ST Segment Elevation and Depression

By behereaxum

Summary

Reading a twelve-lead ECG. To catch a heart attack early, you must master one small but critical stretch of the trace.

Chapters

  1. Reading a twelve-lead ECG. To catch (0s)
  2. That stretch is the ST segment, (8s)
  3. In ST elevation, the segment lifts (24s)
  4. In ST depression, the segment sags (38s)
  5. So compare the ST segment to (50s)

Transcript

Reading a twelve-lead ECG. To catch a heart attack early, you must master one small but critical stretch of the trace. That stretch is the ST segment, the flat line connecting the end of the S wave to the start of the T wave. It marks the brief pause after the ventricles have fully depolarised. Normally it sits level with the baseline, the reference line you measure everything against. In ST elevation, the segment lifts above the baseline instead of staying flat. It's a red flag for a full-thickness heart attack, a STEMI, where a coronary artery is completely blocked. Spot it in two or more neighbouring leads and act fast. In ST depression, the segment sags below the baseline instead of resting on it. This often signals reduced blood flow, or ischaemia, straining the heart muscle when it demands more oxygen than it's getting. So compare the ST segment to the baseline every time. Up means elevation, down means depression, and knowing the difference saves lives.