English: What is atrioventricular block? Atrioventricular (AV) block is a type of heart block where the electrical signal moving through the heart gets delayed or blocked entirely when moving from the upper chambers–the atria—to the lower chambers—the ventricles. This video describes the various degrees and types of AV block, including first degree AV block, second degree type 1 (mobitz I or Wenckebach), second degree type 2 (mobitz II), and third degree (complete) AV block, as well as associated symptoms for each.