I have yet to talk to a neuro that can tell me whether or not to breed a dog unless it is showing symptoms..
I cannot quite understand what you mean here, can you clarify?
I bred two cavaliers that had been MRI'd. I followed the SM protocol and got 2 pups WITH symptomatic SM. .
There sometimes appears to be the SM guidelines as approved by the neurologists at the International Conference in 2006, and a watered down version that is used by breeders.
The breeders version will involve using cavaliers that were MRI scanned before they are 2.5 years ( Grade C, if no SM ) and mating them to unscanned dogs ( Grade D, but only if really not showing symptoms )THIS IS NOT TO THE SM PROTOCOL.
Then there is the two underage dogs ( Grade C mated to Grade C )THIS IS NOT TO THE SM PROTOCOL
I'm not suggesting that this is the case with your breeding, you may be one of those that did a Grade A x Grade A mating and was just very unlucky.
It would certainly help this discussion if you would tell us if the MRI'd cavaliers that produced your 2 pups with symptomatic SM were both scanned, and bred, after the age of 2.5 years?
There aren't enough answers for me to fully jump on the MRI bandwagon. I am afraid that it is going to give people a false sense of security. .
You underestimate people.
Ironically, I know of a woman who had a bitch get an MVD murmur-- dx by echo at age 2. She just turned 11 1/2 and her murmur just got upgraded to a grade III. I just wanted to mention this because I would panic if I had a young dog get a murmur.
There are always exceptions and we could all quote them in a way that will suggest that testing is useless.
Any health testing scheme is a blunt instrument but until we have the magic gene tests they are all we have to protect the breed.
I have read that the average time from first sign of heart murmur to CHF is four years and that has roughly been my experience.
I am sure that many people will tell me about long lived, early onset MVD, dogs such as you have mentioned above. It is less likely that breeders will talk about the other end of the spectrum, the young dogs that died within a few weeks of murmur being detected.