Paramedics Course – ECG Calculating Heart Rate

ECG Calculating Heart Rate

Micro-lecture by the Australian Paramedical College

In today’s micro-lecture, Australian Paramedical College Hon. Snr. Lecturer Sam Willis talks about how to calculate the heart rate of an ECG using two different methods.


ECG Calculating Heart Rate


Today we’re going to talk about how to calculate the heart rate of an ECG using two different methods.

Now, the good news is by today’s standards, you actually don’t necessarily need this skill anymore because modern defibrillators and ECG monitors actually tell you the heart rate. If you’re not able to see the heart rate on the screen, you can calculate it yourself manually, you can use oxygen saturation probes, so it’s one of those skills that’s slowly moving away from paramedic practice.

However, there’s always going to be that case where you actually need to do it manually. Just say, for example, your patient’s got some kind of hypovolemia and you can’t palpate their radial pulse and therefore they’re peripherally shut down and they’re cold and the probe doesn’t pick it up and you do place an ECG on the patient and you’re using a machine that needs upgrading and it doesn’t have it on it. So there’s always going to be that occasion when you need to be able to calculate a heart rate using an ECG.

So I’m going to show you two methods. The first one is the simplest method. However, you do need a calculator. Now, the reason I say you need a calculator because as human beings we do like to prove how great we are. Unfortunately, that leads to errors, which leads to patients being harmed. Now, there are occasions where you don’t need a calculator, for example, with this ECG, but I would always advocate it anyway.

Now, the first method is the divide by 300 methods. So the first thing you need to do is to find two RR intervals, and try your best to follow lead 2. So going back a step here’s your normal 12-lead, so lead 1, lead 2, lead 3, lead AVR, AVL, AVF, V1, 2, 3, V4, V5, V6, plus your 12 ECG. And there’s a couple of things there intentionally missing off of the slides, off of the ECG.

Now, it doesn’t actually matter which view you take this from, but it’s just easier to take it from a lead 2. Now what you do is you find your R wave, and then you find another R wave, and you have a look to see how many large squares there are in between those R waves, and for the purposes of this image there’s these two here but they’re all the same, and you take the number of large boxes and you divide it into 300. So 300 divided by, on this occasion, 2. And this heart rate is 150. So always try and use an R wave that is on the thick line. If you use it in between one of the lines then it’s going to be more complex for you, so 300 divided by 2. That’s great. That one works every time.

Now the other method is this method. So, 30 large squares, you’re going to a longer strip. That’s one of the disadvantages. So you need to count, 1, 2, 3, 4, 5, 6, 7, 8. But what it’s saying here is, 30 large squares are equal to 6 seconds. So what we do is, you’ve taken our 30 large squares, we count how many R waves there are: 1, 2, 3, 4, 5, 6, 7, 8, and we times it by 10, because then that gives you 6 times 10 is a minute, and that’s how that one’s calculated. So that’s 80 beats per minute.

Okay, so that’s the micro-lecture. Please get online and take a look at this stuff as well in your own time.

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