Sinus Rhythm (Nursing)

by Rhonda Lawes, PhD, RN

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    00:01 Hi, welcome to our electrocardiogram video series.

    00:05 In this one, we're going to talk about sinus rhythm.

    00:09 So far, we've covered the components of the ECG paper and broken down the cardiac cycle to see how each phase is reflected as a wave.

    00:17 We also went through the seven basic steps to analyzing any ECG strip.

    00:22 Now we're going to put that to the test.

    00:25 ECGs come in many different forms depending on the health of each patient.

    00:30 By the end of this course, you'll be able to identify most of them.

    00:34 However, before you start diving into the world of pathology, you have to have a good grasp on the basics.

    00:41 You can't recognize sick if you don't know what healthy looks like first.

    00:46 So let's take a look at a normal sinus rhythm ECG strip.

    00:51 Let's take another look at our beating heart here and do a brief recap on the waves and intervals of an ECG strip.

    00:59 Remember, the electrical impulse travels from the atria to the ventricles and its pathway an influence on the heart muscle is what's reflected on the ECG strip.

    01:09 Now the impulse originates in the sinus or the sinoatrial or here's a third name, the SA node - they all mean the same.

    01:18 It travels from the SA node through the left and right atria, causing their contraction which is reflected in the ECG as the p wave.

    01:29 The impulse then heads through to the AV node, but it doesn't just pass through.

    01:35 It gets delayed or slowed down.

    01:37 This delay is documented in the ECG strip as the PR segment.

    01:43 Next, we have the QRS complex, which represents ventricular contraction.

    01:49 This contraction is caused by the impulse entering the ventricles and dispersing through the Purkinje fibers.

    01:56 The next wave is the T wave, which is caused by the repolarization or relaxation of the ventricles.

    02:03 This period of time or interval between ventricular depolarization and repolarization, is represented as the ST segment in an ECG.

    02:13 Finally, we have the U wave, which actually may or may not be present on the ECG strip.

    02:20 Although we don't exactly know what causes it, it's believed to be the result of a delayed repolarization of the Purkinje fibers.

    02:27 So let's do a quick review of how to analyze any strip.

    02:32 Step one, you will analyze the heart rate and rhythm.

    02:38 Remember, you're making sure that you have the same equal distance between the R waves of the QRS, and the p waves.

    02:46 So they should plot along equally, p wave to p wave to p wave, r wave to r wave to r wave.

    02:54 The next step is to analyze the P waves.

    02:57 You should have one P wave for every QRS.

    03:00 They should all look the same and they should measure out equally.

    03:06 Third step is to measure the PR interval.

    03:09 You measure from right where that P wave starts to leave the isoelectric line down to where it starts to dip down again, that is the PR interval.

    03:20 Now, step four is measure the QRS duration.

    03:24 So you're going to measure how wide the QRS is.

    03:28 Step five, take a look at the ST segment.

    03:31 Step six. Look at the T wave, we want to make sure that isn't depressed or elevated.

    03:37 And then step seven, we're going to measure the QT interval.

    03:42 Now a normal P wave is the atrial contraction precedes every QRS complex in a normal sinus rhythm.

    03:50 The rhythm is regular, but can vary slightly during respirations, and that is completely normal.

    03:59 The rate ranges between 60 and 100.

    04:03 Anything below 60 is sinus brady.

    04:06 Anything above 100 is sinus tachycardia.

    04:10 Now the P wave is positive in I and II.

    04:15 Now it's little biphasic in lead V1.

    04:19 But remember, there's a potential of a patient is having problems, we want to really good detailed look at the electrical activity in the heart, we'll use a 12-lead.

    04:29 So those are just referring to different types of leads.

    04:33 If a patient is in the hospital, they're most likely just on 5-leads for regular monitoring.

    04:38 But if we do a 12-lead ECG, that's when we suspect there might be a bigger problem.

    04:45 So when we say the P wave is positive, that means it's up above that isoelectric line It is positive in lead I, lead II and biphasic in lead V1.

    05:00 So let's do it, let's dive in and hit the seven steps with this ECG strip.

    05:07 So first, let's assess the heart rate and rhythm.

    05:11 Now if you count these up, we have a rate of 80.

    05:15 Normal sinus rhythm is between 60 and 100, so we're spot on.

    05:20 Look at the rhythm. Is it regular? Well, measuring the distance between the QRS complexes, yeah, it plots right along, it's regular.

    05:30 And you measure between the P waves.

    05:34 Yeah, it's regular.

    05:36 This is what we would expect to see in a sinus rhythm.

    05:39 So let me show you right where we looked here.

    05:42 We're going to analyze the P waves in step two.

    05:46 So see those blue boxes that have appeared? That's to remind you of what the P waves are.

    05:52 Now look, there is one P wave is present for each of the QRSs, and they all look the same.

    05:59 They don't just want to glance at that.

    06:00 You really want to be disciplined to look at each P wave, make sure that it's there for every QRS.

    06:08 Right, and then step back, and make sure those P waves all look similar.

    06:14 Step three, measure the PR interval.

    06:17 Now take a look at the strip we've provided.

    06:20 You're going to measure from where the P wave starts to the R wave.

    06:25 Now I'm going to pause and let you try and measure that.

    06:28 And then we'll show you the answer on the screen for this particular strip.

    06:35 Step four. Now we're going to measure the QRS duration.

    06:40 Now we have it marked for you here.

    06:42 You want to measure it when that Q wave dips down below that isoelectric line up to the R and to the S.

    06:50 What we're looking for is a normal value, so that's less than 0.12 seconds or 3 small squares.

    07:00 Remember, each tiny square is worth .04 seconds, so 3 x .04 would be .12.

    07:09 And that's the number you're looking for, a QRS that is less than .12.

    07:17 Step five is to look at the ST segment.

    07:20 You want to make sure there's no depression or elevation.

    07:24 Remember, we're comparing that to the isoelectric line.

    07:28 Step six, examine the T wave.

    07:31 Make sure that it's rounded and not peaked or tall.

    07:35 Now the seventh step we talked about, we're looking for QT elongation.

    07:40 Remember, greater than 50, we're in really big trouble.

    07:44 Normal is less than 0.46 in women, and less than 0.45 seconds in men.

    07:51 So you've done it all seven steps.

    07:55 You've walked through this strip to analyze what it looks like to have a normal sinus rhythm strip.

    08:03 Now QT interval extends from the beginning of the QRS complex through the ST segment and to the end of the T wave.

    08:11 And within the cardiac cycle, it represents the entire process of ventricular depolarization and repolarization.

    08:20 So let's review why this is normal sinus rhythm.

    08:23 The heart rate is between 60 and 100.

    08:26 The rhythm is regular.

    08:29 There's a P wave before every QRS and they look the same.

    08:33 The PR interval falls between 0.12 to .20, and the QRS is less than 0.12 seconds.

    About the Lecture

    The lecture Sinus Rhythm (Nursing) by Rhonda Lawes, PhD, RN is from the course The Basics of ECG Strips (Nursing).

    Included Quiz Questions

    1. T wave
    2. P wave
    3. U wave
    4. R wave
    1. Assessing the heart rate and rhythm
    2. Analyzing the P waves
    3. Measuring the PR interval
    4. Examining the ST segment
    1. The P wave comes after each QRS complex.
    2. The rhythm is regular.
    3. The heart rate is between 60 – 100 bpm.
    4. The P wave is positive in leads I and II.
    1. From the beginning of the upslope of the P wave to the beginning of the R wave
    2. From the ending of the upslope of the P wave to the ending of the R wave
    3. From the beginning of the upslope of the P wave to the ending of the R wave
    4. From the ending of the upslope of the P wave to the beginning of the R wave

    Author of lecture Sinus Rhythm (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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