This is a tricky one. There are many non-conducted P waves, which might lead us to thinking this is a third degree block. However, there is NOT AV dissociation. In other words, the atria and ventricles are NOT moving at their own separate, but consistent paces. The P waves have their own regulare rate, but the QRS complexes do not. The QRS coplexes are not regular. They must therefore be associated with the P waves in some way, albeit it inconsistent and haphazard. If any of the P waves get conducted – as there must be because there is NOT AV discoation present – then this is a high grade second degree AV block.