Cardiac disease affects many breeds of dogs, but some more than most. Symptoms of cardiac disease include:
– a swollen abdomen from fluid buildup in the lungs
– fainting because of blocked blood flow
– change in tongue and gum color to a bluish grey because of poor oxygen
– weight loss as your dog loses her ability to store fat
According to the O.F.F.A. here are the 10 most likely breeds to suffer from cardiac disease:

References
1. Your Pure Bred Puppy 2. Small Dog Breed SDB 3. AKC 4. Wikimedia 5. Wall Pappers9 6. Vet Street 7. Dog Time 8. Dog Wall Papers 9. Britannica 10. Dog Breed Info