12 Lead EKG Interpretation12 Lead EKG Interpretation

Cardiac Cardiac Conduction Conduction

SystemSystem

Purkinje fibers

1

2

3

4

5

4

12-Lead Electrodes12-Lead Electrodes A lead is a tracing of the electrical activity A lead is a tracing of the electrical activity

between 2 electrodesbetween 2 electrodes Leads view the heart from the front of the bodyLeads view the heart from the front of the body

Top, bottom, right, and left side of heartTop, bottom, right, and left side of heart Leads view the heart as if it were sliced in half Leads view the heart as if it were sliced in half

horizontallyhorizontally Front, back, right, and left sides of heartFront, back, right, and left sides of heart

Each lead has a positive and a negative Each lead has a positive and a negative electrodeelectrode

Standard 12-Lead EKGStandard 12-Lead EKG

Six limb leadsSix limb leads Leads I, II, III, aVR, aVL, aVFLeads I, II, III, aVR, aVL, aVF

Six chest leads (precordial leads)Six chest leads (precordial leads) V1, V2, V3, V4, V5, V6V1, V2, V3, V4, V5, V6

Information from 12 leads obtained Information from 12 leads obtained from the attachment of only 10 from the attachment of only 10 electrodeselectrodes

View The Leads ProvideView The Leads Provide

II, III, aVF – view inferior wall of heartII, III, aVF – view inferior wall of heart V1 and V2 – view septal wall of heartV1 and V2 – view septal wall of heart V3 and V4 – view anterior wall of V3 and V4 – view anterior wall of

heartheart I, aVL, V5, V6 – view lateral wall of I, aVL, V5, V6 – view lateral wall of

heartheart

Precordial Precordial leadsleads

2nd ICS

1st ICS

3rd ICS

12 Lead EKG Printout12 Lead EKG Printout Standard format 8Standard format 811//22 x 11 x 11 paper paper 12 lead format:12 lead format: II aVR aVR V1 V1 V4 V4 IIII aVL aVL V2 V2 V5 V5 IIIIII aVF aVF V3 V3 V6 V6

Machines can analyze data obtained Machines can analyze data obtained but humans must interpret databut humans must interpret data

I

II

III

aVR

aVL

aVF

V1

V2

V3

V4

V5

V6

Lateral View – I, aVL, V5, V6Lateral View – I, aVL, V5, V6

I

aVL V5

V6

Inferior View – II, III, aVFInferior View – II, III, aVF

II

III aVF

Septal View – V1 & V2Septal View – V1 & V2

V1

V2

Anterior View – V3 & V4Anterior View – V3 & V4

V4

V3

Myocardial InsultMyocardial Insult IschemiaIschemia

lack of oxygenationlack of oxygenation ST depression or T wave inversionST depression or T wave inversion permanent damage avoidablepermanent damage avoidable

InjuryInjury prolonged ischemiaprolonged ischemia ST elevationST elevation permanent damage avoidablepermanent damage avoidable

InfarctInfarct death of myocardial tissue; damage permanent; may have death of myocardial tissue; damage permanent; may have Q Q

wavewave

Evaluating for ST Segment Evaluating for ST Segment ElevationElevation

Locate the J-pointLocate the J-point Identify/estimate where the isoelectric line Identify/estimate where the isoelectric line

is noted to beis noted to be Compare the level of the ST segment to Compare the level of the ST segment to

the isoelectric linethe isoelectric line Elevation (or depression) is significant if Elevation (or depression) is significant if

more than 1 mm (one small box) is seen in more than 1 mm (one small box) is seen in 2 or more leads facing the same 2 or more leads facing the same anatomical area of the heart anatomical area of the heart (ie: contiguous leads-see slide #41, #42)(ie: contiguous leads-see slide #41, #42)

J point – where the QRS complex and ST J point – where the QRS complex and ST segment meetsegment meet

ST segment elevation - evaluated 0.04 seconds ST segment elevation - evaluated 0.04 seconds (one small box) after J point (one small box) after J point

The J PointThe J Point

Coved Coved shape shape usually usually indicates indicates acute injuryacute injury

Concave Concave shape is shape is usually usually benign benign especially if especially if patient is patient is asympto-asympto-matic matic

Significant ST ElevationSignificant ST Elevation ST segment elevation measurementST segment elevation measurement

starts 0.04 seconds after J pointstarts 0.04 seconds after J point ST elevationST elevation

> 1mm (1 small box) in 2 or more contiguous chest > 1mm (1 small box) in 2 or more contiguous chest leads (V1-V6)leads (V1-V6)

>1mm (1 small box) in 2 or more anatomically >1mm (1 small box) in 2 or more anatomically contiguous leads (ie: II, III, aVF; I, aVL, V5, V6)contiguous leads (ie: II, III, aVF; I, aVL, V5, V6)

Contiguous leadContiguous lead limb leads that “look” at the same area of the heart or limb leads that “look” at the same area of the heart or

are numerically consecutive chest leads (ie: V1 – V6)are numerically consecutive chest leads (ie: V1 – V6)

Contiguous LeadsContiguous Leads

Lateral wall: I, aVL, V5, V6Lateral wall: I, aVL, V5, V6 Inferior wall: II, III, avFInferior wall: II, III, avF Septum: V1 and V2Septum: V1 and V2 Anterior wall: V3 and V4Anterior wall: V3 and V4 Posterior wall: V7-V9 (leads placed Posterior wall: V7-V9 (leads placed

on the patient’s back 5on the patient’s back 5thth intercostal intercostal space creating a 15 lead EKG)space creating a 15 lead EKG)

Evolution of AMIEvolution of AMIA - pre-infarct (normal)A - pre-infarct (normal)B - Tall T wave (B - Tall T wave (first few first few

minutes of infarctminutes of infarct))C - Tall T wave C - Tall T wave andand ST ST

elevation (elevation (injuryinjury))D - Elevated ST (D - Elevated ST (injuryinjury), ),

inverted T wave (inverted T wave (ischemiaischemia), ), Q wave (Q wave (tissue deathtissue death))

E - Inverted T wave E - Inverted T wave ((ischemiaischemia), Q wave (), Q wave (tissue tissue deathdeath))

F - Q wave (F - Q wave (permanent permanent marking) marking)

ST Segment ST Segment ElevationElevation

EKG monitoringEKG monitoring Evaluates electrical activity of the heartEvaluates electrical activity of the heart Can indicate myocardial insult and locationCan indicate myocardial insult and location

ischemiaischemia - initial insult; ST depression seen - initial insult; ST depression seeninjuryinjury - prolonged myocardial hypoxia or - prolonged myocardial hypoxia or

ischemia; ST elevation seenischemia; ST elevation seeninfarctioninfarction - tissue death - tissue death

dead tissue no longer contractsdead tissue no longer contracts amount of dead tissue directly relates to amount of dead tissue directly relates to

degree of muscle impairmentdegree of muscle impairment may show Q waves may show Q waves

Contiguous ECG LeadsContiguous ECG Leads EKG changes are EKG changes are

significant when they are significant when they are seen in at least two seen in at least two contiguouscontiguous leads leads

Two leads are Two leads are contiguous if they look at contiguous if they look at the same area of the the same area of the heart or they are heart or they are numerically consecutive numerically consecutive chest leadschest leads

Groups of EKG LeadsGroups of EKG Leads Inferior wall - II, III, aVFInferior wall - II, III, aVF Septal wall - V1, V2Septal wall - V1, V2 Anterior wall - V3, V4Anterior wall - V3, V4 Lateral wall - I, aVL, V5, V6 Lateral wall - I, aVL, V5, V6

aVR is not evaluated in typical groups aVR is not evaluated in typical groups Standard lead placement does not look at posterior Standard lead placement does not look at posterior

wall or right ventricle of the heart - need special wall or right ventricle of the heart - need special lead placement for these viewslead placement for these views

Basic 12-Lead EKG FormatBasic 12-Lead EKG FormatLead I

Lateral wallaVR

not evaluatedV1

SeptumV4

Anterior wall

Lead II Inferior wall

aVLLateral wall

V2

SeptumV5

Lateral wall

Lead III Inferior wall

aVFInferior wall

V3

Anterior V6

Lateral wall

Lateral Wall MI: I, aVL, V5, V6Lateral Wall MI: I, aVL, V5, V6

Source: The 12-Lead ECG in Acute Coronary Syndromes, MosbyJems, 2006.

Inferior Wall MI II, III, aVFInferior Wall MI II, III, aVF

Source: The 12-Lead ECG in Acute Coronary Syndromes, MosbyJems, 2006.

Septal MI: Leads V1 and V2Septal MI: Leads V1 and V2

Source: The 12-Lead ECG in Acute Coronary Syndromes, MosbyJems, 2006.

Anterior Wall MI V3, V4Anterior Wall MI V3, V4

Source: The 12-Lead ECG in Acute Coronary Syndromes, MosbyJems, 2006.

Posterior MI – Reciprocal Changes Posterior MI – Reciprocal Changes ST Depression V1, V2, V3, poss V4ST Depression V1, V2, V3, poss V4

Source: The 12-Lead ECG in Acute Coronary Syndromes, MosbyJems, 2006.

12-Lead Electrode Placement12-Lead Electrode Placement

Case #1Case #1

Case #1Case #1 52 year-old patient complains of 52 year-old patient complains of

indigestion after pizza & beer dinner.indigestion after pizza & beer dinner. VS: 124/82; P – 108; R - 18VS: 124/82; P – 108; R - 18 Is there ST elevation:Is there ST elevation:

I, aVL, V5, V6?I, aVL, V5, V6? II, III, aVF?II, III, aVF? V1, V2?V1, V2? V3, V4?V3, V4?

What are you going to do for this patient?What are you going to do for this patient? (There is no ST elevation)(There is no ST elevation)

Case #2Case #2

Case #2Case #2 62 year-old female developed chest & jaw pain 62 year-old female developed chest & jaw pain

while in the showerwhile in the shower VS: 110/62; P – 66; R – 20VS: 110/62; P – 66; R – 20 Is there ST elevation:Is there ST elevation:

I, aVL, V5, V6?I, aVL, V5, V6? II, III, aVF?II, III, aVF? V1, V2?V1, V2? V3, V4?V3, V4?

What are you going to do for this patient?What are you going to do for this patient? (ST elevation II, III, aVF – Inferior wall MI)(ST elevation II, III, aVF – Inferior wall MI)

Case #3Case #3

Case #3Case #3 45 year-old patient who complains of chest 45 year-old patient who complains of chest

heaviness & lightheadednessheaviness & lightheadedness VS: 90/56; P – 86; R - 22VS: 90/56; P – 86; R - 22 Is there ST elevation:Is there ST elevation:

I, aVL, V5, V6?I, aVL, V5, V6? II, III, aVF?II, III, aVF? V1, V2?V1, V2? V3, V4?V3, V4?

What are you going to do for this patient?What are you going to do for this patient? (ST elevation V2-V5 – anterior infarction)(ST elevation V2-V5 – anterior infarction)

Case #4Case #4

Case #4Case #4 87 year-old female patient complains of 87 year-old female patient complains of

dizziness and being extremely tireddizziness and being extremely tired VS: 88/52; P – 30; R - 16VS: 88/52; P – 30; R - 16 Is there ST elevation:Is there ST elevation:

I, aVL, V5, V6?I, aVL, V5, V6? II, III, aVF?II, III, aVF? V1, V2?V1, V2? V3, V4?V3, V4?

What are you going to do for this patient?What are you going to do for this patient? (ST elevation II, III, aVF, V2-V4)(ST elevation II, III, aVF, V2-V4)

Case #5Case #5

Case #5Case #5 58 year-old male patient who complains of chest 58 year-old male patient who complains of chest

pain radiating down the left arm after working pain radiating down the left arm after working out in the gymout in the gym

VS: 110/72; P – 100; R - 18VS: 110/72; P – 100; R - 18 Is there ST elevation:Is there ST elevation:

I, aVL, V5, V6?I, aVL, V5, V6? II, III, aVF?II, III, aVF? V1, V2?V1, V2? V3, V4?V3, V4?

What are you going to do for this patient?What are you going to do for this patient? (ST elevation II, III, aVF)(ST elevation II, III, aVF)

Case #6Case #6

Case #6Case #6 92 year-old patient complaining of pounding in 92 year-old patient complaining of pounding in

her chest for one hourher chest for one hour VS: 98/66; P – 110; R- 16VS: 98/66; P – 110; R- 16 Is there ST elevation:Is there ST elevation:

I, aVL, V5, V6?I, aVL, V5, V6? II, III, aVF?II, III, aVF? V1, V2?V1, V2? V3, V4?V3, V4?

What are you going to do for this patient?What are you going to do for this patient? (ST elevation V1-V4 – anterioseptal MI)(ST elevation V1-V4 – anterioseptal MI)

Case #7Case #7

Case #7Case #7 36 year-old patient who passed out standing in 36 year-old patient who passed out standing in

line at a bankline at a bank VS: 128/78; P – 80; R - 20VS: 128/78; P – 80; R - 20 Is there ST elevation:Is there ST elevation:

I, aVL, V5, V6?I, aVL, V5, V6? II, III, aVF?II, III, aVF? V1, V2?V1, V2? V3, V4?V3, V4?

What are you going to do for this patient?What are you going to do for this patient? (ST elevation II, III, aVF)(ST elevation II, III, aVF)