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ECG interpretation

ECG interpretation

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ECG interpretation

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  1. ECG interpretation Dr Ally Duncan SpR In Anaesthesia & Clinical Fellow in Undergraduate Medical Education Manchester Royal Infirmary May 2012

  2. Objectives • Justify the reasons for performing an ECG • Develop a structured approach to interpreting an ECG • Practice interpreting ECGs

  3. The ECG “The ECG (electrocardiogram) is a transthoracic interpretation of the electrical activity of the heart.”

  4. The ECG

  5. Why perform an ECG? • It’s part of the admission bundle • Indicated by the patient’s symptoms - symptoms of IHD/MI - symptoms associated with dysrhythmias • Indicated by the patient’s examination findings - cardiac murmur

  6. Quality of ECG? Rate Rhythm Axis P wave PR interval QRS duration QRS morphology Abnormal Q waves ST segment T wave QT interval ECG interpretation

  7. Quality of the ECG • Patient name • Date of the ECG • Is there any interference? • Is there electrical activity from all 12 leads? • Calibration: - speed = 25mm/second - height = 1cm/mV

  8. Calibration

  9. Calibration

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

  11. Rate • 300/number of big squares between R waves • Rate is either: - normal - bradycardic - tachycardic

  12. Rate

  13. Rhythm • Are there P waves? • Are they regular? • Does one precede every QRS complex? • Regular vs. irregular

  14. Axis

  15. Axis

  16. Axis Positive in I and II = NORMAL Positive in I and negative in II = LAD Negative in I and positive in II = RAD

  17. Axis

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

  19. P wave • Are there P waves present? • Bifid = P mitrale (LA hypertrophy) • Pointy = P pulmonale (RA hypertrophy)

  20. P mitrale

  21. P pulmonale

  22. PR interval • Start of P wave to start of QRS complex • Normal = 0.12 - 0.2 seconds (3-5 small squares) • Decreased = can indicate an accessory pathway • Increased = indicates AV block (1st/2nd/3rd)

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

  24. QRS complex • Normal = <0.12 seconds • >0.12 seconds = Bundle Branch Block

  25. QRS complex W I LL ia m = LBBB M a RR o w = RBBB

  26. QRS complex • Is there LVH? • Sum of the Q or S wave in V1 and the tallest R wave in V5 or V6 >35mm is suggestive of LVH

  27. Q waves • Q waves are allowed in V1, aVR & III • Pathological Q waves can indicate previous MI

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

  29. ST segment • ST depression - downsloping or horizontal = ABNORMAL • ST elevation - infarction - pericarditis (widespread)

  30. ST segment

  31. ST segment

  32. ST segment

  33. T wave • Small = hypokalaemia • Tall = hyperkalaemia • Inverted/biphasic = ischaemia/previous infarct

  34. T wave

  35. T wave

  36. T wave

  37. QT interval • Start of QRS to end of T wave • Needs to be corrected for HR • Normal QTc = < 400ms • Long QT can be genetic or iatrogenic

  38. QT interval

  39. ECG quiz

  40. ECG 1

  41. ECG 2

  42. ECG 3

  43. ECG 4

  44. Any questions?

  45. Summary • Discussed the indications for performing an ECG • Introduced an approach to interpreting ECGs • Discussed common ECG abnormalities