The short answer to the title question is, “When the Holter recording wasn’t read and interpreted by a board certified veterinary cardiologist.” But actually, it’s not nearly as simple as that, and this blog is going to be neither a paean to all board certified cardiologists nor an exposé of the commercial services that provide inexpensive, technician-read holter reports with a super-fast turnaround. Hopefully, this account will give other Boxer breeders the same kind of “heads up” I got recently when I had occasion to send the same Holter tape, first to a commercial Holter reading service, and then to a board certified veterinary cardiologist.
A Tale of Two Holter Reports
Before I
begin this little cautionary tale, let me say that I don’t pretend to be an
expert on heart disease. In fact, beyond a short CPR course that I’ve mostly
forgotten, I’ve had no medical training whatsoever. What I’ve learned about
Boxer Cardiomyopathy, or ARVC as it’s now called, was “absorbed” from listening
(and taking notes) to the presentations of researchers and other experts as
secretary to the ABC Health & Research Committee and the ABCF Board of
Trustees, and by taking advantage of the expert knowledge of the cardiologist
who treats my own dogs and who is never too busy to answer questions or explain
heart disease to his clients.
This saga
began with a 5 year-old health-tested bitch that had never been bred and a very
promising young dog whose parents had been health tested and who had “passed”
several health tests himself (DM clear, SAS clear & Thyroid normal), but
had not yet been Holtered. The two prospective breeding partners complemented
each other perfectly, so I threw a Holter monitor on the young dog and sent it
off to one of the commercial Holter reading services, asking that they return
the tape to me after reading it. I
usually send my Holter tapes to a cardiologist for interpretation due to a
friend’s sad experience with one of the “quickie” services, but I wanted a faster
turnaround than the cardiologist provided for a pre-breeding clearance.
In only a
few days, I had a report that showed 5 VPCs and zero (0) supraventricular
ectopics (also called APCs, or Atrial Premature Contractions). The tape was returned
shortly thereafter. Because the early days of my breeding program were haunted
by Boxer Cardiomyopathy (before anyone knew what it was), I wasn’t completely happy
with 5 VPCs in such a young dog, but it was now or never for my bitch, so I
proceeded with the breeding. Then I mailed the tape to the cardiologist to whom
I usually send Holter recordings for interpretation, hoping that some of those
5 VPCs were just artifacts.
The
cardiologist’s report was sent to me within two weeks and read, in part:
“There were a total
of 4, Ventricular Premature Beats (VPC’s or PVC’s) during the monitoring
period. There were frequent singular atrial premature beats during the
recording period. There were runs of supraventricular tachycardia during
the monitoring period. The singular APCs are not as concerning as the runs of
SVT at fast rates. The longest run of SVT was 9 beats duration…”
“Diagnosis: Abnormal 24 hour holter
study”
“Recommendations: I recommend treatment of
these arrhythmias specifically to try to slow down or abolish the runs of fast
SVT. I suggest we begin Atenolol 25 mg tabs --1/2 tab by mouth twice daily....This
type of arrhythmia is not the classic arrhythmia noted in Boxers affected with Arrhythmogenic
Right Ventricular Cardiomyopathy in that they are usually ventricular in
origin. Some Boxers will have this rhythm as the first sign of ARVC and
follow up holter studies may show the development of ventricular arrhythmias.
Alternatively this can be an arrhythmia problem noted in Boxers or other breeds
which is not associated with ARVC.”
Whoa! Only 4 VPCs – fewer than on
the report from the commercial service – but runs of supraventricular
tachycardia and a cardiologist’s recommendation of treatment with Atenolol? Where did that come from?! The first report said there were zero supraventricular ectopics!
A Third Holter Report + an Echo
I immediately called my own
cardiologist to discuss the second Holter report, and to arrange for rental of
a digital Holter monitor (my own monitor is analog, and my cardiologist no longer
processes analog recordings or tapes). Shortly after the monitor was returned
to the second cardiologist, the doctor called personally to give me the bad
news: Although interpretation of the recording wasn’t yet complete, the third Holter
report looked very much like the second. At that point, I made an appointment for
a face-to-face consult at the cardiologist’s clinic, which included an echo to
rule out structural heart disease.
After reviewing the third Holter
report at my cardiologist’s clinic a week or so later, it became obvious that there
was something very, very wrong with the first Holter reading done by the
commercial service. Remember the zero (0) Supraventricular Ectopics noted on
the first report? My cardiologist recorded 23,689 isolated (single) supraventricular
events plus 5 Couplets and 20 Runs. That’s 23,825 supraventricular ectopics,
or 18% of the dog’s total heartbeats!
Cardiologist # 2 also suggested that we consider medication (sotalol) to
slow the fast heart rate.
Frankly, I was blown away. How could
that first Holter have been so completely out of the ballpark? Had the Holter
service sent some other dog’s report?
But that couldn’t be, because the same tape had been returned to me and
sent on to the first cardiologist; and the second cardiologist had produced a
similar report from a different (digital) recording!
As soon as
I got home, I fired off an email to the commercial Holter reading service to
which I had originally sent the tape. I
attached a copy of their Holter report showing 5 VPCs and zero supraventricular
ectopics and excerpts from the reports generated by the cardiologists. A
company rep answered in short order, and said he was going to look into what
had happened and would get back to me.
The next
morning, I received a phone call from the manager of the Holter service. We
talked for about 30 minutes. His
attitude was both apologetic and defensive. At the end of our conversation, I
understood what had happened but was – there’s no other word for it –
incredulous.
Apparently, because a few
supraventricular ectopics (Atrial
Premature Contractions) are no big deal (both cardiologists had said much the
same thing), and because part of the canine side of the business came from individual
owners who were primarily concerned about VPCs
and ARVC and didn’t know what supraventricular ectopics were (I certainly
hadn’t known), those concerned owners tended to call the service for an
explanation when they saw numbers in the “Supraventricular Ectopics” column of
the report. So the people who dealt with dog owners (rather than with the human
and veterinary cardiologists who used the service, presumably) decided that
they would stop confusing their
customers with irrelevant information and simply stopped collecting and reporting
ANY supraventricular activity to individual dog owners.
As noted, the representative I spoke
with was both defensive and apologetic. He repeatedly made the point that a
little atrial arrhythmia was usually nothing to be worried about, but admitted
that there was nothing usual about nearly twenty-four thousand atrial ectopics. He also admitted that the report
generated by his company had, in effect, given my young dog a “pass,” when the
dog clearly had a condition that needed to be addressed by a cardiologist and
that would have been immediately obvious if the “Supraventricular Ectopics”
column had not shown zeros across the board.
By the end of our conversation, the
Holter company representative had assured me that in the future, their reports
would include supraventricular ectopics; and I was left of two minds about the
whole experience: On the one hand, I believe that in the absence of a reliable
gene test, all North American Boxer breeders and owners should Holter their breeding
animals at least once a year and that these fast, inexpensive Holter services
make it possible for everyone to do that – no excuses! And I understand that my dog presented an
unusual situation that I may never encounter again. I still don’t know exactly
what’s wrong with him, or whether the problem is hereditary or might be atrial
myocarditis caused by something like Lyme disease.
On the other hand, it was unsettling
to find that the management of a Holter reading service had felt their
customers were incapable of understanding all the information the service had
been paid to provide and so decided not to provide some of it; and it’s only
human nature to ask, what else did they miss?
The fact is, while some veterinary
cardiologists are prohibitively expensive, some are quite reasonable and are
willing to work with breeders. My inclination at this point is to say, if you
really care about Boxer heart disease, find one of those “reasonable” cardiologists.
Or at the very least, the next time you send a Holter recording to one of the
fast, cheap Holter reading services, ask that their in-house cardiologist read
and interpret your tape, even if it costs a little extra.
