Junctional Rhythms - BMH/Tele

1. Junctional RhythmsJunctional Rhythms
Electrical impulses that originate
from the AV node (junction).

2. AV Node (The Gatekeeper)
Three main functions:
•Slows conduction to allow time
for the atria to contract & empty
its contents (atrial kick) before
the ventricles contract
•Secondary pacemaker (40 – 59 bpm)
•Blocks some of the impulses
from being conducted to the
ventricles when atrial rate is rapid

3. AV Node P Waves
See Overhead Slide 4-1

4. Premature Junctional ContractionPremature Junctional Contraction
A premature junctional contraction (PJC) is an
earl beat that originates in the AV junction.
As a result of increased automaticity within
junctional cells

5. Premature Junctional ContractionPremature Junctional Contraction
Rhythm: Premature ectopic beat causes slight irregularity
Rate: Overall HR depends on rate of underlying rhythm
P waves: P wave may be inverted, come after the QRS
complex, or be lost in the QRS complex.
PRI: 0.12 – 0.20 sec on regular beat; ectopic beat is visible PRI
will be < 0.12 sec; if P wave is late or not visible there will be
no PRI.
QRS: Narrow (< 0.12 sec); sometimes wide

6. Junctional Escape BeatJunctional Escape Beat
An ectopic junctional beat that occurs late
within an underlying rhythm
P wave will be inverted (before the QRS),
hidden (within the QRS), or late &
inverted (after the QRS)

7. Junctional Escape BeatJunctional Escape Beat
Common after a pause in the underlying rhythm:
Sinus arrest
Sinus (exit) block
Nonconducted PAC
Mobitz I

8. Junctional RhythmJunctional Rhythm
Appears secondary to depression of the SA node
Occurs when the SA node is firing at a rate lower
than that of the inherent rate of the AV node
Or if the electrical impulse of the SA node fails to
reach the AV node
If the AV node does receive an impulse within 1 –
1.5 seconds, it is triggered to fire resulting in a
junctional escape beat or rhythm

9. Junctional RhythmJunctional Rhythm
Causes:
Disease of the SA node
Acute MI
Drug Effects (digitalis, quinidine, BB’s, or CCB’s)
May also occur with Complete Heart Block

10. Junctional RhythmJunctional Rhythm
Rhythm: Regular
Rate: 40 – 60 bpm (impulse originates from AV junction)
P waves: Consistently either inverted before QRS, hidden in
QRS complex, or inverted & after the QRS complex
PRI: usually < 0.12 sec but may be 0.12 – 0.20 sec; if P wave is
late or not visible there will be no PRI
QRS: Narrow (< 0.12 sec); sometimes wide

11. Junctional RhythmJunctional Rhythm

12. Accelerated Junctional RhythmAccelerated Junctional Rhythm
Causes:
Enhanced automaticity secondary to digitalis
toxicity
Damage to the AV node secondary to acute
inferior wall MI, heart failure, acute rheumatic
fever, myocarditis, valvular heart disease, and
cardiac surgery (especially valve surgery)

13. Accelerated Junctional RhythmAccelerated Junctional Rhythm

14. Junctional TachycardiaJunctional Tachycardia
Causes:
Enhanced automaticity secondary to digitalis
toxicity
Damage to the AV node secondary to acute
inferior wall MI, heart failure, acute rheumatic
fever, myocarditis, valvular heart disease, and
cardiac surgery (especially valve surgery)

15. Junctional TachycardiaJunctional Tachycardia
Often confused with SVT if the rate is very
fast causing the P wave to become
hidden
If a P wave cannot be differentiated, then it
is acceptable to use the term Paroxysmal
SVT or PSVT to describe the rhythm

16. Junctional TachycardiaJunctional Tachycardia
Rhythm: Regular (usually)
Rate: 101 – 180 bpm (impulse originates from AV junction)
P waves: Consistently either inverted before QRS, hidden in
QRS complex, or inverted & after the QRS complex
PRI: usually < 0.12 sec but may be 0.12 – 0.20 sec; if P wave is
late or not visible there will be no PRI
QRS: Narrow (< 0.12 sec); sometimes wide

17. TIME TO WORKOUT!!!TIME TO WORKOUT!!!

18. ReferencesReferences
Chernecky, C., et al. (2002). Real world nursing survival guide:
ECG’s & the heart. United States of America: W. B. Saunders
Company.
Huff, J. (2006). ECG workout: Exercises in arrhythmia
interpretation (5
th
ed.). United States of America: Lippincott,
Williams & Wilkins.
Walraven, G. (1999). Basic arrhythmias (5
th
ed.). United States
of America: Prentice-Hall, Inc.
www.madsci.com/manu/ekg_rhy.htm