How to Read an ECG for Beginners (Simple Step-by-Step Guide)
If you’re new to ECG interpretation, the easiest way is to follow five core steps: Rate, Rhythm, P Waves, PR Interval, and QRS Complex. These basic checkpoints help you quickly understand what’s happening in the heart’s electrical activity.
1. Determine the Heart Rate
Heart rate is calculated using the R-R interval—the distance between two R waves.
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Regular rhythms: Count the number of large boxes between two R waves, then divide 300 by that number.
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Irregular rhythms: Count how many R waves appear in a 6-second strip (30 large boxes) and multiply by 10 for the average rate.
2. Check Whether the Rhythm Is Regular
A simple trick:
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Take a piece of paper and mark the position of two consecutive R waves.
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Slide the paper along the ECG strip.
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If the marked gaps match other R-R intervals, the rhythm is regular. If not, it's irregular.
3. Identify the P Waves
Look at atrial activity:
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Normal: P waves should be present, upright, and consistent before each QRS complex.
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Abnormal:
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No P waves: Look for a “sawtooth” baseline (atrial flutter).
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Chaotic baseline: May indicate atrial fibrillation.
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4. Measure the PR Interval
The PR interval runs from the start of the P wave to the start of the QRS complex.
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Normal PR interval: 0.10–0.20 seconds (about 3–5 small boxes).
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Long or short intervals may point to conduction delays or heart block.
5. Evaluate the QRS Complex
The QRS complex shows ventricular contraction.
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Normal duration: < 0.12 seconds (less than three small boxes).
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What to look for:
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Sharp, narrow shape = usually normal
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Wide QRS = possible bundle branch block or ventricular rhythm
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Essential ECG Basics for Beginners
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Box timing:
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1 small box = 0.04 seconds
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1 large box = 0.20 seconds
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Wave meanings:
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P wave: atrial contraction
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QRS complex: ventricular contraction
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T wave: ventricular relaxation
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J-point:
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The junction between QRS and the ST segment
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Important for detecting ischemia or early signs of heart attack
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