1. BASIC 12 LEAD ECG INTERPRETATION
Dr. Jeffrey Elliot Field, HBSc. DDS,
Fellow, American Dental Society of Anesthesia
Diploma, the National Dental Board of Anesthesia. 1
4/19/2017 1

2. Objectives To gain a cursory understanding of 12 lead ECG’s 2
4/19/2017 2

3. Basic 12 Lead Interpretation
4/19/2017

4. 12 lead ECG’s give you the opportunity to look for all the arythmias we have studied in a 360 degree view of the heart with the added bonus of being able to diagnose and localize myocardial infarctions ( i.e. areas of muscle damage)
Remember to look at all leads to rule out all of the arrhythmias and abnormalities we have studies thus far.
In particular look first at Leads I , II, and III as these will be the most familiar to you .
4/19/2017

5. In a 12 lead ECG 10 electrodes/leads attached to the patient.
4/19/2017

6. Myocardial Infarction
Myocardial infarctions can be categorized as follows:
-Q-wave MI
-Non Q-wave MI
4/19/2017

7. Q-Wave Myocardial Infarction
This is the classic presentation for MI’s.
The developing MI is seen as ST segment elevation followed by deepening Q-waves in the leads where ST segment elevation was 1st seen.
The ECG changes are accompanied by elevated cardiac enzymes and markers and of course physical signs and symptoms of an MI ( chest pain ,nausea ,vomiting , etc)
4/19/2017

8. Non Q-Wave Myocardial Infarction
In this case you get classic signs and symptoms symptoms of an MI(i.e. elevated cardiac enzymes and markers and of course physical signs of an MI ( chest pain ,nausea ,vomiting , etc)
But non of the usual ECG changes ( i.e. ST segment elevation and deepening Q-waves). In fact sometimes the only clue on the ECG are inverted T-waves.
4/19/2017

9. Cardiac Enzyme changes and Markers for MI
There are 4 markers for cardiac enzymes as follows:
CK-MB isoenzyme
CK-MB isoforms
Myoglobin
Troponin T or Troponin I
4/19/2017

10. Relative Advantages and Disadvantages of the Various cardiac Markers
4/19/2017

11. Specific for cardiac muscle Damage No Yes
CK-MB Isoenzyme
Myoglobin
CK-MB Isoforms
Troponin ( Tor I)
Specific for cardiac muscle
Damage No
Yes
Sensitivity= early rise ( 1-6 hours after damage
YES
Sensitivity=
sustained elevation after damage
Sensitivity= will detect reinfarction soon after the initial episode
Diagnostic use verified by clinical studies
Prognostic Use verified by clinical studies
4/19/2017

12. CK-MB Isoenzyme
Myoglobin
CK-MB Isoforms
Troponin
( Tor I)
Score
3 yes
3 No
2 Yes
4 No
3 Yes
5 yes
1 No
Therefore the best test overall is Troponin T or I. But these will not detect reinfarction and therefore more than one test is required.
The current recommendation is to combine one of the CK-MB tests with one of the Troponin tests.
It should be noted that high troponin levels post MI correlate with poor outcomes.
Finally please note CK-MB also rises in unstable angina ( damaged cells that will recover ) as well as MI ( damaged cells that won’t recover) so it won’t differentiate between unstable angina and an MI
4/19/2017

13. Localizing Myocardial infarctions
Anterior( blockage of left anterior descending artery) –look for ECG changes in leads V1-V4
Inferior ( blockage of right coronary artery or less commonly right circumflex)- look for ECG changes in leads II, III, and AVF
4/19/2017

14. Anterior MI
4/19/2017

15. Inferior MI
4/19/2017

16. Localizing Myocardial infarctions continued
Lateral Infarction ( blockage of circumflex or diagonal branch of the LAD)-look in leads V5, V6 and AVL
Posterior (blockage of right coronary artery or circumflex) –look for mirror image changes to anterior in V1-V4 (i.e. ST depression and dominant R-wave).
4/19/2017

17. Posterior MI
4/19/2017

18. Lateral MI
4/19/2017