The document discusses electrocardiography (ECG) and how it is used to diagnose myocardial infarction (MI). It provides details on: 1) How 12 leads are used to view the heart electrically from different angles and locations, and which 10 electrodes are used. 2) The typical signs seen on an ECG during an MI, including ST segment elevation, pathological Q waves, reduced R waves, and inverted T waves. 3) The sequence of ECG changes that occur during an evolving MI, from initial onset through later stages. 4) How different leads on the ECG can indicate the location of an infarct, such as anterior vs inferior walls.

1. ECG diagnosis

2. Lead Position A typical ECG report shows the cardiac cycle from 12 different vantage points (I, II, III, aVR, aVL, aVF, V1-V6), like viewing the event electrically from 12 different locations (like a 3D perspective).BUT only 10 electrodes are used. Lead I represents activity that is going from the right arm to the left arm Lead II represents activity that is going from the right arm to the left leg Lead III represents activity that is going from the left arm to the left leg aVL is placed on the left arm (or shoulder) aVF is placed on the left leg (or hip) aVR is placed on the right arm (or shoulder) V1- 4th intercostal space to the right of sternum V2- 4th intercostal space to the left of sternum V3- halfway between V2 and V4 V4- 5th intercostal space in the left mid-clavicular line V5- 5th intercostal space in the left anterior axillary line V6- 5th intercostal space in the left mid axillary line

3. NSR

4. Aims 10 ECG rules Heart Rate ECG signs of M.I. Evolution of changes in M.I. Classical Appearences

5. QRS waveform nomenclature R r qR qRs Qrs QS Qr Rs rS qs rSr’ rSR’

6. The 10 rules for a normal ECG .2 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

7. Rule 1 Millivolts Milliseconds 0 200 400 600 -0.5 0 0.5 1.0 P R T Q S PR interval should be 120 to 200 milliseconds or 3 to 5 little squares PR interval

8. Rule 2 Millivolts Milliseconds 0 200 400 600 -0.5 0 0.5 1.0 QRS The width of the QRS complex should not exceed 110 ms, less than 3 little squares P R T Q S

9. Rule 3 The QRS complex should be dominantly upright in leads I and II I II III aVR aVL aVF

10. Rule 4 QRS and T waves tend to have the same general direction in the limb leads I II III aVR aVL aVF

11. Rule 5 All waves are negative in lead aVR P Q T S

12. Rule 6 V 1 V 2 V 3 V 4 V 5 V 6 The R wave in the precordial leads must grow from V1 to at least V4

13. Rule 7 The ST segment should start isoelectric except in V1 and V2 where it may be elevated I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

14. Rule 8 The P waves should be upright in I, II, and V2 to V6 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

15. Rule 9 There should be no Q wave or only a small q less than 0.04 seconds in width in I, II, V2 to V6 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

16. Rule 10 The T wave must be upright in I, II, V2 to V6 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

17. What is the heart rate? (300 / 6) = 50 bpm www.uptodate.com

18. What is the heart rate? (300 / ~ 4) = ~ 75 bpm www.uptodate.com

19. What is the heart rate? (300 / 1.5) = 200 bpm

20. 10 Second Rule As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds. This method works well for irregular rhythms.

21. What is the heart rate? 33 x 6 = 198 bpm The Alan E. Lindsay ECG Learning Center ; http://medstat.med.utah.edu/kw/ecg/

22. Characteristic changes in AMI ST segment elevation over area of damage ST depression in leads opposite infarction Pathological Q waves Reduced R waves Inverted T waves

23. ST elevation Occurs in the early stages Occurs in the leads facing the infarction Slight ST elevation may be normal in V 1 or V 2 R P Q ST

24. Deep Q wave Only diagnostic change of myocardial infarction At least 0.04 seconds in duration Depth of more than 25% of ensuing R wave R P Q T ST

25. T wave changes Late change Occurs as ST elevation is returning to normal Apparent in many leads R P Q T ST

26. Bundle branch block I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 I II III aVR aVL aVF V1 V2 V3 V4 V5 V6 Anterior wall MI Left bundle branch block

27. Sequence of changes in evolving AMI 1 minute after onset 1 hour or so after onset A few hours after onset A day or so after onset Later changes A few months after AMI Q R P Q T ST R P Q ST P Q T ST R P S T P Q T ST R P Q T

28. Anterior infarction Anterior infarction Left anterior descending artery (LAD) I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

29. Inferior infarction Inferior infarction Right coronary Artery( RCA) OR Circumflex (LCX) I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

30. Lateral infarction Lateral infarction Left circumflex coronary Artery OR DAIAGONAL branch of LAD I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

31. Location of infarct combinations aVR V1 V4 I II III LATERAL OR HIGH LATERAL INFERIOR SEPTAL ANT ANT LAT aVL aVF V2 V3 V5 V6

32. Diagnostic criteria for AMI Q wave duration of more than 0.04 seconds Q wave depth of more than 25% of ensuing r wave ST elevation in leads facing infarct (or depression in opposite leads) Deep T wave inversion overlying and adjacent to infarct Cardiac arrhythmias

33. Hay….. wake up we are done