Jon Tardiff, BS, PA-C

12-Lead EKG Interpretation

• I work for Virginia Garcia Memorial Health Center, Beaverton, Oregon.

• And I am a medical editor for Jones & Bartlett Publishing.

Disclosures:

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Goals for today’s ECG Review:

• Determine Right vs Left bundle branch block• Diagnose Acute MI • Diagnose old MI• Location of the infarct• Other Acute Coronary Syndromes• Determine Axis• Other ECG confounders• Pfun!

“Ask questions any time—I like answering them”

What a 12-Lead EKG can help you do

•  Diagnose ACS / AMI•  Interpret arrhythmias* (computer Dx)•  Identify life-threatening syndromes (WPW,

LGL, Long QT synd., Wellens synd., etc)•  Infer electrolyte imbalances•  Infer hypertrophy of any chamber•  Infer COPD, pericarditis, drug effects, and

more!

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73 y.o. male with nausea, syncope

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Acute Inferior MI

ST elevation

What rhythm? (look at V1 for P waves)

(w/septal MI?)

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another example…

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WPW with Atrial Fib

WPW GraphicWolff-Parkinson-White synd.

• short PR• wide QRS• delta wave

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Same pt, converted to SR

Limitations of a 12-Lead ECG

•  Truly useful only ~40% of the time•  Each ECG is only a 10 sec. snapshot•  Serial ECGs are necessary, especially for ACS•  Other labs help corroborate ECG findings

(cardiac markers, Cx X-ray)•  Confounders must be ruled out (dissecting

aneurysm, pericarditis, WPW, LBBB, digoxin, RVH)

The Problem with Bundle Branch Blocks

• Desynchronized contraction of the ventricles• Reduced cardiac output• Worsened heart failure•

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Confounder: Left Bundle Branch Block

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Bundle Branch Blocks (QRS > 120 msec.)

Left BBB (L I, V5, V6: upright QRS with a notch)

Right BBB (V1, V2, MCL1: rsR’ pattern)

R’

S

r

notchIV1

(left-sided lead) (right-sided lead)

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Bundle Branch Blocks Two QRSs

notchI

Healthyventricle

Blockedbundle

R’

S

rV1 slurI

V1 & V2

RBBB

V5 V6

(& I, aVL)

LBBB

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Practice: Bundle Branch Block

RBBB

Which Bundle Branch is Blocked? 1RBBB

Right Bundle Branch Block (Lead V1) 1

LBBB 12-Lead

Which Bundle Branch is Blocked? 2LBBB 12-LeadLeft Bundle Branch Block

(L I, V5, V6)

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Where is the Pathology? Right Bundle Branch Block

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Where is the Pathology?

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Left Bundle Branch Block

Limitations of a 12-Lead ECG

•  They are occasionally wrong!

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Impending AMI with ECG!

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13 hrs later — Acute Anterior MI

Elevated ST segments

ECG Pearls• Lead II is the easiest lead to read / most intuitive• But Lead V1 is our single best lead. • “A Q in III is free.” (isolated Q in L III)• If you know where the + electrode is, you can

read any ECG•

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ECG Lead Placement&

Electrophysiology Review

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IIIIII

Limb Leads

(standardleads)

- ±

+

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Leads I, II, III

I

II III

Normal 12-Lead ECG

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Rapid Interpretation Tips

Dr. Willem Einthoven

• Invented the electrocardiograph• Discovered atrial• Won Nobel Prize for Medicine 1924

3939SA Node AV Node His Bundle BBs Purkinje Fibers

P

Q

R

S

T

II

U

Conduction System

40Q

R

S

P wave axis

R wave axis

…upright in L II

…upright in L II

Lead II

4141

PR

II

Intervals

PR Interval: 120 – 200 mSec (3 – 5 boxes)QRS width: 60 – 120 mSec (1 – 3 boxes) QT/QTc interval: 400 mSec (10 boxes)

QTQRS

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300, 150, 100, 75, 60, 50 Quick, easy, sufficient

Count PQRST in a 6- second strip & multiply x 10 Easy, & more accurate

300 150 100 75 60 6 seconds

Horizontal axis is (mS); vertical axis is electrical (mV)

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Normal Sinus Rhythm

What is the heart rate?

6 seconds

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IIIIIIaVRaVL aVF

Limb (frontal plane) Leads

(augmented leads)

(standardleads)

Normal 12-Lead ECG

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6 Frontal Plane Leads (limb leads)

I

II III

R

L

F

Axis

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Leads I II III aVR* aVL aVF

-

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IIIIIIaVRaVL aVF

V1V2V3V4V5V6

Limb (frontalplane) Leads

(augmented leads)

(standardleads) (anterior

leads)

(lateralleads)

Chest (precordial)Leads

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V Lead Cutaway V Lead Progression

Normal 12-Lead ECG

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New 12-Lead ECG Format

aVL

I

-aVR

II

aVF

III

New 12-Lead ECG Format

aVL

I

-aVR

II

aVF

III

New

Old

Axis Determination

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Why We Care About Axis DeviationsThe axis shifts &

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Axis DeviationHorizontal heart (0°): obesity, 3rd trimester pregnancy. Ascites

Vertical heart (90°): slender build

Left Axis Deviation: LBBB, Anterior MI, Inferior MI, Left anterior hemiblock, LVH

Right Axis Deviation: Anterior MI, Lateral MI, RBBB, COPD, RVH, Left posterior hemiblock

Extreme RAD: Ectopic rhythm (VT), massive MI

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QRS Morphology in Lead II

II60

How to calculate Axis

the computer does it for you!

(if tallest is Lead II = )

Thumbs up / Thumbs down

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Thumbs Up / Down Method

Lead I —Your Left thumbLead aVF —Your Right thumb

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Practice: Axis 3I

F

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Axis Practice 1Normal Axis

I

F64

4I

F

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4Left Axis Deviation

I

F66

5

67

5Right Axis Deviation

68

6

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6Extreme Right Axis Deviation

Lots of ways to read EKGs…

• QRSs wide or narrow?• Regular or irregular?• Fast or slow?• P waves?

• Sinus rhythm or not?• If not, is it atrial fibrillation?• BBB?• MI?

Symptoms:• Syncope is bradycardia, heart blocks, or VT• Rapid heart beat is AF, SVT, or VT

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Step-by-step method for reading a 12-Lead Rapid Interpretation Tips

Rapid Interpretation Tips•  Identify the rhythm. If supraventricular*,

If no LBBB,

If present, •  Rule out other confounders: WPW, pericarditis, LVH,

digoxin effect•  Identify location of infarct, and consider appropriate

treatments: MONA, PCI [or fibrinolytic], nitrate infusion, heparin infusion, GP IIb, IIIa inhibitor, beta-blocker, clopidogrel, statin, etc.

Supraventricular rhythms•  Sinus rhythm•  Atrial fibrillation•  Junctional rhythm•  PSVT / AVNRT•  Atrial tachycardia•  Atrial flutter•  Wandering atrial pacemaker•  MAT

Normal 12-Lead ECG

Rapid Interpretation Tips

Rapid Interpretation Tips•  Identify the rhythm. If supraventricular,

If no LBBB,

If present, •  Rule out other confounders: WPW, pericarditis, LVH,

digoxin effect•  Identify location of infarct, and consider appropriate

treatments: MONA, PCI [or fibrinolytic], nitrate infusion, heparin infusion, GP IIb, IIIa inhibitor, beta-blocker, clopidogrel, statin, etc.

Rapid Interpretation Tips

Rapid Interpretation Tips•  Identify the rhythm. If supraventricular, •  Rule out left bundle branch block. If no LBBB,•  Check for: ST elevation, or ST depression with T

wave inversion, and/or pathologic Q waves. If present,

•  Rule out other confounders: WPW, pericarditis, LVH, digoxin effect

•  Identify location of infarct, and consider appropriate treatments: MONA, PCI [or fibrinolytic], nitrate infusion, heparin infusion, GP IIb, IIIa inhibitor, beta-blocker, clopidogrel, statin, etc.

Ischemia Injury InfarctionNormal

STEMIST elevation, ST depression, T wave inversion, pathologic Q waves

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Percutaneous Coronary Intervention

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RCA before and after stenting

Before stenting After stenting

STEMI: ECG ChangesA. Normal ECGB. Hyperacute T wave changes - increased T wave amplitude and width; may also see ST elevationC. Marked ST elevation with hyperacute T wave changes (transmural injury)D. Pathologic Q waves, less ST elevation, terminal T wave inversion (necrosis)E. Pathologic Q waves, T wave inversion (necrosis and fibrosis) F. Pathologic Q waves, loss of R waves (fibrosis)

(w/onset cx pn)

(20 minutes) (1 hour)

(1 week – years)(>1 hr)

(normal)

MI ECG Patterns

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Why Pathologic Q Waves Form

Normal q Pathologic Q

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STEMI — Typical Progression Acute Inferior MI#1

Acute Inferior MI

ST elevation

Qs Qs

Axis is shifting leftward…

Acute Inferior MI #2

Same Patient~2 hrs later

Worsened ST elevation

Qs Qs

New ST elevation

Acute Inferior MI #3Same Patient 9 days later

Permanent Q waves(inferior wall scar)

But NO anterior infarct (no Qs)

Permanent left axis deviation

Acute Anterior MI Page

45% of MIs

Acute Inferior MI Page

40% of MIs

Acute R Ventricle MI Page

1/3 of Inferior MIs

Acute Lateral MI Page

15% of MIs

Acute Posterior MI Page

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Practice: Infarct Location

Acute Anterior MI

Where is the Pathology? 7 Acute Anterior MI(ST elevation in V1 - V4)

ST Elevation

What is the R wave axis?

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Acute Inferior MI

Where is the Pathology? 8Acute Inferior MI

Acute Inferior MI(ST elevation in II, III, F)

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Acute Inferolateral MI

Where is the Pathology? 9Acute Inferolateral MIAcute Inferolateral MI

(ST elevation in II, III, F, V5, V6)

Note the axis has not shifted yet, because it is early in the AMI, and there are no loss of R waves yet.

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Where is the Pathology? 10Acute Inferior & Right Ventricle MI

Acute Inferior MI & Right Ventricle MI 10

Where is the MI?

Normal V1 – V3

• V1, V2, V3• Large R Waves• Depressed STs

ST Depression

Large R waves

11 Acute Posterior MI

Normal V1 – V3

• V1, V2, V3• Large R Waves• Depressed STs

ST Depression

Large R waves

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Confounders

Rapid Interpretation Tips

Rapid Interpretation Tips•  Identify the rhythm. If supraventricular, •  Rule out left bundle branch block. If no LBBB,

If present, •  Rule out other confounders: WPW, pericarditis,

LVH, digoxin effect•  Identify location of infarct, and consider appropriate

treatments: MONA, PCI [or fibrinolytic], nitrate infusion, heparin infusion, GP IIb, IIIa inhibitor, beta-blocker, clopidogrel, statin, etc.

WPW GraphicWolff-Parkinson-White synd. Wolff-Parkinson-White synd.

•  Short PR, Wide QRS, “Delta” wave

Short PR

Widened QRS

Delta wave

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False Q Waves (the Delta wave)

WPWFalse Q waves mimic MI

Other Confounders

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Benign Normal VariantST Elevation

Mild upsloping ST segments

Pericarditis

Elevated STs in multiple leads

Depressed PR segments

• NO loss of R waves •

Elevated STs in multiple leads

Depressed PR segments

Other Confounders Left Ventricular Hypertrophy

•  Tall R waves in V5, V6; deep S waves in V1, V2

Tall R waves V5, V6

Deep S waves V1, V2

“strain”

Other Confounders: Digoxin(ST Depression)

Depressed ST segments

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ST Depression(a diagnostic challenge)

Can be caused by: • Ischemia• Digoxin effect• Tachycardia• LVH, BBB• Hypokalemia• NSTEMI (Non Q wave MI)

Ischemic ST Depression(a positive exercise ECG)

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Practice: Confounders

1244 y.o. female with history of tachycardia

WPW (short PR, Wide QRS, Delta waves)

false Q waves delta waves

short PR

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121

1330 y.o. male with chest pain

122

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Pericarditis

DepressedPR segments

Elevated ST segments in multiple leads

Elevated ST segments in multiple leads

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Rhythm? Pathology? 14

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Large Old Anterolateral MI

Large Qs V1–V6

Ventricular aneurysm14