HEART NEWS: What's New and Where Next?
by Bruce Cattanach
Boxer '95
(pages 64-67)

In last years Boxer '94 I reported that a total of 1750 Boxers had been heart tested for aortic stenosis (AS). Now, one year later, the number is almost 2188, an increase of 438. This does not quite match the 1994 record of about 500 but exceeds the totals of all earlier years. Breeder support for the heart testing scheme is clearly holding up well.

The most major issue this year has been the standardisation of the grading, and this has obviously had to be dealt with exclusively by the cardiologists. The start was made at the Scottish Boxer Club's Spring show when three cardiologists independently graded all 48 dogs presented. The average scores were similar, but variation in the scoring for some individual dogs was evident. The latter discovery clearly disappointed the cardiologists. I believe the findings were discussed at a veterinary cardiovascular group meeting shortly thereafter, and I suspect that as a result the rigorousness and time taken for grading has now increased. Perhaps also associated with this, the term "localised" has now joined our vocabulary, meaning that some murmurs can only be heard if the stethoscope is placed precisely over the affected site. Thus, a dog might be graded 2 or 0 according to how carefully it is examined. However, the risks of this happening must be declining. From my records, the 1995 scoring by those cardiologists that regularly officiate at shows is much more consistent than ever before.

An observation of particular concern to me at the Scottish was a seeming poor correlation between parent and progeny scores. This principally involved a single family group involving one stud dog and several bitches, all of which had scores of either 0 or 1. The problem was resolved on the initiative of the stud dog owner concerned. Noting for herself that the dog's progeny were not as good as might have been expected, she courageously took the dog to Edinburgh for re-examination. It was then shown that the dog was not murmur-free, as had previously been found, but had a Grade 3 murmur and a high Doppler blood velocity. The dog has now been withdrawn from stud. But what had gone wrong? Could the murmur have been missed in the initial testing? Or could the stenosis have progressed (worsened) with age/time, as it has been shown to do in at least one other breed?

To find the answer, Anne French at Edinburgh has been recalling Boxers that have previously been examined both by stethoscope and by Doppler. Full details of the results are not available but Miss Fuentes tells me the picture is that AS does not generally progress in Boxers, but that it can in those few dogs in which the stenosis (narrowing) has occurred within the aortic valve itself, as opposed to above or below. We therefore have a flaw in our single test system, but at least this is not thought to be large enough that regular annual testing is necessary.

Perhaps the most exciting cardiology event of the year was the evaluation of a phonocardiograph for assessing the heart murmurs. Developed by Swedish veterinary cardiologist, Clarence Kvart, the instrument was brought to Edinburgh to apply to a group of Boxers that had been previously tested by stethoscope and known to have various grades of heart murmurs. The dogs were first independently retested by three cardiologists using the stethoscope, and then Doppler blood velocities were obtained. The instrument behaved brilliantly, proving to sensitive enough to quantitate both the amplitude and duration of even the most minor murmurs, and it could achieve this on the basis of recording only a few heart beats. A specialist is still needed to operate the phonocardiograph, but it may be the instrument of the future for objectively grading murmurs. As a related point of interest, the consistency of stethoscopic scoring among the three cardiologists on this occasion was excellent.

At breeder level, the most progressive action of the year was the decision by Breed Council to adopt a uniform system for describing the heart status of dogs. Up until now, all of us have had difficulty with this. Wording such as "Heart tested clear", and "Free of all known heart defects" have appeared in advertisements, but most such statements are either misleading, ambiguous or even erroneous. With Miss Fuentes approval I put to Breed Council that we present heart scores, like hip scores, using the accepted terminology employed in the Heart Lists. Thus dogs can be described as Heart Score 0, or Heart Score 1, when they have been graded 0 or 1 by cardiologists, and the D for the Doppler pass can be similarly employed. This system simply presents the exact facts. It is not ambiguous and cannot be misinterpreted. I hope everyone will use it.

Finally, we come to the actual breeding results. These are presented in Table 1. It may be noted that unlike the last presentation of the results in Boxer Quarterly I have reinstated the data from dogs with higher grade murmurs. This seemed just about worthwhile since with a reshuffling of parental scores on retesting some further information had become available. Few new dogs have come into this category and the amount of information from this group thankfully remains sparse.

Table 1 Analysis of Breeding Results (To December 1995)
Parental Grades	Grades of Progeny
Sire Dam	0	1	0/1	2	3	4 - 6	Total Progeny
0 x 0	52% (48)	34% (32)	86% (80)	12% (11)	2% (2)	0	93
0 x 1 1x 0	33% (22) 44% (51)	43% (29) 34% (39)	76% (51) 78% (90)	19% (13) 20% (24)	5% (3) 2% (2)	0 0	67 116
1 x 1	29% (22)	47% (35)	76% (57)	17% (13)	3% (2)	4% (3)	75
0 x 2 2 x 0	31% (16) 34% (18)	39% (20) 39% (21)	64% (30) 64% (22)	28% (14) 23% (12)	2% (1) 4% (2)	0 0	51 53
1 x2 2 x 1	30% (14) 26% (9)	34% (16) 38% (13)	64% (30) 64% (22)	23% (11) 21% (7)	6% (3) 15% (5)	6% (3) 0	47 34
2 x 2	50% (7)	36% (5)	86% (12)	14% (2)	0	0	14
0/1 x 3 3 x 0/1	30% (8)	18% (5)	48% (13)	37% (10)	15% (4)	0	27
2 x 3 3 x 2	10% (1)	20% (2)	30% (3)	70% (7)	0	0	10

It can be seen that despite all the difficulties experienced with the grading system over the years, a very clear trend in the frequency of progeny with/without murmurs, and with murmurs of different grades, is evident. The best parents have the best record for producing the best progeny. The hereditary basis of the condition is easy to see. I find this remarkable especially, may I repeat, in view of all the problems with the grading.

A disappointing but not unexpected finding is that at least some of the grade 1 murmurs must reflect a level of AS, and are not just innocent "flow" murmurs as has been hoped. This was of course also a conclusion from the single post mortem study on a dog with a grade 1 murmur described in Boxer'94.

A further observation that can be made is that there is little difference between the results from 0 x 2 and 2 x 0 matings or between 1 x 2 and 2 x 1 matings. This might seem just as should be expected, except for the fact that most grade 2 sires have "passed" on Doppler, while most grade 2 dams have not been Dopplered at all. It would seem that a Doppler pass cannot be equated to murmur-free (HS 0) and probably is not even equivalent to a grade 1 (HS 1). This will surely reflect the fact that the murmurs detected with the stethoscope (or phonocardiograph) identifies levels of abnormality, while the Doppler only identifies those abnormalities that lead to functional changes.

I would like to finish on the most critical question of all. Has all this testing improved the heart status of the breed? I'm afraid that my answer at this time is, "No. Not yet"; and I don't see how it can for a while. There are some positive signs, however. There is the Edinburgh report that the incidence of Boxers being referred to the veterinary schools has reduced. And there also appears to have been some minor change in the incidence of murmurs across the breed. This is shown in Table 2 which gives the results over the last 3 years, the period over which the grading has been relatively stable. Some improvement is suggested.

Table 2 Murmur Grades of Dogs Tested at Shows
Grades
Year	0	1	2	3	4 - 6	Total Number
1993	19%	40%	32%	9%	1%	390
1994	24%	34%	32%	8%	2%	504
1995*	26%	35%	32%	5%	2%	363

*excluding the December 1995 S. Western Boxer Club's testing at Langford

But, what improvement could have been expected? Not much. We still have much the same breeding stock as 3 to 5 years ago and, while most of our major stud dogs have been tested, there is still an enormous pool of untested bitches. Rather magnificently, several significant young stud dogs have been withdrawn from stud on being found to have louder heart murmurs, although the Doppler has let others through. But there is little evidence of selection against bitches with louder murmurs, which I accept is understandable in view of the high murmur incidence. It will take time to have a turnover of the generations which will allow new and hopefully better breeding stock to come through. We desperately need a number of top show males that are free of heart murmurs. Use of these at stud would quickly change the heart status of the breed and so allow more scope for the selection among our bitch population.

Looking back on the 5 years of heart testing I think it would be fair to say that Boxer breeders have had a rough time. They have done their best, truly impressing the cardiologists. But, the ground rules have kept changing. And there has been understandable levels of despair when it is seen that a dog can get a grade 0 one day and then grade 3 another, or consistently get grade 2s in a series of tests and then finally manage a grade 0, so to become rated as one of the best breeding prospects (which will not be true). Surely, there is a level of disillusionment among even the positively-minded breeders. But the point must also be made that such cases are rare. They are exceptions. By and large the system is working well. Otherwise the analysis of the breeding results would have shown nothing. But they do.

At the start of all the effort on hearts I suspect we were all a bit naive; and dare I include the cardiologists here. Despite arguments over Doppler versus stethoscope, there was general faith that the scoring system for murmurs was sound and meaningful. But the past 5 years have been a learning experience, not only for us, but also for cardiologists. Hence, the changes. Hopefully, all is more regulated and standardised now, even if this has meant further tightening up in the grading. Hopefully, too, any remaining problems will soon be resolved. In the next 5 years, if we can stick with it, we will see whether the knowledge gained by the cardiologists can effectively be put into practice by breeders, and a new generation of Boxers with sounder hearts can be created.