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The Basic Components of an ECG Strip (Nursing)

by Prof. Lawes

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    00:01 Hi, welcome to the beginning of our video series on electrocardiograms.

    00:06 Now, in this portion, we're going to talk about the basic components of all ECG strips.

    00:12 Now, you've likely heard about these numbers when you interpret ECGs.

    00:16 But I want to help you understand what they really mean.

    00:20 In this course, we're going to cover the basic components of electrocardiograms or more commonly known as ECG strips.

    00:28 It will be helpful for you to already be familiar with the overall normal functioning of the heart.

    00:33 It's important that you understand how the heart pumps, the conduction system inside the heart muscle, and how blood pumps through and out into the rest of the body.

    00:43 Now, we have several videos that can help you learn more about the heart if this information is new to you.

    00:50 In this video, we will look at how the overall function of the heart as its electrical activity is captured on an ECG strip.

    00:59 After this series, I'll show you how to tie all your knowledge about the heart to this squiggly line of curves and points.

    01:07 I will show you how you can use those squares on the ECG to start identifying which area of the heart is malfunctioning.

    01:16 You'll also be able to start to recognize the difference between a healthy heart and a heart that is in trouble by looking at the heart's electrical activity using different angles.

    01:26 Now, this is what we call a 12-Lead.

    01:29 We'll use ECG strips from the five most common cardiac leads.

    01:33 We use to measure cardiac patients on a telemetry, critical care, or an emergency care area.

    01:39 After this series, you'll have a better understanding of how efficiently the electrical conductions are able to move their unique patients heart.

    01:50 Look at this, here is a look into your very near future when you are a licensed nurse.

    01:57 Nurses often take care of several monitor patients, all at once.

    02:01 So you'll need to quickly and accurately identify which patients are stable, and which patients heart might be in trouble? Now, it may seem overwhelming now, but stay with me, I promise you, you can do this.

    02:15 So don't worry, take a deep breath, we're going to take it one step at a time, together.

    02:21 First, we're going to learn what normal looks like and break down the basic of how the impulse moves through the heart and is recorded on the ECG strip with a healthy normal heart first? Once you have that down, then we're going to go through different cardiac conditions or dysrhythmias, one by one and compare those to the normal heart.

    02:44 So, you'll know, what to look for on an ECG strip, or monitor.

    02:49 So, don't forget about these patients, we'll come back to them.

    02:53 But first, let's take a look at what are the basic components of an ECG strip? If you take a look at a classic ECG strip, you'll see that it's comprised of many curves.

    03:06 Now, each of these curves represents a part of the cardiac cycle.

    03:11 Take a look at this pumping heart.

    03:13 The electrical impulse can be seen in green, and it travels from the atria to the ventricles.

    03:20 Now, its pathway and the effects that it has on the cardiac muscle as it passes through is what's reflected on the ECG strip.

    03:28 The impulse originates in the sinoatrial or SA node.

    03:33 It disperses through the left and right atria causing their contraction.

    03:39 Now, this is what's reflected in the ECG as the P wave.

    03:44 After atrial contraction, the impulse heads down towards the ventricles through the atrial ventricular node or the AV node.

    03:53 Here, it doesn't just pass right through the impulse is delayed or slow down.

    04:00 Now, this delay is reflected in the ECG strip as the PR segment.

    04:05 And it's important because it allows the ventricles to finish filling up with blood before they contract.

    04:12 Next, we have this spiky part called the QRS complex, which represents the impulse reaching the Purkinje fibers inside the ventricles of the heart and stimulating their depolarization or contraction.

    04:26 The next wave is the T-wave.

    04:28 Now, the T-wave is caused by the repolarization or relaxation of the ventricles.

    04:34 This period of time or interval between ventricular depolarization and repolarization is represented as the ST segment in an ECG.

    04:45 Finally, we have the U-wave, which may or may not be present on the strip.

    04:50 Although, we don't exactly know what causes it.

    04:53 It's believed to be the result of a delayed repolarization of the Purkinje fibers.

    04:59 Now, that we've broken down in the cardiac cycle, and we've seen how each part is reflected on the ECG strip, we can get the full picture.

    05:09 Later on, when we see abnormal P waves or elevated ST segments, you'll be able to identify which heart chamber and which part of the cardiac cycle is affected.

    05:21 Let's look at ECG Paper Speed, and how it helps us accurately interpret ECG strips.

    05:28 Look at this monitor.

    05:30 Let's pretend that you just push the Print button and look at the paper coming out of the monitor.

    05:36 Now, no matter how many times you press the Print button, the paper comes out at the same speed.

    05:42 Now, with the paper moving at a constant rate of speed, we can use this to measure how long it takes for an impulse to move through the heart.

    05:52 We can measure how long it takes an electrical impulse to travel by measuring the length of parts on the rhythm strip.

    06:01 So, I want to ask you a question.

    06:02 What is so important about these squares? Well, keep in mind the paper is moving at a constant rate of speed.

    06:11 So this helps us measure time.

    06:14 You see, we have mark there, how many boxes it takes for one second? So let's zoom in a little closer.

    06:20 Now you see that we have the one second bar at the bottom, how many large boxes are there in one second? One, two, three, four, and five.

    06:34 Now there's also some small boxes in there.

    06:38 Let's talk about the actual numbers in math.

    06:41 And we're looking at the ECG paper.

    06:44 So, why does this small box represent 0.04 seconds? Let's take a look.

    06:51 Now, paper moves at 25 millimeters per second, past the recording stylus.

    06:58 By knowing that constant rate, it can help us more accurately estimate how long it's taking that beat to move through the heart muscle? One small box equals 0.04 seconds.

    07:13 And we've figured that because we know the paper moves at a consistent rate.

    07:18 So, one small box equals 0.04 seconds.

    07:22 Five small boxes make up a large box and that equals 0.2 seconds.

    07:28 So how do we get there? I promise just simple math.

    07:31 5 x 0.04 seconds = 0.2 seconds.

    07:37 So, let me ask you a question.

    07:39 How many large boxes would it take to make up one second, if each large box is worth 0.2 seconds? Well, 5 large boxes = 1 second.

    07:54 So, 25 small boxes = 5 large boxes and that's what gives us one second.

    08:01 25 x 0.04 = 1 second.

    08:07 Now, as you're breaking down an ECG strip, it's all about measuring different intervals and spaces.

    08:13 So, take a look at this PR interval.

    08:17 You'll see one blue line at the beginning of the PR interval and the other blue line whereas you stopped measuring.

    08:25 Now, look at how many boxes are in between.

    08:28 One, two, three... there's four.

    08:32 So if we're measuring this PR interval, we know it's four boxes, or 4 x 0.04, which equals 0.16 seconds.

    08:42 So, the length on the strip of this PR interval tells us it's taking 0.16 seconds for the PR interval.

    08:52 Now, a normal PR interval is less than 0.20 seconds.

    08:58 This one is 0.16 seconds, so it's all good.

    09:01 This is a normal PR interval.


    About the Lecture

    The lecture The Basic Components of an ECG Strip (Nursing) by Prof. Lawes is from the course The Basics of ECG Strips (Nursing).


    Included Quiz Questions

    1. Sinoatrial node
    2. Atrioventricular node
    3. Right bundle branch
    4. Left bundle branch
    1. QRS complex
    2. P wave
    3. ST-segment
    4. U wave
    1. T wave
    2. P wave
    3. U wave
    4. ST-segment
    1. 0.04 seconds
    2. 0.2 seconds
    3. 1 second
    4. 1.3 seconds

    Author of lecture The Basic Components of an ECG Strip (Nursing)

     Prof. Lawes

    Prof. Lawes


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