Submitted by Percula1869 on Tue, 11/29/2011 - 08:33

Alright guru's, for us monitor techs out there, what is the best way to differentiate second degree type 2 with 2:1 vs second degree type one?

Dawn's picture

Submitted by Dawn on Tue, 11/29/2011 - 15:01

Once an AV Block starts conducting 2:1, the telltale signs which differentiate Type I from Type II can be difficult to see.  To recognize progressive prolongation of the PR interval, you need to see two P waves in a row conducted.  Here are my suggestions:   Look at a fairly long strip.  If you see two P waves conducted in a row, look at the PR interval.  If the progressive prolongation is there, it is Type I.   Look at the P waves that fail to conduct.  If there are more than one in a row non conducted, or if a P wave is out in the middle of the strip away from the refractory period of the preceding beat, you are looking at a Type II.
Also, Type II often is accompanied by bundle branch block, since Type II blocks are fascicular blocks.   Check the ECG Archives, and I will soon post some of each type for illustration.

Dawn Altman, Admin

Submitted by waltm on Wed, 09/26/2012 - 18:36

Hi Dawn!  I'm new here and love the site.  It's dangerous...I could get lost here and my family might never find me again. :)  I was an EMT instructor in the 70's and 80's and a cardiac tech (CCT, CRAT) and EKG tech instructor since, specializing in Holter analysis.  I do have a question about your response to Percula1869 regarding Type I/Type II blocks.  Are all Type II blocks located in the fascicles?  I've always known that they can be, but it was my understanding that they could occur at the AV node as well, just like third degree AV blocks could be either bilateral bundle branch blocks or nodal (hence third degree AV block with junctional esacpe rhythm).  Have I misunderstood this concept?  Thanks.

Walter A. Mueller, CCT, CRAT

jer5150's picture

Submitted by jer5150 on Fri, 09/28/2012 - 17:01

 

Greetings Walter!  I realize you directed your inquiry towards Dawn, but I'm willing to field your question for you. 

Decades ago, His-bundle electrograms (HBEs) repeatedly demonstrated that Type II A-V blocks are ALWAYS infranodal and, more specifically, they are USUALLY infra-Hisian.  Type II A-V block NEVER takes place at the anatomic level of the A-V node.  It SOMETIMES takes place at the anatomic level of the His bundle and USUALLY takes place in the bundle-branches and fascicles.

In his textbook "Advanced Concepts in Arrhythmias, 2nd ed. pages 250 and 251, Dr. Marriott explains about "Anatomy versus behavior".  I highly recommend that you acquire a copy of this book!  

On page 250, Dr. Marriott says:  "What it all boils down to is that when we say Type I, we mean "probably [A-V] nodal" . . . and when we say Type II, we mean "certainly infranodal . . . "

The table below appear on the facing page (i.e., 251)

 

Type I

Type II

Anatomical

Usually A-V nodal  – sometimes His bundle

Always subnodal  – usually bundle-branches


When Dr. Marriott states that Type II is "always subnodal", I take that to mean that there are absolutely no exceptions to the rule. 

I hope this provides better clarity to your question.

Keywords for anatomic levels:  A-V nodal, Infranodal (a.k.a.:  subnodal), infra-Hisian.

Jason E. Roediger - Certified Cardiographic Technician (CCT)
[email protected]

Submitted by waltm on Sat, 10/20/2012 - 10:27

Thanks for your answer.  I appreciate your insights and references.  Wish I had read it before posting my last comment to your current ECG challenge in which I call it a matter of semantics.  It's obviously more than that.

Walter A. Mueller, CCT, CRAT

jamie_bisson's picture

Submitted by jamie_bisson on Sat, 10/06/2012 - 02:59

OK, this is a relatively simple one....

 

Second degree type 1, is defined as a lengthening PR interval, until you drop a QRS following a P wave. So you will see the normal sinus rhythm with a progressively longer PR interval with each PQRST, then eventully you will have a P wave, no QRS and then another PQRST. The pattern will continue.

 

Type 2 is simply explained as a normal sinus rhythm followed by a P wave, no QRST then a PQRST. If this pattern continues it will be a 2:1 block..... 2 P waves, to every 1 QRS dropped.

 

Hope this helps

Jamie Bisson
http://www.eadvancedhealthcare.com/healthcare-resources/ecg-interpretati...

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