1. Ischemia, Injury & Infarction
12 Lead ECGs:
Ischemia, Injury & Infarction
Thomas Beers, EMS Coordinator
Cleveland Clinic Health System

2. Objectives Definitions Why 12 Leads? Injury/Infarct Recognition
Leads and Views
Reciprocal Changes
Evolution of an AMI
Practice Cases

3. Where do they go?

4. Why 12 Lead ECGs? Demonstrated Advantages
Rapid Identification of Infarction/Injury
diagnosis made sooner in many cases
Administration of critical & time sensitive medications
Decreased Time to Cath Lab Treatment
speeds preparation of & time to cath lab
Increased Index of Suspicion
It is what we can do BEST!

5. Why 12 Lead ECGs? Perceived Disadvantages
No clinical advantage to patient & “our transport times are short”
demonstrated decrease in time to treatment (D2B)
compare to early notification for trauma patients
Increased time spent on scene
demonstrated an avg. <4 min increase
Cost
equipment & training (How many of you have paid for a LP 12 or 15?)

6. Critical Concepts in ACS
Pain is Injury
Pain-Free is the Goal
Time is Muscle
Door to Cath Lab Time is the issue

7. Acquisition & Transmission
ECG quality begins with skin preparation and electrodes
Hair removal
Skin preparation
Age & Quality of Electrodes & Cables
Electrode Placement
Because of the increased “window” to electrical signals, additional steps must be taken to reduce the amount of artifact produced.
Removing excess hair and prepping the skin allows the electrode gel to better penetrate the skin, thus receiving a stronger signal with less artifact.
First we will discuss the techniques themselves, later in the module we will look at strategies to accomplish these additional tasks quickly.

8. Acquisition & Transmission
Hair Removal
Clipper over razor
Lessens risk of cuts
Quicker
Disposable blade clippers available
Most EMS systems use razors
Excess hair presents two problems:
• First, hair may prevent the electrode from adhering well.
• Second, hair may inhibit gel contact and skin penetration.
Some thrombolytic manufacturers recommend that clippers be used to remove chest hair. The intent is to minimize the potential for bleed sites in a patient who may receive a thrombolytic.

9. Acquisition & Transmission
Read the clipper manufacture’s recommendations. This is one model designed for medical applications and may be used near oxygen. In addition the head is disposable, avoiding de-contamination issues.

10. Acquisition & Transmission
Skin Preparation
Helps obtain a strong signal
When measured from skin, heart’s electrical signal about volts
Skin oils reduce adhesion of electrode and hinder penetration of electrode gel
Dead, dried skin cells do not conduct well
When measured from the patient’s skin, the heart’s electrical signal is extremely small, about to volts.
That’s as small as one-ten thousandth of a volt. Compare this with energy from a nine volt battery.
Good skin prep will make the ECG signal as strong as possible, and make the artifact signals as small as possible.

11. Acquisition & Transmission
Rubbing skin with a gauze
pad can reduce skin oil
and remove some of dead skin cells
Simply rubbing the skin with a gauze pad can have a noticeable effect on ECG clarity by:
• Reducing skin oil
• Removing part of the stratum corneum

12. Acquisition & Transmission
Other causes of artifact
Patient movement
Cable movement
Vehicle movement
Once the skin has been prepped and the electrodes applied, there are still other sources of artifact to consider.

13. Acquisition & Transmission
Patient Movement
Make patient as comfortable as possible
Supine preferred
Look for subtle movement
toe tapping, shivering
Look for muscle tension
hand grasping rail, head raised to “watch”
It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact.
When possible, the patient should be in the supine position for a 12-lead ECG.
Sometimes this is not feasible, practical or desirable.
If ECG is not recording in supine position, simply note this on ECG.

14. Acquisition & Transmission
Cable Movement
Enough “slack” in cables to avoid tugging on the electrodes
Many cables have clip that can attach to patient’s clothes or bed sheet
It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact.
When possible, the patient should be in the supine position for a 12-lead ECG.
Sometimes this is not feasible, practical or desirable.
If ECG is not recording in supine position, simply note this on ECG.

15. Here is what lead placement looks like on a patient.

16. Acquisition & Transmission
Vehicle Movement
Acquisition in a moving vehicle is NOT recommended
May or may not be successful
Tips
Pull ambulance over for seconds during acquisition
Acquire ECG while stopped at traffic light
It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact.
When possible, the patient should be in the supine position for a 12-lead ECG.
Sometimes this is not feasible, practical or desirable.
If ECG is not recording in supine position, simply note this on ECG.

17. Acquisition & Transmission
Things to look for
Little or no artifact
Steady isoelectric line

18. What it should look like…
Note how the baseline straightened out by simply repositioning the patient cables and clipping them onto the sheet.
What technique(s) would you consider in order to resolve the muscle artifact?

19. What it should NOT look like

20. Acquisition & Transmission
ECG Accuracy depends upon
Lead placement
Frequency response
Calibration
Paper speed
All of the techniques discussed to this point have related to ECG clarity. We now need to look at what is necessary to ensure ECG accuracy.

21. Traditional Placement
Limb Lead Placement
Traditional Placement
Avoid placing on the trunk!!!
Limb leads should be placed on the limbs. The traditional placement is near the ankles and wrists.
Acceptable Placement

22. Chest Lead Placement V1: fourth intercostal space to right of sternum
V2: fourth intercostal space to left of sternum
V3: directly between leads V2 and V4
V4: fifth intercostal space at left midclavicular line
V5: level with V4 at left anterior axillary line
V6: level with V5 at left midaxillary line
V1 fourth intercostal space to the right of the sternum
V2 fourth intercostal space to the left of the sternum
V3 directly between leads V2 and V4
V4 fifth intercostal space at left midclavicular line
V5 level with lead V4 at left anterior axillary line
V6 level with lead V5 at left midaxillary line

23. Anatomy Revisited RCA LCA right ventricle inferior wall of LV
posterior wall of LV (75%)
SA Node (60%)
AV Node (>80%)
LCA
septal wall of LV
anterior wall of LV
lateral wall of LV
posterior wall of LV (10%)

24. The Three I’s Ischemia Injury Infarct lack of oxygenation
ST segment depression or T wave inversion
Injury
prolonged ischemia
ST segment elevation
Infarct
death of tissue
may or may not show a Q wave

25. Injury/Infarct Recognition
Well Perfused Myocardium
Epicardial Coronary Artery
Lateral Wall of LV
Septum
Positive Electrode
Interior Wall of LV

26. Injury/Infarct Recognition
Normal ECG
ST segments are iso-electric.

27. Injury/Infarct Recognition
Ischemia
Epicardial Coronary Artery
Lateral Wall of LV
Septum
Left
Ventricular
Cavity
Positive Electrode
Interior Wall of LV

28. Injury/Infarct Recognition
Ischemia
Inadequate oxygen to tissue
Represented by ST depression or T inversion
May or may not result in infarct or Q waves
Define ischemia.
Inadequate oxygen to tissue.
Represented by ST depression or T inversion.
May or may not result in infarct (duration of clot and demand).
If infarct develops, may or may not display Q wave.
The direction of ST deviation is a poor predictor of Q wave development.

29. Injury/Infarct Recognition
ST Segment Depression & Inversion
Note widespread ST depression and T waves inverted in several leads.

30. Injury/Infarct Recognition
Thrombus
Ischemia

31. Injury/Infarct Recognition
Prolonged ischemia
Represented by ST elevation
referred to as an “injury pattern”
Usually results in infarct
may or may not develop Q wave
Define injury. Ischemia affecting the epicardium represented by ST elevation.
Lack of oxygenation to tissue
Represented by ST elevation. Refereed to as the “injury pattern”.
Usually results in infarct (presumptive evidence of MI)
If infarct develops, may or may not develop Q wave
The direction of ST deviation is a poor predictor of Q wave development.

32. Injury/Infarct Recognition
ST Segment Elevation
Ask group to look for ST elevation.
The ST elevation implied epicardia ischemia (injury pattern).

33. Injury/Infarct Recognition
Infarcted Area
Electrically Silent
Depolarization

34. Injury/Infarct Recognition
Death of tissue
Represented by Q wave
Not all infarcts develop Q waves
Death of tissue.
Traditionally represented by wide (equal to or greater than 40ms) Q wave.
Not all infarcts develop Q waves.
The direction of ST deviation (elevation or depression) is a poor predictor of Q wave development.

35. Injury/Infarct Recognition
Q Waves
Pathologic Q waves present in II, III and aVF suggest necrosis has occurred in the inferior region of the left ventricle.

36. Injury/Infarct Recognition
What to Look for:
ST segment elevation
Present in two or more anatomically contiguous leads
A normal ECG does NOT rule out any Acute Coronary Syndrome.
ST segment depression represents ischemia, infarction is possible.
ST segment elevation represents epicardial ischemia, and is presumptive evidence of AMI.
Since necrosis may occur under all the these situations, a Q wave MI may follow ST elevation, ST depression or even a normal ECG.

37. Lead “Views”

38. Lead Groups I aVR V1 V4 II aVL V2 V5 III aVF V3 V6 Limb Leads
Chest Leads

39. LIILI-SSAALL
Which coronary arteries are most likely associated with each group of contiguous leads?
I Lateral
aVR
V1 Septal
V4 Anterior
II Inferior
aVL Lateral
V2 Septal
V5 Lateral
Each box represents one lead, and the viewpoint of that lead is indicated.
NOTE: Refer participants to their pocket card where this information is summarized as well.
III Inferior
aVF Inferior
V3 Anterior
V6 Lateral

40. Lateral Wall I and aVL View from Left Arm 
lateral wall of left ventricle I II
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6

41. Lateral Wall V5 and V6 Left lateral chest
lateral wall of left ventricle I II
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6

42. Lateral Wall I, aVL, V5, V6 ST elevation  suspect lateral wall injuryII
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6
Lateral Wall

43. Inferior Wall II, III, aVF View from Left Leg 
inferior wall of left ventricle I II
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6

44. Inferior Wall Posterior View portion resting on diaphragm
ST elevation  suspect inferior injury I II
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6
Inferior Wall

45. Septal Wall V1, V2 Along sternal borders
Look through right ventricle & see septal wall I II
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6

46. Septal V1, V2 septum is left ventricular tissue I II III aVR aVL aVF

47. Anterior Wall V3, V4 Left anterior chest  electrode on anterior chestII
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6

48. Anterior Wall
V3, V4
ST segment elevation  suspect anterior wall injury I II
III
aVR
aVL
aVF V1 V2 V3 V4 V5 V6

49. Reciprocal Changes
We have been looking for infarct based upon the presence of ST elevation.
As mentioned, not every lead is elevated when AMI is present, only the leads looking at the infarct site.
In fact, those leads which look at the infarct site from the opposite perspective tend to produce the opposite changes.
When a lead “sees” the AMI directly, the segment becomes elevated in that lead.
However, when a lead “sees” the infarct from the opposite perspective, the ST segment may be depressed in that lead.

50. Reciprocal Changes II, III, aVF I, aVL, V leads
Because of the way the leads are oriented on the patients body, II, III and aVF are on the bottom looking up.
All the other leads are on the top, looking in.
Therefore, when AMI produces elevation in II, III, and aVF, it also tends to produce depression in the opposing leads.

51. Reciprocal Changes Reciprocal changes
Not necessary to presume infarction
Strong confirming evidence when present
Not all AMIs result in reciprocal changes
Not all AMIs with ST elevation produce reciprocal depression.
Quite simply… some do and some don’t.
When reciprocal depression is noted, the likelihood of AMI is dramatically increased.

52. Reciprocal Changes: Practice
Instructions:
Determine which leads show ST elevation.
Which leads show ST depression.
Localize the area of infarction.
Determine if a reciprocal pattern exists.
ST elevation exists in II, III and aVF. ST depression in I and aVL
Does it fit the reciprocal pattern? Yes.
NOTE: Not every lead on each side of the seesaw must be elevated or depressed in order to assume reciprocal changes. Rather it is more a matter of at least some leads on one end of the seesaw being elevated and some being depressed.

53. 12-Lead ECG AMI recognition Two things to know What to look for
Where you are looking L S A I L S L I I A L

54. AMI Recognition What to look for ST segment elevation
One millimeter or more (one small box)
Present in two anatomically contiguous leads L S A I L S L I I A L

55. Practice Case “Tools” Must take into Account Story Risk factors ECG
Treatment

56. Injury/Infarct Recognition: Practice
EXERCISE: approximately 2 minutes
Instructions:
Review the 12-lead ECG.
Go lead by lead, and pick one good complex in each lead.
Find the J-point and ST segment.
Compare the ST to the TP segment, looking for 1mm (one small box) of elevation (ignore ST depression for now).
Place a checkmark next to any lead with 1mm of ST segment elevation.
Review findings with group, pointing out every J-point and ST segment. Note leads II, III and aVF display elevation.
Remember ST segment elevation is presumptive evidence for AMI. Knowing which part of the heart leads II, III and aVF “sees” would tell you where the infarct is located.

57. Practice Instructions: Review the 12-lead ECG.
Go lead by lead, and pick one good complex in each lead.
Find the J-point and ST segment.
Compare the ST to the TP segment, looking for 1mm (one small box) of elevation (ignore ST depression for now).
Place a check mark next to any lead with 1mm of ST segment elevation.
Localize the area of infarction.
Antero-septal

58. Practice TOMBSTONES Instructions: Review the 12-lead ECG.
Go lead by lead, and pick one good complex in each lead.
Find the J-point and ST segment.
Compare the ST to the TP segment, looking for 1mm (one small box) of elevation (ignore ST depression for now).
Place a check mark next to any lead with 1mm of ST segment elevation.
Localize the area of infarction.
Inferior wall infarction
Note ST depression in I, AVL and V1-V3.
Lets talk about one cause of ST depression, known as reciprocal ST depression.

59. Practice Case 1 48 year old male Pale and wet Overweight, smoker
Dull central CP 2/10, began at rest
Pale and wet
Overweight, smoker
Vital signs: RR 18, P 80, BP 180/110, Sa02 94% on room air

60. Practice Case 1

61. Practice Case 2 68 year old female History of IDDM and hypertension
Sudden onset of anxiety and restlessness,
States she “can’t catch her breath”
Denies chest pain or other discomfort
History of IDDM and hypertension
RR 22, P 40, BP 190/90, Sa02 88% on NC at 4 lpm

62. Practice Case 2

63. BUT WAIT!!!!!!!!!!!!!!

64. STEMI Mimics
LBBB
RBBB
Pericarditis
LVH

65. LBBB vs. RBBB

66. Pericarditis

67. LVH

68. LVH

69. AMI Recognition
A normal 12-lead ECG DOES NOT mean the patient is not having acute ischemia, injury or infarction!!!

70. The Future of STEMI Care
E2B
- Integration of EMS, ED, and Cardiology
- full disclosure of pt outcomes (QI)
- seamless transitions of pt. care

71. Thank You!
Questions, Comments?