A Message from our Cardiac Vet on Bull Terrier Heart Testing
I find that many owners like to understand more about the heart test, what the results mean and whether any other tests are advisable. I hope that this information sheet is of some help.
First of all, a few definitions that might help with the understanding of cardiac disease.
A HEREDITARY cardiac disease is one that is passed on genetically from the parents to the pups. It may not always be expressed as disease that can be detected in the dog, but may lie hiding in the genes, waiting to be passed on and possibly expressed in future generations.
A CONGENITAL heart disease is one that an individual pup is born with.
In most cases this is technically apparent on examination in the young pup, although young pups can be very difficult to examine, so that a murmur may only be detected in larger and older pups.
There are a few congenital cardiac diseases that do not have murmur associated with them. In some instances the disease becomes more obvious as the heart grows and matures.
For example, sub aortic stenosis (SAS), can increase in severity as a pup grows, which is one of the reasons heart testing is performed after 12 months old (18 months old in giant breeds).
A congenital disease is not always inherited from the parents. A pup may develop abnormally in some way as a foetus because of an individual problem.
ACQUIRED heart disease is not present in any way at birth and develops later in life. The dog can have hereditary predisposition to developing an acquired disease, as can be seen with certain breeds being more prone to developing dilated cardiomyopathy (DCM).
A MURMUR is the sound of turbulence when listening to the heart. The heart sounds normally heard with a stethoscope (lub-dup, lub-dup etc) are created by the sound of blood hitting closed valves.
The blood usually flows around the heart smoothly but anything leading to turbulence in the flow may be heard as a murmur (a whooshing sound around the normal heart sounds).
Sometimes minor turbulence is created in the heart when no disease is thought to be present and might be heard as a murmur.
Congenital Heart Disease in Bull Terriers
There are 2 areas of the heart more commonly affected by congenital abnormalities in English Bull Terriers.
Firstly, the aorta, which is the large vessel leaving the heart on the left side with oxygenated blood to transport to all the arteries in the body. This can show stenosis obstruction which makes it more difficult for the left ventricle to pump the blood out through this vessel.
The second area is the mitral valve which is between the left atrium (this chamber receives oxygenated blood from the lungs) and the left ventricle. This valve can also show stenosis and not open properly, thus restricting the passage of blood into the ventricle. It can also leak when closed so that when the ventricle pumps blood out of the aorta, blood leaks back the wrong way into the atrium. These can be seen separately or together.
Because these congenital abnormalities of the aorta and mitral valve are seen more commonly in Bull Terriers it is assumed that there is a hereditary reason for this. I am not aware of detailed genetic research into these conditions in the breed, but stand to be corrected, as it may not have come to my attention, particularly if in another country.
Other congenital conditions can of course exist in Bull Terriers but are only seen at a 'normal' rate of incidence
Absence of a murmur
Bull Terriers who have no murmur or other obvious signs of cardiac disease when a
cardiologist is able to have a good listen, are considered as passing the heart test and this is a great step towards insuring that healthy dogs are used for breeding. It is a test that is to be encouraged and whilst not infallible, it is not costly, and far better than no heart test at all before breeding.
Whilst it is certainly very good news if no murmur can be heard, unfortunately it does not mean that there is definitely no congenital heart disease present and also does not mean that acquired cardiac disease will not develop in the future. For example, the mitral stenosis mentioned, may not give rise to an audible murmur if it occurs alone and SAS may not produce a murmur that can be heard until the dog is older. In an ideal world, given that Bull Terriers are hard to listen to, all dogs to be used for breeding would be scanned, including those without murmurs. However it is understandable that for many owners the cost of the scan is prohibitive and passing the stethoscope heart test is a very good first step towards finding out if your dog has a healthy heart.
Murmurs in Bull Terriers
Bull Terriers are not the easiest dogs to listen to with a stethoscope! The shape of their chest and their muscular build put the heart a long way from the chest wall and, if the dog is excited the breathing and movement sounds produced can make it almost impossible to hear the heart sounds in a few dogs. Any dog in which a murmur can be heard and dogs who are impossible to listen to with a stethoscope should have echocardiography (heart ultrasound scan) performed by a cardiologist if there is a desire to breed from that dog. In the interests of general health
it is better to perform this investigation anyway if a Bull Terrier has a murmur. In some cases the scan might show that the murmur is not associated with cardiac disease and is 'innocent' or physiological and then that dog could be used for breeding. If cardiac disease was confirmed by a scan it would allow the owner to make an informed decision not to use that dog for breeding and also would help determine any need for treatment, monitoring and prognosis.
If a murmur is heard but no scan performed, it would be safer not to breed from that dog, as there is a reasonable chance, that cardiac disease is present and it may be passed on to the pups.
Thank you again for your interest in Bull Terrier health.
Good luck with showing and breeding and have lots of fun with your dogs!
Vicky Ironside MA, VetMB, CVC, MRCVS