First, thanks for visiting MedHelp.org. Mitral valve problems are rarely congenital, but usually acquired. If you are concerned about whether or not your dog suffers from this condition, an ultrasound would provide you with the answer.
Not just designer dogs, but any small breed dog with dental issues can develop mitral valve insufficiency. Your best prevention is to maintain good dental health for your dog.
Best of luck to you and your dog!
I just want to clarify something with you...a cavachon is a Cavalier and Bichon cross, correct?
Yearly (and after about 5 or 6 years every 6 months) your veterinarian can simply listen to the dogs heart and tell a great deal. If a murmur is heard (the main early symptom) then an ultrasound can tell SO much more.
Like Dr. Dew said, blood infections typically coming from dental disease is a major cause of MI.
If you are concerned (and I would not be overly so if he is fine now), then just be sure your veterinarian listens carefully each year!!
Yes, a cavachon is a mix between a Cavalier King Charles Spaniel, and a Brichon Frise, and may I say............. adorable.