12 lead ecg fundamentals: the starting place for … lead ecg fundamentals: the starting place for...

NTI 2009 Preconference

Cynthia Webner, BSN, RN, CCRN-CMC

www.cardionursing.com

Presented By:


Karen Marzlin, BSN, RN,CCRN-CMC


1

12 Lead ECG Skills: Building Confidence for Clinical Practice


Session 803

2

12 Lead ECG Fundamentals: The Starting Place for The Starting Place for The Starting Place for The Starting Place for

Linking Knowledge to PracticeLinking Knowledge to PracticeLinking Knowledge to PracticeLinking Knowledge to Practice




The journey of a thousand miles begins with one step.

- Lao Tsu

4

Framework for the Day

• Understand – don’t memorize

• Physiological basis

• Building blocks

• Start slow – fly wheel effect




5

Electrical Conduction Electrical Conduction Electrical Conduction Electrical Conduction

PathwayPathwayPathwayPathway• SA Node

• Right and left Atrial Conduction

• AV Node

• Bundle of His

• Right and Left Bundle Branches

• Fascicles

• Purkinge Fibers

6

Normal 12 Lead ECGNormal 12 Lead ECGNormal 12 Lead ECGNormal 12 Lead ECGSTANDARD

LIMB LEADS

AUGMENTED

LIMB LEADS CHEST OR PRECORDIAL LEADS

2 Chest Electrodes One Chest Electrode




7

Lead 1 aVR V1 V4

Lead 2 aVL V2 V5

Lead 3 aVF V3 V6

Two Sets of Leads Two Sets of Leads Two Sets of Leads Two Sets of Leads

• Limb LeadsLimb LeadsLimb LeadsLimb Leads

– Standard Limb

Leads

(I, II, and III)

– Augmented Limb

Leads

(aVR, aVL, aVF)

• Chest Leads Chest Leads Chest Leads Chest Leads

–Also called precordial leads

–V1 – V6




9

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

+ -

Importance of the Positive Electrode

Reason 1

• Consider the positive electrode the “eye” or “the camera”

+RA

RV

LA

LV




11

The Camera Looks at Different Parts of

the Myocardium

12

Electrode Placement

Limb Leads




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.

14

Standard Limb LeadsStandard Limb LeadsStandard Limb LeadsStandard Limb Leads

LeadsLeadsLeadsLeads I, II, IIII, II, IIII, II, IIII, II, III




15

Standard Limb LeadsLead I

- + LEAD I

HIGH

LATERAL

WALL

16

Standard Limb Leads

Lead II

-

+

LEAD IIINFERIOR

WALL




17

Standard Limb Leads

Lead III

-

+

LEAD III

INFERIOR WALL

18

Standard Limb Lead

Leads I, II, III

+/-

+

LEAD III

-LEAD I

LEAD II




19

Augmented Limb LeadsAugmented Limb LeadsAugmented Limb LeadsAugmented Limb Leads

LeadsLeadsLeadsLeads aVR, aVL, aVFaVR, aVL, aVFaVR, aVL, aVFaVR, aVL, aVF

UNIPOLAR

20

Augmented Limb LeadsaVR

+

aVR

View of NOTHING related to

LV




21

Augmented Limb LeadsaVL

+

aVL

High Lateral Wall

22

Augmented Limb LeadsaVF

+aVF

Inferior Wall




23

Augmented Limb Leads

Lead Placement: Leads aVR, aVL, aVF

+

+

+aVR aVL

aVF

24

Einthoven’s Triangle

Label Leads I, II, III Then add aVR, aVL, aVF




25

� AVR � AVL

AVF�

26

Chest (Precordial) Leads




27

Electrode PlacementChest (Precordial) Leads

• Lead V1

– 4th ICS, RSB

• Lead V2

– 4th ICS, LSB

• Lead V3

– Midway Between V2 & V4

• Lead V4

– L midclavicular line, 5th ICS

• Lead V5

– L anterior axillary line, same level as V4

• Lead V6

– L midaxillary line, same level as V4

Used with permission from: Aehlert. B (2002). ECG’s made

easy (2nd ed.). St. Louis, MO: Mosby, Inc. Pg. 197.

28

Frontal vs. Horizontal Planes




29

A Closer Look at Chest Leads

The Point of View of the Positive Electrode

• V1 – Septum (RV)

• V2 – Septum

30



• V3 – Anterior

• V4 – Anterior




31



V5 – Low Lateral V6 – Low Lateral

32

Lead 1Left Arm

High Lateral Wall

aVRRight Arm

V14th ICS, RSB

Septal Wall

V4L MCL, 5th ICS

Anterior Wall

Lead 2Left Leg

Inferior Wall

aVLLeft Arm

High Lateral Wall

V24th ICS, LSB

Septal Wall

V5L anterior

axillary, same

level as V4

Low Lateral Wall

Lead 3Left Leg

Inferior Wall

aVFLeft Leg

Inferior Wall

V3Midway Between

V2 & V4

Anterior Wall

V6L midaxillary

line, same level

as V4

Low Lateral Wall




33

Identifying Normal Complexes

ECG Paper – Horizontal AxisNormal 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




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 10

1 2 3 4 5 6

6 X 10 = 60

36




1 2 3 4

Measuring Rate on Regular Rhythms

• Regular rhythms

– Count number of large boxes between R waves and divide into 300:

1 = 300 6 = 50

2 = 150 7 = 43

3 = 100 8 = 37

4 = 75 9 = 33

5 = 60 10 = 30

300 ÷÷÷÷ 4 = 7537

Calculating Rate




Rate Ruler

1 2 3 4

4 big boxes + 2 tiny boxes

4 big + 2 tiny = rate 68

39

ECG Waves and Intervals

40




41

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

42

Normal P Wave Criteria

• Smooth and

rounded

• No more than 2.5

mm in height

• No more than .11

seconds in duration




43

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

44

QS qR QR Qr qRs

R RS rS rSR’ Rs

LetLetLetLet’’’’s Practices Practices Practices Practice




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

ST SegmentThe “J Point”

• “Junction” where

the QRS complex

and the ST

segment meet.




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




49

The Importance of the Positive Electrode

Reason 2

• If a wave of depolarization moves TOWARDthe + electrode, the waveform on the ECG graph will be upright or +

50


Reason 2

• If a wave of depolarization moves TOWARD the – electrode, the waveform on the ECG graph will be downward or –




51


Reason 2

A biphasic wave form occurs when the direction of depolarization is PERPENDICULAR to the +

electrode

Heart aVL

- +

52

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




53

A Closer Look at Lead II

• Lead II normals– P wave: upright and

gently rounded

– QRS: upright

– T wave: upright and smaller than QRS

54

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




55

A Closer Look at aVR

• aVR Normals– P wave: inverted

– QRS: inverted (rSr’ or

rS)

– T wave: inverted

56

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)




57

A Closer Look at aVF

• aVF Normals– P waves: upright and

gently rounded

– QRS: Upright

– T wave: Upright and

smaller than QRS

58

A Closer Look at V1

• Normal V1

– P wave: inverted,

upright or biphasic

– QRS: inverted with rS

pattern

– T waves: inverted or

upright




59

A Closer Look at V2

• V2 Normals– P waves: upright

– QRS: inverted; rSpattern

– T waves: upright,

inverted

60

A Closer Look at V3

• V3 Normals

– P wave: upright

– QRS: equiphasic;

RS pattern

– T waves: Upright




61

A Closer Look at V4

• V4 Normals– P Wave: Upright

– QRS: Upright; qRs

– T wave: Upright

62

A Closer Look at V5

• V5 Normals– P wave: Upright

– QRS: upright; qRs

pattern

– T wave: Upright




63

A Closer Look at V6

• V6 Normals– P wave: upright

– QRS: upright; qRs

pattern

– T wave: upright

64

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




65

Lead 1Left Arm

High Lateral Wall

aVRRight Arm

V14th ICS, RSB

Septal Wall

V4L MCL, 5th ICS

Anterior Wall

Lead 2Left Leg

Inferior Wall

aVLLeft Arm

High Lateral Wall

V24th ICS, LSB

Septal Wall

V5L anterior

axillary, same

level as V4

Low Lateral Wall

Lead 3Left Leg

Inferior Wall

aVFLeft Leg

Inferior Wall

V3Midway Between

V2 & V4

Anterior Wall

V6L midaxillary

line, same level

as V4

Low Lateral Wall

12 Lead ECG Evaluation12 Lead ECG Evaluation12 Lead ECG Evaluation12 Lead ECG Evaluation1. 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 V6.

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?




67

68




69

Utilizing the Bedside Monitor to

Provide 12 Lead ECG Information

70

Three Reasons for Bedside Cardiac Monitoring

Arrhythmia Detection

Ischemia Monitoring

QT Interval Monitoring




71

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)

72

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




73

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

74

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




75

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 co-existing bundle branch block

• Since both rhythms are wide and fast it is often difficult to differentiate

76

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




77

Bedside Cardiac MonitoringLimitations of Lead II

LBBB RBBB

2

V1

2

LVT RVT

78

Five Lead - Lead Placement

Standard 5 Lead Placement Modified 5 lead Placement-MCL6




79

3 Lead Placement for MCL1

80

ECG Fundamentals

Calculating Cardiac Axis




81

Calculating the Electrical Axis

of the Heart• Determining the direction (depolarization)

of the mean electrical impulse of the heart

• Down and to the left

82

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




83

Axis Wheel

84

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

I

II III




85

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 AVL

AVF

86

I

IIIII

AVRAVL

AVF




87

88

Understanding the Axis Wheel

• Remember: The positive and

negative poles of the limb leads make

up the axis wheelNegative

Pole

Positive Pole




89

A Closer Look at Your Axis Wheel

• Finding positive

and negative poles

of each lead

• Reading degrees

of axis

VERSUS

90

Axis Quadrants:

Normal Axis




91

Axis Quadrants:

Left Axis Deviation

Causes:

LV Hypertrophy

Systemic Hypertension

Hypertrophic

Cardiomyopathy

Aortic Valve Stenosis /

Insufficiency

92

Axis Quadrants:

Extreme Axis Deviation

Causes:

Ventricular

Tachycardia




93

Axis Quadrants:

Right Axis Deviation

Causes:

RV Hypertrophy

Pulmonary Hypertension

Pulmonic Valve Stenosis

Chronic Lung Disease

94




95

96




97

98

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




99

Normal Axis: +0 to +90 Degrees

• Lead I: Upright QRS

• aVF: Upright QRS

• It’s always “normal” to be on the up

and up

100

Right Axis Deviation:

+90 to +180 Degrees

• Lead I: Downward QRS

• aVF: Upward QRS

• Fingertips are facing each other,

therefore, they are “right” together




101

Left Axis Deviation:

0 to –90 degrees

• Lead I: Upright QRS

• aVF: Downward QRS

• Fingertips are facing opposite

directions, therefore they are “left”

apart

102

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




103

Hands on LearningHands on LearningHands on LearningHands on Learning

•Axis ReviewAxis ReviewAxis ReviewAxis Review

104

Axis Practice




105

Axis Practice

106

Axis Practice




107

Axis Practice

108

Calculating the Degree of Axis




109

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)

110

“ESPN” Method – Step 2

• S=Sister Lead

– Utilizing the “Criss-Cross”method Find the “Sister”lead to the lead with the most equiphasicQRS complex




111

“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.

112

Axis Practice

Calculating Degrees




113

Calculate Degree of Axis

114


I

II

III




115


116





117

Lead 1Left Arm

High Lateral Wall

Axis Quadrant

aVRRight Arm

V14th ICS, RSB

Septal Wall

V4L MCL, 5th ICS

Anterior Wall

Lead 2Left Leg

Inferior Wall

aVLLeft Arm

High Lateral Wall

V24th ICS, LSB

Septal Wall

V5L anterior axillary,

same level as V4

Low Lateral Wall

Lead 3Left Leg

Inferior Wall

aVFLeft Leg

Inferior Wall

Axis Quadrant

V3Midway Between

V2 & V4

Anterior Wall

V6L midaxillary line,

same level as V4

Low Lateral Wall

118

ECG Fundamentals

Bundle Branch Blocks




119

Conduction System Review

• Left Bundle Branch

– Left anterior fascicle

– Left posterior fascicle

• Right Bundle Branch

• Purkinje Network

• Purkinje Fibers

120

Normal Depolarization

V1

V6

QRS .06-.10 sec

1

2




121

Bundle Branch Block

• QRS complex is 0.12 sec or greater

• Incomplete BBB measures from 0.10 to

0.11

122

Right Bundle Branch BlockCauses

• CAD

• Disease of right side of the heart

• Cor pulmonale

• Cardiomyopathy

• Congenital lesions

• A-S Defects

• Pulmonic Stenosis

• Pulmonary Embolism




123

Normal Depolarization

V1

V6

QRS .06-.10 sec

1

2

124

Right Bundle Branch Block• V1

– Triphasic complex

rsR’ pattern - positive

– Or an M shaped R

wave with right peak

taller

– Or a qR pattern

• V6– Triphasic complex

– qRs with wide S waves

– Positive

V1V6

rSR’ qRs

V1

R qR




125

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

126

Left Bundle Branch Block

Causes

• Left Ventricular Hypertrophy

• MI

• CAD

• Aortic Stenosis

• Cardiomyopathy

• Hypertensive cardiomyopathy




127


V1 = QS

V6 = wide R

QRS = .12 sec or more

V1 = rS

128

Left Bundle Branch Block• V1

– Wide QS or rScomplex - negative

– Slick downstroke

– Nadir <0.06 sec

• V6– Wide R wave with

no initial septal q wave - - positive

V6




129

Left Bundle Branch BlockNadir

• Measure from the

beginning of the

QRS complex to

the bottom valley

of the QRS

< 0.06 sec

130


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




131


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

132


• Often have left axis deviation

• From normal to –60°

• Most often not more than –30°

• High mortality rate if left axis is present




133

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)

134

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 °

• 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

Key for recognizing -60°Axis

- aVR most equiphasic limb lead




135

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

136

Lead 1Left Arm

High Lateral Wall

Axis

aVRRight Arm

V14th ICS, RSB

Septal Wall

Right / Left BBB

V4L MCL, 5th ICS

Anterior Wall

Lead 2Left Leg

Inferior Wall

aVLLeft Arm

High Lateral Wall

V24th ICS, LSB

Septal Wall

V5L anterior axillary,

same level as V4

Low Lateral Wall

Lead 3Left Leg

Inferior Wall

aVFLeft Leg

Inferior Wall

Axis

V3Midway Between

V2 & V4

Anterior Wall

V6Low Lateral Wall

Right / Left BBB




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