There are four stages to the progression of this condition: Stage 1: Although the condition has taken hold and begun to deteriorate your dog's heart there may not be any noticeable symptoms. Stage 2: In this stage symptoms such as shortness of breath, panting and lethargy will begin to appear, especially when your pup is playing or exercising. Stage 3: Now your dog's symptoms will begin to become more obvious. Stage 4: During this final stage of congestive heart failure, your dog's breathing will become difficult even when they are resting. Fluid will likely begin to accumulate in various parts of your pup's body, leading to swollen legs or abdomen, which will make walking difficult and may lead to vomiting. When your dog is in the end stages of congestive heart disease you will notice that your pup has difficulty breathing even while resting, experiences frequent bouts of coughing, develops bluish-grey color gums, possibly faints when standing and will become reluctant to walk. Your dog will also have difficulties sleeping or resting on their side. Many dogs reach a stage where they prefer to sit upright rather than lay down since an upright position can help to ease breathing. Sadly, the symptoms of late stage congestive heart failure cannot be well managed in dogs, and once this stage is reached you may wish to speak with your veterinarian about humane euthanasia.