12 lead essential

8/8/2019 12 Lead Essential

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Topics

q Anatomy Revisitedq The 12 Lead ECG Deviceq

The 12 Lead ECG Formatq Waveform Componentsq Lead Views


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Anatomy Revisitedq RCA

right ventricle inferior wall of LV posterior wall of LV (75%) SA Node (60%) AV Node (>80%)

q LCA septal wall of LV anterior wall of LV

lateral wall of LV posterior wall of LV (10%)


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Anatomy Revisitedq SA nodeq Intra-atrial pathwaysq AV nodeq

Bundle of Hisq Left and Right bundle

branches left anterior fascicle left posterior fascicle

q Purkinje fibers


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The 12 Lead ECG Device

q Device serves as a voltmeter measures the flow of electricity

q Unipolar vs Bipolar Leads


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Bipolar Leadsq 1 positive and 1 negative

electrode RA always negative LL always positive

q Traditional limb leads areexamples of these Lead I Lead II Lead III

q View from a vertical plane


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Unipolar Leadsq 1 positive electrode & 1

negative reference point calculated by using summation

of 2 negative leadsq Augmented Limb Leads

aVR, aVF, aVL view from a vertical plane

q Precordial or Chest Leads V1-V6 view from a horizontal plane


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The 12-Lead ECG FormatLeads typicallyproduced bydevices usedprehospital


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The 12-Lead ECG Format

Fields nottypicallyproduced bydevices usedprehospital


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The 12-Lead ECG Format

Device prints out 2.5 seceach of Leads I, II, IIIthen switches to aVR,aVL, aVF then switches

to V1, V2, V3 and then toV4, V5, V6 (varies bydevice)

Device computer

analyzes all 10 sec of all12 leads but only prints2.5 sec of each group


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The 12-Lead ECG FormatT h

e c om

p u t er

d i a

gn

o si si s

n o t al w

a y s a c c ur a

t e! ! !


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The 12-lead ECG Format

The computer IS veryaccurate atmeasuringintervals &durations


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Waveform Components:

R WaveFirst positive deflection; Rwave includes thedownstroke returning to

the baseline


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Waveform Components:Q Wave

First negative deflectionbefore R wave; Q wave

includes the negativedownstroke & return tobaseline


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Waveform Components:S Wave

Negative deflectionfollowing the R wave; Swave includes departurefrom & return to baseline


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Waveform Components:QRS

q Q waves Can occur normally in several leads

Normal Q waves called physiologic

Physiologic Q waves < .04 sec (40ms)

Pathologic Q

>.04 sec (40 ms)


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Waveform Components:QRS

q Q wave Measure width

Pathologic if greater than or equal to 0.04 seconds(1 small box)


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Waveform Components:QS Complex

Entire complex isnegatively deflected;No R wave present


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Waveform Components:J-Point

Junction between end of QRS andbeginning of ST segment; WhereQRS stops & makes a sudden

sharp change of direction


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Waveform Components:ST Segment

Segment between J-pointand beginning of T wave


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Waveform Components:ST Segment

q Need reference point Compare to TP segment DO NOT use PR segment as reference!

ST TP


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Waveform Components:Practice

q Find J-points and ST segments


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Waveform Components:Practice

q Find J-points and ST segments


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Lead Views


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Limb Leads Chest Leads

I aVR V1 V4

II aVL V2 V5

III aVF V3 V6

Lead Groups


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Inferior Wall

q II, III, aVF View from Left Leg

inferior wall of left ventricle

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6


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Inferior Wall

Inferior Wall

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6

q Posterior View portion resting on diaphragm ST elevation suspect

inferior injury


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Lateral Wall

q I and aVL View from Left Arm

lateral wall of left ventricle

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6


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Lateral Wall

q V5 and V6 Left lateral chest lateral wall of left ventricle

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6


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Lateral Wall

Lateral Wall

q I, aVL, V5, V6 ST elevation suspect

lateral wall injury

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6


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Anterior Wall

q V3, V4 Left anterior chest

electrode on anterior chest

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6


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Anterior Wall

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6

q V3, V4 ST segment elevation

suspect anterior wallinjury


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Septal Wallq V1, V2

Along sternal borders Look through right ventricle & see

septal wall

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6


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Septal

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6

q V1, V2 septum is left

ventricular tissue


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ST Segment Analysis

For each complex, determine whether the ST segment iselevated one millimeter or more above the TP segment


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12-Lead ECG

q AMI recognition Two things to know

What to look for Where you are looking


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AMI Recognition

q What to look for ST segment elevation

One millimeter or more (one small box) Present in two anatomically contiguous

leads

12 lead essential

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