the day after LKA, well over 100 Boxer enthusiasts gathered
in the Midlands for a Heart Seminar staged by the Boxer
Breed Council writes Tim Hutchings, Chairman.
The fact that so many people attended on the day after a show, in the run up to Christmas and with appalling conditions for the drive up just goes to show how much interest there is in the subject of Boxer Hearts at the moment. We had been extremely fortunate that three eminent veterinary cardiologists had offered to give up their Saturday to join us, flying down from Edinburgh on the very early shuttle. Paul Wotton, Jo Dukes-McEwan and Anne French were excellent speakers, with excellent lecturing material and the audience was very appreciative.
Firstly Paul Wotton gave us an overview of the heart problems and symptoms experienced by dogs in general and his examples came from a wide range of breeds. He focused on Cardiomyopathy which is of most concern to us at the moment and, among many other fascinating illustrations, he had several which really brought the seriousness of the subject home to us.
We had two contrasting videos of a Doppler examination: one was of a normal dog and the other was of a dog suffering the advanced stages of Cardiomyopathy. The difference was remarkable and the healthy, powerful pumping of the first compared to the flabby, slack performance of the latter was obvious to all. Paul also had two pictures of hearts, taken at post mortem. The first was a healthy heart from a dog that had died of other causes. It was a plump, taut, rounded muscle, standing proud of the table. The second was from a dog that had died of Cardio and the best way to describe this one was like a dead jellyfish, washed up on the beach.
One of the reasons for this is that in the ‘Boxer form’ of Cardiomyopathy there is significant fibro/fatty penetration of the heart muscle, particularly down the right hand side. This makes the heart extremely inefficient and in an affected Boxer, this alteration in structure and formation of the heart can also cause significant irregularities of the heart rhythm since it is responding less reliably to the electrical stimuli which make a normal heart function properly. In an affected dog, beats from the diseased areas come in early and on an Electro-Cardiogram they are much less ‘peaked’ than a normal powerful beat.
Paul went on to tell us that the type of the disease primarily seen in Boxers was more properly termed Arrhythmogenic Right Ventricular Cardiomyopathy (or ARVC for short). There are a whole range of theories as to what causes it, but the reality is that we don’t know for sure. This refreshing honesty was one of the hallmarks of the vets’ talk. We are still very much at the cutting edge of research into this disease which also benefits and benefits from human research since the human form of Cardiomyopathy is very similar.
The clinical signs of ARVC include lethargy and weight loss, episodic collapse, coughing, laboured breathing, retained fluid in the abdomen, abnormal heart sounds and the ECG abnormalities referred to above, though it was stressed it is a diagnosis of exclusion, making sure that there aren’t any other causes. However, the most insidious aspect of this disease is the fact that it can have a very long pre-clinical phase and the time of onset can vary enormously. In fact, some affected dogs may never show any symptoms at all. This was a theme that Jo Dukes McEwan picked up on and she illustrated the point so well with a picture of an iceberg. The little bit of the iceberg above the surface represented dogs actually suffering from congestive heart failure (which no-one can miss), but below the surface are a potentially large number of dogs in the ‘occult phase’ – some of these may never show any symptoms, others may develop a mild form of the disease later in life, some may develop a serious form. Of course, from a breeding perspective, this grey area represents a real problem since the danger is always that you might be breeding with an animal on the assumption that s/he is clear, only to discover at a later stage that ARVC has struck. At the moment it looks like the age of onset is anytime from five months of age, with the average being around three and a half.
However, Jo did emphasise that there were actions that could be taken to identify some abnormalities that precede development of the disease. One of these is to have an extensive Doppler examination by a Cardiologist. Among many other things, they are looking at the size of the heart (where ventricular enlargement is one of the signs), they look at the efficiency of blood pumping via various ratios and they look for depressed contractility. Jo also stressed the importance of doing this once a year so that trends could be established. She had some excellent graphs from her findings with the Newfoundlands, where the increased size of the heart in particular was obvious once a couple of years’ results had been plotted.
Another method of hopefully spotting the signs early (bearing in mind what Paul had already told us about abnormal ECGs) was to run a 24 hour ECG test via a Holter monitor fixed onto the dog with a combination of tape and a close fitting jacket. With the aid of a charming Glenauld Boxer lady, we were shown how easily this device was fitted and I have to say that the Boxer seemed to get used to it remarkably quickly, even with a large audience crowded around. Once the 24 hour period is up, the tapes are read and examined for evidence of abnormal beats
Jo was completely upfront and said that at the moment there was no categoric way of establishing whether a dog does (or does not) have ARVC but the methods proposed (when repeated regularly) did increase the chances of early identification. Effectively, Jo said, they had the effect of "lowering the water level around the iceberg, exposing as much of the problem as possible, as early as possible." She also said that the older the dog was when it had a normal examination, the more confident you could be.
More positively, Jo spoke about the possibility of a genetic test being established for the disease within a five year time frame. Some good work had already been done on narrowing the search down to a limited number of candidate genes, but we were still some way off. It was clear from Jo’s talk that the disease is inherited and that it is probably autosomal dominant. This means that 50% of a carrier parent’s offspring will be affected, however things are confused by the fact that some of these carrier offspring may never exhibit symptoms. A result of this is that the gene can appear to ‘skip’ generations. For this reason Jo thought it was absolutely essential to track down all siblings in a litter when carrying out research.
After this session, everyone in the room can have been in no doubt about why the vets always recommended that pedigrees of affected animals should be made available, as well as a blood sample taken to assist in the quest for a future genetic test. Of course, pedigree analysis is always going to be complicated by the level of in breeding and line breeding that goes on and also by the fact that affected dogs may remain ‘equivocal’ (or in the grey area) for so long. However, the fact that it is ‘difficult’ should not deter us.
To assist with the research, the vets were unanimous that the services of a funded PhD student would be invaluable and over a three year period, the cost of this was estimated at £75,000. Some early avenues for funding have so far drawn a blank but many of us in the room were left wondering what we could do to help.
Questions rounded off the morning session and one of the key points raised was the possibility of other causes of ARVC, other than the inherited congenital reason. The panel acknowledged that there could be other causes (though some nutrition related theory was discounted). However, they felt it was important to stress that these other possible causes (such as Kennel Cough) probably just pushed a dog from the occult phase into the full disease. They believed that in the majority of cases external factors merely triggered a condition to which the dog was already pre-disposed.
In the afternoon, Anne French gave an excellent update on Aortic Stenosis. I will not go into huge detail on this session since the scheme and the disease will be so much more familiar to you, but it really was useful. Anne had some good charts showing survival, asymptomatic and affected rates for the different grades which certainly gave comfort in the reliability of the testing. However, there was debate about how we maintained consistency between the Cardiologists and about whether the current testing was too tough, especially in respect of bitches. Whilst the Cardiologists were clearly not keen on introducing ‘halves’ into the existing 7 point scale, there was discussion about whether two was an acceptable score for a bitch. The vets also listened to breeder and club concern about the difficulty of securing Cardiologists for shows and about how ‘marginal’ fails were communicated. However, the main thrust of the session was entirely positive. Thanks to Bruce Cattanach’s hard work over many years, the scheme has been a tremendous success and enjoys the support of the breed. Now, having met the Cardiologists behind the scheme as well, I am in no doubt that any teething problems that we encounter can be quickly resolved.
More questions followed and everyone had an opportunity to have their voice heard before it was my pleasure, as Chairman, to present gifts to our three speakers and to acknowledge the hard work that the Breed Council veterinary adviser, Walker Miller (ably assisted by Peter Burroughs and Jane Collins) had put into staging the day. There had been a lot of information given to us during the sessions and it is clearly now the job of the Breed Clubs, via Breed Council to take some positive action to react sensibly, and in a measured fashion, to what we had heard. All those present were encouraged to make sure that their views were heard by their local Clubs. These issues potentially affect us all and it is important that a plan of attack is put in place which is rigorous and which meets the requirements of the breed.
The fact that the whole meeting was conducted in such a business-like fashion, with no ill-will demonstrated during the open debate confirmed to me that the breed is coming together. Talks of rifts and strife help no-one and I am glad that we saw no evidence of it on the day.