Explain what each of the following terms represents on an electrocardiogram (ECG).

a. P wave

b. QRS complex

c. T wave

d. P-R interval

e. S-T segment

Video transcript

Hi, everyone. Let's take a look at this practice problem together in an ECG reading. If it showed ST segment elevation, it could indicate the answer. Options are a ventricular fibrillation B atrial fibrillation, C, myocardial infarction and D all of the above. Well, what does ST segment elevation look like on an ECG? Let's go ahead and compare that to a normal ECG waveform to do. So I am putting up a drawing on the screen. Now, on the left is a normal waveform for one cardiac cycle and on the right is a waveform with ST elevation. Let's talk about the normal waveform. A normal ECG has a P wave, a QRS complex and A T wave. The P wave is highlighted in yellow. The QR S complex is highlighted in green and the T wave is highlighted in orange. So the ST segment elevation involves the ST segment and I have highlighted the ST segment in blue. This segment is located between the end of the S wave and the beginning of the T wave. Now, on the right side of this drawing is the waveform with ST elevation, the P wave QR S complex and T wave are all present. However note that in this wave form, the ST segment again highlighted in blue is above the baseline. Now, the question asked what condition could be indicated by ST segment elevation option. A ventricular fibrillation. This is the sudden rapid and irregular pulses, impulses in the ventricles that causes them to quiver instead of contracting on an ECG, this would show as chaotic irregular waves and valleys. Option B atrial fibrillation. This is when impulses in the atria are so fast that the atria quiver instead of contract atrial fibrillation has a classic, irregularly irregular pattern. In addition, in addition, there are no P waves. So both ventricular fibrillation and atrial fibrillation do not show ST segment elevation. So we can eliminate A AND B. The correct answer is myocardial infarction in a myocardial infarction. There's blockage in one or more coronary arteries and the ST elevation represents the parts of the heart that are damaged. So the correct answer is option C myocardial infarction. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.