ECG Basics · Lesson 13 · Leads, axis and conduction

A repeatable nine-step read

Most missed findings come from jumping to the obvious one. Read in the same order every time and name what you see at each step.

1. Check the basics. Paper speed, gain and calibration; correct electrode placement; patient-level details are outside this simulator.
2. Rate. Atrial and ventricular, separately if they differ. (Lesson 6)
3. Rhythm and regularity. Regular, regularly irregular, irregularly irregular. (Lesson 7)
4. P waves. Present? Upright in II? Same shape each time? One before every QRS, and a QRS after every P?
5. PR interval. 120–200 ms and constant? Lengthening? No relationship? (Lesson 10)
6. QRS. Width (narrow vs ≥ 120 ms), shape in V1 and V6, R-wave progression, pathological Q waves. (Lesson 11)
7. Axis. Leads I and aVF, then refine. (Lesson 9)
8. ST segments and T waves. Elevation or depression by territory, reciprocal change, T inversion. (Lesson 12)
9. QT/QTc. Corrected for rate. (Lesson 5)

Then put it together in one line, compare with a previous ECG if there is one, and relate it to the clinical question.

Practise with hidden answers

In the live simulator, the Hide answers button under the monitor removes the rhythm name and settings from the screen while the trace keeps running. Pick a rhythm, hide the answers, and read it in the nine steps before revealing.

References

1. Mason JW, Hancock EW, Gettes LS, et al. Recommendations for the standardization and interpretation of the electrocardiogram, Part II: electrocardiography diagnostic statement list. Circulation 2007;115:1325–1332.
2. Kligfield P, et al. Recommendations for the standardization and interpretation of the electrocardiogram, Part I: the electrocardiogram and its technology. Circulation 2007;115:1306–1324.