Cavaliers King Charles Spaniels and Heart Disease: Where have we been and where are we going?

Simon Swift , MA, VetMB, CertSAC, MRCVS
Hon Member

Presented at the Annual General Meeting 2009

The initial scheme was set up by Dr Peter Darke at the invitation of the Club in the late 1980’s and I joined the scheme in 1990. I have certified about 2,750 dogs. In the early 1990’s Dr James Wood of the Animal Health Trust in Newmarket analysed the database. This suggested that heart disease was the leading cause of death in Cavaliers (60% according to a survey reported by owners, compared to 11% due to cancer, the next most common). It also suggested that the disease was strongly inherited probably in a polygenic manner and that by breeding from older clear dogs, the disease incidence could be reduced. This research supported many studies that showed that the disease is more common in Cavaliers than any other breed. The mean age of dogs with murmur in Sweden is 7.5 years and many of these die about 3 years later. In the UK and the USA, about ½ of all Cavaliers have a murmur by the time they are 5 years old. There is no evidence that pet cavaliers are treated any differently than any other small breed dog, so the difference is genetic.

The database suggests that 50% of Cavaliers develop murmurs at a later age than the 5 years suggested earlier. However this difference is probably a reflection of the selection of dogs presented i.e. the sample tested is not random but rather selected to be brought to shows as they are thought to be murmur free. In addition, very few older dogs are presented so a small number of dogs can alter the statistics significantly.

Dr Leonnard Swennsen, a Swedish geneticist, developed the breeding guidelines suggesting that dogs used from breeding should be over 5 years before they develop a murmur or their parents should be over 5 years of age before they develop a murmur.

This now contains over 8667 entries and, to date, both GP vets and cardiologists can certify. When the scheme was initially set up, too few cardiologists were present in the UK. However, most of the analysis is from cardiologists as their results are more consistent. Many dogs on the database are free of murmurs and the numbers with murmurs declines as the grade (loudness) increases. Comparing 1991 and 2009, most dogs under 5 were murmur free however most dogs over 6 had a murmur. There was little difference between the two years suggesting little change in incidence over the 18 years. In the GP vet tested dogs a similar change was found but in the 8 - 9 year old.

Disappointingly few dogs are presented at 5 - 6 years of age which is the time that testing is critical according to the breeding programme. A similar scheme is present in Sweden but too few generations have passed through the scheme for evaluation to be useful.

Future Research
The LUPA project is collecting blood from Cavaliers to compare the DNA and try to determine which genes are active in the disease which may help identify which genes may be involved in the disease. Blood has been collected from older dogs that are murmur free and young dogs with murmurs.

The Edinburgh team are looking at leucine rich protein in the mitral valve and comparing it to cornea and cartilage to see if it is specific for the valve. In addition, there have been attempts to use cheek swabs to extract DNA.

Novel Treatments
Spironolactone has recently been licensed in veterinary medicine. It is a mild diuretic that acts by inhibiting a natural hormone called aldosterone that is harmful in the setting of congestive cardiac failure. Although there is little effect clinically, trials suggest that dogs receiving this drug live longer than those receiving a placebo plus standard therapy.

The QUEST study has now been publish which compared Vetmedin to Fortekor (an ACE inhibitor) in dogs with congestive heart failure and showed increased survival (nearly 2 times) in the Vetmedin group. This suggested that if you could only afford one agent, it should be Vetmedin once your dog develops heart failure.

A new Vetmedin-like drug called Levosimendan will shortly be launched in the UK.

Passionate Productions
I was interviewed at the Liverpool Small Animal Teaching Hospital and asked to provide a Cavalier owner for them to film. They were very well informed, knowing the answers to most of the questions they asked. They spent a morning at the Hospital and filmed the Cavalier owner and my interview. They recorded a total of about 23 minutes with me of which about 30 seconds were used. Any positive comments I made about the clubs testing programme and breeding scheme were cut. I was very frustrated by the missed opportunity the film presented. I had hoped that the programme would suggest that people bought their cavalier puppies from accredited breeders who were members of the Club as a testing programme was in place. Sadly that was not the impression left by the programme.

As a result of the programme, the Kennel Club has become much more active and is co-opting the heart schemes into the existing BVA/KC health schemes so that it becomes part of the accredited breeders’ scheme. The scheme will become cardiologist only testing so that there will be a cost implication for owners who want to have their dogs tested. 5 years is the crucial age to have dogs tested and auscultation of the murmur will be sufficient. With time, we may be able to increase this age when dogs must be free of a murmur to 6 years. My hope is that the opportunities presented by this programme will be grasped firmly by the Club to progress with the scheme. Heart disease remains the most common cause of fatal disease in Cavaliers and deserves our full attention.
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