Normal Sinus Rhythm

Hey guys, my name is Brad and welcome to nursing.com. And in today’s video, what we’re going to be doing is we’re going to discuss normal sinus rhythm. I’d like to describe a little bit, physiologically speaking, what we’re seeing with normal sinus rhythm, as well as how to identify this for testing purposes. Without further ado, let’s dive in. 

So whenever we’re talking about normal sinus rhythm, this is the rhythm in which the heart is functioning perfectly, right? That’s the biggest thing that you need to know with normal sinus rhythm. This is whenever the heart is functioning in a homeostatic manner. So before I begin, I would like for you guys to make sure that you’ve already brushed up on your electrical anatomy and physiology of the heart before beginning. If you haven’t, we have resources here on nursing.com to help bring you up to speed.  But it’s very important to understand the electrical conduction system, the anatomy and physiology of the heart before you begin diving into these EKG, because it’s going to help make everything make more sense.  

But in normal sinus rhythm, the heart is functioning perfectly, right? So we basically have proper homeostatic movement of the electrical conduction system from that SA node down to that AV node, eventually going down this bundle of His, the right and left bundle branches, and eventually terminating down into these Purkinje fibers, which also is associated with proper contraction of the atrium and the ventricles as this electrical conduction system it’s generated throughout the heart. So then that begs the question, how is this reflective on an EKG? So whenever we’re solving EKG test questions [email protected], we always use the six step method. Before I dive into that, I think it’s important to let you guys know if you haven’t already checked out our material on how to read a basic EKG strip, and it’s very important that you do so. I’m not going to be going over that here, but make sure that you brush up on that so that you’re brought up to speed and know what we’re talking about as we talk about some of these different P waves, QRS complexes, et cetera. 

So the six step method that we use to identify a rhythm on an EKG question. First, we’re going to look at the heart rate. We’re going to look at the regularity, P:QRS and if there is one QRS complex for every P wave. PR interval length, and the QRS length, ultimately solving. So what does the six step method look like in normal sinus rhythm? So heart rate, what is a normal heart rate that we’re going to see in a patient with normal sinus rhythm, right? We’re going to see 60 to 100 beats per minute. Okay. Regularity. This is looking at the R to R interval. Do we have a normal length between R-R between one R and the next R interval? And are these regular from R to R basically something that you would use calipers for? We will dive into that, but in normal sinus rhythm, yes, what you have is you have regular R to R intervals.   P to QRS. Is there one P for every QRS complex and in normal sinus rhythm, indeed, there is.  Normally, we would see extra P waves in instances, such as various types of heart blocks, not something that you need to worry about in this lesson, if you would like further information on that, check out our resource on that.  PR interval length. Okay. We recall from our basic EKG strip, how to read basic EKGs that a normal PR interval link is 0.12 to 0.20 seconds. And indeed with normal sinus rhythm, this is what we’re going to see. Normal QRS complex length is going to be 0.06 to 0.12 seconds. This is going to be what we’re going to see with normal sinus rhythm. We will have a QRS length of 0.06 to 0.12 seconds.  And finally, we’re going to solve.  

So this is the six step method that we’re going to use in order to read and identify any kind of EKG rhythm on a test question. Now, let’s take this information that we have, and actually implement it into a test question. 

And so now that we have a little practice strip here, that we’re going to take a look at, let’s actually implement our six step method, right? So let’s go ahead and write these out. We have our six step method. Okay. Let’s remember that our sixth step is to actually solve. So that’s what we’re going to do here at the end of this. 

So the first thing that we’re going to do is we’re going to take a look at our heart rate. What is our heart rate? Again, make sure you go check out how to read a basic EKG strip before proceeding, if this is not familiar to you.  You will recall what we have here, this entire thing is a six second strip. So all that we have to do to measure heart rate is to count our number of QRS complexes and multiply by 10. So in this instance, what do we have? 1, 2, 3, 4, 5, 6, 7 QRS complexes multiplied by 10 gives you a heart rate of 70 beats per minute (7 X 10 = 70). And we know that is normal between 60 and 100. So that’s normal. Okay. Check. We got that. Very good. 

The next thing we’re going to look at is our R to R interval. And we want to know, are we regular or are we irregular? But what does that basically mean? Again, we have our QRS complexes. So we’ve got our R waves. We’re going to take a look at all of our R waves. And what we’re basically going to be doing using calipers, usually, is we’re going to measure the distance, the actual distance between this R to R interval. And then we want to compare that to this R to R interval and to this one. And as long as the distance, the length of time between each R to R interval is the same, then you are regular and in normal sinus rhythm, in this instance, we are indeed regular. 

Now, next thing that we’re going to take a look at is our P to QRS ratio. Do we have one P wave for every QRS complex. P wave QRS,  P wave QRS, P wave QRS, so on and so forth. And you want to make sure that you actually look throughout the entire six second strip, because you never know when an extra P wave may end up sneaking in there, and now you’ve actually got a heart block rhythm versus a normal sinus rhythm. Again, this is not a heart block lesson, but nonetheless, just stressing the importance of looking down the entire length of the example strip that you’re given. And in this case, yes, we do indeed have one P wave for every QRS, so that checks off. 

Next thing that we want to do is we want to take a look at our PR interval length. And we know from our basic EKG strip class, how to do that, right? So we’re going to actually count each individual, small little box down here to see how long our PR interval is, recalling that every small little, small individual box is 0.04 seconds and each long box containing five smaller squares is 0.20 in length seconds. So what do we have here? 1, 2, 3, 4, 5 small boxes here on this PR interval. Five times 0.04 is 0.20 (5 X 0.04 = 0.20). Let’s check another one though. 1, 2, 3, 4, 5. Indeed, we do have a PR interval of 0.20 seconds. We know that a normal PR interval is 0.12 to 0.20.  So that checks out. 

And the last thing here is our Q R S length, right? We’re recalling that a normal is between 0.06 and 0.12. So if we actually just taking a look at our QRS length, we would go counting our small boxes. 1, 2, 3. 0.04 times three is 0.12 (0.04 X 3 = 0.12).  Knowing that a normal QRS is between 0.06 and 0.12 seconds, we know this checks out as well.  And without doing anything else, after looking at these six steps, we know without a doubt, what we’re dealing with here is normal sinus rhythm. And this is the way in which you’re going to use the six step method to solve any EKG test question. And this is an example of what normal sinus rhythm may look like. 

So to summarize some of our key points surrounding reading a normal sinus rhythm EKG strip, remember in normal sinus rhythm, this is an instance in which the heart is functioning perfectly. We have a homeostatic conduction of the electrical system moving from the SA node to the AV node down the bundle of His eventually terminating in those Purkinje fibers. And also remembering that this electrical conduction should also be correlated with an appropriate contraction of both atria, as well as both ventricles. Knowing that a normal heart rate in normal sinus rhythm is 60 to 100 beats per minute. We would be regular with one P wave for every single QRS complex. Also knowing that our PR interval length will indeed be normal falling between that 0.12 and 0.20 second range. And as well, our QRS complex length will also be normal volume between that 0.06 and 0.12 second range.

Guys, I really hope that this video helped bring a little bit more clarity to what solving the normal sinus rhythm EKG strip would look like. Again, I highly encourage you to check out our electrical A and P of the heart lessons, as well as how to read a basic EKG strip again if any of this didn’t make any sense. I hope that you guys go out there and be your best selves today. And as always, happy nursing.