12 Lead EKG Analysis

1. 12 – Lead EKG Analysis Advanced Cardiology

2. The Need Prior to the ‘60s management for an MI consisted of bed rest and HFTB The ‘70s brought us Percutaneous Transluminal Coronary Angioplasty (PCTA) and Coronary Artery By-Pass Graft (CABG) The ‘80s saw the advent of thrombolytics

3. The Need CABG and PCTA were the first direct management for stopping the infarct not available in all hospitals Thrombolytics are efficient and can be found in virtually all emergency departments

4. The Need Studies indicate “time is muscle” the sooner reperfusion therapy is initiated the more heart muscle is saved early recognition is the key to saving heart muscle

5. The Need “One of the primary methods to speed the recognition of myocardial infarction rests in the hands of the non-physician to recognize myocardial infarction” - AHA 12-Lead EKG is a “vital sign”

6. ECG Basics Cardiac monitor as a voltmeter leads of the 12-lead time seconds and milliseconds placement of the leads which each lead “sees” components of the QRS Q waves: pathological Vs. physiological

7. ECG Basics J point and ST segment deviations QRS duration: abnormal Vs. normal R wave progression

8. The “voltmeter” The basic function of the monitor is to detect current flow as measured on the patient’s skin the cardiac monitor produces an indirect measurement on the electrical activity of the heart the care giver must interpret the significance of the voltage changes and apply them to the clinical presentation of the patient

9. Overview of the 12-Lead Initially the 12-Lead is intimidating too many wires and stuff too many funny looking lines on the paper “What de hell am I supposed to be looking at?” Like pharmacology “… it is your friend”

10. Overview of the 12-Lead Format the 12-lead only provides a 2.5 second view of each lead you only need one complex from each lead there is usually one continuous rhythm strip to assess rate and rhythm

11. Overview of the 12-Lead Time intervals and duration are expressed in milliseconds example normal PRI <0.20 seconds becomes <200 milliseconds move decimal three places to the right

12. Overview of the 12-Lead Voltage expressed vertically time expressed horizontally each small box is 1 mm each large box is 5 mm standard calibration is 1 mV will produce a 10 mm deflection

13. Lead Placement Terminology electrode device which contains conductive gel and is applied to the patient’s skin cable refers to the wire which connects to the electrode

14. Lead Placement Terminology lead two fold manner actual tracing obtained position of the electrode

15. Lead Placement 12-Lead composition six limb leads I, II, III, AVR, AVF, AVL six chest (precordial) leads V1-V6

16. Limb Leads LIMB LEADS GO ON THE LIMBS!!! Leads I, II, and III are the most common limb leads these leads have a distinct negative and a distinct positive pole therefore they are considered bipolar

17. Limb Leads Lead I positive electrode is at the left wrist negative electrode is at the right wrist Lead II positive electrode is at the left foot negative electrode is at the right wrist Lead III positive electrode is at the left foot negative electrode is at the left wrist Each lead measures the electrical potential between the positive and negative poles

19. Einthoven’s Triangle Formed b y joining Lead I, II, and III at their ends Einthoven’s Law I + III = II The height of the QRS in Lead I added to the height of Lead III yields the height of the QRS in Lead II Lead II should have the tallest QRS of the bipolar leads

20. Augmented Limb Leads Leads AVF, AVL and AVR have a distinct positive pole but no distinct negative pole therefore they are considered unipolar instead of a distinct negative pole they have multiple negative poles creating a negative field, which the heart is the center or the heart is the negative pole

21. Augmented Limb Leads Augmented voltage (AV) AVR positive pole is on the right arm AVL positive pole is on the left arm AVF positive pole is on the left leg

22. Chest Leads Also known as percordial leads are unipolar positive electrode is placed on a specific location on the chest the heart is the theoretical negative electrode at this point you should understand electricity flows from negative to positive

23. Chest Leads - Placement

24. Chest Leads Lead Placement Step 1 find the Angle of Louis move just to the right of the sternal border and find the second rib just below the second rib is the 2nd ICS move down 2 ICS to the 4th ICS place electrode V1 here

25. Chest Leads Lead placement Step 2 move directly across the sternum to the 4th ICS left side and place V2 here Step 3 move down 1 ICS (5th) and move to the midclavicular line place V4 here

26. Chest Leads Lead placement remaining electrodes are positioned in relation to V2 and V4 Step 4 V3 is midpoint between V2 and V4 Step 5 draw an imaginary horizontal line from V4 to the midaxillary line

27. Chest Leads Lead placement Step 6 place V5 in the anterior axillary line where the arm joins the chest Step 7 place V6 in the midaxillary line V4 - V6 should be a horizontal line

28. What each lead “sees” Each positive electrode can be thought of as a camera the are 12 positive electrodes so there are 12 views of the heart what each electrode sees is determined by two factors left ventricular dominance positive electrode position

29. What each lead “sees” Left ventricular dominance the EKG does not directly measure all of the heart’s electrical activity it does not see all the current flowing through the heart only a net result of the electrical tug of war

30. What each lead “sees” Left ventricular dominance the QRS is not a display of all the electrical activity in the right and left ventricle it is the net result of a tug of war between the right and left ventricle the left ventricle is larger than the right so it overpowers the right

31. What each lead “sees” Left ventricular dominance the QRS complex represents the electrical activity occurring in the left ventricle

32. What each lead “sees” Positive electrode placement the position of the positive electrode on the body determines the portion of the left ventricle seen

33. ISAL I inferior See septal All anterior Leads lateral Inferior II, III, AVF Septal V1, V2 Anterior V3, V4 Lateral V5, V6, I, AVL

34. What each lead “sees” Certain limb leads share a common position for the positive electrode II, III, AVF positioned on the left leg they look at the same area of the heart but from different perspective

35. QRS Complex R - wave first positive deflection of the QRS complex begins as soon as the EKG leaves the isoelectric line in an upward direction and continues until it returns to the isoelectric line

36. QRS Complex Q- wave a negative deflection that precedes the R - wave begins when the EKG leaves the isoelectric line and continues until it reaches the isoelectric line

37. QRS Complex S - wave negatively deflected complex negative deflection following the R- wave

38. “Q” - waves Q - waves can be either physiological or pathological physiological (ok) < 40 ms (one small box) < 1/3 amplitude of R - wave pathological (bad) > 40 ms > 1/3 amplitude of R - wave

39. QS Complex When the entire complex is negatively deflected, it is called a QS complex. A QS complex is considered equivalent to a wide Q wave. NOTE: When an rS complex is present, students often overlook the small R wave and erroneously label the complex a QS. It will be helpful to point out the difference while reviewing some of the early ECGs. When the entire complex is negatively deflected, it is called a QS complex. A QS complex is considered equivalent to a wide Q wave. NOTE: When an rS complex is present, students often overlook the small R wave and erroneously label the complex a QS. It will be helpful to point out the difference while reviewing some of the early ECGs.

40. ST Segment ST segment marks the beginning of ventricular repolarization begins exactly where the QRS complex ends junction between QRS complex and ST segment is called the J - point

41. ST Segment ST segment: The ECG segment between the J-point and the beginning of the T wave. The ST segment is probably the single most important element to identify on the ECG when looking for evidence of AMI. ST segment: The ECG segment between the J-point and the beginning of the T wave. The ST segment is probably the single most important element to identify on the ECG when looking for evidence of AMI.

42. ST Segment ST segment is normally isoelectric but can be either elevated or depressed (above or below isoelectric) myocardial ischemia, injury, or infarction can cause elevation ST segment elevation above 1 mm is bad

43. Practice Find J-points and ST segments EXERCISE: Have participants turn to of the course guide and locate the J-Point and ST segment in each of the first three complexes. They are not yet concerned with ST elevation or depression, simply identifying the J-point and ST segment. Review the first three complexes with the group. Continue the exercise with the next three complexes, then review them with the group.EXERCISE: Have participants turn to of the course guide and locate the J-Point and ST segment in each of the first three complexes. They are not yet concerned with ST elevation or depression, simply identifying the J-point and ST segment. Review the first three complexes with the group. Continue the exercise with the next three complexes, then review them with the group.

44. Practice Find J-points and ST segments Review J-points and ST segment with group with the group.Review J-points and ST segment with group with the group.

45. ST Segment Compare to TP segment In order to determine if the ST segment is elevated it is necessary to have a reference point. The TP segment is the best reference to the isoelectric line. Do not compare the ST segment to the PR segment because the PR can be depressed, giving the illusion of ST segment elevation. In order to determine if the ST segment is elevated it is necessary to have a reference point. The TP segment is the best reference to the isoelectric line. Do not compare the ST segment to the PR segment because the PR can be depressed, giving the illusion of ST segment elevation.

46. QRS Duration QRS duration is a measurement of the time required for ventricular activation normally requires 80-100 ms for an electrical impulse to travel down the electrical conduction system of the ventricles and cause depolarization >120 ms bad

47. R - Wave Progression Morphologies (shape) of the QRS complexes seen in the chest leads usually follow a predictable pattern from V1 - V6 V1 QRS is primarily negative as the leads progress the QRS become more positive should be positive by V6

48. R - Wave Progression Patterns observed in the V - Leads in which the QRS changes from primarily negative to positive in V-6 is called R - Wave Progression the area in which the “flip” occurs is called the transition zone usually happens at V3 or between V3 and V4

49. R - Wave Progression Many factors can affect poor R - wave progression MI is one of them

50. ST Segment Analysis This time find not only the J-point, but determine if the ST segment is elevated one millimeter or more above the TP segment. #1 No #2 Yes #3 Yes #4 No #5 Yes #6 NoThis time find not only the J-point, but determine if the ST segment is elevated one millimeter or more above the TP segment. #1 No #2 Yes #3 Yes #4 No #5 Yes #6 No

51. Essential 12-Lead ECG Interpretation Goals Recognize and localize AMI on the ECG Feel comfortable with 12-lead interpretation Note to the speaker: This module has been structured to instill confidence and dispel concerns regarding the difficulty of 12-lead ECG interpretation. While many aspects of 12-lead interpretation do require much study and practice, it is a simple matter to identify the pattern of ST segment elevation produced by AMI. After a brief review of essential terminology, participants move directly into AMI recognition and localization. In fact, participants will be able to recognize and localize myocardial infarction approximately 30 minutes into this module! A fact that may be worthy of mention at the onset of your presentation.Note to the speaker: This module has been structured to instill confidence and dispel concerns regarding the difficulty of 12-lead ECG interpretation. While many aspects of 12-lead interpretation do require much study and practice, it is a simple matter to identify the pattern of ST segment elevation produced by AMI. After a brief review of essential terminology, participants move directly into AMI recognition and localization. In fact, participants will be able to recognize and localize myocardial infarction approximately 30 minutes into this module! A fact that may be worthy of mention at the onset of your presentation.

52. 12-Lead ECG This is an example an “in-hospital” 12-lead ECG. Diagnostic 12-lead ECGs taken in the field obtain the same information, but are often in a slightly different format. Let’s compare a typical “in-hospital” 12-lead to a field 12-lead ECG.This is an example an “in-hospital” 12-lead ECG. Diagnostic 12-lead ECGs taken in the field obtain the same information, but are often in a slightly different format. Let’s compare a typical “in-hospital” 12-lead to a field 12-lead ECG.

53. 12-Lead ECG At the bottom of this 12-lead are the rhythm strips (highlighted). In this case three leads are seen, sometimes there are fewer. Any of the 12-leads can be shown as rhythm strips, the users define which leads they want to see. In the field you probably will obtain the rhythm strips first, and will see three leads simultaneously. You can configure the device to show you any of the six limb leads on the rhythm strip (I, II, III, aVR, aVL or aVF). At the bottom of this 12-lead are the rhythm strips (highlighted). In this case three leads are seen, sometimes there are fewer. Any of the 12-leads can be shown as rhythm strips, the users define which leads they want to see. In the field you probably will obtain the rhythm strips first, and will see three leads simultaneously. You can configure the device to show you any of the six limb leads on the rhythm strip (I, II, III, aVR, aVL or aVF).

54. 12-Lead ECG The format of the 12-lead ECG is very standard. While there are a few exceptions, the format you see here is typical of what you will see in most 12-lead ECGs done in North America. The format of the 12-lead ECG is very standard. While there are a few exceptions, the format you see here is typical of what you will see in most 12-lead ECGs done in North America.

55. 12-Lead ECG The machine begins by printing out leads I, II, and III simultaneously. After a mere 2.5 seconds the machine switches in to three new leads, aVR, aVL, aVF. Two and a half seconds later it prints V1, V2 and V3. Finally it prints V4, V5 and V6. The computer analyzes all 10 seconds of all 12-leads although it prints out only 2.5 seconds of each group. The machine begins by printing out leads I, II, and III simultaneously. After a mere 2.5 seconds the machine switches in to three new leads, aVR, aVL, aVF. Two and a half seconds later it prints V1, V2 and V3. Finally it prints V4, V5 and V6. The computer analyzes all 10 seconds of all 12-leads although it prints out only 2.5 seconds of each group.

56. 12-Lead ECG The 12-lead can provide a computer generated interpretation. The computer’s interpretive algorithm is designed to favor “specificity”. In other words, when the machine says “ACUTE MI SUSPECTED” it needs to always be right. The program is almost perfect in that regard, and when you see “ACUTE MI SUSPECTED” the machine is right about 98% of the time. However, in order to attain that specificity, if the computer isn’t absolutely sure that an AMI is present, it will not say anything about it. Depending on the version of the software in your 12-lead machine, the computer may miss as many as one third of the cases where AMI could be suspected on the ECG. In other words YOU are the primary interpreter, the computer is your backup.The 12-lead can provide a computer generated interpretation. The computer’s interpretive algorithm is designed to favor “specificity”. In other words, when the machine says “ACUTE MI SUSPECTED” it needs to always be right. The program is almost perfect in that regard, and when you see “ACUTE MI SUSPECTED” the machine is right about 98% of the time. However, in order to attain that specificity, if the computer isn’t absolutely sure that an AMI is present, it will not say anything about it. Depending on the version of the software in your 12-lead machine, the computer may miss as many as one third of the cases where AMI could be suspected on the ECG. In other words YOU are the primary interpreter, the computer is your backup.

57. 12-lead ECG The computer is very good at measuring intervals and durations. For example, it is actually much better than we are at measuring the PR-interval and the QRS width. This information is always provided, however, it may be expressed in unfamiliar terms. While we typically express these intervals and durations in seconds, the 12-lead expresses them in milliseconds. It is a simple matter to convert milliseconds to seconds.The computer is very good at measuring intervals and durations. For example, it is actually much better than we are at measuring the PR-interval and the QRS width. This information is always provided, however, it may be expressed in unfamiliar terms. While we typically express these intervals and durations in seconds, the 12-lead expresses them in milliseconds. It is a simple matter to convert milliseconds to seconds.

58. 12-Lead ECG To convert seconds to milliseconds simply move the decimal three places to the left. If the QRS is measured by the 12-lead as 80 milliseconds, that equals 0.08 seconds. Question: If the 12-lead measures the PR interval at 160 milliseconds is that within normal limits? Answer: Yes, it’s the same as 0.16 seconds.To convert seconds to milliseconds simply move the decimal three places to the left. If the QRS is measured by the 12-lead as 80 milliseconds, that equals 0.08 seconds. Question: If the 12-lead measures the PR interval at 160 milliseconds is that within normal limits? Answer: Yes, it’s the same as 0.16 seconds.

59. 12-Lead ECG Some of you may be wondering how anyone can make a sound interpretation with only 2.5 seconds shown in each lead. Ask the group to look at the highlighted beat in the lead two rhythm strip, ask them to determine the rate and rhythm. Of course it cannot be done. As you well know, when you use an ECG to determine the cardiac rate and rhythm, certain sampling time is required. Usually, at least a six second tracing is necessary, and complex rhythms may require even more sampling time. However, do not be intimidated by the short sampling time in each of the 12-leads. What is different about 12-lead interpretation is this: Only one beat from each lead is needed to make an interpretation. The 2.5 seconds in each lead is usually long enough to capture one good, representative beat. Recognition of AMI involves analyzing the shape of one beat in each lead. With that in mind let’s look at the shape of the waveforms in each lead.Some of you may be wondering how anyone can make a sound interpretation with only 2.5 seconds shown in each lead. Ask the group to look at the highlighted beat in the lead two rhythm strip, ask them to determine the rate and rhythm. Of course it cannot be done. As you well know, when you use an ECG to determine the cardiac rate and rhythm, certain sampling time is required. Usually, at least a six second tracing is necessary, and complex rhythms may require even more sampling time. However, do not be intimidated by the short sampling time in each of the 12-leads. What is different about 12-lead interpretation is this: Only one beat from each lead is needed to make an interpretation. The 2.5 seconds in each lead is usually long enough to capture one good, representative beat. Recognition of AMI involves analyzing the shape of one beat in each lead. With that in mind let’s look at the shape of the waveforms in each lead.

61. 12-Lead ECG AMI recognition Two things to know What to look for Where you are looking The first level of 12-lead interpretation is simply a matter of knowing two facts: 1. What changes an AMI can place on the 12-lead, and 2. Knowing which part of the heart that each lead “sees.” Lets look at each in more detail. The first level of 12-lead interpretation is simply a matter of knowing two facts: 1. What changes an AMI can place on the 12-lead, and 2. Knowing which part of the heart that each lead “sees.” Lets look at each in more detail.

62. AMI Recognition What to look for ST segment elevation One millimeter or more (one small box) Present in two anatomically contiguous leads ST segment elevation, measured at the J-point, of 1mm or more is considered an abnormal finding. When that elevation is found in at least two anatomically contiguous leads, it is considered presumptive evidence of AMI. NOTE: The concept of anatomically contiguous leads is simple, but may be difficult to explain. Essentially it means two leads looking at adjoining areas of tissue. The difficulty comes when trying to determine which leads are contiguous with other leads. Here is one explanation: If two leads have the same name (i.e., lateral or inferior) they are contiguous. Also, in the chest leads, if they are numerically consecutive, they are also contiguous. For example V2 is called a septal lead, and V3 an anterior lead, but they are anatomically contiguous.ST segment elevation, measured at the J-point, of 1mm or more is considered an abnormal finding. When that elevation is found in at least two anatomically contiguous leads, it is considered presumptive evidence of AMI. NOTE: The concept of anatomically contiguous leads is simple, but may be difficult to explain. Essentially it means two leads looking at adjoining areas of tissue. The difficulty comes when trying to determine which leads are contiguous with other leads. Here is one explanation: If two leads have the same name (i.e., lateral or inferior) they are contiguous. Also, in the chest leads, if they are numerically consecutive, they are also contiguous. For example V2 is called a septal lead, and V3 an anterior lead, but they are anatomically contiguous.

63. ST Segment Elevation Presumptive evidence of AMI Indication for acute reperfusion therapy With an appropriate clinical presentation, ST segment elevation is presumptive evidence of acute myocardial infarction. These patients benefit from immediate reperfusion, usually in the form of a thrombolytic drug or PTCA (Percutaneous Transluminal Coronary Angioplasty). NOTE: In later modules of this program the participant will be introduced to the full spectrum of Acute Coronary Syndromes (ACS). You may opt to acknowledge that other criteria for reperfusion will be added in later in the program. However, it is appropriate to begin with ST segment elevation. With an appropriate clinical presentation, ST segment elevation is presumptive evidence of acute myocardial infarction. These patients benefit from immediate reperfusion, usually in the form of a thrombolytic drug or PTCA (Percutaneous Transluminal Coronary Angioplasty). NOTE: In later modules of this program the participant will be introduced to the full spectrum of Acute Coronary Syndromes (ACS). You may opt to acknowledge that other criteria for reperfusion will be added in later in the program. However, it is appropriate to begin with ST segment elevation.

64. Significant Indicators on the 12 - Lead The are many indications of myocardial ischemia, injury, or infarction Pathological Q waves ST segment elevation/depression > 1 mm Poor R wave Progression

65. 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. 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.