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1. 12 Lead Interpretation
2. Objectives Ischemia, injury and infarction
ECG complex review
J point
ST segment
STEMI recognition
3. Ischemia to Infarct
4. The ECG Complex The J point is the point where the S wave ends and the ST segment begins
ST elevation is measured after the J point
The ST segment is compared to the base line
The base line or isoelectric line is found at the bottom of the calibration bar
5. ST Segment Starts with the J point
Ends with the beginning of the T wave
Elevation or depression of the ST segment is measured 0.08 seconds (2 small squares) to the right of the J point
6. PR Interval Begins at the end of the P wave
Ends at the beginning of the QRS
When determining the isoelectric or baseline find the PR interval of 2 consecutive complexes, draw a line using a straight edge and measure ST elevation from this line; this is the most accurate way to determine if the ST segment is elevated
7. TP Segment Begins at the end of the T wave
Ends at the beginning of the P wave
Can be used as a back up to the PR interval to determine the baseline when assessing ST elevation
Not as accurate as the PR interval
8. Hyperacute T-wave As an acute myocardial infarction develops various 12 lead ECG changes occur
Initially the 12 lead ECG may show tall or hyperacute T-waves signifying cardiac ischemia – may only be present for a short time after ischemia has begun (5 to 30 minutes)
Paramedics may not see this change as many patients wait for at least 30 minutes to call EMS
9. ST segment elevation Usually seen with in the first few hours after the onset of symptoms
Changes may be very subtle or pronounced
Any elevation in 2 contiguous leads is significant
ST segment elevation greater than 1mm or 2mm in precordial leads (V1 through V6)
1mm = 1 small square on the ECG paper
For more information on ST segment abnormality click on this link:
http://www.madsci.com/manu/ekg_st-t.htm
10. Tombstones Pronounced ST segment elevation may appear as tombstones
Tombstones are a result of the fusing of the ST segment and T wave
11. Pathological Q wave Indicate a loss of viable myocardium
May develop 1 to 2 hours after the onset of symptoms but can take anywhere from 12 to 24 hours to develop
Abnormal Q waves are at greater then one third of the R wave height deep and greater then 1mm (or 1 small square) wide
Q waves may be visible in a patient without infarct but will not meet the parameters to be considered abnormal
12. Reciprocal Changes
13. Reciprocal Changes ST segment depression seen in the opposite leads from ST segment elevation
Highly sensitive as an indicator of acute MI
Frequently seen in larger infarctions
14. The 12 Lead Printout
16. Practice Locate the J point in each of the above complexes
Identify ST segment abnormalities
Click the mouse to check your answers
17. Normal 12 Lead Notice where the J point is for one complex in each lead
Also look at the ST segment for one complex in each lead
This an example of a 12 lead that the Zoll E series will generate
18. Practice ECG # 1 Look for the J point and ST elevation in the above 12 lead
Look for reciprocal changes
Which lead groups are involved?
What area of the heart is involved?
Which coronary artery feeds this area of the heart?
19. Answer ECG # 1 Leads II, III, aVF all have ST elevation, these are contiguous inferior leads
Leads I, aVL, V2, V3 and V4 all have ST depression signifying reciprocal changes
These changes are consistent with an acute inferior MI
In 90% of the population the inferior aspect of the heart blood supply is via the right coronary artery
20. Practice ECG # 2 Look for the J point and ST elevation in the above 12 lead
Look for reciprocal changes
Which lead groups are involved?
What area of the heart is involved?
Which coronary artery feeds this area of the heart?
21. Answer ECG # 2 ST elevation in Leads I, aVL, V2, V3, V4, V5
Lead II and III show reciprocal changes as well as evidence of an old MI (in the form of a pathological Q wave)
Lateral leads (I, aVL and V5) as well as Anterior and septal lead groups (V2, V3 and V4)
Anterior and Lateral are the main areas of the heart involved
Left anterior descending and the left circumflex arteries supply this area of the heart
22. Practice ECG # 3 Look for the J point and ST elevation in the above 12 lead
Look for reciprocal changes
Which lead groups are involved?
What area of the heart is involved?
Which coronary artery feeds this area of the heart?
23. Answer ECG # 3 ST elevation in leads II, III and aVF
Reciprocal changes in leads I, aVL, V2 and V3
Leads II, III and aVF are contiguous inferior leads
This is an acute inferior MI
This area of the heart is supplied by the right coronary artery in 90% of the population
24. Practice ECG # 4 Look for the J point and ST elevation in the above 12 lead
Look for reciprocal changes
Which lead groups are involved?
What area of the heart is involved?
Which coronary artery feeds this area of the heart?
25. Answer ECG # 4 ST elevation in leads I, V2, V3, V4, V5, V6 and aVL
Reciprocal changes shown in leads III and aVF
V3 and V4 are anterior leads, I, aVL, V5 and V6 are lateral leads
This is an acute anteriolateral MI
Left anterior descending and left circumflex arteries supply these areas of the heart
26. Practice ECG # 5 Look for the J point and ST elevation in the above 12 lead
Look for reciprocal changes
Which lead groups are involved?
What area of the heart is involved?
Which coronary artery feeds this area of the heart?
27. Answer ECG # 5 ST elevation in leads II, III, aVF and V6
Reciprocal changes in leads V2, V3 and V4
II, III and aVF are inferior leads, V6 is a lateral lead and ST elevation must be present in at least 2 leads that view the same area of the heart
This is an acute inferior MI
The inferior area of the heart is supplied by the right coronary artery in 90% of the population
28. Practice ECG # 6 Look for the J point and ST elevation in the above 12 lead
Look for reciprocal changes
Which lead groups are involved?
What area of the heart is involved?
Which coronary artery feeds this area of the heart?
29. Answer ECG # 6 ST elevation in leads V1, V2, V3 and V4
There are no obvious reciprocal changes
V1 and V2 are septal leads, V3 and V4 are anterior leads
This is an acute anterioseptal MI
The left anterior descending artery supplies this area of the heart
30. Thank You for participating in Sunnybrook – Osler Centre for Prehospital Care online education!If you have any questions please bring them with you to class!