What does a normal ekg look like versus an abnormal one from an undetected heart attack ?

Need to see it: Silent (or misdiagnosed) heart attacks may be as common as 30-40% of all heart attacks, detected when an ECG is done that demonstrates typical or suspicious changes compared to a normal or prior ecg. Heart attacks can occur in different locations, and may not involve the entire thickness of the heart wall, so the abnormal ECG can vary quite a bit, so a simple verbal description is not possible.

A normal EKG: Because some areas of the heart are electrically silent, one can have a full blown heart attack with an entirely normal ekg. When the ekg is destined to become abnormal, it often lags, not showing changes early on: hence the need for "serial ekgs" (done daily). The adage "treat the patient, not the ekg" hasn't changed over the years.