So what I want to show you is the five-step method to interpreting EKGs like a boss. My name is Nicole Weaver. I've been a nurse for 10 years and I've worked in ICU and emergency departments. I have looked at so many EKGs in my lifetime and we're gonna start with normal sinus rhythm because if you know normal it becomes really really easy to identify what's abnormal.
In fact I will teach you normal so that on the abnormal rhythms, all you have to know is what's different instead of memorizing all the criteria. Just learn what's different. So the first step of the five-step method is, is it regular? Regular means there's an equal amount of space between every QRS complex or the beats are coming regularly.
There's two ways you can do this. One, I like to just get a piece of paper and mark where those QRSs are and then march out that little piece of paper on my EKG graph to see if it's all even. It's a really quick, rudimentary way to do it. Another way you can do it that's more accurate is to actually count the number of small boxes between two QRS complexes and then count the number between the next two, count the number between the next two. If you're within one to two on every single one, so you've got 20, 21, 20, 20, that's regular, okay?
If you've got 20 and then 38 and then 22 and then 42, that's a problem, okay? That means it's irregular. So first step is regular. Normal sinus rhythm will be regular. The second thing you need to look at, the second step is rate.
Normal heart rate, the normal firing of the SA node is 60 to 100 beats per minute. Any slower is too slow, any faster it's too fast. So in order to check rate, there's two main ways we recommend to do this. If you have a six second strip like the one that you see here, then you can just count the total number of QRS complexes in that strip, multiply it by 10. So in this case you've got seven beats in six seconds, which means you've got 70 beats in a minute. So 70 beats per minute would be your estimate.
It's okay that these are relative estimates because you're really just trying to see, is it too fast or too slow? In this case, we know it's okay. The other method you can use is the 1500 method. I like this one because it's super accurate.
You're going to count the small boxes between two QRS complexes and then divide that into 1500. So if you've got 22 small boxes and you say 1500 divided by 22, you're going to see 68. So our six second strip method got us 70. Our 1500 method got us 68. It's a little more accurate. However, if you have an irregular rhythm, meaning there might be 22 boxes here and 36 boxes here, that 1500 method isn't gonna be accurate. So you're best to grab a six second strip or to count a full minute. Either way, you want to find out what the rate is. Normal and normal sinus rhythm is gonna be between 60 and 100. Third step, look at your P to QRS ratio.
First thing is, are there P waves? If there are no P waves, We definitely know there's a problem because the atria aren't contracting like they should. What you should have is one P wave for every QRS.
In other words, your P to QRS ratio should be one to one. You might also have an issue where you have multiple P waves and less QRSs, in which case your ratio is three to one or four to one or five to one. That's a problem. So P to QRS ratio should be one to one. The next thing you want to look at, step four, is your QRS complex.
Again, your QRS complex should be less than 0.12 seconds or less than three small boxes. If it's any wider than that, we know we've got issues going on. And finally, we're going to take a look at that PR interval. This is step five. Our PR interval, again, tells us the communication time between the SA node and the AV node should be less than 0.20 seconds.
If it's any longer than that, we know we've got some heart block issues going on, so we need to look a little closer. So to recap your five steps for a normal sinus rhythm, it's regular, the rate is between 60 and 100, you have one P for every QRS, your QRS complex is narrow or less than 0.12 seconds, and your PR interval is normal or less than 0.20 seconds. That's normal.
Remember, you're not alone in this. We've got you. Happy nursing.