A useful 7 step approach to ECG rhythm analysis is described.
- Tachycardia or bradycardia?
- Normal rate is 60-100/min.
2. Pattern of QRS complexes
- Regular or irregular?
- If irregular is it regularly irregular or irregularly irregular?
3. QRS morphology
- Narrow complex — sinus, atrial or junctional origin.
- Wide complex — ventricular origin, or supraventricular with aberrant conduction.
4. P waves
- Absent — sinus arrest, atrial fibrillation
- Present — morphology and PR interval may suggest sinus, atrial, junctional or even retrograde from the ventricles.
5. Relationship between P waves and QRS complexes
- AV association (may be difficult to distinguish from isorhythmic dissociation)
- AV dissociation
- complete — atrial and ventricular activity is always independent.
- incomplete — intermittent capture.
6. Onset and termination
- Abrupt — suggests re-entrant process.
- Gradual — suggests increased automaticity.
7. Response to vagal manoeuvres
- Sinus tachycardia, ectopic atrial tachydysrhythmia — gradual slowing during the vagal manoeuvre, but resumes on cessation.
- AVNRT or AVRT — abrupt termination or no response.
- Atrial fibrillation and atrial flutter — gradual slowing during the manoeuvre.
- VT — no response.
Follow links below for examples of individual rhythms.
Narrow Complex (Supraventricular) Tachycardias
Broad Complex Tachycardias
- Ventricular tachycardia
- Antidromic atrioventricular re-entry tachycardia (AVRT).
- Any regular supraventricular tachycardia with aberrant conduction — e.g. due to bundle branch block, rate-related aberrancy.
All regular BCTs should be considered to be VT until proven otherwise.
P waves present
Not every P wave is followed by a QRS complex (= AV node dysfunction)
P waves absent
For escape rhythms to occur there must be a failure of sinus node impulse generation or transmission by the AV node.
- Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
- Hampton, JR. The ECG In Practice, 6e
- Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric, 6e
- Wagner, GS. Marriott’s Practical Electrocardiography 12e
- Chan, TC. ECG in Emergency Medicine and Acute Care
- Mattu, A. ECG’s for the Emergency Physician
LITFL Further Reading
- ECG BASICS — Waves, Intervals, Segments and Clinical Interpretation
- ECG A to Z by diagnosis –alphabetical diagnostic approach to the ECG
- ECG CLINICAL CASES — ECG’s placed in clinical context with a challenging Q&A approach
- 100 ECG Quiz — Self-assessment tool for examination practice
- ECG Reference SITES and BOOKS — the best of the rest
- LITFL ECG IMAGE Database — Searchable database of LITFL ECG’s
- ECG and Cardiology Eponymous Syndromes — Cheats guide to eponymous emancipation
- ECG Exam Template — a framework for answering ECG exam questions.