Step 6: Examining the T Wave (Nursing)

by Rhonda Lawes, PhD, RN

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    00:01 We've made it to step six.

    00:04 Can you pause for just a minute, and remember the first 5 steps on your own? Okay, I hope you did that without looking at your notes.

    00:19 Number 6 is to examine the T wave.

    00:22 Now the T wave represents the repolarization, or the relaxation of the ventricles.

    00:28 We've got that highlighted for you in our graphic.

    00:32 Now, the T wave should be rounded and upright, but not tall, or peaked.

    00:37 If the T wave looks abnormal, it may not be pathological, but you definitely need to follow up and do further assessment.

    00:45 Take a closer look at that T wave.

    00:47 I want you to become comfortable with what they look like when they're normal.

    00:51 Look at the first half of the T wave, you'll notice it's a nice gradual slope, then look at the last half, it's a lot steeper.

    01:00 So T waves, normal T waves are not symmetrical.

    01:04 There's nothing wrong with this patient's T wave.

    01:07 We expect the first part to be a gradual slope, and the last part to be a more steep slope.

    01:14 Now if we're going to get real fancy here, it's usually about 1/8 but less than 2/3 of the amplitude of the R wave.

    01:23 That is a mouthful, you likely not have to really use this on a regular basis but we want you to know when your eye notices something is off, this is one way to specifically measure it.

    01:37 So a normal T wave can be from 1/8, but less than 2/3 of the amplitude of the R wave.

    01:44 You remember how to measure the amplitude of the R wave? The isoelectric line all the way to the top of the peak, which is the R wave.

    01:53 Now when you measure the amplitude of the T wave, it's still the isoelectric line to the top of the T wave.

    02:01 And that should be 1/8 of the amount or at least less than 2/3 of the amplitude of the R wave.

    02:10 Now the T wave amplitude rarely exceeds 10 millimeters, and the T wave follows the same direction of the QRS deflection.

    02:18 This is a positive QRS, right because it's above the isoelectric line.

    02:23 It's also a positive T wave because it's above the isoelectric line.

    02:29 Now peaked T wave, see the difference in this we've given you different leads here.

    02:34 So you can see what the T wave may look like.

    02:36 This could be an indication of an extra high serum potassium, or maybe even an evolving MI.

    02:44 Best takeaway? If that T wave doesn't look normal, and it's peaked, you need further assessment.

    02:52 Now I've got some other examples here about the T wave and potassium levels, because this can be an indication of hyperkalemia or high potassium.

    03:01 But keep in mind, an ECG really isn't that sensitive for hyperkalemia.

    03:06 So you would want to have lab work to check and see if there was a problem.

    03:11 Profound hyperkalemia can lead to heart block and asystole.

    03:16 Okay, that's worth repeating.

    03:18 Why do we get so worked up about potassium levels? Well, if you start seeing some peaked T waves that indicate it could be a potassium level, it's always a good practice just to check even though you know that's not absolutely definitive.

    03:34 If you're getting a clue like that, you always want to follow up.

    03:39 We're real worried about potassium levels because extremely high potassium levels can lead to death, specifically heart block and asystole and that would be the death.

    03:51 Now the T waves appear peaked initially with decreased amplitude of the P waves, and then the QRS becomes prolonged.

    04:00 So this is what you're going to see in the progression.

    04:03 You see there, how the wave changes, right? So it progresses and the changes that you're seeing is the amplitude is getting shorter, smaller, smaller, smaller, see that from the first one down to the fifth one.

    04:18 And then the QRS becomes wider and prolonged.

    04:22 These are the types of changes you would see as potassium level gets higher, but know if you saw rhythm, that just like one of those, you wouldn't know what the exact level of the potassium was, you would have to draw lab work.

    04:36 Now what about an inverted T wave? What makes the T wave inverted? Well, if you look at this, the left example, the T wave is the same deflection, direction as the QRS, but in the right one, it's different.

    04:54 Now there's a range of reasons that a T wave can be inverted.

    04:56 The patient may be asymptomatic and their heart is otherwise normal but the patient could be experiencing an evolving heart attack.

    05:05 So the patient may have some structural heart disease like coronary heart disease or left ventricular hypertrophy, you definitely want to follow up on it.

    05:14 So the left one is what we expect to see in most people but the right one doesn't mean they're in imminent danger but you should follow up and get a closer history of the patient and make sure you're aware of their vital signs and how stable they're feeling in your assessment.

    About the Lecture

    The lecture Step 6: Examining the T Wave (Nursing) by Rhonda Lawes, PhD, RN is from the course The Basics of ECG Strips (Nursing).

    Included Quiz Questions

    1. It is asymmetrical.
    2. It is peaked.
    3. It follows the opposite direction of the QRS.
    4. It has a higher amplitude than the R wave.
    1. A peaked T wave
    2. An asymmetrical sloped T wave
    3. An absent T wave
    4. A depressed T wave
    1. Coronary heart disease
    2. Left ventricular hypertrophy
    3. An otherwise normal heart
    4. Hypokalemia
    5. Hyperkalemia

    Author of lecture Step 6: Examining the T Wave (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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