Relax and Learn At the Farm 2012

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1 Relax and Learn At the Farm 2012 Session 2: 12 Lead ECG Fundamentals 101 Cynthia Webner DNP, RN, CCNS, CCRN-CMC, CHFN Though for Today Mastery is not something that strikes in an instant, like a thunderbolt, but a gathering power that moves steadily through time, like weather. - John Champlain Gardner Jr. ( ) Cardiovascular Nursing Education Associates 1 2 The ECG is a graphic recording of electrical activity spreading through the heart 12 lead ECG provides 12 different views of electrical activity Each bedside monitoring lead provides one view Electrical Conduction Pathway SA Node AV Node Bundle of His AV Junction Right and Left Bundle Branches Anterior and Posterior Fascicles PurkingeFibers 3 4 P QRS P wave: atrial depolarization QRS: ventricular depolarization T wave: ventricular repolarization PR interval: AV conduction time QRS width: intraventricular conduction time ST Segment: sustained ventricular depolarization QT interval: used to reflect ventricular repolarization time QT Interval T Lead 1 avr V1 V4 Lead 2 avl V2 V5 Lead 3 avf V3 V6 PR Interval QRS ST Segment 5 6 1

2 Normal 12 Lead ECG STANDARD LIMB LEADS AUGMENTED LIMB LEADS CHEST OR PRECORDIAL LEADS Dual and Single Electrode Leads Bipolar Leads One positive electrode One negative electrode Records difference in electrical potential between selected electrodes - Unipolar Leads One positive electrode One negative reference point Zero electrical potential Center of heart - Dual Electrode Leads Single Electrode Leads 7 Leads I, II, and III Leads avr, avl, avf V1-V6 Note: Technically all leads are bipolar. 8 Importance of the Positive Electrode Reason 1 Consider the positive electrode the the camera (exploring electrode) Electrode Placement Limb Leads Bedside Monitoring RA LA RV L V 12 Lead ECG 9 10 The Ground Note: Nothing travels toward the right leg as a positive electrode. Standard Limb Leads Leads I, II, III The right leg is the ground used to absorb any excess electrical activity. 11 Each Standard Limb Lead uses 2 surface electrodes per lead 12 2

3 Standard Limb Leads (Bipolar Leads) Lead Placement: Leads I, II, III Augmented Limb Leads Leads avr, avl, avf _ Lead I RA LA High Lateral Wall of LV of LV L L 13 Each Augmented Limb Lead uses one surface electrode per lead 14 Augmented Limb Leads (Unipolar Leads) Lead Placement: avr, avl, avf 6 Limb Leads Nothing RA - LA High Lateral Wall of LV of LV L L AVR AVL Chest (Precordial) Leads (Single ElectrodeLeads) AVF

4 Frontal vs. Horizontal Planes Frontal plane: Leads I, II, III, avf, avl, avf Horizontal plane: V1-V6 leads 19 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 midclavicularline, 5 th ICS Lead V 5 L anterior axillary line, same level as V 4 Lead V 6 L midaxillaryline, same level as V 4 Electrode Placement Chest (Precordial) Leads A Closer Look at Chest Leads The Point of View of the Positive Electrode V1 Septum (RV) V2 Septum A Closer Look at Chest Leads The Point of View of the Positive Electrode V3 Anterior V4 Anterior A Closer Look at Chest Leads The Point of View of the Positive Electrode 6 Precordial (Chest) Leads V5 Low Lateral V6 Low Lateral RA LV V6 RV V5 V1 V2 V3 V

5 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 Lateral Leads Lead 2 Left Leg 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 avf Left Leg V3 Midway Between V 2 & V 4 Anterior Wall V6 L midaxillary line, same level as V 4 Low Lateral Wall Inferior Leads Septal Anterior Leads Note! Posterior wall of the left ventricle and the right ventricle are not captured on the standard 12 lead ECG. Identifying Normal Complexes

6 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 Normal P Wave Criteria Smooth and rounded No more than 2.5 mm in height No more than.11 seconds in duration 33 P Waves P waves represent atrial depolarization and spread of electrical impulse through the atria Upslope of P represents depolarization of right atrium Downslope of P represents depolarization of left atrium Lead II Tall P waves could indicate RA hypertrophy A fat P wave could indicate LA hypertrophy Lead V1 A predominate 1 st half of biphasic P wave could indicate RA hypertrophy A predominate 2 st half of a biphasic P wave could indicate LA hypertrophy 34 RA Hypertrophy LA Hypertrophy

7 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 Let s Practice 37 Let s Practice QS qr QR Qr qrs R RS rs rsr Rs ST Segment In limb leads the ST segment is normally isoelectric but may be slightly elevated or depressed by less than 1mm In precordial leads ST segment is elevation is normally not more than 1 to 2 mm Clinical Application: Do not accept ST elevation in limb leads Do not accept ST depression in V leads Junction where the QRS complex and the ST segment meet. ST Segment The J Point 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 Clinical Application: T waves should be subordinate to the associated QRS

8 3 The Importance of the Positive Electrode Reason 2 Normal Ventricular Depolarization Septum depolarizes from left to right 2. Both ventricles depolarize from endocardium to epicardium 3. Basal portions of ventricles depolarize last 4. Mean direction of depolarization is downward, leftward, and posterior How Leads Record Positive electrode is the recording electrode or camera lens Negative electrode or reference point tells camera which way to shoot If positive electrode sees depolarization approaching it, it records an upright complex If positive electrode sees depolarization heading away from it, it records a negative complex. If depolarization is proceeding perpendicular to a lead, no deflection is recorded 44 A Closer Look at Lead I A Closer Look at Lead II Lead 1 Normals P waves: Upright and gently rounded QRS Complex: Upright T Waves: Upright and smaller than QRS 45 Lead II normals P wave: upright and gently rounded QRS: upright T wave: upright and smaller than QRS Note: Must be upright 46 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 47 A Closer Look at avr avr Normals P wave: inverted QRS: inverted (rsr or rs) T wave: inverted Note: Must be negative 48 8

9 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) A Closer Look at avf avf Normals P waves: upright and gently rounded QRS: Upright T wave: Upright and smaller than QRS A Closer Look at V1 Normal V1 P wave: inverted, upright or biphasic QRS: inverted with rs pattern T waves: inverted or upright 51 V2 Normals P waves: upright A Closer Look at V2 QRS: inverted; rs pattern T waves: upright, inverted 52 V3 Normals P wave: upright A Closer Look at V3 QRS: equiphasic; RS pattern T waves: Upright V4 Normals P Wave: Upright A Closer Look at V4 QRS: Upright; qrs T wave: Upright

10 V5 Normals P wave: Upright A Closer Look at V5 V6 Normals P wave: upright A Closer Look at V6 QRS: upright; qrs pattern QRS: upright; qrs pattern T wave: Upright T wave: upright Normal V1-6: R Wave Progression 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 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 Lead 2 Left Leg 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 avf Left Leg 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 the QRS in avr negative? 9. Is QRS width normal? 10. If >0.12 sec differentiate between RBBB and LBBB and ventricular ectopic focus by shape in V1 and V Is depolorization in each lead normal? 10. 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? 60 10

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12 Three Reasons for Bedside Cardiac Monitoring Utilizing the Bedside Monitor to Provide 12 Lead ECG Information Arrhythmia Detection Ischemia Monitoring QT Interval Monitoring 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) 69 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 RCA Lesion / MI: Monitor Lead III LAD Lesion / Anterior Wall MI: Monitor Lead V3 70 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 71 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 72 12

13 Lead 1 Left Arm High Lateral Wall avr Right Arm V1 4 th ICS, RSB Septal Wall Ectopy/Aberrancy V4 L MCL, 5 th ICS Anterior Wall Lead 2 Left Leg 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 QUESTIONS Lead 3 Left Leg ST Monitoring avf Left Leg V3 Midway Between V 2 & V 4 Anterior Wall ST Monitoring V6 L midaxillary line, same level as V 4 Low Lateral Wall Ectopy/Aberrancy Knowing is not enough; we must apply. Willing is not enough; we must do. Johann Wolfgang von Goethe Thank you! 75 13