ECG Interpretation: How To Interpret ECG [Micro Lecture]

In this micro-lecture APC Hon. Snr. Lecturer Sam Willis discusses interpreting an ECG. In terms of the process used, there are ways to mix a number of different methods; what is shown here is just a summary such as observing the QRS and P-wave.

ECG Interpretation Lecture Part 10

Welcome to this micro lecture. Today we’re going to talk about how to interpret an ECG.

So, you’ve managed to get the ECG dots onto your patient, and you’ve printed the ECG out, and this is what you’re presented with. You will already probably have your own methods for interpreting ECG. I’m hoping that what I tell you here either complements it or builds upon what you already know.

In terms of the process you use, you can probably mix a number of different methods, but what I’d like to show you is just a summary. Now, the first thing I would do when I’ve printed the ECG off is to have a look at the rate, to look at the speed of the heart.

Now, on most ECGs, it actually tells you what it is up here, so it will actually automatically give you the ECG rate. If it doesn’t, you can use a number of different calculations, including the ones that I’ve shown you in these workshops, in these lectures. So, the rate is really, really important.

Then what I would do, and remember, guys, the things I’m about to tell you are all done in lead two. So when you’ve printed it off, try and get yourself a 30 second strip of lead two, or even 10 seconds, that would be fine. 30 seconds is about as big as the gold standard, but 10 seconds is fine, too.

The first thing you look at is the rate. Second thing you look at is, is there a P wave in the ECG? You have to ask yourself, is there is a P wave before every QRS? Yes, yes, yes, yes … good. That means that atria are contracting. Is the P wave nice and round? Yes, it is. Is it less than five small squares, is the PR interval less than five small squares? One, two, three, yes, it is. So, that’s perfect.

Then you need to look at the QRS complex. Is there a QRS after every P wave? Yes, yes, yes, yes, yes. So, this is the QRS complex here. This is the Q, this is the R, and this is the S. Is it nice and straight? Yes, it is, straight up, straight down. Is the QRS interval less than two and a half small squares? Yes, it is. Good.

Is there a T wave after every QRS complex?

Yes, yes, yes, yes, yes – So, that means the ventricles are relaxing nicely. The QRS, as you know, represents ventricular contraction or ventricular depolarization. And that’s ventricular repolarization or ventricular relaxation.

So we’ve had the rate, the P wave, the QRS, and the T wave. Then, at this point, you can start looking at the regularity. So, it is regular? Is the distance between the R intervals regular? Yes, it is. And then, finally, start looking for anything abnormal.

So, you can talk, for example, look at ST segment elevation or depression, by looking at the J point here.

After this point, you really do need to start looking at the 12 lead ECG, and that’s not something we’re going to go in in this stage.

So, I hope this micro lecture on basic ECG interpretation has helped you guys. You can always reread any of this stuff, build on your knowledge by reading any time. We’re going to be doing more micro lectures on the 12 lead ECG as well.

My name’s Sam Willis (APC Hon. Snr. Lecturer) and I hope you’ve enjoyed it.

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