A recent announcement by the FDA states that there may be a possible link between certain pet foods and Dilated Cardiomyopathy (DCM) in dogs. The FDA still does not know how the foods may cause the heart disease but they have received reported data and have shared this data with the public (see first link below); the investigation is still ongoing.
The FDA has identified several brands for having the most reported cases. Many of the foods are dry food, more than 90% of the foods were "grain free" and 93% had peas and/or lentils. If you are thinking of changing your pet's food due to this concern, you may want to avoid dry foods, choose food without peas or lentil and avoiding the label that states grain free.
Grain in pet food is not necessarily bad. Grain gained a bad rap as being a common allergen extrapolated from gluten allergies in people. A purina article states, "The reality is that true food allergies are extremely low in dogs and cats, and the offending substances usually are not grains.” In fact, grains are a good source of sub nutrients and are beneficial for most dogs. That means the chance of your dog having a grain allergy is small."
Signs of Dilated Cardiomyopathy may include coughing, labored breathing, exercise intolerance, lethargy, weight loss and poor appetite.
So what should I feed my dog? See second link below.