ECG Interpretation Jocelyn

8/7/2019 ECG Interpretation Jocelyn

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What is ECG ?

The electrocardiogram (ECG or EKG) is a noninvasive test that is

used to reflect underlying heart conditions by measuring theelectrical activity of the heart. By positioning leads (electricalsensing devices) on the body in standardized locations, informationabout many heart conditions can be learned by looking for

characteristic patterns on the ECG.


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General information

Purpose ofECG- To detect heart problems orblockages in the coronary arteries.

- To draw a graph ofthe electrical impulses moving through the heart

- Torecord heart rate and regularityofheart beats

- To diagnose a possible heart attack orotherheart disorders

Discomfort / painHow longWho does itWhere its done

-No pain-5 minutes-Technician

-Nurse

-Doctor

- Doctor office orclinic

- At hospitalbedside

Average costRisk/complicationSpecial equipmentResult reading

when

$$$$$-None-ECG machine

-Electrodes

-Alcohol or gel

-Immediately


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Electrodes placementElectrode placement forprecordialleads (for12-lead ECG option)

V1 4th intercostal space, right ofsternum

V2 4th intercostal space, left ofsternum

V3 Midwaybetween V2 and V4

V4 5th intercostal space, in the midclavicularline

V5 Same level as V4, at anterioraxillaryline (between V4 and V6)

V6 In 5th intercostal space, in the midaxillaryline

Red Right arm

Black Right leg

yellow left arm

Green left leg


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Chambers of the heartA Atria

The left and right atria are separated by theinteratrial septum.

Right atrium: receives deoxygenatedsystemic blood from the SVC, IVC, andthe coronary arteries

Left atrium: receives oxygenated bloodreturning from the lungs via the 4pulmonary veins.

B- Ventricles

Are at higher pressure for pumping bloodinto the pulmonary and the systemiccirculation

Right ventricle: receives blood from theright atrium and contracts to eject bloodinto the pulmonary circulation via thepulmonary artery.

Left ventricle: receives blood from theleft atrium and contracts to eject blood

into the systemic circulation via the aorta


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Impulse Conduction & the ECG

Sinoatrial node

AV node

Bundle of His

Bundle Branches

Purkinje fibers


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Pacemaker of the heart

What is a naturalpacemaker?

The heart's "natural" pacemaker is called the sinoatrial (SA) node orsinus node. It's a small mass of specialized cells in the top of theheart's right atrium (upper chamber). It makes the electricalimpulses that cause your heart to beat.

A chamber of the heart contracts when an electrical impulse movesacross it. For the heart to beat properly, the signal must traveldown a specific path to reach the ventricles, the heart's lower(pumping) chambers.

The natural pacemaker may be defective, causing the heartbeat tobe too fast, too slow or irregular. The heart's electrical pathwaysalso may be blocked.


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Pacemaker of the heart

SA Node : Dominant pacemaker

Rate : 60 100 Beats / minute

< 60 bradycardia > 100 tachycardia

AV Node : Back up pacemaker

Rate : 40 - 60 Beats / minute

> 60 accelerated junctional rhythm

> 100 junctional tachycardia

Ventricularcells : Back up pacemaker

Rate :


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The PQRST

P wave - Atrialdepolarization

T wave - Ventricularrepolarization

QRS -Ventriculardepolarization


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How to read an ECG ?

The ECG paper

Horizontally:One small box - 0.04 secOne large box - 0.20 sec

Vertically:One large box - 0.5 mV


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When you are holding an ECG stripin your hand get a quick look,

and while looking at it

answer these questions.

The 5 steps to interpret an ECG


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1- Rate = Rapid ? or Slow ?

1 big box = 3oo beats / min ( duration 0.2sec )

2 big boxes = 150 beats / min ( duration 0.4sec )

3 big boxes = 100 beats / min ( duration 0.6 sec )

4 big boxes = 75 beats / min ( duration 0.8 sec )

5 big boxes = 60 beats / min ( duration is 1.0 sec )

6 big boxes = 50 beats / min

How to determine the rate


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2 - Rhythm = Regular? or Irregular?

If it is regular if the number of large boxes between QRS complexes isthe same all over the strip. If not, then the rhythm may be irregular

Regular rhythm Irregular rhythm


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3 - P wave

Look at the rhythm and ask yourself:

- Are Pwaves present?

- Do P waves have a normal shape - usually upright and rounded on the rhythmstrip?

- Are all the P waves similar in size and shape?- Do all the P waves point in the same direction?

P wave absent Inverted P wave


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4 - QRS complexLook at the QRS and ask yourself

- Are all the complexes the same size and shape?

- What is the duration of the QRS complex? (Normal duration is no more than 0.10-0.12 seconds (3 smallboxes); if greater, it indicates a Bundle Branch Block(BBB) or originating from the ventricles)

- Are all the QRS complexes the same distance from the T waves that follow them?

- Do all the QRS complexes point in the same direction?

- Are any QRS complexes present that appear different from the other QRS

complexes on the strip? If so, measure and describe each one individually.


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5 - PR intervalLook at the P to R interval and ask yourself

- What is the duration of the PR interval? (Normal 0.12 to 0.20 seconds)- Is the PR interval constant?

Note: if PR >0.20 sec Atrio-Ventricular Block

if PR < 0.12 sec Presence of an accessory pathway (Wolf Parkinson white Syndrome)

The P to R interval represents the time it takes an impulse to travel from the atria

through the AV node, bundle of His, and bundle branches to the Purkinje's fiber.Location :The P to R interval extends from the beginning of the P wave to thebeginning of the QRS complex.Duration :0.12 to 0.20 seconds .The P to R interval is important in order to determine if there's a heart block orconduction system disease.


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WolfParkinson White Syndrome

Delta wave

&

PR < 0.12 sec

Accessorypathwaybetween the left Atria & the left Ventricle(Bundle ofKent)


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BLOCKS

AV block-A

degree AV blockst1-1

to themarriedP present all the time & isfollowing QRS only the PR interval is >0.20sec or 1 large Box


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degree AV blocknd2-2

1degree Mobitznd

2-I

The PR interval is progressively widened until a P isdropped ( P without a QRS )

:2degree Mobitznd2-II

The PR interval is constant (may be normal orwidened) until suddenly a P is dropped (P without aQRS) and it is more dangerous than the Mobitz 1


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degree AV block orrd3-3

Complete Heart Block

There is a complete dissociation between the Atria & theVentricles, there is no relation between the Ps & the QRSs

The Atria have their own rate (faster) & the Ventricles have

their own rate (slower)


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(BBB)Bundle Branch Blocks-B

These are blocks within the ventricular bundlesmainly consist of Left & Right Bundle BranchBlocks.


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The Key to recognizing a Bundle Blockis to find an R-R wave

.

:The criteria consist of

QRS > 0.12 sec

&

Presence of2 R waves (R-R)


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Right Bundle Branch Block (RBBB)-1

In the RBBB the Right Ventricular firing islate.

The QRS complex will be a QRRS complex

In V1-V2

R=Left Ventricular Depolarization

R=Delayed Right Ventricular Depolarization(Lead V1)


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Left Bundle Branch Block LBBB-2

In the LBBB the Left Ventricular firing isdelayed

The QRS complex will be a QRRS complex

In V5-V6

R= Right Ventricular Depolarization

R=Delayed Left Ventricular Depolarization(Lead V5)


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ST Elevation

One way todiagnose anacute MI is tolook for:Elevation ofthe

ST segment.


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ST Elevation (cont)

Elevation of the STsegment (greaterthan 1 small box)in 2 leads isconsistent with amyocardial

infarction.


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Do you think this person is having a myocardial

infarction. If so, where?


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Interpretation

Yes, this person is having an acute anteriorwall myocardial infarction.


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Other MI Locations

Now that you know where to look for ananterior wall myocardial infarction letslook at how you would determine if the MIinvolves the lateral wall or the inferior wallof the heart.


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Other MI Locations

First, take alook at thispicture oftheheart.

Anterior

portion of the

heart

Lateral portion

of the heart

Inferior portion

of the heart


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Other MI Locations

LimbLeads: I, II & III Augmented Leads

AVR, AVL & AVF

PrecordialLeads

V1 V6


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Anterior MI

Remember the anterior portion of the heartis best viewed using leads V1- V4.

LimbLeads Augmented Leads PrecordialLeads


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Lateral MI

So what leads doyou

lateralthink the

ofthe heartportion

is best viewed?

LimbLeads Augmented Leads PrecordialLeads

Leads I, aVL, and V5- V6


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Inferior MI

Now how aboutinferiorthe

oftheportion

heart?

Leads II, III and aVF


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Putting it all Together

Now, where do you think this person ishaving a myocardial infarction?


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Inferior Wall MI

. Note the ST elevationinferiorMIThis is anin leads II, III and aVF.


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How about now?


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Anterolateral MI

wallanteriorthebothThis persons MI involves)!aVL, and, I6V-5Vwall (lateral) and the4V-2V(


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My Questions

Please interpret the following rhythms


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ECG Interpretation Jocelyn