The Boxer Heart
Anybody who has an interest in Boxers should be aware of the Heart problems that boxers can have and make sure that they test their animals and always buy a puppy from heart tested parents. All good breeders are aware of the heart testing schemes and will have tested their animals.
HANDOUT SHEET ON HEART MURMURS FOR NEW OWNERS OF A
JAYTOPHER BOXER PUPPY
Please read the whole document for you information but do not panic. As you will note from the pedigrees your puppy came from heart tested dogs. Both the Sire and the Dam had excellent heart scores and should produce puppies with equally excellent heart scores.
About the Current Scheme
The current Heart testing scheme has been in operation for 10 years. The current heart scoring system DOES NOT make allowances for half scores in heart testing. Dogs are graded either 1 or 2 you will not see a dog graded 1.5 or 0.5. If there is a shred of doubt when scoring a dog, then a one MUST be graded as a two, unless the dog is dopplered (an ultra sound scan carried out by a veterinary cardiologist) in this case a more accurate figure can be given.
Basically, the specific recommendations for breeding are:
All breeding stock should be screened by a cardiologist. Those animals which are free of heart murmurs (grade 0) may be considered free of Aortic and Pulmonic Stenosis, and are suitable for breeding purposes. Those animals which have a minor murmur (grade 1) may be accepted as normal and are suitable for breeding. Bitches who are scored over a 1, therefore as a grade 2, are considered acceptable as brood bitches provided they are mated to a clear dog, either a 0 or a 1. Dogs with murmurs of a grade 2 or louder, should not be used as stud dogs. Except in exceptional circumstances, then only to a clear bitch. The reason being is because a bitch is only able to have a limited number of puppies in her lifetime, whereas a dog can sire thousands of puppies, therefore doing more damage.
Genetics is not an exact science, we all know of a 0 being mated to a 0, yet some of the pups may be graded a 2, but the heart testing scheme is beginning to reduce the problems of heart disease among boxers, and by following breed guidelines reputable breeders are now beginning to see the rewards of heart testing by testing breeding animals before they are bred from.
It is recommended by The Breed Council that breeders hand this information to all new owners.
Heart murmurs have been found to be common among boxers.
It should be emphasised that these do not affect health in the great majority (95%) of dogs.
The few dogs with very loud murmurs however, may be subject to fainting and there may even be sudden death.
Aortic stenosis is the heart condition most commonly associated with these heart murmurs, but cases of pulmonic stenosis and cardiomyopathy, as found in other breed, may also be detected.
Typically, clinical signs of aortic stenosis first appear in the young adult, but on rare occasions puppies can be affected.
It should be stressed that minor "flow" murmurs are commonly found in young Boxer puppies, as in other breeds, but most disappear by about 16 weeks of age. Even if they persist there may be no cause for alarm if they are quiet. Such genuine "flow" murmurs" are not associated with heart disease in the adult.
The incidence of Boxers with severe aortic stenosis has increased in recent years, although the numbers of cases are still very low in relation to the number of dogs bred.
To rectify the situation, the Boxer breed council has, with the aid of veterinary cardiologists throughout the country, developed a system of testing based on simple stethescopic examination by the cardiologists. A breeding control scheme has also been established.
Therefore, should a heart murmur or any heart condition other than a genuine puppy "flow" murmur be recognised in a Boxer, it should be referred through the vet in charge to one of the cardiologists. The breeder and breed council geneticist should be informed of their result.
Dependant on the findings the condition may be treatable. If the puppy "flow" murmur is loud and persists the vet in charge may recommend that further advice be sought from a specialist cardiologist.
AORTIC STENOSIS - is one of the most common heart defects occurring in boxers. Aortic Stenosis is narrowing of the aorta, right below the aortic valve, which forces the heart to work harder to supply blood. Reduced blood flow can result in fainting and even sudden death. The disease is inherited but its mode of transmission is not known at this time. Diagnosis must be made by a veterinary cardiologist, after detection of a heart murmur. Breeding dogs must be properly tested for this disease and affected dogs must NOT be bred from.
In aortic stenosis, there is a partial obstruction to the flow of blood as it leaves the left side of the heart (the left ventricle) through the main blood vessel (the aorta) that carries blood to the rest of the body. The obstruction ranges from small nodules to a fibrous band, most commonly just below the aortic valve ("subvalvular aortic stenosis"). Due to the obstruction, the heart must work harder to pump out an adequate blood volume. Clinical signs and long-term outcome depend on the degree of narrowing, or stenosis.
There is a mildly increased risk of aortic stenosis in the German shepherd, German short-haired pointer, Great Dane, Samoyed and Bulldog.
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a general consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
Dogs with mild stenosis will generally show no clinical effects and have a normal life expectancy. With moderate to severe stenosis, signs will be variable. Because of the narrowing in the aorta as the blood leaves the left ventricle, your dog's heart must work harder to pump an adequate volume of blood to the rest of the body. Depending on the degree of obstruction, your dog's heart may be able to compensate at rest but not keep up with the body's demands during exercise. Thus you may see reduced exercise tolerance - your dog just seems to run out of steam - or fainting due to inadequate blood supply to the brain.
In response to the obstruction to blood flow, the heart muscle becomes thicker over time (left ventricular hypertrophy). As the condition progresses, your dog's heart becomes less able to compensate and you and your veterinarian may see signs associated with left-sided heart failure such as tiring on exercise, difficulty in breathing, coughing, and/or poor growth. Changes in the heart muscle can also lead to abnormal heart rhythms (cardiac arrhythmias) and sudden death.
Your veterinarian can do various tests (see below) to determine the severity of the defect. Based on the results, he or she will discuss with you the long-term prognosis, and ways to manage this condition in your dog.
In young animals (less than 6 months of age) there may be no clinical signs. Thus the first indication that your dog may have a problem may come when your veterinarian hears a heart murmur during physical examination. Some low-grade murmurs are "innocent" and disappear by 6 months of age, but if the murmur is significant, your veterinarian will suggest a diagnostic workup to determine the cause. He or she will listen very carefully to your dog's heart to determine the point of maximal intensity of the murmur and when the murmur occurs during the cardiac cycle. Other diagnostic aids include chest x-rays, an electrocardiogram (ECG) and/or ultrasonograph if available. To determine the extent of the narrowing, the pressure gradient across the aortic valve (between the left ventricle and the aorta) can be measured using special procedures for which your veterinarian can refer your dog to a specialist.
In an older animal or when the obstruction is pronounced there may be clinical signs associated with left-sided heart failure.
Based on the results of these various tests, your veterinarian will discuss with you the prognosis and long term management of your pet. S/he will also be able to tell you if any (and how much) change has occurred in the heart already as a result of the stenosis.
In dogs with mild aortic stenosis, there is no special treatment required. The dog should not be used for breeding and littermates should be carefully screened. Your veterinarian may suggest antibiotics in certain circumstances as a precaution against infection of the abnormal valve tissue.
With moderate to severe stenosis, the dog's exercise should be restricted. Beta-blocking drugs may be prescribed by your veterinarian to try to minimize the effects of left ventricular hypertrophy. Your veterinarian will recommend other therapy if required to manage congestive heart failure. Medical management for congestive heart failure is similar no matter what the cause, and consists of medications to support the heart muscle and decrease the work load of the heart, together with dietary recommendations.
Various surgeries have been attempted to alleviate the obstruction with limited success. The surgery itself carries a high risk, and there is little, if any, increase in survival rates compared with dogs whose condition is managed medically.
pulmonic STENOSIS - As part of normal circulation in the body, the right side of the heart (the right ventricle) pumps blood to the lungs to receive oxygen. The oxygenated blood goes back to the left side of the heart from which it is pumped out to the rest of the body.
Blood flows from the right ventricle of the heart through the pulmonic valve into the pulmonary artery and then onto the lungs. With pulmonic stenosis, there is partial obstruction of normal blood flow, most commonly due to a malformation of the pulmonic valve ("pulmonic valve dysplasia") but the abnormality may be immediately above or below the valve as well.
The effect of this partial obstruction is to force the heart to work harder to pump blood to the lungs. The extent to which a dog will be affected depends on the degree of narrowing (stenosis) of the valve area. With severe stenosis the dog will likely develop congestive heart failure due to the increased workload of the heart.
Pulmonic stenosis is one of the most common congenital heart defects in all species.
There is a breed predisposition in the following breeds of dog:
The English bulldog and the mastiff are at most risk for pulmonic stenosis. In English bulldogs, pulmonic stenosis occurs commonly with an abnormal left main coronary artery branch, arising from a single right coronary artery. In this breed the condition is more common in males.
There is also an increased risk of pulmonic stenosis in the beagle, wire-haired fox terrier, Chihuahua, miniature schnauzer, Samoyed, Boykin spaniel, West Highland white terrier, cocker spaniel, Airedale terrier, and Scottish terrier. It has also been found in boxers.
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a general consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
In its milder forms, the slight thickening of the pulmonary valve will cause minimal or no obstruction and your dog will not be affected. However with more severe thickening of the valve, the obstruction to blood flow from the right side of the heart will cause varying degrees of heart damage which worsens with age. With moderate-to-severe pulmonic stenosis, your dog may experience signs associated with low cardiac output and/or right-sided heart failure, such as respiratory difficulties, fainting, tiring with exercise, abnormal cardiac rhythms, abdominal swelling due to an enlarged liver or the accumulation of fluid because of failing circulation, or sudden death.
Based on your dog's physical examination and diagnostic tests such as chest x-rays and an electrocardiogram, your veterinarian will discuss with you the severity of the pulmonic stenosis. If there are significant changes evident, he or she will suggest further tests to determine the pressure gradient across the pulmonic valve. (Normally there is no pressure difference between the right ventricle of the heart and the pulmonary artery to the lungs.) Where there is a pronounced pressure gradient, surgery to correct the stenosis should be considered.
The first indication that your dog has a problem may be when your veterinarian hears a heart murmur on an early physical examination. Alternately, you may see signs in your dog related to heart disease, such as fainting or fatigue with exercise. Your veterinarian will listen carefully to try to determine the location of the murmur and to differentiate it from an "innocent" murmur which disappears by about 6 months of age. If the murmur is significant, your veterinarian will suggest further tests such as a chest x-ray, electrocardiogram, and cardiac ultrasound to help determine the cause, and to see what changes if any have already occurred in the heart as a result of the defect.
Once pulmonic stenosis has been diagnosed, Doppler echocardiography or cardiac catheterization can be done to measure the pressure gradient between the right ventricle and the pulmonary artery, to determine the severity of the obstruction. Based on these test results your veterinarian will discuss with you the long term prognosis for your dog and whether surgical correction of the defect should be considered.
CARDIOMYOPATHY - Cardiomyopathy is a serious inherited disease in which the heart muscle becomes inflamed and doesn't work as well as it should. There may be multiple causes including genetic predisposition and viral infections. The disease occurs most often in Doberman pinscher and Boxer and may result in heart failure and sudden death. The signs usually include exercise intolerance and fainting. Treatment depends on the type of the disease and may include medications or implantable devices.
Cardiomyopathy refers to disease of the heart muscle (the myocardium) without malformation of the heart or its valves. There is a breed predisposition to dilated cardiomyopathy in giant breeds, as well as in Doberman pinschers and boxers. Cardiomyopathy can also develop as a result of some toxins or infections.
There are 3 types of cardiomyopathy:
Dilated cardiomyopathy. This is by far the most common type in the dog. There is dilation of the chambers of the ventricles of the heart with some increase (hypertrophy) in the heart muscle mass, and a loss of the normal contracting abilities of the ventricles.
Hypertrophic cardiomyopathy. In this form of cardiomyopathy, there is a tremendous increase in the mass of the heart muscle in the ventricles, with a resultant decrease in chamber size. Relatively few cases of hypertrophic cardiomyopathy in dogs have been reported, and no significant breed predisposition has been identified. Most of the dogs affected have been male.
Restrictive. This type has not been reported in dogs.
The heart works harder to compensate for the loss of contractility, eventually leading to congestive heart failure. The abnormalities in the heart muscle cells give rise to irregular heart rhythms which may cause sudden death.
Dilated cardiomyopathy is seen more often in Doberman pinschers than in all other breeds combined. It also occurs in giant breed dogs including the Great Dane, St. Bernard, Irish wolfhound, and Scottish deerhound. A distinctive form of cardiomyopathy occurs in the boxer, with extensive changes in the heart muscle and serious rhythm abnormalities, but without the dramatic dilation of the ventricles seen in other breeds.
Dilated cardiomyopathy is also seen in English cocker spaniels. In all breeds affected, it is more common in males.
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have only listed breeds for which there is a strong consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
Giant breeds with dilated cardiomyopathy typically show signs associated with abnormalities of heart rhythm (particularly atrial fibrillation) and generalized heart failure. These signs may include weakness, loss of appetite, weight loss, depression, episodes of collapse, respiratory difficulties, a soft cough (especially at rest), and an enlarged abdomen. There is severe enlargement of all 4 chambers of the heart. Dogs are affected in middle-age on average, although they may be affected as early as a few months of age. Abnormalities may be seen on an electrocardiogram before there are any clinical signs.
In addition to signs of heart failure as outlined above, a distinctive feature of this disorder in Doberman pinschers and boxers is that the abnormal heart rhythms that are seen originate most commonly in the ventricles, and are quite serious. As well, Dobermans often have left atrial rather than generalized enlargement of the heart and boxers may show no heart enlargement.
In Doberman pinschers there is a relatively long period of 2 to 4 years without clinical signs of illness ( the "occult" phase), during which changes occur in the heart muscle and rhythm disturbances progressively worsen. Sudden death occurs in about 25% of these dogs. Others will go on to develop congestive heart failure. Weight loss is often sudden and dramatic in these dogs. Death usually occurs fairly soon after clinical signs develop, often within 6 months.
In Boxers, there are 3 distinct stages of cardiomyopathy:
Stage I. An irregular heart rhythm is discovered incidentally during a routine examination or examination for other purposes. The dog has no clinical signs of illness.
Stage II. These dogs are examined because of intermittent episodes of collapse or weakness. On examination an abnormal heart rhythm (generally originating in the ventricles) is found.
Stage III. These dogs show signs of heart failure which may include weakness, depression, exercise intolerance, a soft cough (particularly at rest or at night), and a loss of appetite, weight loss which may be dramatic and fainting or collapse.
The episodes of fainting, collapse, or weakness are generally due to abnormal rhythms in the heart, because of the damaged heart muscle. For this reason, regular monitoring by electrocardiogram is the best way of assessing the progression of cardiomyopathy in these dogs. Dogs in either of the first stages may develop heart failure at any time.
For all dogs with dilated cardiomyopathy, the arrhythmias that can cause fainting or collapse can also cause sudden death. Up to 50% of affected dogs die suddenly, often without having shown any other signs of the disorder.
Once dogs with cardiomyopathy develop congestive heart failure, the prognosis is poor.
X-rays generally show an enlarged heart, predominantly on the left side. Boxers may show no abnormalities on radiographs.
In both Dobermans and Boxers with cardiomyopathy, there may be no abnormalities on radiographs, on physical exam, or on the resting electrocardiogram. If cardiomyopathy is suspected and all routine diagnostic tests are normal, a 24 hour ambulatory electrocardiogram (a Holter monitor) is recommended. The unobtrusive monitor is worn by the dog during its normal activities, and records irregular heart rhythms.
Decisions about treatment are based on several factors: whether the dog is showing clinical signs such as weakness or collapse, what arrhythmias are seen on the electrocardiogram, and whether congestive heart failure is present. If your dog has an abnormal heart rhythm without any evidence of congestive heart failure, your veterinarian may prescribe anti-arrhythmic drugs, depending on the severity of the arrhythmia.
Episodes of collapse indicate a serious arrhythmia and must be treated as an emergency.
Treatment for dogs with signs of congestive heart failure involves rest, diet restrictions, and drugs to stabilize and support the failing heart as well as to control the arrhythmias. If low doses of anti-arrhythmic drugs are effective, then the heart can often be stabilized. Serious ventricular arrhythmias that can only be controlled by high doses of anti-arrhythmic drugs have a poorer prognosis.
New treatments are being used in Dobermans and Boxers with cardiomyopathy in an attempt to delay the onset of congestive heart failure or sudden death.
Breeding advice
Affected individuals and their parents should not be used for breeding. Siblings should only be used after careful screening.
There are ways to approach the control of this disease. Although signs of heart failure are often not evident until middle age, abnormalities on the electrocardiogram are often apparent earlier. In affected breeds with a family history of cardiomyopathy and in ALL Doberman pinschers, breeding animals should be evaluated yearly for evidence of cardiac arrhythmias, using an ambulatory (Holter) monitor if possible. Dogs in which occult dilated cardiomyopathy has been identified (i.e. no clinical signs) should not be used for breeding.
The aims of the Boxer heart testing scheme is to try and ascertain the prevalence of heart murmurs, abnormal heart rhythms and other specific heart conditions. It is also to confirm the cause of heart murmurs or abnormal rhythms by further investigations of any affected dogs.
To collate data for investigation of a possible genetic basis to any specific heart problems in the breed.
To advise the owner, breeder, and dog's veterinary surgeon when an abnormality has been found, and to advise and recommend any further investigations that may be required.
Methods of Heart Testing
Auscultation - examining with a stethoscope
This is an essential part of examining the animal’s heart and circulation. Any heart murmurs are identified, timed, localised and graded (0-6 no half measures!) A careful note of the heart rhythm is also made.
Heart murmurs are a feature of most congenital heart defects (CHD) and mitral valve disease. Some common forms of congenital heart disease include aortic stenosis (AS), patent ductus arteriousus (PDA), and pulmonic stenosis (PS). Abnormal heart rhythms may occur without murmurs in dilated cardiomyopathy (DCM).
It may be difficult for a cardiologist to detect a quiet murmur in a noisy room or in a dog which fidgets. Some murmurs can increase or alter at different heart rates like after exercise or excitement.
If a significant murmur is detected the cardiologist may advise the condition be further investigated. Although all veterinary surgeons will listen to your dog’s heart, breed club schemes use veterinary cardiologists, vets who have received training, and have passed post-graduate exams and are able to grade heart murmurs in a way which is consistent with other cardiologists.
Electrocardiograph (ECG)
This is always indicated when or if an abnormal heart rhythm is detected. It is most often used to screen for DCM (dilated cardiomyopathy) though it is less sensitive at detecting CDH or MVD.
Echocardiogram (with Doppler)
Two dimensional echocardiography allows visualization of a 'slice' through the heart in real time. It allows measurements to be taken and compared with normal values for the breed or size of the dog. Severe CHD, MVD, or DCM are usually evident using these techniques. However, Doppler is also required to confirm the diagnosis of the specific type of CHD, and to identify mildly affected animals. It will confirm whether or not there is a significant cause of the heart murmur, or whether it is innocent In some cases, it is difficult to be certain whether the dog has mild disease or an innocent murmur.
Doppler will allow the cardiologist to give a prognosis about the severity of any disease. Veterinary cardiologists normally carry our Doppler examinations, as this is a very skilled technique which requires considerable expertise and experience.
CONSULTANT CARDIOLOGIST: Anne French, MVB DVC MRCVS, Lecturer in Veterinary Cardiology, The University of Edinburgh, Summerhall, Edinburgh EH9 1QH. Tel. 0131 6506061
SECRETARY TO THE BOXER BREED COUNCIL: Mrs Wendy Brooks, Jinnybrux Bungalow, Alford Road, Mablethorpe, Lincs LN12 1PX. Tel. 01507 472156
VETERINARY ADVISOR TO BREED COUNCIL: Walker G Miller BVMS DBR MRCVS. Walkon Boxers, High Kirkland, Leswalt, Stranraer, DG9 0RH Tel. 01776 870211
I would recommend that you have your Boxer heart tested for your peace of mind.
The simple test for Aortic Stenosis can be done at a recommended Cardiologist practice (the Boxer Breed Council website – has a list of recommended cardiologists) or contact your local breed club who often have heart testing at shows.
This can be done any time after the dog is 1 year of age.
