Hi, welcome to our video series on electrocardiograms.
In this one, we're going to learn about atrial dysrhythmias; PACs or premature atrial contractions.
So, this is the normal sinus rhythm.
Now, we start every part of this video series with a normal sinus rhythm strip
because we want you to know what normal is
and then compare the dysrhythmia that we're looking at, so you'll recognize abnormal.
Now, look at the ECG below.
This is normal sinus rhythm but look at some of those beats.
There's a few beats that are off. Now, we'll highlight those beats for you,
so you know exactly what I'm talking about. See how they come in early?
That's why they're called premature atrial contractions.
Now, we call them premature because they come in early,
but look at those early beats we have highlighted for you.
See how they're still a P wave?
So, we know the atrium is involved, it's just not as consistent.
So, if you measure the distance between QRS complexes,
it will be mostly consistent except for a very set pattern where the PACs come in.
So, we're back with our patients. Let's try and diagnose another one.
This time, we need to check on this lady.
Once again, we can already tell this doesn't quite look like a normal sinus rhythm.
It doesn't look too bad, but at a glance, I can't tell what the problem is.
So, let's go through our seven basic steps to pinpoint
what's going on inside our lovely patient's heart.
Once again, let's recap. The electrical impulse travels from the atria to the ventricles.
Its pathway is being reflected on the ECG paper.
Now, the impulse originates at the SA or sinoatrial node and travels through the atria.
Now, this causes the atrial repolarization or contraction and forms the P wave on the ECG strip.
Now, at the AV node, the impulse is delayed,
and it's reflected on the ECG strip as an isoelectric line called the PR segment.
Then, the impulse courses through the Purkinje fibers.
This causes depolarization or a contraction of the ventricles
which is reflected on the paper as the spikey QRS complex.
Next, the interval of time between depolarization and repolarization of the ventricle
in reflected as a flat or isoelectric line called the ST segment.
And finally, the ventricles repolarize or relax which forms the T wave.
Okay, so let's take a look at these waves.
You see what we have highlighted for you, the PR segment.
We're looking at the P wave and the QRS complex.
Now, we have those early beats or PACs marked for you.
So, just take a minute, look at them, and see what's different about those two PACs,
premature atrial contractions, as compared to the other beats you see on the strip.
So, you know we have these seven steps.
This is how we're teaching you if you're beginning to learn how to interpret an ECG strip.
The more systematic you are in walking through each one of these steps,
the more consistent you'll be in interpreting them.
So, I'm not going to read them to you this time because I know you're familiar with them.
If this is the first video you're watching with us,
pause it and take a minute and read these steps. Now, here's a study tip.
Don't just read the steps. When you read number one, assess the heart rate and rhythm,
that is just a reminder where you need to stop and think, okay, how do I do that?
How do I look at the heart rate? How do I look at the rhythm?
And I want you to do that with all seven steps.
So, whether this is your first video series with us, or you've seen the other videos,
I want you to pause the video and think through each one of these seven steps
as to how you would do that.
It'll be a great review for moving that information into your long-term memory,
and that's where it needs to be on an exam or in your nursing practice.
So, step one, we're going to assess the heart rate and rhythm.
Make sure you have six seconds of a strip.
You can count the QRS complexes and multiply that by 10 to calculate the beats per minute.
Now, I know there are more precise ways to do that,
but this is just to give you an estimate of what the heart rate is.
Keep in mind, if you have an ECG paper, then you also have a patient on a monitor,
and that will give you an exact heart rate per minute.
Now, identify the six seconds and count those QRS complexes
and multiply by 10 is laid out here for you.
So, you'll see in a strip, you count each one of those that fall within a six-second strip
and multiply that by 10 to get the heart rate you see on the screen.
Now, I've got calipers up there again.
Remember, we talked about how we don't usually still use those.
It's an old school tool. They're the original tool, but when you see those in our videos,
that's to remind you that you are going to physically measure the space and the time.
So, you'll likely do it with digital calipers,
but if you don't have a monitor in front of you like when you're practicing with your strips,
you'll actually use something to help you consistently measure
the spaces and distances on an ECG strip.
Now, looking at the rhythm, this one is a little more challenging
because when you're first learning, students want to say, this is not regular.
Well, it actually is for the most part. So, we're talking about regular.
When you look at these, most of the QRS complexes are equally spaced.
But we have a couple beats that come in a little early
and that's a clue to us that it's a premature atrial contraction. So, is it regular?
Yes, except for a couple beats.
Now, step two, we're going to look at the P waves.
You'll see that the ones before those early beats look a little different.
Now, why do you think that is? Well, this heart isn't playing by all the rules, right?
When you see those QRS complexes that have the P waves
that look like most of the other P waves on the strip, it's following the rules.
It's in time, it's consistent, you have a regular rhythm.
But those early beats, look at those P waves. Ah, look, they're a little different.
That should make sense because it's a premature atrial contraction.
So, this is happening a little bit outside of the normal rules.
So, in sinus rhythm, you have a normal P wave or atrial contraction.
It's before every QRS. In sinus rhythm with PACs,
you have a little bit irregular P wave that's located in front of that.
It's there, but it looks a little odd.
Now, keep in mind the difference between sinus rhythm
with PACs and sinus tachycardia with PACs is just the overall heart rate.
If it's greater than 100, we would call it sinus tachycardia.
That's why it matters that you know what the rate is as you move through the seven steps.
Now, next, you're going to measure the PR interval.
Again, we've - we're assuming that if you're watching this video with us,
you've already watched the video series that teach you exactly how to measure that.
We've got some pictures up there to remind you,
but if you're feeling uncomfortable with this,
don't forget to check out the more beginning videos in this series.
So, step three, measure the PR interval, and it should be consistent in the sinus beats.
So, for every one of the sinus beats, you're going to see a very consistent PR.
Now, P waves are there for each complex.
They don't necessarily look the same in the PACs,
but you should have a very consistent PR interval with all the sinus beats.
Step four, measure the QRS duration.
So, the QRS duration should be within the normal range, less than 0.12 seconds.
Step five, take a look at the ST segment. Do you notice any depression or elevation?
And we know we need to do further assessment if you do.
Look at that T wave. It should be rounded and not peaked or tall.
Now, that might be difficult to see depending on how fast the heart rate is going.
Now, measure the QT interval can also be a little problematic,
but it should be within the normal range.
Now, it's one thing for you to listen to me explaining this,
but what I want you to be sure of is that you have this information stored where you need it,
where you can retrieve it. So, this is a great video to watch multiple times,
to stop and pause, and make sure you can answer those questions
and understand how we got those answers.
That will help you really begin to master the concepts.
So, looking at this and wrapping it up, heart rate 60-100 would make this sinus rhythm with PACs.
Now, if this heart rate was faster, and it often can be with PACs,
we would be sinus tachycardia with PACs.
The rhythm? How's that? Clear as mud. It's regular but a little irregular with the PACs.
We would call that regularly irregular. Which is different than atrial fibrillation.
Remember, that is all over the map and the QRS differences
are totally different throughout the strip.
This, you can see there is pretty consistent order except for the beats that have PACs.
Now, every QRS complex has a P wave.
The PR interval is within normal ranges for the sinus beats
and the QRS is also within normal range.
So, thank you for watching this part of our video series today.