This information is taken from the BOXER BREED COUNCIL UK website in 2009
Below is information about 2 hereditary heart health issues that do affect Boxers. Responsible Boxer breeders are planing their breeding so these health problem can be eliminated
The information below is a guide only, if you would like more information follow the link provided
Note: All our adults are heart tested prior to breeding. All puppies have a preliminary heart test prior to leaving. Although the information below states you can breed a dog/bitch with a Grade 1 reading and some Aust. Breeders regularly breed with dogs that have Heart Murmurs we only breed & highly recommend you purchase a puppy/adult from 0 scored dogs - dogs that do not have a heart murmur.
We have not had a heart murmur in our breedings / pedigrees to date since the comencement of heart testing in NSW, and we are proud of this record. We are constantly vigilant in our screening
Recommendations For The Control of Aortic Stenosis (October 1993)
By Bruce Cattanach - Steynmere Boxers
The following points should be noted:
The revised recommendations being proposed are based on a number of veterinary conclusions, some of which have been modified in the light of recent research findings. Further developments are possible. However, it should be stressed that, as initially, the recommendations are liable to err conservatively, this being necessitated by the observed high incidence of dogs with heart murmurs and the need to avoid excessive restraint upon breeding programmes.
Recommended actions are based upon the incidence of normal, rather affected dogs. This warranted by
* The probable mode of inheritance determined from studies in other breeds.
* The family studies which are now yielding direct evidence to show that the progeny deriving from the "best" parent are far less at risk of having murmurs associated with aortic stenosis than from others.
The Heart has four chambers. The upper two chambers are called atria (atrium - single), the lower two chambers are called ventricles. The heart is also considered to have a left and right side. i.e left and right atria, left and right ventricles. In addition to these chambers, the heart also has a series of valves which control the flow of blood.
Blood flows from the body into the right atrium. It is stored there briefly, before being pumped into the right ventricle. The right ventricle pumps blood into the lungs, where it becomes oxygenated. It flows from the lungs into the left atrium, it is held here breifly before going into the left ventricle. The left ventricle contains the largest muscle within the heart and this is used to pump blood to all parts of the body.
The following describes BRIEFLY what Aortic Stenosis is:-
A heart murmur is the sound produced when blood flow through the heart becomes turbulent. Murmur's are graded in severity from 0 to 6 where 0 is murmur free and 6 is severe. Aortic Stenosis is a congenital narrowing at the entrance of the aorta which supplies blood to the body. It usually takes the form of a fibrous ring below the aortic valve (Sub-Aortic Stenosis).
The left ventricle has to pump with greater force to push the blood past the narrow valve. This results in a thickening of the heart muscle wall, it enlarges just like any other muscle because it is working harder. As a result of the thickening, the narrowing is made worse. Blood supply to the muscle itself is restricted, thus the muscle is working harder but with restricted blood flow.
BREEDING AND TESTING RECOMMENDATIONS
for dealing with UK Boxer Cardiomyopathy (BCM)
(Accepted by Breed Council at their April, 2008 meeting)
In considering how the problem of UK Boxer cardiomyopathy (BCM) may be resolved it should be noted that:
- The disease is believed to have a dominant single gene inheritance meaning that only one parent may responsible for affected pups in a litter.
2. The gene has a variable penetrance, meaning that clinical signs of disease does not always develop when
the gene is present. Clinical signs of BCM can therefore appear to skip generations.
3. The disease appears to show variation in expression meaning that the course of the disease may be different both within and between lines:
- In one major family group (Family 1), the effects may occur early and be severe with a rapid deterioration, bloating, coughing, and exercise intolerance. The median age of death is under 4 years. There is, however, a ‘tail’ to the distribution with cases also being detected at ages up to 9 years or more, and some dogs that carry the gene may never develop the disease.
- In two other families (Families 2 & 3) the early effects appear less severe and have a later onset. There may be episodic collapse (fainting), and arrhythmias (abnormal heart beats) before other more serious signs appear as the disease progresses. The most serious signs may never develop. The median age of death in these families is about 7 yrs.
- Spontaneous cases may also be occur and may be attributable to viruses, thyroid problems, or be of unknown origin. These have commonly involved older animals. These are not based on an inherited defect.
4. Veterinary diagnosis for BCM relies upon a range of examinations and tests including auscultation to listen for abnormal heart sounds and rhythm, troponin blood testing to indicate heart damage, standard ECG and 24 hour ECG (“Holter”) monitoring to detect arrhythmias, and ultrasound (echocardiography) and X-ray imaging to detect abnormalities of the heart, both size, and function. The troponin assay offers a simple pre-screen but has yet to be fully validated as a reliable test for BCM. Holter currently offers the best prospective early screen for signs of the disease but it is important to recognize that a negative result only means that a dog does not have detectable signs of BCM at the time of testing and does NOT necessarily mean that a dog does not carry the gene.. Annual re-testing will therefore be a basic requirement. A positive Holter result indicates abnormality and further veterinary testing for definitive diagnosis may then be needed.
5. A full diagnosis, a selection of auscultation, echocardiography, ECG analysis, and Holter monitoring, together with routine blood tests to rule out other causes of arhythmias. Blood samples collected primarily for troponin testing can also be used for DNA studies. If the affected boxer should die apost mortem examination of the heart, with histopathology, may also be advocated.
- Progeny analysis is the only method of determining if a seemingly unaffected Boxer carries the gene responsible for cardiomyopathy.
Forms for submitting:
- blood samples for troponin testing (at Glasgow University or Beaufort Cottage Labs - through Glasgow);
- Holter analysis and other diagnostic tests (at cardiology referral centres);
- post mortem heart tissue (at LiverpoolUniversity);
are available from the Health Committee, Breed Council, and member Clubs.
Preliminary risk assessment
Before considering breeding control procedures the following points should be noted:
2. The level of risk of an affected ancestor passing BCM on to its descendents depends upon the distance back in the pedigrees (see below).
a. the 50% expectation of transmission of the gene from carriers; and
b. the recognition that the most common type of BCM is expressed early in life.
Then, if the gene is present, a significant proportion of the progeny will be expected show the disease within the first few years of life, and these would be detected in any general health screen.
The application of the progeny analysis has greatest application for stud dogs from the early onset family (Family 1) and having significant numbers of progeny. The current estimate for the numbers of progeny required is 65 and the minimum progeny age (Family 1) is 4 years. The rationale is that as the numbers of progeny increase, if all are healthy, then as progeny numbers and ages increase, the risks of BCM being present in the tested parent diminishes). Progeny test analysis is of therefore of limited value for stud dogs that have had, or may be expected to have little stud work and is generally of no use for bitches.
An important attribute of the progeny test is that descendents of animals so cleared can be considered free of BCM risk, unless risk is introduced from another source.
2. Troponin testing
Elevated levels of troponin in the blood (>0.15ng/ml at GlasgowUniversity) signifies heart muscle or heart muscle damage of any cause or significant arrhythmia. As such it is being proposed as an economical pre-screen for BCM. Although the test is still being assessed, its use is currently recommended for all dogs at risk.
3. Holter monitoring
Holter monitoring offers the potential for identifying dogs that have developed arrhythmias due to BCM. It may have its greatest use for testing stud dogs at family risk of carrying the BCM gene but may be of less use for identifying rapid early onset BCM when echocardiograpy is advised.
It should be noted that a normal Holter result does not establish that a dog that is genetically free of the gene; it is not even clear exactly what constitutes a normal finding. Thus one critical observation, the number of ectopic, abnormal heart beats (VPCs), is variable, changing from day to day, week to week and month to month. However, when VPCs occur in pairs or runs, this gives good evidence that BCM is developing. Currently, <50 VPCs over a 24 hour period signifies normality, 50 – 200 VPCs represents an ambiguous result, with re-testing recommended, and >200 VPCs may be indicative of developing BCM, but the other attributes may influence the evaluation. (Exact criteria are yet to be finalised.)
4. Echocardiography and X-ray radiography
Echocardiography and X-rays allows visualisation of abnormal heart function and detection of heart failure (lung congestion). As such it can be of use in severe early onset cases where heart failure has, or is about to develop.
5. DNA testing
At this time there is not yet a DNA or gene test for BCM, however work in the US is progressing. Until such time as a DNA test becomes available the only means of limiting the spread of the disease is by careful breeding control
The following describes BRIEFLY how the heart works:-
* The high incidence of dogs with heart murmurs
* The further need to avoid other heart conditions such as pulmonic stenosis and cardiomyopathy
The recommendations have three basic objectives:
To allow breeders to evaluate their own stock and conduct their own family studies with dogs of all ages.
To provide breeders with a means of breeding away from, or avoiding aortic stenosis and, hopefully other heart conditions.
To provide research information on heart defects that will ultimately be fed back into the breed.
Specific Recommendations For Breeders
* A. In the case of adults i.e. over 12 months of age:
All stock should be screened by designated cardiologists.
Those which are free of heart murmurs (Grade 0) may be considered free of aortic stenosis, and suitable for breeding purposes.
Those which have only minor (Grade 1) murmurs may, for the moment be accepted as normal and therefore suitable for breeding purposes.
Stock with Grade 2 murmurs may be re-screened (up to three times)
* Those which on any re-screening obtain a Grade 1 score, or even found to be murmur free, may be considered suitable for breeding.
* Those which are consistently found to have Grade 2 or louder murmurs should normally be discarded for breeding purposes, unless in the case of bitches there is no alternative other than to disband the whole of a kennels breeding stock. When
* Selected bitches should be mated only to stud dogs that are considered to be normal (as described above), preferably murmur free.
* At most only one or two litters should be taken with the objective of breeding a murmur free replacement.
In the case of dogs with murmurs consistently no louder than Grade 2, Doppler echocardiography may be a further option. Those with blood velocities below 2.0 m/s may, for the present be considered suitable for
breeding. Other useful Grade 2 dogs might, for the present be available for stud to a strictly limited number of bitches. These bitches should be murmur free or have at the most only Grade 1 murmurs. Dogs with Grade 3 or louder should never be considered for breeding purposes, even if they have a blood velocities below 2.0 m/s.
Bitch owners are strongly advised to use only tested and proven normal dogs at stud.
Dog owners are advised to offer only tested and proven normal dogs for stud purposes and ensure, before accepting bitches for service, that their owners are complying with recommended control procedure. At owners risk, stud services could be provided for untested, non-show bitches both of whose parents are murmur free or having Grade 1 murmurs.
Stock incidentally identified as having heart abnormalities other than aortic stenosis, e.g. cardiomyopathy or pulmonic stenosis, should not be considered for breeding purposes.
* B. In the case of young stock i.e. under 12 months of age: Puppies aged 6 – 12 months can usefully be tested in the same manner as adults but the results must be interpreted with discretion. Because aortic stenosis develops progressively it cannot be assumed that those that are free of murmurs or have Grade 1 murmurs will be found to be so as adults; there prospects may nevertheless be considered relatively good. On the other, those found to have Grade 2 or louder murmurs are unlikely to become suitable prospects for breeding purposes, and may be at risk of developing the clinical effects of aortic stenosis in later life. The testing of puppies is strongly recommended. Their retesting as adults is essential, however.
To aid breeders implement the recommended breeding control procedures, a list of dogs which are murmur free (Grade 0) or have only minor murmurs (Grade 1) is continually being collated and updated. Copies are available form the Breed Council secretary or secretaries of breed clubs.
Most breed clubs hold heart-testing clinics with designated cardiologists in attendance at one of their shows each year. Private testing can be
obtained by referral through owner’s vets. A list of designated cardiologists may be obtained from the Breed Council secretary or breed club secretaries or heart delegates.
Cardiologists may advocate ultrasound scanning and Doppler echocardiography for dogs with Grade 3 or louder murmurs as means of evaluating the severity of the condition, i.e. for purely veterinary reasons.
Baby puppies aged 8 – 12 weeks commonly have minor "flow" murmurs, which usually disappear by about 16 weeks. These are not known to be associated with heart disease in the adult. However, puppies with loud, harsh murmurs should be referred through one’s vet to cardiologists for evaluation.
It is strongly recommended that prior to importing stock for breeding purposes, purchasers should ensure that prospective imports are suitably heart tested by qualified cardiologists to ensure they are free of heart defects.
All breeding stock prior to export abroad should similarly be heart tested and established as normal. In the case of young stock (under one year of age) only those which are free of heart murmurs and have murmur-free or Grade 1 parents should be considered eligible for export, except with the express agreement with purchasers SAS Testing: Auscultation versus Doppler
The two test procedures screen for different things. Auscultation screens for physical changes whereas Doppler screens for changes related to function. There is a relationship between the two, but it is not direct or exact.
Auscultation screens for more than just impaired function. It is the better system especially for mass screening of a breed. But if you want a veterinary diagnosis or prognosis then Doppler is the tool of excellence.
Auscultation versus Doppler - This subject seems to go round and round. I understand that the following would be more correct: If a dog is auscultated BY A CARDIOLOGIST WITH GREAT EXPERIENCE IN BOXER HEART TESTING(such as a few selected ones we have in the UK) and this dog is found not to have a heart murmur, then it will not be found to have SAS on subsequent Doppler either.
But in practice cardiologists vary, experience even among this specialised group varies, dogs can even vary as they are being tested so that screening has to take more than a few minutes, etc, etc, so there are all kinds of loop holes in the above basic principle.
Beyond this, there are the few exceptional cases where seemingly murmur-free dogs really have developed both murmurs and stenosis, as determined by Doppler, with age. This exceptional scenario has been found with dogs that uniquely had an abnormality develop within the aortic valve itself, not below (sub-aortic stenosis) as is commonly found
And as has been pointed out elsewhere auscultation is far more effective for a national control scheme and for single kennels testing numbers of dogs over the years.
At all levels auscultation wins – especially if you want to achieve something.
And then of course, there is probably more variation with Doppler scoring than auscultation.
Auscultation recognises sound, sound is caused by any type of anomaly within the aorta, lumps and bumps (as in the noise of a rocky stream) as well as a more severe effect that causes partial closure and forces the blood to travel faster making a noise (as the end of a hose). So in principle, the auscultation picks up the minor manifestations of AS that do not impair blood flow – it is more sensitive for effects that are the
basis of the thickening it detects abnormality but not necessarily function, and Doppler measures function – by blood velocity.
Doppler "passes" can therefore be achieved in auscultation positive dogs by the fact that there is not a definite narrowing, not increased blood flow, only the turbulence detected by auscultation. So Doppler is not expected to pick up Grade 1s or even many Grade 2s. This is at the level of velocity currently defined as normal. In the UK the "pass" rate has clearly been set too high at 2.0 m/s.
Beyond this there is liable to be as big or bigger variation in Doppler scoring by different vets than even with auscultation. The quote here is that it took our lead cardiologists 18 months of scoring every day to begin to get consistent results The positive for Doppler is that it clearly defines the disease in sufficiently affected dogs – which valve is involved and even perhaps where, within, below, above the valve, and presents a definitive quantitative diagnosis and prognosis in sufficiently affected dogs. It is the classic tool for this purpose.
Physiological murmurs are often talked about but I am not aware of any dog with a minor murmur that has been found on pathology/autopsy to have a normal AS – free heart. Clearly there are minor murmurs in puppies which are transitory and do not relate to adult conditions. And murmur grade is highly sensitive to external effects like excitement, activity or anything that makes the heart beat faster. Test conditions have to be standard. This is central to current research: are there any boxers that have absolutely normal hearts, what influences grades, and velocity? I am pleading with breeders to retest some of there Grade 0 dogs to see if any always grade as such, but!!! And one would then want to see what the pups heart status is when both parents are absolutely free of murmurs. But again!!!
All the above is specific to Boxers, please note. In Newfoundland’s, for example, with their big barrel chests, then auscultation is not so valuable and Doppler has to be used.
Whatever the arguments, the UK system is working and it has to work on the basis of the breeding data – given appropriate breeder action
So, the bottom line is still – with the necessary level of testing – auscultation still picks up LOWER LEVELS OF THE CONDITION WHICH IN MORE SEVERE FORM CAUSES SAS than Doppler. (It’s all a play on word’s, which gives a mixed message. I think when vets talk about SAS they are talking about a dog being affected to a level they can recognise by Doppler blood velocities (high). Lower levels of the effect, meaning no actual stenosis (narrowing) but still lumps and bumps which are milder effects, but which do not represent stenosis proper, still cause sound.)
More information available on our Boxer Links page