I wonder if undetected arrythmia isn't implicated in many cases of sudden cardiac death. A member of my family died suddenly of a Heart Attack, but there were warning signs of arrythmia-- an abnormal heart rate(that didn't repeat when tested once in the hospital.) My advice in the case of any such abnormal rhythym is to get a portable device such as a holter monitor to wear for a sufficient length of time to determine if there is an irregular heart beat that occurs intermitently. Then if there is, you have the information that you need to make better decisions regarding devices, drugs, etc. to treat the underlying cause.