EKG Interpretation, part 7: Junctional Rhythms

by Cathy Parkes July 05, 2020

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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