It is possible dehydration caused the abnormal ekg but I am with Spade. Question your doctor about what it means and find out if it warrants an appointment with a cardiologist. From what I understand EKG machines can give false positive readings but a possible heart attack is something in my opinion that needs to be investigated. Take care and keep us posted on how you are doing.
My understanding is that " inferior infarction" is a medical term for "heart attack". What did your doctor tell you? Are you following up with a cardiologist?