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?
-2nd degree AV block type I (Mobitz I)
-Intermittent 2:1 AV block
-Av block, second degree-Mobitz type II (Wenckebach)
-AV block, 2:1
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.