Dr. Meurs opened by introducing the other member of the OSU team who are conducting the BCM study funded by the ABC and AKC foundations: Alan W. Spier, D.V.M.; Alex L. Magnon, B.S. (A 3rd year graduate student in Molecular Biology); and Nicola A. Wright, BS in Animal Sciences (Ms. Wright oversees all the organizational aspects of the study - pedigree analysis, heart samples, etc.). Due to a staff shortage at OSU, Dr. Spier was unable to accompany Dr. Meurs to ABC, and Dr. Meurs had to fly back to Ohio immediately following her presentation.
HISTORY OF BCM:
1980: Dr. Neil Harpster of Angell Memorial Hospital in Boston characterizes a heart disease he was seeing in some of his boxer patients as Boxer Cardiomyopathy (BCM). He originally thought the disease progressed in the following three stages:
Type I -- Irregular heartbeats, no symptoms.
Type II -- Irregular heartbeats, fainting spells (syncope).
Type III -- Dilated, "flabby" heart, congestive heart failure, coughing, breathing difficulties.
1991: Dr. Bruce Keene identifies a family of boxers with dilated cardiomyopathy (see "Type III" above) that responds favorably to L-Carnitine supplements.
1993: Dr. John-Karl Goodwin identifies a family of boxers with ventricular premature contractions (VPC's).
1997: Dr. Meurs'study begins. The current study is limited to dogs over two years of age that can come to OSU for a complete workup every year. The initial workup includes blood samples for genetic analysis, and a pedigree analysis. Dog with aortic/sub-aortic stenosis are not used in Dr. Meurs'study.
WHAT HAS BEEN LEARNED?
Myocardial disease in boxers is primarily an electrical disease; less than 10% of affected boxers have "dilated cardiomyopathy."
Most boxers affected with BCM have normal echocardiograms -- echoes are useful primarily for diagnosing AS/SAS.
Many affected dogs have no symptoms; some live a normal life and die of a noncardiac disease.
One of the best indicators of affected status is VPC's on Holter reports. ( Dr. Meurs also checks the diet and exercise of each dog to see if that has any bearing on affected status.) One (1) VPC on a 3-minute ECG suggests that the dog may have greater than 50 VPC's/24 hours when Holtered.
STATISTICS:
Of the 188 mature boxers in Dr. Meurs study, 157 had no clinical signs of BCM, while 31 had fainting spells. When Holtered:
81% had at least one VPC/24 hours.
50% had greater than 10.
36% had greater than 50.
31% had greater than 100.
22% had greater than 500.
0.4% had greater than 3000.
At this point in Dr. Meurs' presentation, she asked for questions from the floor. The following issues were discussed during the question & answer session:
Dr. Meurs does not consider the "grade" of BCM (whether the Holter test shows runs, paired beats, etc.) to be more significant than total numbers of VPC's She was given the example of a five (5) year old male with 23 total VPC's/24 hrs, consisting of one bigeminy run, one trigeminy run, a paired beat, and 16 isolated VPC's Dr. M. said that, from the data she has collected so far, that was just as good an outcome as if the dog had had 23 isolated VPC's
Dr. Meurs believes that BCM is inherited in an autosomal (not sex-related) dominant manner. That means that two affected parents can produce unaffected offspring; and two unaffected parents cannot produce affected offspring. There is no way of knowing which affected boxers are homozygous (double dominant) for BCM.
Boxers tend to have more VPC's as they get older.
Most boxers with BCM do not have heart murmurs.
Treatment with Betapace (Sotalol) may reduce the numbers of VPC's with few side effects (it reduced VPC's in 51 - 99% of dogs on which it was used in tests); but we don't know if reducing the numbers of VPC's will prolong the dog's life.
Questions were asked about using blood or saliva tests for genetic screening for BCM. Dr. Meurs replied that most canine genetic tests that have been developed have been based on human models. She said there is currently no human model for BCM. However, there may be testing underway on a similar human disease; in that case, scientists doing human and canine research may be able to exchange information.
Dr. Meurs thinks the proposed ABC/OFA Holter database will be useful to researchers, and thinks we should continue to encourage ABC members to Holter their boxers annually. She is very grateful for the opportunity to pursue this study given her by the joint ABC and AKC Foundation funding.
