Become a Resus Member for FREE! Get access to Resus learning resources and learn about upcoming events SUBSCRIBE [email protected]

Module 2: The P wave and Blocks

Advertise Your Event

Do you have an upcoming event that your would like to share with colleagues? We would love to hear from you!

Click on the “contact” button below, fill out the details in the pop-up and hit “submit”.

Subscribe to Resus

Get the latest updates on our Conferences PLUS our Webcasts and Education Newsletters. And it's FREE!

  • We respect your privacy
  • This field is for validation purposes and should be left unchanged.

Register Now:

The Primary Exam
Learn More
Emcore
Learn More

P waves and Mobitz Blocks

The P wave

Look at the P waves- are they upright in II and inverted in aVR if so then normal, otherwise it’s ATRIOVENTRICULAR JUNCTIONAL OR ECTOPIC ATRIAL RHYTHM

Is There a Mobitz Block?

If the QRS complexes are clumped, think of a Mobitz Block.

Look for the P waves. Are there more P’s than QRS’s? If so, it might be a Mobitz.

The key is the P-P interval. It must be constant. If not, then think of premature atrial contractions. If the P-P interval is constant and there are more P’s than QRS’s then think of:

  1. Atrial flutter
  2. Mobitz Block(p-p intervals are constant in Mobitz II, p-r interval lengthens in Mobitz I)
    1. Beware the Moritz II with 2:1 block where the P’s are hidden in the T wave and it may look like sinus rhythm.
  3. Complete Heart block- QRS’s will be regular and the p-r interval varies

A 58 yo male presents with dizziness. What does the ECG show?

Let’s use the system so far, on this ECG.

RATE

No of QRS complexes x 6 – 11 x 6 = 66

P WAVES

Upright in I, upright in II , inverted in aVR? If not, it is an ATRIOVENTRICULAR JUNCTIONAL OR ECTOPIC ATRIAL RHYTHM

The p waves are upright in II and inverted in aVR

Are the p waves related to the QRS?

If not, are there more P waves than QRS’s: If so there are only 5 diagnoses

  1. Premature atrial contractions (The p-p interval is not constant)
  2. Atrial flutter
  3. Mobitz I (p –p interval constant p-r lengthens before dropped beat)
  4. Mobits II (p-p interval constant, p-r is constant before dropped beat)
  5. Complete Heart Block: (QRS is constant as coming from below AVN ie., the QRS complexes aren’t clumped, like in Mobitz I and II. The p-r interval varies.

In this case there are no flutter waves, so it’s not atrial flutter. The p-p interval is constant, so it isn’t premature atrial contractions either.

Given that the QRS complexes are clumped and not regular, as you would expect in CHB, it is either a Mobitz I or II.

Look at the p-r interval next. It increases, then a QRS is dropped. It is therefore a Mobitz I.

One good thing to do with ECG’s like this is to ‘map them’, i.e.., mark the P waves and the QRS’s and determine which p wave produces a QRS. Then determine the PR interval. Here is an example below, for this ECG.

Therefore this is a Mobitz I, or Wenckeback block.

Module 3: The QRS

Posted in ,

admin

Leave a Comment