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8
Introducing the Atrial
Rhythms
Introducing the Sinus
Rhythms
• Objectives
– Discuss the origin of the atrial rhythms
– Recall the components of the electrical
conduction system of the heart
– Identify a wandering atrial pacemaker rhythm,
including EKG characteristics
– Describe a premature atrial contraction,
including EKG characteristics
– Identify atrial flutter rhythm, including EKG
characteristics
Introducing the Sinus
Rhythms
• Objectives (continued)
– Describe atrial fibrillation rhythm, including
EKG characteristics
– Describe supraventricular tachycardia,
including EKG characteristics
– Discuss clinical significance of atrial rhythms
– Describe EKG characteristics of WolffParkinson-White syndrome
Origin of the Atrial Rhythms
• The rhythms are classified according to
the heart structure in which they begin, or
their site of origin
• Sinoatrial (SA) node fails to generate an
impulse, atrial tissues, or internodal
pathways may initiate an impulse
Origin of the Atrial Rhythms
• These are Atrial Dysrhythmias
• Rhythms not considered life-threatening or
lethal; They must however, provide
continuous assessment
Components of Electrical
Conduction System of the Heart
• Electrical impulse
originates in SA node
• Travels through atria via
internodal pathways
• AV node, brief pause,
bundle of His
• Right and left bundle
branches
• Purkinje fibers into the
ventricular musculature
Electrical Conduction System of
the Heart
Pacemaker Sites
Wandering Atrial Pacemaker
Rhythm
• They occur when pacemaker sites wander,
or travel, from SA node to other
pacemaker sites in atria, internodal
pathways, or AV Node
• SA node remains basic pacemaker
Wandering Atrial Pacemaker
Rhythm
• Observation of at least three different P
waves required
• Size and shape of P waves vary
according to site of origin
• The P waves may appear upright,
inverted, or absent waveforms
Wandering Atrial Pacemaker
Rhythm
• The absence of P wave may indicate P
wave buried in QRS complex
• PR interval may be regular, vary based
on point of origin
• Produces no symptoms and only
recognized by EKG observation
Wandering Atrial Pacemaker
Wandering Atrial Pacemaker
Rhythm
Multifocal Atrial Tachycardia
(MAT)
• A variant of wandering atrial pacemaker
• Occurs when the rate reaches 100 bpm
or greater
• May be confused with atrial fibrillation
• Observed in patients with advanced
chronic obstructive pulmonary disease,
digoxin toxicity, and electrolyte
imbalances.
Multifocal Atrial Tachycardia
(MAT)
Premature Atrial Contractions
(Complexes) or PACs
• A single electrical impulse that originates
outside the SA node in the atria
• Can occur in the atria, AV junction, or in
the ventricles
• The premature beat is a complex that
arises earlier than next expected beat
Premature Atrial Contractions
(Complexes) or PACs
• The word contraction commonly used to
describe premature beats
• All complexes represent only electrical
activity of the heart
• Complexes do not show mechanical
activity.
• Should use complexes rather then
contraction
Premature Atrial Complexes
• An incomplete, or noncompensatory,
pause often follows a PAC
– Looks like normal complexes of
underlying rhythm
– Underlying rhythm is interrupted due to PAC
– After noncompensatory pause, underlying
rhythm of heart returns, and continues
until next PAC occurs
Premature Atrial Complexes
Figure 8-2 Premature Atrial
Complexes
Premature Atrial Complexes
• Two sequential PACs
– Occur in pairs
• Atrial bigeminy
– Every other beat PAC
• Atrial trigeminy
– Every third beat PAC
Premature Atrial Complexes
• Remember
– Premature atrial complexes look very
much like the normal complexes of the
underlying rhythm
Premature Atrial Complexes
• Causes include
– Use of stimulants (caffeine, alcohol) hypoxia,
increased sympathetic tone, imbalances of
electrolytes, digitalis toxicity
• When any premature beat occurs more
than six times per minute it is termed
“frequent”
Reentry Dysrhythmias
• The reactivation of myocardial tissue for a
second or subsequent time by the same
impulse
• Short circuit of electrical conduction
system
• Develops when course of electrical
impulse is delayed or blocked
Reentry Dysrhythmias
• Due to this delay, electrical impulse
allowed to travel in only one direction
• The impulse moves in cycle throughout
heart tissue
• A series of fast depolarizations ensues
Reentry Dysrhythmias
Reentry Dysrhythmias
• Causes of reentry
– Due to conduction delays or blocks
include hyperkalemia, myocardial
ischemia, and certain antidysrhythmic
medications
• Specific rhythms include
– Atrial flutter, atrial fibrillation, premature
atrial complexes, and paroxysmal
supraventricular tachycardia
Atrial Flutter Rhythm
• Presence of regular atrial activity with a
picket fence, or sawtooth pattern
• Single irritable site in atria initiates
many electrical impulses at a rapid rate
• Normal P wave not produced
• Electrical impulses conducted
throughout atria at fast rate
Atrial Flutter Rhythm
• Rather than the presence of normally
appearing P waves, flutter (or sawtooth)
waves, also known as F waves, are
patterned
• AV node becomes “gate keeper” to
ventricles
– Based on number of impulses AV node
accepts, ventricular response is
established
Atrial Flutter Rhythm
• Conduction ratio 2:1
– Two atrial contractions for each ventricular
contraction
• Conduction ratio 4:1
– Four atrial contractions for each ventricular
contraction
– An atrial rate of 300 bpm will parallel a
ventricular rate of 75 bpm
Atrial Flutter Rhythm
• Atrial flutter with a slow ventricular
response
– Ventricular rate of less than 60 bpm
• Atrial flutter with a rapid ventricular
response
– Ventricular rate of 100-150 bpm
Atrial Flutter
Atrial Flutter