LBBB and 2nd degree AV block, mobitz type I

Mobitz II 2nd degree AV block is usually a sign of bilateral bundle branch disease. One of the two bundle branches should be completely blocked; in this example the left bundle is blocked. The nonconducted sinus P waves are most likely blocked in the right bundle which exhibits 2nd degree block. Although unlikely, it is possible that the P waves are blocked somewhere in the AV junction such as the His bundle.