The loss of appetite is common in animals with heart failure but can also be caused by a variety of other medical problems. (vetmed.tufts.edu)
It also tends to develop in older pets with other medical problems. (cuvs.org)
If your pet is on a prescription diet for other medical problems (diabetes, bladder stones, kidney disease, etc) you should ask your veterinarian before feeding your dog cashews. (dogs.lovetoknow.com)