalities. Of the
abnormalities noted, 12 had arrhythmias, five had axis deviation (3 L and 2 R), and one
had first degree A-V block. This again from a total of 121 boxers.
Remember that the EKG only runs for 6
minutes. The arrhythmia has to be VERY significant to display itself consistently on an
EKG. IF the arrhythmia occurs regularly (those with Boxer Cardiomyopathy do NOT), then a
single arrhythmia every six minutes would correspond with 10/hour, or 240 per 24 hours.
This is more than twice the number of PVC's many investigators feel definitely mark the
presence of BCM, or if you believe some of Dr. Meurs’ data, could be almost FIVE
times the number she considers significant. We have no idea what percent of boxers
affected with BCM this EKG data "caught," but I don't think it takes much
imagination to see how serious our problem could be if the 15-16% "caught" at
ABC really do have BCM, and if this, as I believe, only represents a small portion of
those actually affected.
This year (1998), many abnormalities were
again noted, including one dog that Dr Harpster arranged emergency treatment for, as he
was afraid its arrhythmia (repeated runs of ventricular fibrillation) would kill the boxer
before it got home. The owners were NOT aware there was a problem with the dog, as it had
had NO symptoms. Some may find it interesting that great efforts were made this year to
make the testing more private and confidential.
Now for the points I took home from Dr.
Meurs’ talk: Dr. Meurs is a vivacious and warm speaker, and gets to the
"meat" of the matter quickly. She started with a description of the study, and
thanked all who contributed. She expressed being overwhelmed with the support she had
received from ABC members. Dr. Meurs then reviewed her data, and attempted to anticipate
questions and address them. Here is a review of some of the topics she discussed.
MODE
OF INHERITANCE OF BCM
Many of us have suspected that BCM is
passed on by an autosomal recessive mode of inheritance, because to outward appearances,
it seems to skip generations. However, Dr. Meurs calls it "the silent killer,"
because without Holter monitor data, we really have no idea how many asymptomatic dogs
actually have BCM, but just never have any symptoms. She discussed in her talk a family of
five dogs, both parents and three puppies from one litter. All dogs were over five years
old. Both parents were affected (the data that follows is from foggy memory, not notes, so
please be kind <G>). One had 240 PVC's, the other, 2400. Of the puppies, one had
500, another "some" (30-60, I believe), and one had ZERO. If BCM were autosomal
recessive, two affected individuals could ONLY produce 100% affected offspring, so Dr.
Meurs thinks that BCM is AUTOSOMAL DOMINANT. "Autosomal" means that it is not
sex linked - that the incidence is the same in males and females.
HOW MANY ABNORMAL BEATS ARE SIGNIFICANT?
Dr. Meurs later described the basis for the
numbers used to differentiate "affected" from "not affected." She
reviewed for us approximately three studies of Holter data in various breeds of dogs. I
know one of the studies was a very large one, of beagles. This study determined that a
normal number of PVC's/24 hours for dogs was nine (yes, one digit) or less. One of the
other studies was a multiple breed study. This study found most dogs had (I think I am
remembering this correctly) 10-20 or LESS. One of the dogs tested as "normal"
had 54 PVC’s; significantly, it was a BOXER. Dr. Meurs used the data derived from
these studies to justify her opinion that - even giving boxers the "benefit of the
doubt" - your boxer should certainly have 50 or fewer PVC's per 24 hours.
RULING OUT OTHER CAUSES OF HEART PROBLEMS
Dr. Meurs also discussed parvovirus, having
anticipated questions about whether BCM could be the result of either environmental parvo
infection, or some iatrogenic problem resulting from vaccination programs. She spent some
time discussing this in detail. What I took away from this part of her talk was that they
ARE able to isolate parvovirus in cases of heart failure proven to be secondary to parvo;
but have NEVER, NEVER, EVER isolated parvovirus from dogs that had been determined to have
BCM.
In a subsequent one-on-one conversation, Dr
Meurs also discussed attempts to investigate a possible role of thyroid hormone, or
derangements thereof, in the cause of BCM. She said researchers had found no correlation
between thyroid values and BCM.
HOW
DO WE SCREEN FOR BCM?
Dr. Meurs stressed that echos, of any
description, color doppler or not, are a very poor screen for BCM, as 90% (YES, NINETY) of
those dogs with full-blown BCM have NORMAL echoes. She discussed the problem many of us
have in getting local cardiologists to do anything but echoes. Dr. Meurs again mentioned
that BCM is unfortunately misnamed, in that it is NOT generally a disease of the heart
muscle (though it is in some cases), but in the great majority of cases, is a disease of
the electrical conduction system of the heart that initiates and regulates the heart beat.
She did discuss the few cases of heart muscle failure in boxers, and stated that these
VERY FEW dogs may actually have another disease, and are more likely to respond to
L-carnitine therapy.
Dr. Meurs said that ideally, all boxers
would have a thorough exam, echo, and Holter, but that if money were an issue, a cardiac
auscultation (examination with a stethoscope) by a cardiologist, and a Holter were a
pretty good screening program. In another private conversation, a breeder approached her
while I was speaking to her, saying she had been informed that she had "wasted"
her money on color dopplers. Dr. Meurs and her associate, Dr. Spier, said that the money
was not wasted, as it was an excellent screen for aortic stenosis and other valve
problems, but that it just was not a screen for BCM.
HOW
WIDESPREAD IS BCM?
Dr. Meurs gave some statistics regarding
Holter monitor findings in her study at the meeting, but in a private phone call
graciously gave me some updated statistics she had prepared for cardiology meeting after
her return from ABC: 17% of those boxers studied (over 100 now) had zero PVC's. 50% of
those studied had 0-100 PVC's per 24 hours, 25 % had 100-1000, and 25% had OVER 1000. So,
50% were in the category most investigators believe represent affected dogs.
Dr. Meurs did not have a breakdown of the
50% that had 100 or fewer PVC’s, though most investigators believe dogs with 50-100
PVC's/24 hours are "suspicious," if not affected. The dogs with fewer than 100
PVC's tended to be younger dogs (two-five years) and very old dogs. We have no data yet to
tell us whether the two year old with 50 PVC's will later become the eight year old with
1000. Dr. Meurs said the mid-range of PVC's (100-1000) tended to be in dogs four-six years
old, and that the dogs with more than 1000 PVC's tended to be older dogs (I am assuming
she meant older than six).