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Second-degree AV Block

ECG Basics: Second-degree AV Block With Characteristics of Type I and Type II

Thu, 09/01/2016 - 11:51 -- Dawn

This strip shows a second-degree AV block.  During most of the strip, 2:1 conduction is present.  At the beginning, however, two consecutive p waves are conducted, revealing progressive prolongation of the PR interval.  This usually represents a Type I , or nodal, block:  progressive refractoriness of the AV node.   However, the wide QRS ( possibly left bundle branch block), and the fact that the non-conducted p waves are "out in the open" where they should have conducted, points to Type II - an intermi

Second-Degree AV Block, Type I

Sat, 06/13/2015 - 22:07 -- Dawn

This ECG is from an 80-year-old woman who had an acute inferior wall M.I. with a second-degree AV block.
Some people incorrectly call ALL second-degree AV blocks that are conducting 2:1 "Type II".  This is incorrect, as Mobitz Type I can also conduct with a 2:1 ratio.  The progressive prolongation of the PR interval will not be seen with a 2:1 conduction ratio, because there are not two PR intervals in a row.

Second-degree AV Block,Type I, With 2:1 Conduction

Fri, 04/04/2014 - 23:17 -- Dawn

This ECG is a follow-up to last week's ECG of the WEEK, which presented an AVB that was mostly conducted 2:1, and proved to be a "Type II" block when it conducted 3:2 with consistent PR intervals at the end.  We often just use the term, "2:1 AVB", rather than try to discern the Mobitz type, realizing that the most important feature of a 2:1 block may be that it automatically cuts the heartrate in half.

ECG BASICS: Second-degree AV Block, Type II

Sat, 05/25/2013 - 13:12 -- Dawn

Today's basic rhythm strip illustrates second-degree AV block, Type II.  Even though there is fine baseline artifact present, it is easy to measure the P-to-P interval, and your students will be able to see that every third P wave falls in the T wave.  The PR intervals are constant and the atrial rate is about 110/min.  The ventricular rate results from a 3:1 conduction ratio, and is less than 30/min.

Second-degree AV Block, Type I

Sat, 02/16/2013 - 18:52 -- Dawn

This 67 year old man is noted to have a slightly irregular pulse.  At the beginning of this ECG, he appears to be in NSR with a first-degree AV block.  Twice, P waves are non-conducted.  Careful measurement of the P to P interval shows that it is regular, there are no PACs noted.  The PR interval changes very subtly by lengthening just before the non-conducted P waves.  A hint when non-conducted P waves are noted, first check for non-conducted PACs.  If the sinus rhythm is regular, check the PR interval before the non-conducted beat, and the PR interv

jer5150's picture

Jason's Blog: ECG Challenge of the Week for Oct. 21-28, 2012

No clinical patient data available for this 12-lead ECG.

What does this tracing show?  Choose the correct answer from the list below.

(1.)  Sinus bradycardia with atrial bigeminy; conducted APBs; prominent U-waves; RBBB
(2.)  Sinus rhythm with 3:2 and 2:1 Type II AV block; RBBB
(3.)  Sinus rhythm with atrial bigeminy; both conducted and nonconducted APBs; RBBB

APBs = atrial premature beats
RBBB = right bundle-branch block

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