Liz Buchanan BVSc MRCVS
Hello - I'm afraid I'm not sure what the white at the back of the throat is, but getting out of breath easily is a warning sign, especially with existing heart disease and it may be important to rule out fluid / odema amongst other things, so we would recommend an early vet appointnent. Perhaps if you call and mention what it's for (breathlessness), they may be happy to triage the case (that is, assign a priority order as to how quickly your dog needs to be seen). It does sound as if there is high potential for this case to be an emergency. Possibilities may include a foreign body, odema, worsening heart disease, thickening saliva, dental disease, cancer, lungworm, burns to the throat or other causes of pain (causing panting). I hope that they can get to the bottom of it for you - tests may well be needed. Please would you let us know how you get on?