I have a TVD affected bitch - had clear auscultation from our Vet, clear auscultation from cardiologist, failed the echo. Had one litter between her auscultation and the echo - all pups cleared an echo at 12 months.

The board certified veterinary cardiologist that does my echoes has quoted that 20% of dogs that pass auscultation go on to have TVD diagnosed during the echo.