In second-degree atrioventricular nodal block — also known as Wenckebach block or Mobitz Type I AV block ... This is called 2:1 AV block, as depicted below: When 2:1 AV block is present ...
In second-degree type II AV nodal block (a.k.a. Mobitz Type II AV block), the AV node becomes completely refractory to conduction on an intermittent basis. For example, three consecutive P waves ...