A client is being evaluated for a possible myocardial infarc…

A client is being evaluated for a possible myocardial infarction, but he is not sure when the pain started because he has a history of gastroesophageal reflux. He has had intermittent chest pain, with some episodes of dizziness and fatigue, over the last week. Which diagnostic result will be most helpful in determining whether the client has suffered cardiac injury?