Algorithm for Rhythm Interpretation

S in u s R h ythmw / 1 st A V B

N o rm a l S in usR h ythm

Is th e P R in te rva lG rea ter tha n 0 .2 0?

(4 0 -6 0 )Ju n c tio n a l

(6 0 -1 0 0)A cce le ra tedJu n c tio n al

(1 00 an d A b ove)Ju n c tio n a l

T a ch yca rd ia

W h a t is th e H R ?

(2 0 -4 0 )Id io ve n tricu la r

(4 0 -1 0 0 )A cc e le ra ted

Id io ve ntricu la r

(1 00 an d A b ove)V e n tricu la r

T a ch yca rd ia(L e tha l R hyth m )

W h a t is th e H R ?

Is th e Q R SL e ss th a n 0 .1 2?

A re th e P w a vesIn ve rted or ab sen t?

A tria l F lu tte r

Is th e re a "S aw T oo th"P a tte rn o r F lu tte r

W a ve s?

Is the re a P w a ve fo r eve ry Q R S ?

S in usA rrh yth m ia

A tria lF lu tte r

A tria lF ib rilla t ion

A re the re F lu tte rW a ve s?

(S a w to o thP a tte rn )

T h e re a reN o P w a ves

Is the re a P w a vefo r e ve ry Q R S ?

Is th e R to R in te rva l R e gu la r?Yes No

Yes No

Yes No Yes Yes

Yes No

Yes No

Yes No

Pacemakers of the Heart• SA node:Primary heart rate

60-100 BPM• Rhythms associated with SA

node are Sinus rhythms. Atrial Fibrillation/Atrial Flutter occur in the Atrial cavity.

• AV Junction: Primary heart rate 40-60 BPM

• Rhythms associated with AV Junction are Junctional (narrow QRS, Inverted or No P wave.)

• Purkinje Fibers: Primary heart rate 20-40 BPM

• Rhythms associated with Purkinje Fibers are Idioventricular, and Ventricular Arrhythmias.

How to measure an ST segment

The point where the QRS complex and the ST segment meets is called the “Junction” or “J” Point

ST-segment elevation in the Shape of a “Smiley” face (upward concavity) is

usually benign, particularly when it occurs in an otherwise healthy,

asymptomatic patient.

ST-segment elevation in the shape of a “frowny” face (downward concavity) is more often associated with an acute

injury pattern

The PR- and TP-segments are used as the baseline from which to determine the presence of ST-segment elevation or depression.

ST-segment Elevation

ST-Segment Depression

Differentiation of Second- andThird-Degree AV Blocks

Differentiation of Second- andThird-Degree AV Blocks

More P’s than QRSs

PR fixed?

no

QRSs thatlook alike and

regular?

no

yes

yes

yes

2nd-degree AV blockFixed

Mobitz II

3rd-degree AV block

2nd-degree AV blockVariableMobitz I

Wenckebach

Atrioventricular Blocks: PR intervals IMPORTANT

1st AVB: The PR interval is greater than 0.20. Electrical Conductivity taking longer pathway from SA to AV junction. Found in Sinus Rhythms, and interpreted as SR w/ 1st AVB.Example above:HR78 PR=.32 QRS=.08 QT=.36 SR w/1st AVB.

2nd Degree AVB Mobitz type 1 (Wenckebach): The PR interval lengthens with each cycle until a QRS is dropped, then the cycle is restarted. Example above: HR68 PR=.16-.32 QRS=.08 QT=.36 SR w/ 2nd degree Type I (Wenckebach)

Atrioventricular Blocks Continued

2nd degree AVB(Mobitz type II): The PR interval remains constant/fixed with every conducted beat. Rhythm can have multiple nonconduted P waves. Example Above: HR78 PR=.18 QRS=.16 QT=.44 SR,BBB w/ 2nd degree Mobitz type II

2nd degree AVB Mobitz type II (2:1 conduction): The PR interval remains constant/fixed with every conducted beat. Rhythm shows 2 P waves for every QRS. The Rhythm can have two or more consecutive P waves non-conducted with a QRS beat. Example above: HR42 PR=.24 QRS=.10 QT=.32 SB w/ 2nd degree AVB Mobitz type II(2:1 conduction)

Third Degree Complete Heart Block:

3rd Degree Heart Block: The Atria and Ventricles beat independentlyOf each other. The SA node generates the P waves with an avg.HR of 60-100 BPM. The ventricular beats are generated from a secondary pacemaker(either Junctional(Narrow QRS:HR above 40 BPM) or Ventricular(Wide QRS:HR below 40 BPM))Example Above:Ventricular Rate/Rhythm: 37 bpm/Regular Atrial Rate/Rhythm: 81 bpm/RegularPR interval: Varies QRS duration: 0.10 sec QT interval: 0.60 secIdentification: 3rd degree AVB (Complete Heart Block) w/ Junctional Escape Pacemaker(QRS 0.08-0.10 sec)Example Below:Ventricular Rate/Rhythm: 29 bpm/Regular Atrial Rate/Rhythm: 115 bpm/RegularPR interval: Varies QRS duration: 0.14 sec QT interval: 0.48 secIdentification: 3rd Degree AVB (Complete heart Block) w/ Ventricular Escape Pacemaker(QRS 0.12-0.14 sec)

3 Steps to Pacemaker Rhythm InterpretationS tep #1

P acing O K F ailure to P ac e

Is the Inherent R atethe P acemaker's R ate ?

P acing O K C omponent F ailure

Is the R ate of the consecutivespikes the same as the

P acemakers rate ?

A re thereP acing S pikes ?

S tep #2

C apture O K F ailure to C apture

D o A ll S pike sC apture ?

S tep #3

S ens ing O K F ailure to S ens eIf L ate,O versens ing (U nderpacing)

If E arly, U ndersens ing (O verpacing )

Is S ens ing P roper?A fter an inherent beat, D oes the

P acemaker fire at the set rate interval?

No Yes

Yes No Yes No

Yes No

Yes No

Pacemakers are LAZY, they only work if they HAVE to!!

•Rate: This is set and will be maintained unless there is a problem. •Sensitivity: Think “Eyes of the pacemaker”. Depending on what it “sees”, the pacemaker will pace or not pace. •Millamps (mA, also known as output): This is the amount of energy the pacemaker needs to make a heart beat by “capturing” the heart muscle. The pacemaker can fire but if there is not enough energy to grab or capture the heart muscle, it won’t make a beat. •Pacemaker complexes are WIDE. This is normal because the wire is placed in the Right ventricle and all beats that come from the ventricle are WIDE.

Atrial and Ventricular Pacing

(DDD or AV sequential)

An AV sequential pacemaker (dual chamber pacemaker) has a wire in both the ventricle and the atrium. So you will see two spikes, one before the P wave and one before the QRS complex.

    Demand (synchronous, non-competitive)        Pacer fires ONLY when needed        Synchronized to the patient’s rhythm        Inhibited when patient’s rhythm is sensed Fixed (asynchronous, competitive)        Fires REGARDLESS of patient’s own rhythm        So it “competes” with the patient’s own rhythm         R on T is a possibility, which can lead to VT or VF

Failure to Pace (Pacemaker

Problem)

Failure to Sense (Can’t See appropriately)

THE BIG THREE

Failure to Capture (not enough milliamps to make a contraction)

THE BIG THREE CONT…

Oversensing = Underpacing 

•The pacemaker is “seeing” beats that aren’t really beats. •Therefore, it inhibits, or doesn’t pace as frequently as it should. •This is NOT good for the patient who needs those beats for cardiac output (which is blood flow to your brain all the way through to your pinky toe) 

Undersensing = Overpacing 

•The pacemaker doesn’t “see” all the beats the patient’s own heart is making.So it fires, or paces, more than it should.