Atrioventricular Blocks


    62 year old male with dizziness.

    62 year old male with dizziness.


    Question 1: Why isn't this complete heart block?

    Question 2: During the periods of 2:1 AV block, is the level of the block in the AV node, or the Bundle of His?

    Question 3: Does this patient need a pacemaker?

    Question 4: Why is there 2:1 AV block at times and Wenckebach at other times?

    Key Findings

    -Sinus rhythm

    -2nd degree AV block type I (Mobitz I)

    -Intermittent 2:1 AV block

    Coding for Boards

    -Sinus rhythm

    -Av block, second degree-Mobitz type II (Wenckebach)

    -AV block, 2:1


    Question 1: During the periods of Wenckebach and periods of 2:1 AV block, there is some communication between the atrium and ventricle. Therefore, complete heart block is not occurring.

    Question 2: The combination of a long conducted PR interval and the concomitant presence of Wenckebach suggests that the level of the block is in the AV node rather than the distal His-Purkinje system.

    Question 3: Perhaps. If they are on AV nodal blocking agents, these should be stopped. If that is not the case or not possible, they may need pacing.

    Question 4: The sinus rate is such that the P waves are occuring very close to the interval at which the AV node can only handle every other beat. With subtle oscillations in the sinus rate, the P waves may occur at times the a second beat can conduct with a longer PR interval.