EKG Interpretation, part 7: Junctional Rhythms

by Cathy Parkes July 05, 2020

In this article, you will learn about the different junctional dysrhythmias, including junctional rhythms, junctional bradycardia, accelerated junctional rhythms, and junctional tachycardia. The EKG Interpretation video series follows along with our EKG Interpretation Flashcards, which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI exams, and NCLEX.

As we explained in our article on the natural pacemakers of the heart, a junctional rhythm is the secondary backup for the heart. When the sinus node fails to kick off an electrical impulse to make the heart beat, the atrial foci are the first backup, and if that fails, the junctional foci are the next backup.

The inherent rate of a junctional rhythm is slower than a normal heart rate, usually between 40 and 60 beats per minute. The key characteristic of a junctional rhythm is an abnormal P rate. The P rate will be either absent, inverted, in the wrong place, or with a very short PR interval. When you encounter an EKG strip on a test, looking for those abnormal P wave conditions can help you identify a rhythm as junctional.

Junctional rhythm on EKG

Junctional rhythm

All the rhythms we will explain in this article are technically junctional rhythm, but this section covers regular junctional rhythms, or junctional rhythms with the expected heart rate.

Rhythm regularity (atrial and ventricular)

This rhythm is regular; its movement pattern is repeated the same way across the entirety of the EKG strip. There are equal distances between the R waves, meaning the ventricular rhythm is regular. The P waves, though they look strange, are also regular; they have an equal distance between them. So the atrial rhythm is also regular.

Because we are dealing with a regular rhythm, this enables us to use one of the standard methods for calculating heart rate.

Heart rate

In this example, we can use the small box method. There are approximately 34 small boxes between each R wave. 1500 divided by 34 is 44. This means 44 beats per minute.

Remember that junctional rhythms have an inherent rate between 40-60 BPM.

Components

The P wave in this rhythm is inverted, which is not normal. This is a clear sign we are looking at a junctional rhythm.

The QRS complex is narrow, which rules out a ventricular rhythm. So, with all of the clues we have gathered thus far, we can fairly safely conclude that this is a junctional rhythm.

Treatment

Treatment of junctional rhythms is typically not necessary. However, if the heart rate is too slow to maintain adequate cardiac output, then atropine can be used to increase the heart rate.

One important tip to keep in mind is that you would NOT use digoxin in patients with junctional dysrhythmias. Digoxin toxicity is one of the most common causes of junctional rhythms.

Studying Pharmacology? Both atropine and digoxin are some of the key important meds covered in our Pharmacology flashcards for nursing students.

Junctional bradycardia on EKG

Junctional bradycardia

Rhythm regularity (atrial and ventricular)

This rhythm is regular; you can see that its movement pattern is repeated the same way across the entirety of the EKG strip. There are equal distances between the R waves, meaning the ventricular rhythm is regular. The P waves, though they look strange, are also regular; they have an equal distance between them. So the atrial rhythm is also regular.

Because we are dealing with a regular rhythm, this enables us to use one of the standard methods for calculating heart rate.

Heart rate

If we use the small box method to calculate this heart rate shown above, we can see that there are 46 small boxes between the R waves. 1500 divided by 46 is 33. This means 33 beats per minute, which is a very slow heart rate.

Components

The P wave in this rhythm is inverted, which is not normal. This indicates a junctional rhythm.

The QRS complex is narrow (under three small boxes wide), which rules out a ventricular rhythm. With these clues, we know it is a junctional rhythm.

Treatment

Treatment of junctional rhythms is typically not necessary. However, if the heart rate is too slow to maintain adequate cardiac output, then atropine can be used to increase the heart rate.

Again, remember that you would NOT use digoxin in patients with junctional dysrhythmias as it is contraindicated.

accelerated junctional rhythm on EKG

Accelerated junctional rhythm

Rhythm regularity (atrial and ventricular)

This rhythm is regular; you can see that its movement pattern is repeated the same way across the entirety of the EKG strip. There are equal distances between the R waves, meaning the ventricular rhythm is regular. The P waves, though they look strange, are also regular; they have an equal distance between them. So the atrial rhythm is also regular.

Because we are dealing with a regular rhythm, this enables us to use one of the standard methods for calculating heart rate.

Components

With this accelerated junctional EKG strip, we see that the P wave is missing, which is our clue that tells us this is junctional.

Heart rate

If we use the small box method to calculate this heart rate shown above, we can see that there are 18 small boxes between the R waves. 1500 divided by 18 is 83. This means 83 beats per minute. We know it's not a regular junctional rhythm because that inherent rate is supposed to be between 40-60 BPM, and this rate is higher at 83. Accelerated junctional rhythms have an expected rate of 60-100 BPM.

If you have been following along in this series, you may be wondering why the otherwise normal heart rate of 60-100BPM is considered accelerated in this case. This is because junctional rhythms originate from the AV junction, which has a slower intrinsic rate than that of the SA node.

Sinus Rhythms vs. Junctional rhythms
Characteristic Sinus rhythms Junctional rhythms
Electrical impulse origin SA node AV junction
Bradycardia <60 bpm <40 bpm
Intrinsic ("normal") rate 60-100 bpm 40-60 bpm
Accelerated rate n/a 60-100 bpm
Tachycardia >100 bpm >100 bpm

 

 

junctional tachycardia on EKG

Junctional tachycardia

Rhythm regularity (atrial and ventricular)

This rhythm is regular; you can see that its movement pattern is repeated the same way across the entirety of the EKG strip. There are equal distances between the R waves, meaning the atrial rhythm is regular.

Because we are dealing with a regular rhythm, this enables us to use one of the standard methods for calculating heart rate.

Heart rate

If we use the small box method to calculate this heart rate shown above, we can see that there are 13 small boxes between the R waves. 1500 divided by 13 is 115. This means 115 beats per minute. We know that any rate above 100 BPM is considered tachycardia, so we know this is tachycardia.

Components

In this strip, you can see there is a flat line where the P wave is supposed to be, so the P wave is actually missing. That is your clue that this is a junctional rhythm. We know it's not a regular junctional rhythm because that inherent rate is supposed to be between 40-60 BPM, and this rate is much higher at 115. This fits the bill for junctional tachycardia.

The QRS complex is also normal, as expected with a junctional rhythm.

Stay tuned for our next article where we will show you some wide QRS complexes in ventricular rhythms!


Full Transcript

In this video, we are going to talk about junctional rhythms.

So if you recall, we have the SA node or sinus node. And if that fails, then the atrial foci take over. And if that fails, then the junctional foci in the AV junction take over.

The inherent rate of a junctional rhythm is a little slower, so it's between 40 and 60 beats per minute.

And the key characteristic of a junctional rhythm is that the P wave is messed up. It's either absent, it's inverted, it happens after the QRS complex instead of before, or we have a very short PR interval.

So you'll definitely want to be looking for those things to be able to identify a rhythm as junctional.

So in this video, we will talk about a junctional rhythm, a junctional bradycardia rhythm, an accelerated junctional rhythm, as well as a junctional tachycardia rhythm.

Okay, here we are looking at a junctional rhythm.

So if we first assess the regularity of this strip, we will see that it's actually very regular. We have equal distance between our R waves. Our P waves are messed up. You can see they're inverted as opposed to upright and smooth. However, we have an equal distance between those P waves. So both the ventricular and atrial heart rhythms are regular.

If we calculate the heart rate, so because we are dealing with a regular strip, we can use the small box method to do this. So we have approximately 34 small boxes between these R waves. So if I take 1,500, divide it by 34, I get 44 beats per minute, which is right in that range we talked about with junctional rhythms, right? Junctional rhythms will have an inherent rate between 40 and 60 beats per minute.

And if we look at the different components, like we said, the P wave is inverted. That is not normal. That's our other big clue that this is a junctional rhythm.

Our QRS complex is nice and narrow, so that's how we know we're not dealing with a ventricular rhythm. So this is a junctional rhythm strip.

Treatment of a junctional rhythm is typically not necessary. However, if the heart rate is too slow to maintain adequate cardiac output, then atropine can be used to increase the heart rate.

The other thing you should keep in mind is you want to avoid the use of digoxin in patients with junctional dysrhythmias. And in fact, digoxin toxicity is one of the most common causes of junctional rhythms. So you definitely have to be careful with digoxin.

Now we are looking at a junctional bradycardia strip.

So again, we have a regular strip.

And if we calculate the heart rate between these R waves, there are 46 small boxes between the R waves. If we take 1,500 divided by 46, we get 33 beats per minute. So this is a very slow rhythm that is regular.

Again, we're looking at a junctional rhythm because it's slow and because we have this messed-up P wave again. It's inverted here as well.

QRS complex is nice and narrow, under three small boxes wide.

With junctional bradycardia, the heart rate is under 40 beats per minute. So in this case, we have 33 beats per minute. So that fits the bill here, and that's how we know we are looking at a junctional bradycardia strip.

In terms of treatment, again, like I shared with the last strip, if the heart rate is too slow to maintain adequate cardiac output, then the patient may need to be given atropine to increase that heart rate. And again, we're definitely to want to watch digoxin, because digoxin toxicity can lead to junctional rhythms such as this.

Okay, now we are looking at an accelerated junctional rhythm.

So again, the strip is regular. We have equal distance between our R waves, but we can see that we are missing our P waves, which is one of the things that will happen when you have a junctional rhythm. So we know this isn't normal sinus rhythm because we're missing these P waves.

Let's look at the rate. If we count the number of small boxes between the R waves, we will see that there are approximately 18. If we take 1,500, divided by 18, we get 83 beats a minute. We know it's not junctional rhythm because the inherent rate of junctional rhythm is between 40 and 60 beats per minute, so it's a little faster than that.

With accelerated junctional rhythms, we can expect a heart rate between 60 and 100 beats per minute, which is the same range we see with normal sinus rhythm, but again, we're missing the P wave, and that's why we don't have normal sinus rhythm here.

We are finally looking at a junctional tachycardia strip.

We can see that it's a very regular strip, but it's very fast.

So since we're dealing with a regular rhythm, we can do the small box method to calculate the heart rate. We have approximately 13 small boxes between R waves. So if we take 1,500, divide it by 13, we get 115 beats per minute. So it's definitely a tachycardia.

It's not sinus tachycardia because we don't have this P wave. We just have this little flat line where the P wave should be. So it is a junctional rhythm. But with a normal junctional rhythm, the inherent heart rate should be between 40 and 60. With accelerated, it's between 60 and 100. With junctional tachycardia, the heart rate will be over 100. In this case, we have approximately 115 beats per minute, so that fits the bill for junctional tachycardia.

So we have normal QRS too, just to point that out, because when we move into my next video, which will talk about ventricular rhythms, we'll notice that this QRS will get wide.

So stay tuned, and we'll get through the rest of these dysrhythmias. Thanks for watching!


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