ECG Level 1 Tutorial: Analyze the Waveforms
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Tutorial: Analyze the Waveforms
This module will teach the basic waveforms on ECG and a stepwise approach of how to analyze them. Practice each step and get feedback on your performance.
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Tutorial: Analyze the Waveforms P conducted to QRS?
Lessons
42
Times Practiced
1284
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Progress
Accuracy
Efficiency
Accuracy
Efficiency
1 Anatomy Anatomy
2 Waveform Identification Waveform Identification
3 Waveform Identification #2 Waveform Identification #2
4 Determine the heart rate Determine the heart rate
5 Do you have Rhythm? Do you have Rhythm?
6 P waves! Where are you? P waves! Where are you?
7 How many P waves? How many P waves?
8 P wave Size and Shape P wave Size and Shape
9 PR Interval PR Interval
Current lesson 10 P conducted to QRS? P conducted to QRS?
11 QRS Width QRS Width
P conducted to QRS?
Is the P wave "conducted" to the QRS? Very good question. In a normal heartbeat the answer is yes because the following events occur:

The electrical impulse is initiated by the SA node:
impulse starts at the SA node

is conducted through the atria:
conduction through the atria

down through the AV node (with a little delay from slow conduction):
conduction through the AV node

and finally conducted to the ventricles:
depolarization of the ventricles

Therefore: the SA node is generating both the P wave and the QRS complex. When this happens, we say that the P wave is conducted to the QRS. 

This can also occur if the atrium generates the P wave (instead of the SA node). This occurs in abnormal rhythms where the acting pacemaker is in the atrium instead of the SA node.

When P waves are conducted down to the ventricles, we will see on the ECG:
  • the PR interval is normal or long
  • a QRS complex is present
  • the P wave occurs before the QRS
WHY these criteria are required?
  • the PR interval length is created by the delay due to normal slow conduction in the AV node
  • if the electrical signal makes it down to the ventricles, then a QRS complex will be generated
  • everything must happen in this order which creates a P wave before the QRS
Before we have explaioned abnormal rhythms, you might be thinking that all these details are super obvious. However, there are rhythms with no P waves or P waves that come AFTER the QRS. You can also have missing QRS complexes or pretty much any combination of strangeness that you could imagine. Therefore, always look for the threesome of the: P wave, PR Interval normal or long, and QRS complex in that order. If any one of these is missing, something abnormal will be happening in the ECG.

This lesson might seem like a small detail, but it is a very important concept: we are dedicating an entire lesson on it. Try the practice sessions and see how you do.