Step II First degree AV block

[hst]

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I am a little confused by the explanation of first degree AV block in Uworld

explanation reads: First Degree Heart Block: P wave always follows QRS, unlike other heart blocks

Is this right? My thinking was that P wave would follow QRS in the setting of a PVC.

Question ID 3765. Uworld for step II

 

[sahell]

1st degree heart block is just a long PR interval.

 

[niko327]

What they are probably trying to say is that the P wave and the QRS are still associated. As the poster above has already mentioned, the problem with first degree AVB is that the impulse is delayed within the AV node prior to being conducted to the ventricles thus resulting in a fixed but long PR interval.

The real thing that question is probably testing is whether or not you understand the difference between a conduction problems happening within the AV node versus just below the AV node (intranodal vs infranodal block). Which are considered dangerous and why.