ECG Library


Heart Blocks ECG 41

  1. Second Degree Type I AV Block
  2. 2:1 AV block

Some P waves conduct to the ventricles on this ECG tracing, however it is clear that some do not. There does appear to be a prolonging PR interval before dropped beats (second degree type I AV block), however at times P waves are randomly not conducted (2:1 AV block). Note the irregular R-R intervals making 3rd degree heart block unlikely.

The rhythm on this ECG needs to be distinguished from high grade AV block which is a form of 3rd degree AV block that can occur when some P waves are conducted through the AV node to the ventricles, however quite a few are not. The R-R intervals will vary unlike in true 3rd degree AV block (complete heart block) where they are regular. There is no definite Wenkebach periodicity seen in high grade AV block.

Related Topic Reviews: Second Degree Type I AV Block, 2:1 AV Block