In second-degree type II AV nodal block (a.k.a. Mobitz ... intermittent basis. For example, three consecutive P waves may be followed by a QRS complex, giving the ECG a normal appearance, then ...

This ECG has both second degree AV block with 2:1 block and second degree type I AV block. Note that intermittent P waves conduct to the ventricles on this ECG tracing, however it is clear that ...