For the Nutritional Management of Dogs with Heart Disease. Heart disease and heart failure are conditions frequently found in aging dogs. Typically, heart disease can cause the heart to become enlarged, leading to fluid retention and discomfort for your dog. Fluid retention is in response to a less efficient heart muscle and can be made a bigger problem with foods that are high in sodium. Prescription Diet h/d Canine dog food is formulated to help manage dogs with the symptoms of heart disease and related fluid retention. The nutritional formulation of Prescription Diet h/d may also be useful for pets with a variety of conditions.