Nursing school EKG

8/7/2019 Nursing school EKG

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RHYTHM

INTERP


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Conduction System of the Heart


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Conduction System

Sinus Node

Bachmanns Bundle

Inter-nodal pathways

AV Junction

AV node

Bundle ofHis

Ventricular System Bundle Branches

Purkinje Fibers


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HEART ANATOMY

Coronary Circulation


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Electrode Placement

Basic 5 lead placement

1. Red- Left Leg

2. Black- Left Arm3. White- Right Arm

4. Green- Right Leg

5. Brown- V1 or 4th IC right of sternum


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12 Lead Placement

1. V1- 4th IC right of sternum

2. V2- 4th IC left of sternum

3. V4- 5th IC mid clavicular4. V3- Midway V2 and V4

5. V5- Anterior axillary 5th IC

6. V6- Mid-axillary 5th ICV4r, V8, V9


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Lead Views

V1,V2- Septum

V3,V4- Anterior

V5,V6-Lateral

1- Lateral

2- Inferior

3- Inferior

aVL- Lateral

aVF- Inferior


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12 Lead


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P Wave

The first deflection in

the cardiac cycle

Represents

depolarization of theatria

Normally rounded

Normal measures0.10 sec. or less


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PRInterval

Represents the time

from onset of atrial

depolarization to the

onset of ventriculardepolarization

Duration is normally

0.12-0.20 seconds


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QRS Complex

Represents conduction ofthe electrical impulsefrom the bundle ofHISthrough the ventricles(ventriculardepolarization)

Largest deflection on theECG tracing because itrepresents thedepolarization of the

larger ventricular musclemass

Duration of 0.10 secondsor less


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ST Segment

Represents end ofventriculardepolarization and

beginning ofventricularrepolarization

Considered elevated

if above the baselineor depressed if it isbelow the baseline both signs ofMI


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J point

Point marking the end

of the QRS complex

and the beginning of

the ST segment


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T Wave

Represents the latter

phase of ventricular

repolarization

Normally rounded

Always follow the

QRS because

repolarization always

follows depolarization


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5 Steps To Interpret A Strip

1. Determine the regularity of the P waves(measure R-R )Is it regular?

2. Calculate the heart rate (fast or slow?)

3. Identify and examine the P waves (all thesame? One before each QRS?)

4. Measure the PR interval (Normal range?)

0.12 to 0.205. Measure the QRS complex (narrow or

wide) less than 0.12


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Normal Sinus Rhythm

Regular

Rate 60 100

Normal size, shape, and direction( positive in lead II)

PR interval Normal (0.12 0.20 seconds)

QRS complex normal ( 0.10 seconds orless)


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Normal Sinus Rhythm


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Sinus Bradycardia


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Sinus tachycardia


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Sinus Arrhythmia


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Sinus Arrest

(Sinus Pause)


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Ectopic Pacemakers

The P waves will be different in

configuration from the sinus P waves

because the impulse originates in an

ectopic site and follows a different

conduction pathway to the AV node.


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SVT

Originates in an atrial ectopic site producing a rapid, regular, 140-

250 bpm rhythm

Starts and stops abruptly, occurring in bursts, or paroxysms.

Commonly initiated by a PAC; by definition 3 or more PACs at a

rapid rate {140-250}


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Atrial Flutter

Originates from an ectopic site in the atria that fires at a rate of 250-400 bpm

Atrial muscles respond to this rapid firing by producing saw toothed pattern called

flutter waves

Av node is bombarded by these impulses but can only conduct a certain number to

the ventriclesAv node blocks at least half of the impulses


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Atrial Fibrillation

Originates from an ectopic pacemaker site in the atria firing at a rate greater than 400

bpm

The impulses are so rapid it causes the atria to quiver instead of contract producing

irregular wavy deflections


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First degree AV block

The sinus impulse is conducted to the AV node where it is delayed longer

than usual before being conducted to the ventricles

PRI is prolonged


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Second Degree AV Block, Type I

(Mobitz I or Wenckebach) Sinus impulse is conducted normally to the AV node where each impulse

has a harder time being conducted, taking successively longer with each

beat until one beat is completely blocked


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Second degree AV Block Type II

(Mobitz II) P waves are identical and regular with some of them being blocked

P-P rate is faster then the R-R rate

PRI of the beats that are conducted is normal and regular


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Third Degree Av Block

(Complete Heart Block)

Atria continue to be paced by the sinus node at a rate of

60-100

Ventricles are paced by either the AV junction at a rate

0f 40-60 or by a ventricular ectopic site at a slower rate Absence of conduction from atria to the ventricles


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What to do?

1st degree block-is it meds? Hyperkalemia, MI(inferior wall/RCA), aging.

2nd degree I-common after acute inferiorMI,usually temporary and resolves on its own.Medications can cause this. Sometimes normal.Seldom serious but watch can progress.

2nd degree type II-anterior wall MI, age, lesscommon than type I but more serious. Has

potential to progress to 3rd

degreesuddenly.PACE, Chronotropics-atropine notdrug of choice. May see hypotension(dopamine)


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Simultaneous Depolarization of

Ventricles

Lets review!

Normal electrical

pathway-originates in

the sinus node andfollows the normal

conduction pathways

to the ventricles,

depolarizing bothventricles at the same

time


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Sequential Depolarization

With ventricular rhythms,

impulse bypasses normal

pathway and an ectopic

beat originates from a site

in one ventricle therefore

that ventricle depolarizes

first than the other.

Conduction is slowing so

QRS is widened.


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Bundle Branch Blocks

The origination of bundle branch blocks is

in the SA node

T

he block is in the ventricle which resultsin sequential depolarization and a widened

QRS complex


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Bundle Branch Block

Obstruction of

impulse in one of the

branches of the

bundle ofHis


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Ventricular Arrhythmias

Premature Ventricular Contractions

(PVCs)

VentricularT

achycardia Ventricular Fibrillation

Accelerated Idio-ventricularRhythm

Ventricular Standstill


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Premature Ventricular Contractions

QRS is premature

P wave isn't associated with the premature QRS

QRS is widened ( > 0.12 sec.)

St segment and T wave slopes in the opposite direction of the QRS-

because depolarization is abnormal, so is repolarization Pause after the PVC is usually compensatory


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Causes ofPVCs

PVCs are common with advancing age, in

normal and diseased hearts

Some causes include stress, alcohol ingestion, caffeine, tobacco,

MI, ischemia, cardiomyopathy, heart failure,

ingestion of some medications, electrolyte

imbalance, reperfusion, cardiac surgery, andcontact of the myocardium by invasive

catheters


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VentricularTachycardia

Regular

Rate- 140-250

No P waves associated with QRS

Widened QRS

Originates in an ectopic focus


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Ventricular Fibrillation

A disorganized, chaotic, focus in the ventricles take control of the heart

Ventricles no longer beat in an organized manner but quiver

asynchronously


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Ventricular Standstill

Asystole

The absence of all electrical activity in the

heart

M

ay or may not showP

waves

Nursing school EKG

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