introducing the junctional rhythms

Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley

For the Dental Hygienist

CHAPTERCHAPTER

Understanding EKGsA Practical Approach

9Introducing the Junctional Introducing the Junctional RhythmsRhythms

Introducing Junctional Rhythms

• Objectives– Discuss the origin of junctional rhythms– Recall the components of the electrical

conduction system– Identify premature junctional contractions,

including EKG characteristics– Identify a junctional escape rhythm, including

EKG characteristics

Introducing Junctional Rhythms

• Objectives (continued)– Identify an accelerated junctional rhythm,

including EKG characteristics– Identify a junctional tachycardia rhythm,

including EKG characteristics– Discuss the clinical significance of the

junctional rhythms

Origin of Junctional Rhythms

• Rhythms that are initiated in the area of the AV junction are called junctional rhythms

• Although junctional rhythms are not considered to be lethal, or life-threatening, you should recall that patient assessment is the most important indicator of clinical significance

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

P Waves in Junctional Rhythms

• Normally P waves are seen before each QRS

• Impulse in junctional rhythm is traveling away from (+) electrodes, P wave will be inverted or negative

• The P wave can be hidden in the QRS or follow the QRS complex

Impulse Direction

•The location of the impulse changes the position of the ‘P’ wave

•Impulse originates in AV Node and retrograde backward to SA Node

•Causing a negative deflection on ECG of ______ Wave?

•The impulse will follow normal route and ______ wave will be _______ deflected on the ECG?

The Premature Junctional Contraction (PJC)

• Are initiated from a single site in the AV junction and arise earlier than the next anticipated complex of the underlying rhythm

• If SA node depolarized by ectopic beat, a noncompensatory pause occurs and underlying rhythm is interrupted

The Premature Junctional Contraction (PJC)

• PJC can also cause compensatory pause, a pause that occurs after ectopic beat and underlying rhythm is uninterrupted

Premature Junctional Complexes

Premature Junctional Contraction (Complexes) or PJCs

• PJCs are less common than PACs or PVCs

• As with all ectopic beats, it is easier to identify PJCs if rhythm is sinus or bradycardia

• When interpreting PJCs, you must also determine the underlying rhythm

Junctional Escape Rhythms

• The SA node may fail to generate an impulse, or if rate falls below that of the AV node, then AV node will assume the role of pacemaker

• This ability is a safety feature

• Intrinsic rate of the AV node is 40-60

Junctional Escape Rhythm

• Junctional escape beat – Isolated junctional beat occurs

• Junctional escape rhythm– Series of junctional escape beats occur,(sometimes termed junctional bradycardia

when rate < 40 bpm• Causes

– SA node disease, hypoxia, increased parasympathetic (vagal) tone, cardiac drugs, or complete heart block

Junctional Escape Beats

Junctional Escape Rhythm

Accelerated Junctional Rhythms

• Caused by increased automaticity in AV junction, causes junction to discharge impulses at fast rate, then intrinsic rate (40-60 bpm)

• Rate is usually around 60 to 100 bpm

• Causes include– Hypoxia, digitalis intoxication, inferior wall MI,

and rheumatic fever

Accelerated Junctional Rhythm

Junctional Tachycardia Rhythms

• Rhythm that arises from AV junctional tissue at a rate of 100 to 180 bpm

• If observed to start or end abruptly referred to as paroxysmal rhythm

• It may be indistinguishable from supraventricular tachycardic rhythms

• Causes– Underlying ischemic heart disease,

frequent ingestion of stimulants, anxiety, hypoxia, Medications such as digitalis, or rheumatic heart disease

• Treatment– Aimed at identifying and treating the

underlying cause of the dysrhythmia

Junctional Tachycardia Rhythms

Junctional Tachycardia

Clinical Significance of Junctional Rhythms

• Premature Junctional Contractions– Based on frequency of their occurrence and

patient’s condition– Isolated PJCs are of minimal significance– Frequent (> than 6/min) more serious

dysrhythmias may develop– Management includes only close observation

• Junctional Escape Rhythm – Based on patient’s heart rate and clinical

condition– Intrinsic rate of AV junction = 40 to 60 bpm– Watch for signs of compromise– If decreased perfusion observed, treat with

oxygen, and consider drug therapy– May be tolerated at 50 to 60 bpm

• Accelerated Junctional Rhythm– Generally well tolerated by patient– May suggest the possibility of digitalis toxicity– Patient must be carefully monitored for

occurrence of other, more serious dysrhythmias

• Junctional Tachycardia Rhythm– May be well tolerated in healthy hearts– Not tolerated in patients with cardiac

compromise– May report feeling heart “running away or

fluttering”– Treatment based on patient’s clinical

appearance, signs, and symptoms

introducing the junctional rhythms

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