A 73 year old woman with dizziness.

2 to 1 AV block

• every other P wave is conducted to the ventricles
  • 2 to 1 AV block starts after the 5th QRS in this 3 channel recording. The first non-conducted P wave is indicated with an arrow.
• the PR interval of conducted P waves is constant
  • in this lady there is a long PR interval (and left bundle branch block)
• 2 to 1 AV block cannot be classified into Mobitz type I or II as we do not know if the 2nd P wave would be conducted with the same or longer PR interval.