Final answer:
The ST segment elevation is the earliest EKG sign of an infarct.
Step-by-step explanation:
An elevation of the ST segment above baseline is often seen in patients with an acute MI (Myocardial Infarction) on an EKG. The ST segment represents the time interval between ventricular depolarization and repolarization, and its elevation can indicate ischemia or injury to the heart muscle. This is considered as the earliest EKG sign of an infarct.