Is it possible to determine that you're going to have a heart attack by doing ecg?

Usually not: A resting ECG will usually tell if you are currently having or have had a heart attack in the past. It will not usually predict future risk. A stress ECG can predict the risk of a future heart attack. This predictive power is increased by adding simultaneous nuclear imaging to the stress test.

No: Can show it is happening, or suggest it has happened, but is not predictive generally.