When a dog has an enlarged heart the dog may experience symptoms such as, Episodes of weakness or collapse, Fainting, loss of consciousness, Difficulty in breathing, rapid and excessive breathing, shortness of breath, Coughing, Lethargy, Unwillingness to move, Exercise intolerance and Anorexia which is a loss of appetite.
If you notice any of those symptoms in your dog suddenly or gradually occurring the dog should be checked out by a vet to see for sure if they have an enlarged heart.
The only way to know for sure if the dog does have an enlarged heart to actually have the dog examined and X ray done so if possible take the dog to the vet.
The cause of a dog to have an enlarged heart is valvular insufficiency.
Disease of the dogs heart muscle also known as cardiomyopathy, irregularities of rhythm, and narrowing of some of the major blood vessels can also an enlarged heart.
The dog may still live a long normal life with an enlarged heart but sometimes a dogs enlarged heart does sadly shorten the dogs life.