With heart disease at the forefront of many present-day American boxer breeders’concerns, the ABC Health & Research Committee invited Dr. Bruce Cattanach, Bsc, PhD, DSc, FRS, to give a presentation at the 2001 ABC on the UK Heart Control Scheme for Aortic Stenosis.

Dr. Bruce Cattanach presents the
UK Heart Control Scheme for Aortic Stenosis.

Dr. Cattanach has been a noted breeder/exhibitor of boxers in England since 1949 under the Steynmere prefix. Ch. Steynmere Night Rider had a strong influence on boxer bloodlines in the UK, and English Ch. Steynmere Summer Gold - imported to the US as an adult - appears in many North American pedigrees through his descendents, Chs. Berena’s Gemini Splashdown and Tribute to Fa Fa. Dr. Cattanach is a geneticist by profession, and has specialized in the cause and analysis of genetic defects. Until his recent "semi-retirement," Dr. C. was Director of the Medical Research Council Mammalian Genetics Unit in the UK. He also worked on the genetic effects of radiation in the USA in the 1960s, and in fact, it was on his return to the UK in 1969 he took a Cherokee Oaks bitch back to the UK to found his present-day Steynmere breeding.

Dr. Cattanach was instrumental in eradicating the crippling, hereditary, neurological disease, Progressive Axionopathy, from the British boxer in the 1980s, and is currently working with British cardiologists and breeders to lessen the very widespread incidence of Aortic/Subaortic Stenosis in British bloodlines. At the end of Dr. C.’s talk, he received a standing ovation from the 200+ people who attended. :-)

Dr. Cattanach has added a postscript to his ABC talk as a result of subsequent discussions of AS on the Showboxer-L e-mail list. The postscript also answers questions and issues raised during Dr. Cattanach’s presentation. It appears at the end of this article.

Editor’s note: The following notes are taken from Slides used by Dr. Cattanach in the course of his presentation. These illustrate his main points. VZ

THE UK HEART CONTROL SCHEME FOR AORTIC STENOSIS
PRESENTED AT THE 2001 ABC BY DR. BRUCE CATTANACH
copyright 2001 Dr. Bruce M. Cattanach

Slide 1 The Start/Initial Findings
Slide 2 Actions Taken
Slide 3 Tests for Aortic Stenosis (AS/SAS)
Slide 4 Heart Murmurs, Doppler Blood Velocity and AS
Slide 5 Selection of a Test System
Slide 6 The UK Breed Council Breeding Control Scheme
Slide 7 Summary of Results
Slide 8 What Further Can Be Done?

 

Slide 1 The start/initial findings: 1. Breeder reports to the Breed Council of heart associated deaths among young boxers in the late 1980s: some 30 cases had been reported over the two previous years. 2. A heart survey was conducted at the British Boxer Club’s 1990 championship show: About 30% of 125 dogs tested had heart murmurs of a type consistent with a heart disease known as aortic stenosis. The veterinary literature recognised the Boxer as a breed in which aortic stenosis occurred. The condition had a genetic basis -- it was inherited (data from a study of Newfoundlands). The Edinburgh cardiology group reported that about 45% of all cases of aortic stenosis across all breeds referred to the university were Boxers...and that the incidence had climbed greatly over the previous 10 years. Back to Top

Slide 2  Actions taken: 1. A panel of three breeders was set up by the UK Boxer Breed Council. This included Dr. Cattanach as geneticist and a specially interested cardiologist, Virginia Luis Fuentes, from Edinburgh University. 2. The panel’s goal was to recommend a means of dealing with the problem. The following descriptions of the problem and the available diagnostic tests were given: Aortic Stenosis: A narrowing (stenosis) of the aorta: Typically, narrowing is below the valve, subaortic (SAS), but can locate above, or even affect the valve itself. The condition shows a range of effect: The severest form comprises a fibrous ring. 1. The ring narrow the aorta, increases blood velocity, and reduces blood supply to the body/brain. 2. The increased blood velocity causes noise, i.e., heart murmurs. 3. The redeuction in blood supply to the brain may lead to fainting and even death. Milder forms exhibit fibrous nodules or a roughening of the walls of the aorta. 1. Nodules/roughness cause turbulence in the blood flow. 2. Turbulence causes noise, i.e., minor heart murmurs. 3. No restriction of blood flow need occur. 4. Murmurs may have no functional significance. Back to Top

Slide 3   Tests for Aortic Stenosis (AS/SAS): 1. Pathology (autopsy): As used in Newfoundland research on inheritance. 2. Auscultation: Use of the stethoscope to assess the magnitude of murmurs. Cannot distinguish between AS and PS (Pulmonary Stenosis). 3. Phonocardiography: Use of this equipment to assess the magnitude of murmurs. Probably cannot distinguish between AS and PS. 4. Doppler echocardiography: Measures the velocity of blood flow attributable to narrowing (stenosis). May allow a visualisation of the abnormality that is causing the murmur. The classical tool for clinical (severe) cases. Back to Top

Slide 4   Heart murmurs, Doppler blood velocity and AS: No murmur (Grade 0): May be considered free of AS (big question on that point)??? Doppler scan results of 0.8 - 1.4m/s (in non-AS breeds). Grade 1 murmurs: Described as "flow" murmurs. The dog is clinically normal (has no symptoms). The murmur has no functional significance (causes no impairment). A Doppler scan is likely to be under 2.00m/s. The dog may have a mild form of AS. Grade 2 murmurs: The dog is clinically normal. The murmur has no functional significance. The Doppler scan may range from about 1.7 - 2.5m/s Almost certainly some degree of AS/ Grade 3 murmurs: May be clinically significant. Functional problems are likely. The Doppler scan may range from about 2.0 - 3.0m/s. Clearly AS. Higher grade murmurs (4 - 6): Clinically significant AS. Functional problems expected/certain. Doppler scans up to 6.00m/s. Liable to fainting/sudden death at exercise. Back to Top

Slide 5   Selection of a test system: Auscultation: Doppler Echocardiography: Advantages: Advantages: Simple/available in the UK. Economical. Allows whole kennels to be screened. Screens for all levels of AS. Distinguishes AS from PS. May firmly diagnose the condition (at more serious levels). Offers prognosis/evaluation. 2D echo may allow visualisation of abnormality. The veterinary tool of choice for diagnosis. Disadvantages: Disadvantages: Variable (at least one grade range). Does not distinguish AS from PS. Hypothetical risk of misdiagnosis. Limited availability. Costly. Limited application for whole kennels. Does not recognise most minor levels of AS. Can be variable (0.5m/s variability expected). Good correlation between murmur grade and blood velocity with murmur grades 2 - 6 only. Auscultation screens for PHYSICAL abnormality. Doppler screens for FUNCTIONAL abnormality. Back to Top

Slide 6  THE UK BREED COUNCIL BREEDING CONTROL SCHEME The Heart Panel made the following recommendations, which were accepted by the Breed Council: 1. Primary test system should be auscultation carried out only by cardiologists experienced in Boxer heart testing (see the UK Heart List at http://www.boxerunderground.com/uk) on grounds of economy greater potential application believed greater sensitivity 2. Tests applicable only to dogs over 1 year old. 3. Grade 0 (murmur-free) and Grade 1 accepted as normal. 4. Retesting Grade 2s two or three times is recommended, and the "best" score is accepted. 5. In addition, for Grade 2 males, Doppler, as carried out only by experienced cardiologists, is suggested. A normal blood velocity is taken to be under 2.00m/s (too high, in Dr. Cattanach’s opinion). 6. Dogs with Grades 0 and 1, or with accepted Doppler blood velocities may have their names included in a Heart List, with owners’ permission. The Heart List is available to all in print format through UK breed clubs and is now on a web site at http://www.boxerunderground.com/uk ** Dr. Cattanach illustrated his talk with a graph showing the results of breeding dogs with different grade murmurs together and a table of the grades of dogs tested at shows from 1997 - 2000. The graph showed that the severity of heart murmurs in the progeny were dependent upon the severity of heart murmurs in the parents. The table showed the unfortunate effects of increasingly "tougher" and more standardised heart testing over the years. Both the graph and table may be viewed on the UK Heart List web site. ** Back to Top

Slide 7  Summary of Results: 1. From a very high rate of referral of Boxers with severe clinical AS in the 1980s, there are now almost none -- across the whole country. 2. The incidence of dogs tested at shows and found to have Grade 3 and louder murmurs has now declined significantly. Therefore, selective breeding for dogs with minor or no murmurs, as detected by auscultation alone, is effective in reducing the incidences of clinical AS -- in Boxers. 3. It may be difficult to reduce the incidences of dogs with Grade 2 murmurs, due to the influence of untested parents, of pet dogs of unknown breeding coming to be tested, and the uncertainty about the genotype of murmur-free dogs. 4. Further veterinary and genetical research upon AS in Boxers is needed. Back to Top

Slide 8  What further can be done? 1. Investigate the pathology of murmur-free and Grade 1 dogs. Do they have any pathological changes indicative of AS? 2. Re-test, by auscultation, Grade 0 dogs under rigorous conditions. Do any remain murmur-free? Perhaps re-test with other methods also, Doppler, 2D echo. Do we have any Boxers that are truly free of AS? 3. Investigate litters from matings of any genuine Grade 0/AS-free parents. Do genuine Grade 0/AS-free Boxers breed true? 4. Identify the litter sizes of dogs with/without murmurs. Questions 3 and 4 are genetic questions. The answers could indicate the mode of inheritance of AS. Back to Top

NEXT: Postscript to Dr. Cattanach’s ABC talk on the UK Heart Scheme



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