12 Lead ECG Skills: Building Confidence for Clinical Practice. Presented By: Cynthia Webner, BSN, RN, CCRN-CMC. Karen Marzlin, BSN, RN,CCRN-CMC

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1 12 Lead ECG Skills: Building Confidence for Clinical Practice NTI 2009 Preconference Session 803 Presented By: Karen Marzlin, BSN, RN,CCRN-CMC 1 12 Lead ECG Fundamentals: The Starting Place for Linking Knowledge to Practice 2

2 The journey of a thousand miles begins with one step. - Lao Tsu Framework for the Day Understand don t memorize Physiological basis Building blocks Start slow fly wheel effect 4

3 Electrical Conduction Pathway SA Node Right and left Atrial Conduction AV Node Bundle of His Right and Left Bundle Branches Fascicles Purkinge Fibers 5 Normal 12 Lead ECG STANDARD LIMB LEADS AUGMENTED LIMB LEADS CHEST OR PRECORDIAL LEADS 2 Chest Electrodes One Chest Electrode 6

4 Lead 1 avr V1 V4 Lead 2 avl V2 V5 Lead 3 avf V3 V6 7 Two Sets of Leads Limb Leads Standard Limb Leads (I, II, and III) Augmented Limb Leads (avr, avl, avf) Chest Leads Also called precordial leads V1 V6

5 Leads Two Electrodes on Patient One positive electrode One negative electrode Records difference in electrical potential between selected electrodes + - Leads I, II, and III One Electrode on Patient One positive electrode One reference point Zero electrical potential Center of heart Leads avr, avl, avf V1- V6 9 Importance of the Positive Electrode Reason 1 Consider the positive electrode the eye or the camera LA + RA RV LV

6 The Camera Looks at Different Parts of the Myocardium 11 Electrode Placement Limb Leads 12

7 The Ground Note: Nothing travels toward the right leg as a positive electrode. The right leg is the ground used to absorb any excess electrical activity. Standard Limb Leads Leads I, II, III 14

8 Standard Limb Leads Lead I - LEAD I + HIGH LATERAL WALL 15 Standard Limb Leads Lead II - LEAD II INFERIOR WALL + 16

9 Standard Limb Leads Lead III - LEAD III INFERIOR WALL + 17 Standard Limb Lead Leads I, II, III - LEAD I +/- LEAD II LEAD III + 18

10 Augmented Limb Leads Leads avr, avl, avf UNIPOLAR 19 Augmented Limb Leads avr avr + View of NOTHING related to LV 20

11 Augmented Limb Leads avl avl + High Lateral Wall 21 Augmented Limb Leads avf Inferior Wall avf + 22

12 Augmented Limb Leads Lead Placement: Leads avr, avl, avf avr + avl + + avf 23 Einthoven s Triangle Label Leads I, II, III Then add avr, avl, avf 24

13 AVR AVL AVF 25 Chest (Precordial) Leads 26

14 Electrode Placement Chest (Precordial) Leads Lead V 1 4 th ICS, RSB Lead V 2 4 th ICS, LSB Lead V 3 Midway Between V 2 & V 4 Lead V 4 L midclavicular line, 5 th ICS Lead V 5 L anterior axillary line, same level as V 4 Lead V 6 L midaxillary line, same level as V 4 Used with permission from: Aehlert. B (2002). ECG s27 made easy (2nd ed.). St. Louis, MO: Mosby, Inc. Pg Frontal vs. Horizontal Planes 28

15 A Closer Look at Chest Leads The Point of View of the Positive Electrode V1 Septum (RV) V2 Septum 29 A Closer Look at Chest Leads The Point of View of the Positive Electrode V3 Anterior V4 Anterior 30

16 A Closer Look at Chest Leads The Point of View of the Positive Electrode V5 Low Lateral V6 Low Lateral 31 Lead 1 Left Arm High Lateral Wall avr Right Arm V1 4 th ICS, RSB Septal Wall V4 L MCL, 5 th ICS Anterior Wall Lead 2 Left Leg Inferior Wall avl Left Arm High Lateral Wall V2 4 th ICS, LSB Septal Wall V5 L anterior axillary, same level as V 4 Low Lateral Wall Lead 3 Left Leg Inferior Wall avf Left Leg Inferior Wall V3 Midway Between V 2 & V 4 Anterior Wall V6 L midaxillary line, same level as V 4 Low Lateral Wall 32

17 Identifying Normal Complexes 33 ECG Paper Horizontal Axis Normal speed 25 mm/ sec Smallest box 1mm x 1mm 1 small box 0.04 sec 1 large box 0.20 sec 5 large boxes 1.0 sec

18 ECG Paper Vertical Axis Voltage or amplitude Measured in millivolts(mv) or millimeters (mm) EKG machine calibrated so that 1 mv produces a deflection measuring exactly 10 mm tall 1 small box = 1 mm high 1 large box = 5 mm high Measuring Rate on Irregular Rhythms Irregular rhythms Count number of R-R intervals in a 6 second strip and multiply by X 10 = 60 36

19 Measuring Rate on Regular Rhythms Regular rhythms Count number of large boxes between R waves and divide into 300: 1 = = 50 2 = = 43 3 = = 37 4 = 75 9 = 33 5 = = = Calculating Rate

20 Rate Ruler 4 big + 2 tiny = rate big boxes + 2 tiny boxes 39 ECG Waves and Intervals 40

21 P Waves P waves represent atrial depolarization and spread of electrical impulse through the atria First half of P represents depolarization from the SA node though the RA to the AV node Down slope of P wave represents stimulation of the LA 41 Normal P Wave Criteria Smooth and rounded No more than 2.5 mm in height No more than.11 seconds in duration 42

22 QRS Complex Not every QRS complex contains a Q wave, R wave and S wave!! Q always negative (below baseline) R first positive above the baseline R second positive above the baseline S negative deflection following R wave or second component to entirely complex S second negative deflection 43 Let s Practice QS qr QR Qr qrs R RS rs rsr Rs 44

23 In limb leads the ST segment is normally isoelectric but may be slightly elevated or depressed by less than 1mm ST Segment In precordial leads ST segment is elevation is normally not more than 1 to 2 mm ST Segment The J Point Junction where the QRS complex and the ST segment meet.

24 T Waves Represents ventricular repolarization Slightly asymmetrical Usually oriented in the same direction as the previous QRS Not normally > than 5mm (limb leads) to 10 mm (precordial) high 48

25 The Importance of the Positive Electrode Reason 2 If a wave of depolarization moves TOWARD the + electrode, the waveform on the ECG graph will be upright or + 49 The Importance of the Positive Electrode Reason 2 If a wave of depolarization moves TOWARD the electrode, the waveform on the ECG graph will be downward or 50

26 The Importance of the Positive Electrode Reason 2 A biphasic wave form occurs when the direction of depolarization is PERPENDICULAR to the + electrode - + Heart avl 51 A Closer Look at Lead I Lead 1 Normals P waves: Upright and gently rounded QRS Complex: Upright T Waves: Upright and smaller than QRS 52

27 A Closer Look at Lead II Lead II normals P wave: upright and gently rounded QRS: upright T wave: upright and smaller than QRS 53 A Closer Look at Lead III Lead III normals P wave: upright and gently rounded QRS Complex: Upright T wave: Upright and smaller than QRS 54

28 A Closer Look at avr avr Normals P wave: inverted QRS: inverted (rsr or rs) T wave: inverted 55 A Closer Look at avl avl Normals P waves: Upright or inverted QRS: Upright or inverted T wave: Upright or inverted (but no down sloping of ST) 56

29 A Closer Look at avf avf Normals P waves: upright and gently rounded QRS: Upright T wave: Upright and smaller than QRS 57 Normal V1 A Closer Look at V1 P wave: inverted, upright or biphasic QRS: inverted with rs pattern T waves: inverted or upright 58

30 A Closer Look at V2 V2 Normals P waves: upright QRS: inverted; rs pattern T waves: upright, inverted 59 V3 Normals A Closer Look at V3 P wave: upright QRS: equiphasic; RS pattern T waves: Upright 60

31 V4 Normals A Closer Look at V4 P Wave: Upright QRS: Upright; qrs T wave: Upright 61 V5 Normals A Closer Look at V5 P wave: Upright QRS: upright; qrs pattern T wave: Upright 62

32 V6 Normals A Closer Look at V6 P wave: upright QRS: upright; qrs pattern T wave: upright 63 Normal V1-6: R Wave Progression The R wave becomes taller and the S wave becomes smaller as the electrode is moved from right to left This pattern is called R wave progression 64

33 Lead 1 Left Arm High Lateral Wall avr Right Arm V1 4 th ICS, RSB Septal Wall V4 L MCL, 5 th ICS Anterior Wall Lead 2 Left Leg Inferior Wall avl Left Arm High Lateral Wall V2 4 th ICS, LSB Septal Wall V5 L anterior axillary, same level as V 4 Low Lateral Wall Lead 3 Left Leg Inferior Wall avf Left Leg Inferior Wall V3 Midway Between V 2 & V 4 Anterior Wall V6 L midaxillary line, same level as V 4 Low Lateral Wall Lead ECG Evaluation 1. Atrial rate 2. Ventricular rate 3. Regular / Irregular 4. P wave for each QRS 5. Underlying rhythm 6. Are P waves abnormal in any lead? 7. Calculate P-R Interval is it constant or changing. 8. Is QRS width and shape normal in each lead? 9. If > 0.12 sec differentiate between RBBB and LBBB and ventricular ectopic focus by shape in V1 and V Are ST segments normal in all leads? If abnormal, is the pattern repeated in a contiguous lead. 11. Are T Waves normal in all leads? If abnormal, is the pattern repeated in a contiguous lead? 12. What is the length of the QT interval? 13. What is the Axis? 14. If there is a pacemaker is it pacing, capturing and sensing in the appropriate chambers?

34 67 68

35 Utilizing the Bedside Monitor to Provide 12 Lead ECG Information 69 Three Reasons for Bedside Cardiac Monitoring Arrhythmia Detection Ischemia Monitoring QT Interval Monitoring 70

36 Arrhythmia Monitoring Candidates Primary purpose for all patients on cardiac monitor Purpose Detection of and prompt intervention for life threatening arrhythmias Leads of Choice V1 V6 (or MCL6) 71 Ischemia (ST) Monitoring Candidates Patients admitted with Acute Coronary Syndrome Patients post PCI Patients admitted to Chest Pain Center or Chest Pain Center protocol Purpose To monitor changes in ST segments (compared to baseline) in select leads Leads of Choice Based on area of known or potential ischemia 72

37 QT Interval Monitoring Candidates Initiation of antiarrhythmic therapy with medications that prolong QT Other medications that prolong QT Other conditions that prolong QT Purpose To monitor for increase in QT interval to identify and intervene in patients at high risk for Torsades de Pointes Leads of Choice Lead where an accurate QT Interval can be measured Patient can be changed to another lead to run a strip to measure QT or 12 lead can be done if QT not easily measured in V1 or V6 73 Comparing Bedside Monitoring to the 12 Lead ECG Bedside Monitoring 12 Lead ECG Remember View of Positive Electrode (Camera) Importance of Lead Placement Identify Correct Lead on Rhythm Strip 74

38 Arrhythmia Monitoring When a patient has a wide complex tachycardia it is important to determine if the tachycardia is: Ventricular tachycardia Or SVT (including atrial arrhythmias) with a coexisting bundle branch block Since both rhythms are wide and fast it is often difficult to differentiate 75 Why V1 and V6 (MCL6) for Arrhythmia Monitoring V1 Looks different for ventricular tachycardia and bundle branch block Helps to determine if rhythm is ventricular tachycardia (VT) or SVT with a bundle branch block Position of V1 electrode 76

39 Bedside Cardiac Monitoring Limitations of Lead II V1 LBBB RBBB LVT RVT Five Lead - Lead Placement Standard 5 Lead Placement Modified 5 lead Placement- MCL6 78

40 3 Lead Placement for MCL1 79 ECG Fundamentals Calculating Cardiac Axis 80

41 Calculating the Electrical Axis of the Heart Determining the direction (depolarization) of the mean electrical impulse of the heart Down and to the left 81 More About Axis Axis is determined by the sum of all electrical activity As depolarization moves through the conduction pathway the direction is constantly changing; however the overall thrust of activity is in one direction Most of the electrical activity is directed towards the left ventricle due to the size of the myocardium required to eject blood The ventricle that requires the most of the depolarization activity is the ventricle which determines the direction of axis 82

42 Axis Wheel 83 Bipolar Frontal Plane Leads Lead I Left arm positive Right arm negative Lead II Left leg positive Right arm negative Lead III Left leg positive Left arm negative II I III 84

43 Unipolar Frontal Plane Leads Reference point in center of chest telephoto lens avr Right arm positive avl Left arm positive avf Foot (left leg) positive AVR AVF AVL 85 AVR AVL I III II AVF 86

44 87 Understanding the Axis Wheel Remember: The positive and negative poles of the limb leads make up the axis wheel Negative Pole Positive Pole 88

45 A Closer Look at Your Axis Wheel Finding positive and negative poles of each lead VERSUS Reading degrees of axis 89 Axis Quadrants: Normal Axis 90

46 Causes: LV Hypertrophy Systemic Hypertension Hypertrophic Cardiomyopathy Aortic Valve Stenosis / Insufficiency Axis Quadrants: Left Axis Deviation 91 Causes: Ventricular Tachycardia Axis Quadrants: Extreme Axis Deviation 92

47 Causes: RV Hypertrophy Pulmonary Hypertension Pulmonic Valve Stenosis Chronic Lung Disease Axis Quadrants: Right Axis Deviation 93 94

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49 97 Let Your Hands Determine Axis Use Lead I and avf Left hand represents QRS in Lead I Right hand represents QRS in avf Fingertips will point in the same direction as the QRS complex Handy Method of Axis Calculation developed by J. Cooper, PhD., American College of CV Nursing 98

50 Normal Axis: +0 to +90 Degrees Lead I: Upright QRS avf: Upright QRS It s always normal to be on the up and up 99 Right Axis Deviation: +90 to +180 Degrees Lead I: Downward QRS avf: Upward QRS Fingertips are facing each other, therefore, they are right together 100

51 Left Axis Deviation: 0 to 90 degrees Lead I: Upright QRS avf: Downward QRS Fingertips are facing opposite directions, therefore they are left apart 101 Extreme Axis: -90 to 180 Degrees Lead I: Downward QRS avf: Downward QRS Fingertips are both facing downward therefore the axis is down and out and your fingers need to run for help 102

52 Hands on Learning Axis Review 103 Axis Practice 104

53 Axis Practice 105 Axis Practice 106

54 Axis Practice 107 Calculating the Degree of Axis 108

55 Calculating Degree of Axis ESPN Method Step 1 E=Equiphasic (First determine quadrant) Find the QRS complex in the limb leads which is the most equiphasic OR Find the smallest QRS complex (height of R wave minus depth of S wave) 109 ESPN Method Step 2 S=Sister Lead Utilizing the Criss-Cross method Find the Sister lead to the lead with the most equiphasic QRS complex 110

56 ESPN Method Step 4 If positive locate the positive pole of that lead on the axis wheel to determine degrees. If negative locate the negative pole of that lead on the axis wheel to determine degrees. 111 Axis Practice Calculating Degrees 112

57 Calculate Degree of Axis 113 Calculate Degree of Axis I II III 114

58 Calculate Degree of Axis 115 Calculate Degree of Axis 116

59 Lead 1 avr V1 V4 Left Arm High Lateral Wall Axis Quadrant Right Arm 4 th ICS, RSB Septal Wall L MCL, 5 th ICS Anterior Wall Lead 2 avl V2 V5 Left Leg Inferior Wall Left Arm High Lateral Wall 4 th ICS, LSB Septal Wall L anterior axillary, same level as V 4 Low Lateral Wall Lead 3 avf V3 V6 Left Leg Inferior Wall Left Leg Inferior Wall Axis Quadrant Midway Between V 2 & V 4 Anterior Wall L midaxillary line, same level as V 4 Low Lateral Wall 117 ECG Fundamentals Bundle Branch Blocks 118

60 Conduction System Review Left Bundle Branch Left anterior fascicle Left posterior fascicle Right Bundle Branch Purkinje Network Purkinje Fibers 119 Normal Depolarization 2 V 6 1 QRS sec V 1 120

61 Bundle Branch Block QRS complex is 0.12 sec or greater Incomplete BBB measures from 0.10 to Right Bundle Branch Block Causes CAD Disease of right side of the heart Cor pulmonale Cardiomyopathy Congenital lesions A-S Defects Pulmonic Stenosis Pulmonary Embolism 122

62 Normal Depolarization 2 V 6 1 QRS sec V V1 Right Bundle Branch Block Triphasic complex rsr pattern - positive Or an M shaped R wave with right peak taller Or a qr pattern V1 V1 V6 Triphasic complex qrs with wide S waves Positive V6 rsr R qr qrs 124

63 Right Bundle Branch Block Secondary T wave changes: T wave should go in the opposite direction to the last part of the QRS complex represents altered repolarization Primary T wave changes: T Waves that go in the same direction as the last part of the QRS complex indicate probable ischemia 125 Left Bundle Branch Block Causes Left Ventricular Hypertrophy MI CAD Aortic Stenosis Cardiomyopathy Hypertensive cardiomyopathy 126

64 Left Bundle Branch Block V 6 = wide R V 1 = QS QRS =.12 sec or more V1 = rs 127 Left Bundle Branch Block V1 Wide QS or rs complex - negative Slick downstroke Nadir <0.06 sec V6 Wide R wave with no initial septal q wave - - positive V6 128

65 Left Bundle Branch Block Nadir Measure from the beginning of the QRS complex to the bottom valley of the QRS < 0.06 sec 129 Left Bundle Branch Block Ischemia Secondary T wave changes: T waves should be in the opposite direction from the last part of the QRS complex represent altered repolarization Primary T wave Changes: T waves that go in the same direction as the last part of the QRS complex represent probable ischemia 130

66 Left Bundle Branch Block Injury An elevated J point is normal in the presence of a deep S wave as long as ST remains concave smile If ST becomes rounded then you may have injury - frown 131 Left Bundle Branch Block Often have left axis deviation From normal to 60 Most often not more than 30 High mortality rate if left axis is present 132

67 Left Anterior Hemiblock Causes Ischemia Valvular disease Cardiomyopathy Congenital heart disease Rarely normal Blood supply received from septal branch of LAD (or AV nodal artery of RCA) 133 Left Anterior Hemiblock Block of anterior superior fascicle of the LBB Left axis deviation - 30 to 75 Become suspicious at - 30 Definitive at 40 to 45 Common at -60 Key for recognizing -60 Axis - avr most equiphasic limb lead Commonly seen in anterior wall MI Low mortality if isolated Left anterior hemiblock in association with RBBB during AMI Associated with left main occlusion and high mortality 134

68 Left Anterior Hemiblock Lead 2, Lead 3 and avf rs pattern Small r waves Slightly wide / deep S waves Increased limb lead voltage Lead 1 and avl qr pattern Normal QRS duration 135 Lead 1 Left Arm High Lateral Wall Axis Lead 2 Left Leg Inferior Wall avr Right Arm avl Left Arm High Lateral Wall V1 4 th ICS, RSB Septal Wall Right / Left BBB V2 4 th ICS, LSB Septal Wall V4 L MCL, 5 th ICS Anterior Wall V5 L anterior axillary, same level as V 4 Low Lateral Wall Lead 3 Left Leg Inferior Wall avf Left Leg Inferior Wall Axis V3 Midway Between V 2 & V 4 Anterior Wall V6 Low Lateral Wall Right / Left BBB 136

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