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Junctional Dysrhythmias
Fast & Easy ECGs, 2nd E – A SelfPaced Learning Program
Fast & Easy ECGs, 2E
1
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Junctional Dysrhythmias
• Originate in AV
junction (area
around AV node and
bundle of His)
• Can result from
suppression or
blockage of the SA
node, increased
automaticity of the
AV junction or a
reentry mechanism
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Junctional Dysrhythmias
• Key characteristics
– P’ waves may be inverted with a short P’R interval,
absent (as they are buried by the QRS complex),
or follow QRS complexes
– QRS complexes usually normal unless there is an
intraventricular conduction defect, aberrancy or
preexcitation
I
Fast & Easy ECGs, 2E
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Effect of Junctional Dysrhythmias
• If the atria are depolarized concurrently or
after the ventricles, the atria are forced to
pump against the contracting ventricles, which
contract with much greater force
– Results in a loss in atrial kick, decreased stroke
volume, and, ultimately, decreased cardiac output
• Decreased cardiac output can also occur with
slow or fast junctional dysrhythmias
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Premature Junctional Complex (PJC)
• Single early
electrical
impulse
that arises
from the AV
junction
• Disrupt
regularity of
underlying
rhythm
Q
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Causes of PJCs
• Typically
result from
increased
automaticity
• Other causes
include:
Fast & Easy ECGs, 2E
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Effects of PJCs
• In the healthy heart, isolated PJCs are of little
clinical significance
• Patient may be asymptomatic or may
experience palpitations
• Frequent PJCs (more than 4 to 6 per minute)
warn of more serious conditions and may
cause hypotension due to a transient decrease
in cardiac output
I
Fast & Easy ECGs, 2E
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Treatment of PJCs
• Generally do not require treatment
• PJCs caused by the use of caffeine, tobacco, or
alcohol, or with anxiety, fatigue, or fever can
be controlled by eliminating the underlying
cause
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Junctional Escape Rhythm
• Arises
from AV
junction
at rate of
40 to 60
BPM
I
Fast & Easy ECGs, 2E
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Causes of Junctional Escape Rhythm
• Junctional
escape
rhythm is
brought
about by AV
heart block
or conditions
that interfere
with SA node
function
• Other causes
include:
Q
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Junctional Escape Rhythm
• Rates of greater than 50 beats per minute are
usually well tolerated
• Slower rates can cause decreased cardiac
output and may lead to symptoms (chest pain
or pressure, syncope, altered level of
consciousness, hypotension)
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Accelerated Junctional Rhythm
• Arises
from AV
junction
at rate
of 60 to
100
BPM
I
Fast & Easy ECGs, 2E
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Causes of Accelerated Junctional
Rhythm
• Due to
increased
automaticity
or irritability
of the AV
junction
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Accelerated Junctional
Rhythm
• Usually well tolerated
• However, it may predispose patients with
myocardial ischemia to more serious
dysrhythmias
• Also, because the atria are depolarized by way
of retrograde conduction and may actually
follow ventricular depolarization, atrial kick
may be prevented resulting in decreased
cardiac output
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Accelerated Junctional
Rhythm
• Given the heart rate seen with accelerated
junctional rhythm, the patient is typically
asymptomatic
• Treatment is directed at identifying and
correcting the underlying cause
• Patient should be continually observed for
signs of decreased cardiac output
• Temporary pacing may be indicated if the
patient is symptomatic
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Junctional Tachycardia
• Fast
ectopic
rhythm
that arises
from
bundle of
His at rate
of 100 to
180 BPM
I
Fast & Easy ECGs, 2E
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Causes of Junctional Tachycardia
• Due to
enhanced
automaticity
and
commonly
the result of
digitalis
toxicity
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Junctional Tachycardia
• Short bursts of junctional tachycardia are well tolerated
in otherwise healthy people
• Palpitations, nervousness, anxiety, vertigo,
lightheadedness, and syncope are frequently seen
• Sustained rapid ventricular rates and retrograde
depolarization of the atria results in incomplete
ventricular filling during diastole leading to
compromised cardiac output in patients with
underlying heart disease
– Loss of atrial kick may cause up to a 30% reduction in
cardiac output
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Junctional Tachycardia
• Increases in cardiac oxygen requirements may
increase myocardial ischemia and frequency
and severity of the patient’s chest pain
• Can extend the size of MI; cause congestive
heart failure, hypotension, and cardiogenic
shock; and possibly predispose the patient to
ventricular dysrhythmias
Fast & Easy ECGs, 2E
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Atrioventricular Nodal Reentrant
Tachycardia
• Some people
have an
abnormal extra
anatomical
pathway
(congenital in
nature) within
or just next to
the AV node
Fast & Easy ECGs, 2E
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Atrioventricular Nodal Reentrant
Tachycardia (AVNRT)
• Early beats can
trigger AVNRT
• Most common
regular supraventricular
tachycardia
• Occurs more
often in
women than
men
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Preexcitation
• Some people have accessory conduction
pathways that provide a direct connection
between the atria and ventricles, thereby
bypassing the AV node and bundle of His
– These accessory pathways allow atrial impulses
to depolarize the ventricles earlier than usual
– This condition is called preexcitation
Fast & Easy ECGs, 2E
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Preexcitation
• One type of preexcitation is
Wolff-Parkinson-White
(WPW) Syndrome
• Here, the bundle of Kent, an
accessory pathway,
connects the atria to the
ventricles, bypassing the AV
node
• Key ECG features include:
– QRS complexes that are
widened with slurring of the
initial portion (delta wave)
– PR interval is usually
shortened (less than 0.12
seconds)
Fast & Easy ECGs, 2E
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Preexcitation
•
•
•
Another type of preexcitation
is Lown-Ganong-Levine (LGL)
Syndrome
In LGL syndrome, the
accessory pathway, referred
to as the James fibers, is
within the AV node
This accessory pathway
bypasses the normal delay
within the AV node but
ventricular conduction
occurs through the usual
ventricular conduction
pathways
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Preexcitation
• Because ventricular depolarization occurs
through the normal ventricular conductive
pathway the only indication of LGL on the ECG
is shortening of the PR interval as a result of
the accessory pathway bypassing the delay
within the AV node
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Preexcitation
• Unless tachycardia is present, WPW and LGL are
usually of no clinical significance
• However, preexcitation (specifically WPW) can
predispose the patient to various
tachydysrhythmias
• The most common tachydysrhythmia is
atrioventricular reentrant tachycardia (AVRT),
followed by atrial fibrillation and atrial flutter
– Atrial fibrillation and atrial flutter seen with WPW are
extremely dangerous
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrioventricular Reentrant Tachycardia
• AVRT, also known as circus movement
tachycardia (CMT), results from a reentry
circuit that includes the AV node and an
accessory pathway from the atria to the
ventricle such as the bundle of Kent
• This reentry circuit is physically much larger
than the one associated with AVNRT
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrioventricular Reentrant Tachycardia
• Reentry
through an
accessory
pathway can
take one of
two
directions,
orthodromic
conduction
or
antedromic
conduction
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrioventricular Reentrant Tachycardia
• Orthodromic AVRT
– Because of the normal conduction to the
ventricles, regular, narrow QRS complexes are
seen
• Antedromic AVRT
– Because the accessory pathway initiates
conduction in the ventricles outside of the bundle
of His, the QRS complex is often wider than usual,
with a delta wave
Fast & Easy ECGs, 2E
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Supraventricular Tachycardia
• Collectively, the three types of tachycardia
discussed in this chapter and the tachycardias
referred to in the previous two chapters are
referred to as supraventricular tachycardia as
they originate from above the ventricles
Fast & Easy ECGs, 2E
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Treatment of Supraventricular
Tachycardia
• Determine whether tachycardia is the primary
cause of the presenting symptoms or
secondary to an underlying condition that is
causing both the presenting symptoms and
the faster heart rate
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Supraventricular
Tachycardia
• Maintain patent airway and assist breathing as
necessary
• If oxygenation is inadequate or the patient
shows signs of increased breathing effort, provide
supplementary oxygen
• Attach an ECG monitor to the patient, evaluate
blood pressure and oximetry, and establish IV
access
• If available, obtain a 12-lead ECG to better define
the rhythm, but do not delay immediate
cardioversion if the patient is unstable
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Supraventricular
Tachycardia
• Symptomatic patients who are experiencing raterelated decreased cardiac output should receive
immediate synchronized cardioversion
– If the patient is conscious, consider establishing IV access
before cardioversion and administering sedation
– However, avoid any delay in cardioversion if the patient is
extremely unstable
• If not hypotensive, the patient with a regular narrowcomplex SVT may be treated with adenosine while
preparations are made for synchronized cardioversion
– Stable patients may await expert consultation because
treatment has the potential for harm
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Supraventricular
Tachycardia
• If adenosine or vagal maneuvers fail to convert SVT, if
it recurs after such treatment, or if these treatments
reveal a different form of SVT such as atrial fibrillation
or flutter, consider the use of longer-acting AV nodal
blocking agents, such as the nondihydropyridine
calcium channel blockers (verapamil and diltiazem) or
beta-blockers
• Frequent attacks may require radiofrequency ablation
• In the clinical setting, patients who have had a recent
MI or heart surgery may need a temporary pacemaker
to reset the heart’s rhythm
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
35
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
36
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
37
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
38
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
39
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
40
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
41
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
42
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
43
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
44
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• Junctional rhythms originate in the AV junction
• Impulses originating in the AV junction travel upward
and cause backward or retrograde depolarization of
the atria resulting in inverted P’ waves in lead II with
a short P’R interval, absent P waves or P waves that
follow the QRS complexes
• With junctional dysrhythmias the QRS complexes are
usually normal unless there is an intraventricular
conduction defect, aberrancy or preexcitation
Fast & Easy ECGs, 2E
45
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• A premature junctional complex (PJC) is a single early
electrical impulse that arises from the AV junction
• Junctional escape rhythm arises from the AV junction
at a rate of 40 to 60 beats per minute
• Accelerated junctional rhythm arises from the AV
junction at a rate of 60 to 100 beats per minute
• Junctional tachycardia is a fast ectopic rhythm that
arises from the bundle of His at a rate of between
100 and 180 beats per minute
Fast & Easy ECGs, 2E
46
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• In AVNRT, fast and slow pathways are located
within the right atrium in close proximity to or
within the AV node
– These pathways can allow for development of SVT
• Preexcitation syndromes occur when accessory
conduction pathways exist between the atria and
ventricles that bypass the AV node and bundle of
His and allow the atria to depolarize the
ventricles earlier than usual
– Preexcitation is diagnosed by looking for a short PR
interval
Fast & Easy ECGs, 2E
47
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• In WPW syndrome, the bundle of Kent, an
accessory pathway, connects the atria to the
ventricles, bypassing the AV node
– Criteria for WPW include a PR interval less than 0.12
seconds, wide QRS complexes due to a delta wave
(seen in some leads)
– Patients with WPW are vulnerable to PSVT
• In LGL, there is an intranodal accessory pathway
that bypasses the normal delay within the AV
node.
– Criteria for LGL include a PR interval less than 0.12
seconds and a normal QRS complex
Fast & Easy ECGs, 2E
48
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• AVRT results from a reentry circuit that
includes the AV node and an accessory
pathway from the atria to the ventricle such as
the bundle of Kent
– This reentry circuit is physically much larger than
the one associated with AVNRT
• Reentry through an accessory pathway can
take one of two directions, orthodromic
conduction or antedromic conduction
Fast & Easy ECGs, 2E
49
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.