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Atrial Dysrhythmias
Fast & Easy ECGs, 2nd E – A SelfPaced Learning Program
Fast & Easy ECGs, 2E
1
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrial Dysrhythmias
• Originate in the
atrial tissue or in the
internodal pathways
• Are among the most
common types of
dysrhythmias,
particularly in
persons older than
60 years of age
Q
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrial Dysrhythmias
• Believed to be caused by three mechanisms:
– Enhanced automaticity
– Circus reentry
– Afterdepolarization
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Fast & Easy ECGs, 2E
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Atrial Dysrhythmias
• Can diminish the strength of the atrial
contraction and affect ventricular filling time
– This can lead to decreased cardiac output and
ultimately decreased tissue perfusion
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrial Dysrhythmias
• Key characteristics include:
– P’ waves (if present) that differ in appearance
from normal sinus P waves
– Abnormal, shortened, or prolonged P’R intervals
– QRS complexes that appear narrow and normal
I
Fast & Easy ECGs, 2E
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Premature Atrial Complexes (PACs)
• Early beats
that
originate
outside the
SA node
before it
has a
chance to
depolarize
Fast & Easy ECGs, 2E
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Premature Atrial Complexes (PACs)
• Produce an irregularity in the rhythm
– P’-P and R’-R intervals are shorter than the P-P
and R-R intervals of underlying rhythm
• Have P’ waves that are upright (in lead II)
preceding each QRS complex but have a
different morphology (appearance) than the P
waves of underlying rhythm
• Followed by a noncompensatory pause
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Noncompensatory Pause
• Is a pause where
there are less
than two full R-R
intervals between
the R wave of the
normal beat
which precedes
the PAC and the R
wave of the first
normal beat
which follows it
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Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Causes of PACs
• Most
common
cause of
PACs is
enhanced
automaticity
• Other causes
include:
I
Fast & Easy ECGs, 2E
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Effect of PACs
• Isolated PACs seen in patients with healthy
hearts are considered insignificant
• Asymptomatic patients usually only require
observation
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Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effect of PACs
• May predispose patient with heart disease to
more serious atrial dysrhythmias:
– atrial tachycardia
– atrial flutter
– atrial fibrillation
• Can serve as an early indicator of an
electrolyte imbalance or congestive heart
failure in patients experiencing an acute
myocardial infarction
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Grouping of PACs
• PACs can be
described by
how they
are
intermingled
among
normal
beats
Bigeminal
Every other
beat is a
PAC
Trigeminal
Every 3rd
beat is a
PAC
Quadrigeminal
Every 4th
beat is a
PAC
Fast & Easy ECGs, 2E
Q
12
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Aberrantly Conducted PAC
• Occurs when a
PAC travels
through the
ventricular
conduction
pathway
abnormally
resulting in an
abnormal looking
QRS complex
– For this reason
they can be
confused with
PVCs
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Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Blocked PAC
• Occurs when an
atrial impulse
arrives too early,
before the AV
node has a chance
to repolarize
• As a result, the P’
wave fails to
conduct to the
ventricles
• Identified by a
premature P’
wave that is not
followed by a QRS
complex
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of PACs
• Generally do not require treatment
• PACs caused by the use of caffeine, tobacco,
or alcohol or by anxiety, fatigue, or fever can
be controlled by eliminating the underlying
cause
• Frequent PACs may be treated with drugs that
increase the atrial refractory time
– This includes beta-adrenergic blockers and
calcium channel blockers
Fast & Easy ECGs, 2E
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Wandering Atrial Pacemaker
• Pacemaker site
shifts between
SA node, atria
and/or AV
junction
– This produces
its most
characteristic
feature – P’
waves that
change in
appearance
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Causes of Wandering Atrial Pacemaker
• Generally
caused by
inhibitory
vagal effect
of
respiration
on SA node
and AV
junction
• Other
causes
include the
following:
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Wandering Atrial Pacemaker
• Wandering atrial pacemaker is rarely serious,
having no effect on cardiac output
• Normal finding in children, older adults, and
well-conditioned athletes
Fast & Easy ECGs, 2E
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Treatment of Wandering Atrial
Pacemaker
• No treatment is necessary for patients
experiencing wandering atrial pacemaker
– However, chronic dysrhythmias are a sign of heart
disease and should be monitored
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrial Tachycardia
• Rapid
dysrhythmia
(rate of 150
to 250 BPM)
that arises
from the
atria
• Rate is so
fast it
overrides
the SA node
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Causes of Atrial Tachycardia
• Digitalis toxicity is
the most common
cause of atrial
tachycardia
• Also, sudden
onset atrial
tachycardia is
common in
patients who have
Wolff-ParkinsonWhite syndrome
• Other causes
include:
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Atrial Tachycardia
• Symptoms can develop abruptly and may go
away without treatment
• Short bursts are well-tolerated in otherwise normally healthy
people
• Alternatively, they may last a few minutes or as
long as one to two days, sometimes continuing
until treatment is delivered
• With the rapid heartbeat seen with atrial
tachycardia, there is less time for the ventricles to
fill.
– This can reduce stroke volume and lead to decreased
cardiac output
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Atrial Tachycardia
• Can significantly compromise cardiac output
in patients with underlying heart disease
• Fast heart rates increase oxygen requirements
– May increase myocardial ischemia and potentially
lead to myocardial infarction
I
Fast & Easy ECGs, 2E
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Atrial Tachycardia with Block
• Due to the rapid atrial rates seen with atrial tachycardia, the AV
junction is sometimes unable to carry all the impulses
– This is called atrial tachycardia with block
• This then results in more than one P’ wave preceding each QRS
complex
• Most commonly, only one of every two beats (a 2 to 1 block) is
conducted to the ventricles
Fast & Easy ECGs, 2E
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Treatment of Atrial Tachycardia
• Treatment is dependent on the type of
tachycardia and symptom severity
– Directed at eliminating the cause and decreasing
ventricular rate.
– Patients who are symptomatic (e.g., chest pain,
hypotension) should receive oxygen, an IV infusion
of normal saline administered at a keep-open rate,
and prompt delivery of synchronized
cardioversion, use of vagal maneuvers or
medication administration.
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Atrial Tachycardia
• Synchronized cardioversion is indicated if the
patient is symptomatic
– In the conscious patient, consider sedation before
cardioversion
• However, do not delay cardioversion
– If this fails to convert the rhythm, the energy level
may be increased
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Atrial Tachycardia
• If the patient is stable, vagal maneuvers and
drug therapy (adenosine) may be used
• If these treatments fail to resolve the
tachycardia, calcium channel blockers
(verapamil, diltiazem) and beta-adrenergic
blockers (if no contraindications exist) may be
considered
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Atrial Tachycardia
• Atrial overdrive pacing may be employed to
stop this dysrhythmia
• If the dysrhythmia is related to WPW
syndrome, catheter ablation may be indicated
• Procainamide, amiodarone, or sotalol may be
considered in wide complex tachycardias
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Multifocal Atrial Tachycardia (MAT)
• Pathological
condition
that
presents
with
changing P
wave
morphology
and heart
rates of 120
to 150 BPM
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Appearance of Multifocal Atrial
Tachycardia (MAT)
• MAT is often misdiagnosed as atrial fibrillation
with rapid ventricular response but can be
identified by looking closely for clearly visible
but changing P’ waves
– P’ waves change in morphology as often as from
beat to beat resulting in three or more differentlooking P waves
• Varying PR intervals and narrow QRS
complexes also seen
Fast & Easy ECGs, 2E
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Causes of Multifocal Atrial Tachycardia
(MAT)
• Is more common
in the elderly
• It is usually
precipitated by
acute
exacerbation
(with resultant
hypoxia) of
COPD, elevated
atrial pressures,
or heart failure
• Other causes
include:
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Multifocal Atrial Tachycardia
(MAT)
• Patient may complain of palpitations
• Signs and symptoms of decreased cardiac
output, such as hypotension, syncope, and
blurred vision, may be seen
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Multifocal Atrial
Tachycardia (MAT)
• Appropriate therapy is treatment of the
underlying condition
• In symptomatic patients treatment may
include administering calcium channel
blockers (verapamil, diltiazem)
– Beta-adrenergic blockers are typically
contraindicated because of the presence of severe
underlying pulmonary disease
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Supraventricular Tachycardia (SVT)
• Arises from
above the
ventricles
but cannot
be
definitively
identified as
atrial or
junctional
tachycardia
because the
P’ waves
cannot be
sufficiently
seen
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Supraventricular Tachycardia (SVT)
• This group of tachycardias includes
paroxysmal SVT (PSVT), nonparoxysmal atrial
tachycardia, MAT, AV nodal reentrant
tachycardia (AVNRT), atrioventricular
reentrant tachycardia, and junctional
tachycardia
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Supraventricular Tachycardia (SVT)
• Sometimes wide QRS complexes are seen
– Due to an intraventricular conduction defect or
other condition such as aberrant conduction
– Makes assessment of SVT difficult as it appears to
be ventricular tachycardia
• Called wide complex tachycardia of unknown origin
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrial Flutter
• Results from
circus reentry
– Impulse from
SA node
circles back
through atria,
returning to
the SA node
region and
repeatedly
restimulating
the AV node
over and over
at a rate of
250 to 350
BPM
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Appearance of Atrial Flutter
• On the ECG, the P waves lose their distinction
due to the rapid atrial rate
• Waves blend together in a saw-tooth or picket
fence pattern called flutter waves, or F waves
– Produces atrial waveforms that have a
characteristic saw-tooth appearance called flutter
waves (F waves)
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Causes of Atrial Flutter
• Usually caused
by conditions
that elevate
atrial pressures
and enlarge
the atria
• Another cause
is increased
automaticity
• Other causes
include:
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Atrial Flutter
• Often well-tolerated
• The number of impulses conducted through
the AV node determines the ventricular rate
(i.e. 3:1 conduction ratio)
– Slower ventricular rates (< 40 BPM) or faster
ventricular rates (> 150 BPM) can seriously
compromise cardiac output
I
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Atrial Flutter
• Vagal maneuvers may make flutter waves
more visible by transiently increasing the
degree of the block
• In patients experiencing an associated rapid
ventricular rate who are symptomatic but
stable, treatment is directed at controlling the
rate or converting the rhythm to sinus rhythm
Fast & Easy ECGs, 2E
41
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Atrial Flutter
• Symptomatic patients (e.g., hypotension, signs
of shock, or heart failure) should receive
oxygen, an IV infusion of normal saline
administered at a keep-open (TKO) rate, and
prompt treatment
• Synchronized cardioversion should be
considered in unstable patients
– If necessary, the energy may be increased with
subsequent shocks
Fast & Easy ECGs, 2E
42
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Atrial Fibrillation
• Results for
chaotic,
asynchronous
firing of
multiple areas
within the atria
I
Fast & Easy ECGs, 2E
43
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Appearance of Atrial Fibrillation
• Totally irregular rhythm with no discernible P
waves
– Instead there is a chaotic baseline of fibrillatory
waves (f waves) representing atrial activity
Fast & Easy ECGs, 2E
44
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Causes of Atrial Fibrillation
• Atrial fibrillation is
more common
than atrial
tachycardia or
atrial flutter
• It can occur in
healthy persons
after excessive
caffeine, alcohol,
or tobacco
ingestion or
because of fatigue
and acute stress
• Other causes
include:
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Effects of Atrial Fibrillation
• Leads to loss of atrial kick decreasing cardiac
output by up to 25%
• Patients may develop intra-atrial emboli as the
atria are not contracting and blood stagnates
in the atrial chambers forming a thrombus
(clot)
– Predisposes patient to systemic emboli (stroke)
Fast & Easy ECGs, 2E
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© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Atrial Fibrillation
• If the rate of ventricular response is normal,
the dysrhythmia is usually well tolerated and
requires no immediate intervention
• Patients experiencing atrial fibrillation and an
associated rapid ventricular rate who are
symptomatic but stable, treatment is directed
at controlling the rate or converting the
rhythm to sinus rhythm
Fast & Easy ECGs, 2E
47
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Treatment of Atrial Fibrillation
• Symptomatic patients (e.g., hypotension, signs
of shock, or heart failure) should receive
oxygen, an IV infusion of normal saline
administered at a TKO rate, and prompt
synchronized cardioversion
– If necessary, the energy level may be increased
with subsequent shocks
Fast & Easy ECGs, 2E
48
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
49
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
50
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
51
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
52
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
53
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
54
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
55
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
56
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
57
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Practice Makes Perfect
• Determine the type of dysrhythmia
I
Fast & Easy ECGs, 2E
58
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• Atrial dysrhythmias originate outside the SA node
in the atrial tissue or in the internodal pathways
• Three mechanisms responsible for atrial
dysrhythmias are increased automaticity,
triggered activity and reentry
• Key characteristics for atrial dysrhythmias:
– P’ waves (if present) that differ from sinus P waves
– Abnormal, shortened, or prolonged P’R intervals
– QRS complexes that appear narrow and normal
(unless there is an intraventricular conduction defect,
aberrancy or preexcitation)
Fast & Easy ECGs, 2E
59
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• With wandering atrial pacemaker the pacemaker
site shifts between the SA node, atria and/or AV
junction
– Produces its most characteristic feature, P’ waves that
change in appearance
• Premature atrial complexes (PACs) are early
ectopic beats that originate outside the SA node
– Produce an irregularity in the rhythm
– P’ waves should be an upright (in lead II) preceding
the QRS complex but has a different morphology than
the P waves in the underlying rhythm
Fast & Easy ECGs, 2E
60
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• Atrial tachycardia is a rapid dysrhythmia (rate of 150 to
250 beats per minute) that arises from the atria
• Multifocal atrial tachycardia (MAT) is a pathological
condition that presents with the same characteristics
as wandering atrial pacemaker but has heart rates of
120 to 150 beats per minute
• Supraventricular tachycardia arises from above the
ventricles but cannot be definitively identified as atrial
or junctional because the P’ waves cannot be seen with
any real degree of certainty
Fast & Easy ECGs, 2E
61
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.
Summary
• Atrial flutter is a rapid depolarization of a single
focus in the atria at a rate of 250 to 350 beats per
minute
– Produces atrial waveforms that have a characteristic
saw-tooth or picket fence appearance
• Atrial fibrillation occurs when there is chaotic,
asynchronous firing of multiple areas within atria
at a rate greater than 350 beats per minute
– Produces a totally irregular rhythm with no discernible
P waves
Fast & Easy ECGs, 2E
62
© 2013 The McGraw-Hill Companies, Inc. All rights reserved.