The main heart problems that a dog may experience are failure and hypertension. In both cases the causes are not fully clear but could be due to either a genetic predisposition or a natural life course (unless genetic, they almost always occur in older dogs). Specific diets to treat a dog with heart problems, should be agreed upon with one's veterinarian of choice. Supplements, on the other hand, can be used to maintain proper functioning of the circulatory system whether you have a puppy or an adult dog.