It has often been said that our dogs are "all heart" and fortunately most of these hearts are working beautifully, but we do occasionally examine patients whose hearts are not quite working up to par. In fact, according to the American veterinary medical association, about 1 in 10 dogs nationally, or about 4.2 million dogs have some form of heart disease. This disease can be a heart valve disease which we see more commonly in the smaller breeds, or be a heart muscle disease, called cardiomyopathy, which we see more commonly in the large and giant breeds.