Quick Review:
Basic Arrhythmia Review
Review the following rhythms:
Sinus Rhythm
Sinus Bradycardia
Sinus Tachycardia
How to measure a sinus pause/sinus arrest in seconds
Atrial Fibrillation
Atrial Flutter
Supraventricular Tachycardia
PAC’s
PVC’s
Rhythms with multiple PVC’s
Junctional Rhythm/Junctional Escape
Accelerated Junctional
Junctional Tachycardia
First degree AV Block
Second degree AV Block Type I (Wenchebach)
Second degree AV Block Type II (Mobitz type II)
Third degree AV Block
Bundle branch block
Idioventricular rhythm
Accelerated Idioventricular rhythm
Ventricular tachycardia
Non-sustained Ventricular Tachycardia (NSVT)
Ventricular fibrillation
Asystole
Paced rhythms: Ventricular pacing and AV (dual chamber)
pacing
Failure to capture
Failure to sense
Failure to pace
There will be more
than one strip on
the competency for
some of these
rhythms.
Topic
Page(s)
Background info
1-2
Sinus rhythms (brady and tachy) 4 – 5
Atrial dysrhythmias
5–6
SVT
7
Pauses
7
Junctional rhythms
7 – 10
Blocks
10 – 13
BBB
14
Ventricular dysrhythmias
14 – 17
Paced rhythms
18 - 19
Know how to calculate a rate from a strip (both ventricular rate and atrial rate)
About the Competency
1. It’s multiple choice
2. The competency is mostly rhythm strips asking you to interpret them.
3. The answers should be far enough apart to make up for how we could each could measure something
differently. Example: I may measure a PR interval at 0.12 and you may get 0.14 – the possible
answers should be far enough apart to make the correct answer apparent.
4. Passing score is 84%. There are 40 questions on the exam.
Last updated 9/16, 3/18, 7/18
1
The Basics
I.
II.
II.
Conduction system – electrical cells are arranged in a system of pathways
A. Understanding is essential in the understanding of arrhythmia interpretation
B. Impulse originates in the SA Node  travels through the atria by way of the intra-atrial pathways
AND to the AV Node via the intra-nodal pathways  Bundle of HIS  down the right and left
bundle branches within the ventricle  Purkinje fibers stimulating contraction
Intervals & Waves

PR interval (PRI) - begins at the first
sign of the P wave and ends at the first
deflection of the QRS. Normal PRI is
0.12 - 0.20 seconds. If < 0.12 seconds
– short PRI (it may be a junctional
rhythm). If > 0.20 seconds – the delay
is in the AV node (consider
interpretation “first degree AV block”).

QRS Complex (QRS) – a large complex
of three waves that signify ventricular
depolarization. To measure the QRS
complex: it starts with the beginning of the first deflection of the QRS (whether it’s a Q or an R wave)
and ends at the completion of the S wave. Usual measurement is < 0.12 seconds (0.06 – 0.10 for
some sources).

QT Interval (QTI) – Not part of this competency

R-R Interval. This interval is used to determine ventricular rate and regularity. Can do the same with
the P – P interval to measure atrial rate if it differs from the ventricular.
Graphing Paper
A. Each small square is 1mm X 1mm. Standard graphing speed is 25 millimeters per second.
B. Horizontal (across) Axis – time measurement.
1. If you look at the very top (or bottom of some ECG strips) – there are lines in the margin; “tic”
marks. The distance between two “tic” marks varies with machine – most are either 1 or 3
seconds.
2
2. If you look at the grid – every 5th line is heavier than the other lines. There are 4 lighter lines
between. The distance between the two heavier lines = 0.20 seconds, therefore the time
between the lighter lines = 0.04 seconds. In a six second strip, there will be 30 large squares.
B. Vertical (up and down) Axis – voltage or amplitude
1. Voltage is represented as a positive or negative reflection on the ECG paper. The stronger
the current the higher/lower the deflection
2. The distance between the two heavier lines = 0.5 millivolts (mV), therefore the voltage
between the lighter lines = 0.1 mV (1 mm)
III.
Inherent Rates
A. Each of the three major areas of the
conduction system has its own built in
rate, which can initiate impulses.
1. SA node – 60-100 beats per minute.
The SA node should normally be in
control of the rate.
2. AV Junction – 40-60 beats per minute
3. Ventricle – 20-40 beats per minute
B. These are no concrete rules; each area
can beat at higher rates or lower rates
depending on condition
1. Example – if the ECG rate was
between 20 and 40 beats per minute,
the electrical impulse that stimulated
the rhythm probably originated within
the ventricle, but could also have
originated from one of the other areas
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C. The fastest of the inherent rates will become the pacemaker, overriding all other stimuli
1. Irritability – a site may become irritable, discharging impulses at a faster than normal rate
a) Example – if the SA node is discharging at a rate of 72 and the AV junction begins to
discharge at a rate of 94, the AV junction will become the pacemaker
b) Early beats (ectopic beats) are also from an irritable focus outside of the normal pathway.
PAC’s come from irritable tissue in the atria (but not the SA node). PJC’s come from
irritable tissue from the “junction” or area around the AV node and PVC’s come from the
ventricles.
2. Escape – A built in safety mechanism in case the normal pacemaker slows down for some
reason. Usually an escape rhythm or an escape beat is at a slower rate.
IV.
Assessing Heart Rate
Ways to assess:
V.

There are a number of “tools” available that you can use – rate cards, rate rulers, etc.

Six second strip: Count the number of QRS complexes within the 6 seconds and multiply by 10.
Process
 Is the rhythm regular or irregular
 Heart rate (if extra P waves, atrial rate)
 P waves – upright, in front of the QRS, one for each complex
 PR interval
 QRS complex
 Anything unusual?
Sinus Rhythms
Sinus Rhythm
Rhythm
Regular
PR interval
0.12 – 0.20
Rate
60 - 100
P wave
One for each QRS
All similar size/shape and upright
in lead II
QRS
Other
0.06 – 0.10. Varies somewhat on source. None
Rule of thumb is < 0.12
4
Sinus Bradycardia
Rhythm
Regular
Rate
Less than 60
PR interval
0.12 – 0.20
QRS
0.06 – 0.10 Varies somewhat on source.
Rule of thumb is < 0.12
P wave
One for each QRS
All similar size/shape and upright in lead
II
Other
None
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Sinus Tachycardia
Rhythm
Regular
Rate
Greater than 100
PR interval
0.12 – 0.20
QRS
0.06 – 0.10 Varies somewhat on
source. Rule of thumb is < 0.12
P wave
One for each QRS
All similar size/shape and upright in lead II
As rate gets faster, starts to collide with
previous T wave
Other
None
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5
Atrial Arrhythmias
PAC’s The 4th and 7th beats in the above strip are PAC’s. Both early beats have a distinguishable P wave.
PAC’s
Rhythm
The early ectopic beat
(PAC) will make the
rhythm irregular
PR interval
Usually within normal
limits
Rate
Depends on underlying
rhythm
QRS
Nonconducted: P wave
without a QRS complex
Conducted: Has a QRS
following. QRS may be
normal width or wider.
P wave
The P wave in the PAC will be early (premature) and
may look different than the regular P waves. It may
also be hidden in the previous T wave.
Other
 PAC’s may be single beats, may come every
other beat (bigeminal), every third beat
(trigeminal) or every 4th beat (quadrigeminal).
 They may also occur in pairs (couplet)
 Three or more PAC’s in a row = atrial tachycardia
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Atrial Fibrillation (A-fib)
Rhythm
Irregularly irregular
PR interval
None
Rate
Cannot determine atrial
rate. Ventricular rate is
variable.
QRS
Usually configuration and
duration are normal
P wave
Absent. Baseline is a fibrillation wave
Other
 A fairly common rhythm in hospitalized
patients with cardiac or pulmonary
chronic conditions.
6
Atrial Flutter (A-flutter)
Rhythm
Atrium – regular
Ventricular – typically
regular
PR interval
Not measured in A-flutter
Rate
Atrial rate: 250 – 400
Ventricular - Varies
P wave
Typical sawtoothed pattern
Multiple P waves for each QRS
QRS
Usually within normal
range
Other
 Flutter is usually expressed as a ratio. The
sample strip is a 4:1 ratio.
 Rhythm may have a variable ratio.
 Rhythm may flip back and forth between A-fib
and A-flutter
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SVT = supraventricular tachycardia.
SVT is a catch all phrase when you are unable to determine what type of tachycardia is present. Atrial
tachycardia, multiffocal atrial tachycardia, junctional tachycardia, etc. are all forms of SVT. For the
GHS competency, if you cannot determine what type of tachycardia – it is SVT
Rhythm
Usually regular
PR interval
Cannot be measured
Rate
Greater than 100
(tachycardia)
QRS
Usually configuration and
duration are normal
P wave
Cannot determine if the wave between the
QRS’s is a T wave or a P wave.
Other
If the rhythm is slow enough that you can
see distinct P waves – you should call it by
it’s more accurate name (i.e. atrial
tachycardia).
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7
Arrest/Sinus Pause
You will most likely see a pause on your test that will ask you to measure how long the pause is in seconds.
To measure the pause – count the number of small boxes between the two R waves. Each small box is 0.04
seconds long. Multiply the number of small boxes by 0.04.
The sample strip has about 75 small boxes. 75 x 0.04 = 3.00 seconds.
Junctional Arrhythmias
Junctional Rhythms (or AV nodal rhythms) originate in the area of the AV node or junctional tissue.
 Junctional rhythms generally occur when the conduction system above the AV node has failed (SA node
not working and junctional tissue/AV node initiated the beat) or because the junctional tissue is irritable
and initiating beats faster than the SA node.
 Because the impulse starts in the middle of the conduction system, the electrical current will travel 2
directions – back up to the atria (retrograde conduction) and down the Bundle of HIS and rest of the
ventricular part of the conduction system.
 Because of the back-wards flow through the atria – this will cause changes in the P wave.
The “P” rules for Junctional rhythms.
 Invisible – many times you cannot find the P wave at all when the atria contract at the same time as
the ventricles. It’s actually buried within the QRS.
 Upside-down (inverted) in front of the QRS – occurs when the electricity gets to the atria before the
ventricles
 Inverted or upright but behind the QRS – occurs when electricity gets to atria after the ventricles
 If an inverted P wave is present in front of the QRS, the PR will be short – Less than 0.12.
8
PJC’s Take note of the 3rd QRS complex in the sample. See the upside-down P wave in front of it? This
example is an inverted P wave in front of the QRS and it has a short PR interval.
Rhythm
Rate
P wave
The early ectopic beat
Depends on underlying
The PJC will be early (premature) and follow the “P”
(PJC) will make the
rhythm
rules for junctional rhythms.
rhythm irregular
PR interval
QRS
Other
If the P wave is in front of Usually normal
 PJC’s are most often single beats.
the QRS – it will usually
 They may come in the same patterns as PAC’s
be less than 0.12
or PVC’s (bigeminal, trigeminal, or
quadrigeminal).
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 The only difference between Junctional Rhythm, Accelerated Junctional and Junctional Tachycardia is
the Heart Rate. They all will have the same “P” rules as stated above but the ventricular rate (heart rate)
will make it fall into the 3 different categories.
Junctional rhythm: between 40 – 60
Accelerated Junctional: between 60 – 100 J
Junctional Tachycardia: greater than 100
Junctional Rhythm
Rhythm
Regular
PR interval
If the P wave is in front of
the QRS – it will usually
be less than 0.12
Rate
40 - 60
QRS
Usually normal
P wave
Follows “P” rules
Other
The sample strip shows an inverted P wave prior to
the QRS and a HR of 50
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Accelerated Junctional
Strip is a rate of 80
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Accelerated Junctional
Rhythm
Generally regular
PR interval
If the P wave is in front
of the QRS – it will
usually be less than
0.12
Rate
Accelerated junctional
is 60 - 100
QRS
Usually normal
P wave
Follows the “P” rules.
Other
 Not a common rhythm. Caused by irritability in the
junctional tissue.
 The sample strip shows the P wave on the upslope of
the T wave. It’s behind the QRS – so cannot be a sinus
rhythm.
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Junctional Tachycardia
Rhythm
Generally regular
PR interval
If the P wave is in front of
the QRS – it will usually
be less than 0.12
Rate
Greater than 100
If rhythm very fast – may
not be able to determine
and need to call SVT
QRS
Usually normal
P wave
Follows the “P” rules.
Other
 Sample strip shows no P wave and a rate of 130
 Occurs due to irritability in the junctional tissue
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Heart Blocks
There are 4 types of Atrioventricular (AV) Blocks
 First Degree AV Block
 Second Degree AV Block Type I
 Second Degree AV Block Type II
 Third Degree AV Block
This list also follows severity of the type of block with First Degree being least clinically significant and Third
Degree being most serious.
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First Degree AV Block
Not an actual block but a slowing of conduction through the AV node
Rhythm
Regular
PR interval
Longer than 0.20 seconds
Rate
Generally within normal
limits.
QRS
Usually normal
P wave
Present, one for each QRS
 Can occur with Sinus Bradycardia, Sinus
Tachycardia, or Sinus Arrhythmia
 It may be the result of treatment with
antiarrhythmic or beta blocker medications. It
may also be due to Digoxin toxicity. Some
disease processes may also cause it.
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The dropped/blocked P waves are
indicated by the *
Second Degree AV Block – Type I / Wenckebach
The AV node is not functioning well and there is a progressive delay in getting impulses through the node until
one is dropped and then the cycle starts over again. Two samples of Wenckebach – above and below.
Rhythm
Atrial rhythm = Regular
Ventricular rhythm =
irregular – grouped
pattern
PR interval
Progressively lengthening
PR interval until a P wave
appears without a QRS
complex (blocked P)
Rate
Atrial rate > ventricular rate
QRS
Usually normal
P wave
Normal size – one for each except the blocked P
waves.
In the strip above, every 4th beat is dropped and in
the strip below, every third beat is dropped.
 The progressively lengthening PR intervals until a
beat is dropped is the hallmark for this rhythm.
 Typically a transient rhythm and most patients
are asymptomatic.
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Wenckebach – PR gets longer till a QRS is dropped leaving only the P wave.
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Key Note: There are only 2 rhythms for this test that have a variable PR interval:
Second degree heart block Type I – Wenckebach and Third degree heart block
Second degree Type II – 2:1 ratio
Second Degree AV Block – Type 2 / Mobitz Type II
Rhythm
Atrial rhythm = Regular
Ventricular rhythm =
regular
PR interval
PR interval stays
consistent!
Rate
Atrial rate > ventricular
rate.
Ventricular rate may be
slow depending on the
amount of block
QRS
Usually normal but can be
> 0.12.
P wave
Normal shape but more P waves than QRS
complexes.
Document the ratio of P waves to QRS complexes:
the sample strips shows 2:1. It can also be 3:1, 4:1
or it may vary.
 If the pattern of conduction ratio is constant – i.e.
2:1 or 3:1 – the rhythm may look regular.
 Less common but more serious than Wenckebach.
 If block is causing symptoms related to slow rate,
intervention is needed.
Second degree Type II (3:1 ratio)
12
Second degree AV block Type II is one of the strips frequently missed on arrhythmia tests (it’s usually
mistaken for third degree heart block). Key features to remember:
 More P waves than QRS complexes
 Consistent PR intervals
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Third Degree AV Block (Complete Heart Block)
The AV node is not functioning. No impulses get from the atria to the ventricles – total block. The Atria and
Ventricles are functioning independently of one another.
Rhythm
Both atrial rate and
ventricular rates are
regular but different from
one another.
Rate
Atrial rate > ventricular
rate. Intrinsic rate for the
ventricles is 20 – 40 but the
rate may be higher due to
the body trying to
compensate.
PR interval
Varies with no pattern
QRS
Usually wide because the
 The ventricular rate (pulse rate) is often slow.
beat initiates in the
 The patient may require a permanent pacemaker
ventricle. If the spot which  May occur after an MI or after mitral valve
initiates the QRS is close to
replacement.
the AV node – the QRS
may be normal width.
*
*
P wave
Normal size and shape. More P waves than QRS
complexes. P waves and QRS complexes occur at a
separate rate and may march through the QRS
complexes (see strip above and when you map out
the P waves – some are buried in the QRS
complexes – I know this because the next P wave
comes when expected). Note the sample rhythm
strip above – the hidden/buried P waves have a *
above them.
Another sample of 3rd degree
AV block. Note the varying PR
intervals with the atrial rate
marching through the QRS
complexes (* above the buried
P waves).
This is the rhythm that is
frequently mistake for Second
degree heart block Type II.
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Heart Block Tips
 When you have more P waves than QRS complexes, march out your P waves. If you find P waves,
buried in QRS complexes/T waves – it is likely to be 3rd HB
 Must measure PR intervals. Varying PR interval is either Wenckebach or 3rd degree. Consistent PR
interval is likely to be 2nd degree type 2.
 1st degree HB – no extra P waves
Bundle Branch Blocks
Bundle Branch Blocks





Impulse conduction in the bundle branches is delayed due to disease, due to drug interactions or
congenital dysfunction. Because the impulse is delayed in part of the bundle branch pathway, they
QRS interval will be wider than normal (> 0.12 seconds).
A bundle branch block can not be determined by viewing a single lead alone.
To determine if it is a left vs. right bundle branch block, a 12-lead ECG is needed.
Any rhythm with a QRS >0.12 seconds should be termed to have either a “wide QRS” or “intraventricular conduction defect”. The term bundle branch block should be confirmed either by physician
history or 12 –EKG.
Bundle branch blocks can occur with any rhythm: sinus, atrial fib, atrial flutter, heart blocks, etc.
For the rhythm above: HR about 70, PR interval 0.20, QRS 0.16 = SR with BBB
For rhythm below: HR 66, PR interval 0.16, QRS 0.18 = SR with BBB
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Ventricular Arrhythmias
Single PVC
PVC’s Probably the easiest ectopic beat to recognize because of it’s “wide and bizarre” shape.
Rhythm
The early ectopic beat
(PVC) will make the
rhythm irregular
Rate
Depends on underlying
rhythm
PR interval
No PR for the PVC.
QRS
The PVC is wide and
bizarre and comes early
(premature)
P wave
No P wave for a PVC because the beat originated in
the ventricle. It is possible to see a buried P wave
somewhere in the T wave but you usually don’t see
it.
Other
 Very common in the general population.
 Generally not treated unless they become
frequent and interfere with blood pressure.
 Occur due to an irritable focus in the ventricles
 Can come in a variety of shapes and sizes.
Unifocal – same shape.
Multifocal – different shapes
 Can come in patterns: every other  bigeminal.
Every third  trigeminy. Every fourth 
quadrigeminy.
 Two PVC’s in a row is a couplet.
A couplet is 2 PVC’s in a row
15
The strip below contains Multifocal PVC’s. Multifocal PVC’s look different from one another because they
come from different areas in the ventricle. If they come from the same place, they will look the same –
Unifocal (the couplet above has 2 PVC’s that look alike – they are unifocal)
Three or more PVC’s in a row that converts back to the patient’s
usual rhythm is usually called NSVT  Non-sustained Ventricular
Tachycardia.
The above strip is an example of NSVT – Non-sustained Ventricular Tachycardia. Three or more PVC’s in a
row is Ventricular Tachycardia. It’s good to identify how many beats in the run and how fast the episode of
NSVT is. This example would be an 8 beat run of VT at a rate of 214.
Ventricular Tachycardia (VT)

An EMERGENCY – this is potentially a lethal rhythm
Rhythm
Usually Regular
PR interval
None
Rate
Usually 150 – 250 but can
be slower.
QRS
Wide and bizarre
P wave
Typically do not see P waves at all. You may see
one behind the QRS complex but this is not typical.
Other
 The patient may have a pulse with this rhythm.
 Polymorphic VT Vs Monomorphic VT – not on
this test.
16
Patient in A-fib
going into
Ventricular
Tachycardia
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Ventricular Fibrillation (V-Fib)




Lethal Rhythm – an EMERGENCY
There will be no pulse with this rhythm.
Chaotic baseline without any discernable beats. Can be “fine” (minimal upward/downward deflection)
or “course” (more rough looking).
No P waves. No QRS complexes. No intervals to measure. No heart rate.
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Asystole/Ventricular Standstill
No electrical activity
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Idioventricular Rhythm (Ventricular Escape Rhythm)



Occurs when the atria (SA node) and AV node fail to initiate a beat for the patient.
Intrinsic rate for the ventricles is 20 – 40 but it can go faster (accelerated idioventricular) and may be
slower (agonal/dying heart rhythm).
No P waves. Wide QRS complexes.
AIVR rate 40 - 100
Agonal Rhythm Rate < 20
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Pacemakers!
# 1 This review is only covering the very basics of how pacemakers look on telemetry in preparation for the
Arrhythmia Competency.



Pacemakers are used when the normal conduction system fails to work properly. It may also be used
with certain conditions that puts the patient at risk for a dangerous or lethal rhythm.
Pacing rhythms may be very difficult to interpret because of the many new features that pacemakers
have.
Pacemakers – there are external pacers (transcutaneous), temporary pacers
(transvenous/epicardial), and permanent pacers. Implantable cardiac defibrillators have pacing
functions also.
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Revised NASPE/BPEG generic code for antibradycardic pacing
I
II
III
IV
V
Chamber(s)
paced
Chamber(s)
sensed
Response
to sensing
Rate
modulation
Multisite
pacing
O = None
O = None
O = None
O = None
O = None
A = Atrium
A = Atrium
T=
Triggered
R = Rate
modulation
A = Atrium
V=
Ventricle
V=
Ventricle
I = Inhibited
V=
Ventricle
D = Dual
(A+V)
D = Dual
(A+V)
D = Dual
(T+I)
D = Dual
(A+V)
You do NOT
need to know
this for the
arrhythmia
test!
Basic Principles:
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Output
o Milliamperes (mA)
o The energy delivered to create a beat (p wave or QRS)
AV interval
o Set in milliseconds. Creates a PR interval
Sensitivity
o Millivolts (mV).
o The ability of the pacer to “see” the patients intrinsic heart rhythm.
Demand pacing
Most patients are on demand pacing meaning that if the pacer “see”s the patients own rhythm, it will
inhibit itself from firing
Pacemaker Spike = the energy provided by the
pacemaker creates a visible spike on the rhythm
strip. This means the device had “fired”. See the
“atrial pace” and “ventricular pace to the right.
Capture = After the spike, the heart should
respond by contracting creating either a P wave
(for atrial lead of pacemaker) or QRS complex
(for ventricular lead of the pacemaker). See the
P wave following the atrial spike and the QRS
after the ventricular spike.
Sensitivity = The ability of most pacemakers to “see” the patient’s own beats and prevent itself from firing if
there is no need. The sensitivity is a value that can be adjusted so the pacemaker “sees” what it’s supposed to.
Patients may have an AV pacemaker (atrial + ventricular) – also called dual chamber pacing. They may have
a pacemaker that is pacing only the atria or the ventricles. Atrial pacing will not be covered in this
competency. Ventricular pacing – the lead is only in the ventricle.
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Atrial pacing
 Some patients only need atrial pacing, some will need both atrial and ventricular pacing
 Will see a PR interval before the QRS.
 May not see the P wave
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Ventricular pacing
 Ventricular pacing only
 No P waves (no atrial kick)
 No PR intervals
 Ventricular spike with ventricular capture
 Expect the QRS to be wide and bizarre
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AV pacing
 Pacing atria and ventricles (preserves atrial kick)
 See both atrial and ventricular pacer spikes
 Will see a PR interval before the QRS.
 May not see the P wave
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Failure to Fire (Failure to pace) is when you should see a pacemaker spike and there isn’t one. You can see
the strip below has a big problem. First – there is a pacemaker. You can see the spike and the very small
QRS (so it does capture). The problem is there aren’t enough spikes and the patient doesn’t have much heart
activity on their own.
Failure to Capture: You see a pacer spike and no capture following. There may be something wrong with
the pacemaker settings or the patient. See the lone pacer spike in the strip below? It is not followed by a QRS
complex. This is failure to capture.
Failure to Sense: The pacemaker spikes are firing at inappropriate times. For instance, you should not see a
pacemaker spike in the T wave or right after the T wave. The pacemaker should have “seen” that beat and
prevented itself from firing.
Review the strip below. Note the two pacemaker spikes where they should not be. The pacemaker is not
“seeing” or sensing the patient’s own beats and firing inappropirately
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Revised 7/13, 11/14