topics

10/20/25

arrhythmia; describe

rate

regular

P; rate

impossible

Figure 45 Overlapping Rates in Supraventricular Tachycardia

RATE (bpm)

100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250

Sinus Tachycardia

Atrial Tachycardia

Atrial Flutter

Junctional

Tachycardia

Junctional Rhythms 149

48. You now know about four more arrhythmias—those that originate in the AV junction. You have learned the characteristics that these arrhythmias share and how they differ from rhythms that originate in other pacemaker sites. You also learned that several

of the tachycardias cannot always be differentiated, because they might have similar

rate ranges and obscured P waves. When this situation exists, you can only describe the

rhythm as a Supraventricular Tachycardia, rather than giving it a specific name. Now

you must practice applying this knowledge to actual interpretation of rhythm strips.

Turn to the Practice Strips at the end of this chapter and practice applying your new

knowledge until you feel very comfortable in this area.

Practice Strips

150

KEY POINTS

■ Rhythms that originate in the AV junction include:

• Premature Junctional Complex

• Junctional Escape Rhythm

• Accelerated Junctional Rhythm

• Junctional Tachycardia

■ Junctional arrhythmias will create an inverted

P wave because the atria are depolarized via retrograde

conduction.

■ A junctional impulse will depolarize the ventricles in a

normal manner at about the same time that the atria are

being depolarized with retrograde conduction.

■ A junctional rhythm can have the inverted P wave occurring before, during, or after the QRS complex.

■ All junctional arrhythmias will create an inverted P wave,

but some low atrial impulses can also cause inverted

P waves.

■ All junctional arrhythmias will have a PRI of less than

0.12 second.

■ The rules for Premature Junctional Complex are:

Regularity: depends on regularity of underlying

arrhythmia

Rate: depends on rate of underlying arrhythmia

P Waves: will be inverted; can fall before, during, or

after the QRS complex

PRI: can only be measured if the P wave precedes the QRS complex; if measurable,

will be less than 0.12 second

QRS: less than 0.12 second

■ A PJC is an irritable ectopic.

■ The normal inherent rate of the AV junction is 40–60 bpm.

■ If higher pacemaker sites fail, a junctional escape pacemaker might take over control of the heart. This is called

Junctional Escape Rhythm.

■ The rules for Junctional Escape Rhythm:

Regularity: regular

Rate: 40–60 bpm

P Waves: will be inverted; can fall before, during, or

after the QRS complex

PRI: can be measured only if the P wave precedes the QRS complex; if measurable,

will be less than 0.12 second

QRS: less than 0.12 second

■ If the AV junction becomes irritable, it can speed up and

override higher pacemaker sites. This arrhythmia is

called Junctional Tachycardia.

■ Junctional Tachycardia is usually divided into two categories, depending on rate:

60–100 bpm Accelerated Junctional Rhythm

100–180 bpm Junctional Tachycardia

■ The rules for Accelerated Junctional Rhythm are:

Regularity: regular

Rate: 60–100 bpm

P Waves: will be inverted; can fall before, during, or

after the QRS complex

PRI: can be measured only if the P wave precedes the QRS complex; if measurable,

will be less than 0.12 second

QRS: less than 0.12 second

■ The rules for Junctional Tachycardia are:

Regularity: regular

Rate: 100–180 bpm

P Waves: will be inverted; can fall before, during, or

after the QRS complex

PRI: can be measured only if the P wave precedes the QRS complex; if measurable,

will be less than 0.12 second

QRS: less than 0.12 second

■ If a rapid arrhythmia is regular, has no visible P waves,

and has a rate range common to other arrhythmias,

thereby making more accurate identification impossible, the arrhythmia is termed Supraventricular

Tachycardia.

SELF-TEST

Directions: Complete this self-evaluation of the information

you have learned from this chapter. If your answers are all

correct and you feel comfortable with your understanding

of the material, proceed to the next chapter. However, if you

miss any of the questions, you should review the referenced

frames before proceeding. If you feel unsure of any of the

underlying principles, invest the time now to go back over

the entire chapter. Do not proceed with the next chapter

until you are very comfortable with the material in this

chapter.

Junctional Rhythms 151

Questions Referenced Frames Answers

1. What does the P wave look like in a junctional

rhythm?

5, 6, 7, 8, 10, 11, 17, 44 The P is always inverted, even

though it is often hidden in the

QRS complex.

2. How do you explain the unusual configuration of the

P wave in junctional rhythms?

2, 3, 4, 5, 6, 7 The atria are depolarized via

retrograde conduction. Since the

electrical flow will be traveling

away from the positive electrode

in Lead II, the wave form will be

negative.

3. Will the QRS complex be normal in a junctional

rhythm?

3, 5, 10 Yes, even though atrial

depolarization is retrograde,

ventricular depolarization will be

normal. The QRS complex should

measure less than 0.12 second.

4. Does an inverted P wave always indicate a junctional

rhythm?

8, 9, 12, 13, 14 No, atrial rhythms can also have

inverted P waves if the impulse

originated low enough in the atria.

You can differentiate between

the two by looking at the PRI; in

a junctional rhythm it will be less

than 0.12 second.

5. Where will the P wave be located in a junctional

rhythm?

6, 7, 10, 15, 16, 17, 41 It can fall before or after the QRS

complex, or it can be hidden

within the QRS complex. In the

latter, it will appear as if the

rhythm has no P wave at all.

6. What is the biggest clue to a junctional rhythm? 8 the inverted P wave

7. What is a PJC? 19, 20, 21, 25, 43 A Premature Junctional Complex

is a single beat that originates

from an irritable focus in the AV

junction.

8. Will a PJC have a P wave? 22, 23, 25 Yes, the P wave will be inverted,

either before or after the QRS

complex or it can be hidden

within the QRS complex.

9. What will the PRI be for a PJC? 23, 25 If the P wave is in front of the

QRS complex, the PRI will be

less than 0.12 second. Otherwise,

there will be no PRI.

10. Does a PJC come earlier or later than expected in the

cardiac cycle?

19, 20, 25 earlier

11. What will the QRS measurement be for a PJC? 24, 25 Since conduction through the

ventricles is normal, the QRS

measurement should be less than

0.12 second.

12. What is the normal, inherent rate for the AV junction? 26, 27, 28, 44 40–60 bpm

13. What is a Junctional Escape Rhythm? 26, 27, 28, 33, 34, 42 It is an escape mechanism that

occurs when a higher pacemaking

site fails and the AV junction has

to take over at its own inherent

rate of 40–60 bpm.

152 Chapter 6

Questions Referenced Frames Answers

14. Is Junctional Escape Rhythm regular or irregular? 29, 33 regular

15. What will the P waves look like for this arrhythmia? 30, 33 They will be inverted: they can fall

before or after the QRS complex

or can be hidden within the QRS

complex.

16. Will the PRI measurement be normal for a Junctional

Escape Rhythm?

31, 33 No, if the P wave precedes the

QRS, the PRI will be less than

0.12 second. If it falls within the

QRS or after the QRS, there will

be no PRI.

17. What is the rate range for an Accelerated Junctional

Rhythm?

35, 36, 37, 40 60–100 bpm

18. Is Accelerated Junctional Rhythm regular or irregular? 37, 40 regular

19. What is the P wave like in Accelerated Junctional

Rhythm?

36, 37, 40 Just like the P wave in all other

junctional rhythms: it is inverted

and can fall before, during, or

after the QRS complex.

20. Is the QRS measurement normal for Accelerated

Junctional Rhythm?

36, 37, 40 Yes, since the conduction through

to the ventricles is normal, the

QRS should measure less than

0.12 second.

21. What is the rate range for Junctional Tachycardia? 35, 39, 40 100–180 bpm

22. Is a Junctional Tachycardia regular or irregular? 38, 39, 40 regular

23. What does the P wave look like in Junctional

Tachycardia?

38, 39, 40 It is probably not visible since

the rate is so fast that it might

be hidden in the T waves, or it

might be hidden within the QRS

complex. If it is visible, it will be

inverted either before or after the

QRS complex.

24. Is the QRS measurement normal for Junctional

Tachycardia?

38, 39, 40 Yes, it should be less than

0.12 second.

25. Is the PRI measurement normal for Junctional

Tachycardia?

38, 39, 40 No, if the P wave precedes the

QRS complex, the PRI will be

less than 0.12 second. Otherwise,

there will be no PRI.

26. When can you call an arrhythmia a Supraventricular

Tachycardia?

45, 46, 47, 48 only when you have a regular

rhythm, in a tachycardia range

with no visible P waves, and at a

rate that is common to more than

one arrhythmia, thereby making

more accurate identification

impossible

27. Which arrhythmias commonly need to be described

as Supraventricular Tachycardias?

45, 46, 47, 48 The most common ones are

Atrial Tachycardia and Junctional

Tachycardia, although the term

is also used to describe Sinus

Tachycardia and Atrial Flutter.

28. At what rate would you expect to have trouble

discerning P waves and might consider calling an

arrhythmia Supraventricular Tachycardia?

47 usually 150–250 bpm, although

you may lose the P waves at

slower rates

Junctional Rhythms 153

PRACTICE STRIPS (answers can be found in the Answer Key on page 557)

6.1

Regularity: ______________________________________ PRI: ____________________________________________

Rate: ___________________________________________ QRS: ___________________________________________