Atrial fibrillation with entrance block, nonparoxysmal junctional tachycardia with type I (Wennckebach) exit block




Figure 1 - Lead II - rhythm strip 

This is atrial fibrillation with entrance block, nonparoxysmal junctional tachycardia with type I (Wennckebach) exit block


Figure 2 - Ladder diagram

There are no discernible P waves. You might be misled that there are distortions in the terminal portions of the T waves but they are not consistent and you cannot march them out. So, there is atrial fibrillation (AF).

AF, however, cannot generate regularly occurring patterns. Thus, there is a AF with entrance block. Entrance block denotes failure of an impulse to reach, enter, suppress, reset, or discharge a dominant pacemaker.The next dominant pacemaker that can generate a regular pattern is the AV junction. However some of the impulse from the AV junction is blocked (exit) and this creates a pattern/group-beating. Group-beating is marker of a Wenckebach periodiocity.

To give us an idea of the AV junction rate, we will use the 3:2 pattern or the 2 QRS and 3 junctional beats. The RR interval of R2 to R4 is about 1320 ms. So, we divide 1320/3 and we get 440 ms as the interectopic interval or a rate of about 136 bpm ( small squared method = 1500 / (440/40) ) for the AV junction or there is junctional tachycardia. Because this pattern is persistent then this is non-paroxysmal junctional tachycardia.

In the ladder diagram, the AF is blocked and the approximate origin of the junctional beats is set at an interectopic interval of about 440 ms (~11 small squares).There is a 3:2 and 2:1 pattern as shown in the ladder diagram.


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1 comment:

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