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Step 1: Rate and Rhythm#
Calculate the heart rate. Regular rhythm at 60-100 bpm = sinus rhythm. Above 100 = tachycardia, below 60 = bradycardia.
Step 2: Axis#
Look at leads I and aVF. If both are positive = normal axis.
Step 3: P Waves#
Are P waves present before every QRS? Are they normal morphology?
Step 4: PR Interval#
Normal: 0.12-0.20 seconds. Short PR = WPW. Prolonged = first-degree AV block.
Step 5: QRS Duration#
Normal < 0.12s. Wide QRS = bundle branch block, hyperkalemia, or ventricular rhythm.
Step 6: ST Segment#
ST elevation = STEMI (or pericarditis). ST depression = ischemia or digoxin effect.
Step 7: T Waves#
Peaked T waves = hyperkalemia. Inverted T waves = ischemia.
Step 8: QT Interval#
Corrected QT > 440ms in men or > 460ms in women = prolonged. Risk of torsades de pointes.
Step 9: U Waves#
Prominent U waves = hypokalemia or hypothyroidism.
Step 10: Put It All Together#
Match the combination to the diagnosis. UPSC CMS favourite combinations: AF with RVR, LBBB, STEMI patterns, and hyperkalemia ECG changes.
Common ECG Diagnoses in UPSC CMS#
| Condition | Key Finding |
|---|---|
| STEMI | ST elevation in contiguous leads |
| NSTEMI | ST depression + T wave inversion |
| AF | Irregularly irregular, no P waves |
| VF | Chaotic waveform, no QRS |
| Hyperkalemia | Peaked T, wide QRS |
Study Tips#
Practice 50 ECGs daily for 2 weeks using free online resources. Memorize the criteria for LVH, RVH, and the criteria for STEMI equivalents.
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References & further reading
Every clinical claim in this article is anchored to a primary source. Click through to verify, and use the same habit in your revision.
Revision history
- 19 September 2026 — Initial publication
Frequently asked questions
How many ECG questions come in UPSC CMS?
Typically 3-5 ECG-based questions appear in UPSC CMS Paper I and II combined. They test rate, rhythm, axis, and specific diagnoses like STEMI, AF, and hyperkalemia.
Is ECG interpretation important for NEET PG too?
Yes, NEET PG also includes 2-4 ECG interpretation questions. The same framework applies to both exams — mastering it once covers both.
What is the best resource for ECG learning?
Dubin's Rapid Interpretation of EKGs for basics, plus free online ECG simulators for practice. Our AI tutor can explain any ECG strip interactively.
Related reading
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