Which option best describes ST segment changes to assess for ischemia?

• A. Rhythm regularity
• B. Premature beats
• C. Baseline variability
• D. Elevated or depressed ST segments

Answer: (D)

Ischemia shows up on the ECG as changes in the ST segment. The ST segment is the flat portion between the end of the QRS and the start of the T wave, representing a moment when the ventricles are electrically plateaued. When there isn’t enough blood flow to the heart muscle, currents of injury shift the ST segment away from the baseline. If the injury is transmurally severe, you’ll see ST segment elevation; if the ischemia is subendocardial or demand-related, you’ll often see ST segment depression. These ST changes are a primary sign clinicians look for when assessing for ischemia.

So, the description of elevated or depressed ST segments is the best indicator of ischemia on ECG. Rhythm regularity, premature beats, and baseline variability are broader rhythm or artifact considerations and don’t specifically identify ischemia in the same targeted way.