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.
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