How to read an ECG rhythm strip
Other platforms explain it with text and video. In VMS you practice it on the patient.
Every rhythm strip is read with the same five questions. Answer them in order and the rhythm usually names itself.
Step by step
Know the grid
At standard speed, one small box is 0.04 seconds and one large box is 0.20 seconds. [1]
Rate
Count the QRS complexes in a 6-second strip and multiply by 10, or divide 300 by the number of large boxes between two beats. [1]
Rhythm
Are the beats evenly spaced? Regular, regularly irregular or irregularly irregular. [1]
P waves
Is there one P wave before every QRS, and do they all look the same? [1]
PR interval
Normal 0.12 to 0.20 seconds (3 to 5 small boxes). Longer suggests a heart block. [2]
QRS width
Normal under 0.12 seconds (3 small boxes). Wide suggests a ventricular origin or a bundle branch block. [2]
Name it and look at the patient
Put the answers together, name the rhythm, and check the pulse and the patient before acting. [1]
Common errors
- Naming the rhythm before going through the steps.
- Treating the monitor instead of the patient.
- Missing an irregularly irregular rhythm (atrial fibrillation).
Practice it in VMS
In VMS you do this on the patient, not on paper: every step goes on the checklist with a score, and in Teach mode Blocky tells you what comes next.
VMS cases that train this skill
Sources
Facts and steps follow AAMC Core Entrustable Professional Activities (Core EPAs); NCCPA PANCE Content Blueprint. VMS is not affiliated with these organizations. Updated: 2026-10-11.