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ECG interpretation for beginners - 1

ECG interpretation for beginners - 1. Paul Williams Cardiology Specialist Registrar. How to read ECGs?. 1) Have a system! 2) See lots – pattern recognition. Absolute basics. A system. Quality of ECG? Rate Rhythm Axis P wave PR interval QRS duration QRS morphology Abnormal Q waves

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ECG interpretation for beginners - 1

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  1. ECG interpretation for beginners - 1 Paul Williams Cardiology Specialist Registrar

  2. How to read ECGs? 1) Have a system! 2) See lots – pattern recognition

  3. Absolute basics

  4. A system • Quality of ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval

  5. The normal ECG

  6. Check quality of ECG • Patient name • Date of ECG • ? interference • 12 leads • Rhythm strip (II or V1) at bottom • Scale: • 25mm/s horizontal • 10mm/mV vertical • Little square=0.04s; big square=0.2s

  7. A system • Quality of ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval

  8. Rate • Computer calculated rate usually correct • Still need to manually calculate! • 300/RR interval in big squares • If irregular – average 5 • Rate is either: • Normal • Bradycardia • Tachycardia

  9. Rate

  10. Rhythm • Different to rate! • First thing to ask: is there a clear P wave before each QRS? (lead II) • Regular vs irregular (paper trick….) • Tachyarrhythmiasvsbradyarrhythmias (separate talk) • Commonest rhythm is SR (ie. normal) • Commonest arrhythmia is AF

  11. Axis Coronal/frontal plane Normal axis is about 60 degrees LAD = axis < -30 degrees RAD= axis > 90 degrees

  12. Axis trick Positive in I and II = normal Positive in I Negative in II = LAD Negative in I Positive in II = RAD

  13. A system • Quality of ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval

  14. P wave • Are there P waves….? • Pointy = P pulmonale (RA hypertrophy) • Bifid = P mitrale (LA hypertrophy) • Not very accurate or useful….

  15. PR interval • Start of P wave to start of QRS • Normal = 0.12-0.2s • Too short – can mean WPW syndrome (ie. an accessory pathway), or normal! • Too long –means AV block (heart block) - 1st/2nd/3rd degree

  16. A system • Quality of ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval

  17. QRS complex • Should be <0.12s duration • >0.12s = BBB (either LBBB or RBBB) • ‘Pathological’ Q waves can mean a previous MI (? territory) • >25% size of subsequent complex • Q waves are allowed in V1, aVR and III

  18. BBB Look at V1 and V6 W I LL ia M = LBBB M a RR o W = RBBB

  19. QRS complex • Is there LVH? • Sum of the Q or S wave in V1 and the biggest R wave in V5 or V6 >35mm • (R wave in aVL >11mm) • Not actually very useful….

  20. A system • Quality of ECG? • Rate • Rhythm • Axis • P wave • PR interval • QRS duration • QRS morphology • Abnormal Q waves • ST segment • T wave • QT interval

  21. ST segment • ST depression • Downsloping or horizontal = abnormal • Ischaemia (coronary stenosis) • If lateral (V4-V6), consider LVH with ‘strain’ or digoxin (reverse tick sign) • ST elevation • Infarction (coronary occlusion) • Pericarditis (widespread) • These are usually in ‘territories’ eg. anterior/lateral/inferior etc. and will be present in contiguous leads

  22. T wave • Peaked (hyperkalaemia or normal young man) • Inverted/biphasic (ischaemia, previous infarct) • Small (hypokalaemia) • No pot, no tea!

  23. QT interval • Don’t worry about too much… • Start of QRS to end of T wave • Needs to be corrected for HR • Various formulae • eg. Bazett’s: • Computer calculated often wrong • Long QT can be genetic (long QT sy.) or secondary eg. drugs (amiodarone, sotalol) • Associated with risk of sudden death due to Torsades de Pointes

  24. Question 1 • What is the rate, rhythm and axis? • Any other abnormalities?

  25. Question 2 • What is the rate, rhythm and axis? • Any other abnormalities?

  26. Question 3 • What is the rate, rhythm and axis? • Any other abnormalities?

  27. Question 4 • What is the rate, rhythm and axis? • Any other abnormalities? • How would you manage this patient?

  28. Question 5 • What is the rate, rhythm and axis? • What is the main problem with the patient?

  29. Take home messages • Remember your system! • See lots (pattern recognition)

  30. Further reading ECG made easy, 7th ed – Hampton ECG Interpretation made Incredibly Easy, 4th ed – Springhouse (? nurses) www.Emedu.org/ecg

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