Module title = Tutorial: Analyze the Waveforms

Lesson title = How many P waves?

This is lesson 7 of 11 in this module

This lesson will focus on the ratio of P waves to QRS's.

When there are more P waves:

some P waves are not getting conducted to the ventricles due to conduction block in the AV node

When there are more QRS's:

a QRS is being generated but no P wave is being generated
this occurs when the AV node or the ventricles generate the QRS

For the following ECG's:

count all the P waves
count all the QRS complexes
if not equal, then find the extra or missing items

In this example, we have 7 P waves and 5 QRS's. Therefore, there are more P waves and in this example, it is due to a conduction block. Blue ovals indicate the missing QRS complexes.
P wave without a QRS

What do you think about this example?
Lots of P waves

Crazy, all those skinny little P waves! Did you count 16 and only 4 QRS's, so there are WAY more P waves than QRS complexes. When this happens, there is a conduction block (in the AV node) which we will teach you about later.

P waves are usually very regular. Thus we should expect a P wave where the red arrow is. This P wave is not visible because the QRS is superimposed on the P wave, making it virtually impossible to see him. Poor little guy; it's just not fair sometimes. The T waves are not readily seen in this ECG. Sometimes, T waves or P waves do not show up in every lead.
regular P waves

How about this ECG?
only 2 P waves

It has 2 P waves (blue arrows) and 7 QRS's. The red arrows point to T waves.

Now it is your turn. Go practice. This skill is a little bit challenging, so some people might get frustrated.

Lesson 7 of 11

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Module title = Tutorial: Analyze the Waveforms

Lesson title = How many P waves?