Second degree AV block overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]
Overview
Second degree AV block is a disease of the electrical conduction system of the heart. It refers to aconduction block between the atria and ventricles. The presence of second degree AV block is diagnosed when one or more (but not all) of the atrial impulses fail to conduct to the ventricles due to impaired conduction. Second-degree AV block can be of one of the two types: Mobitz I and Mobitz II. Mobitz I, or Wenckebach block , consists of progressive prolongation of PR interval, until loss of conduction to the ventricle occurs (missed beat). Mobitz I block is rarely symptomatic and does not require treatment. On the other hand, Mobitz II AV block is characterized by a constant PR interval with intermittent missed beats. The missed beats can occur with varying frequency such as occasional to 3:1 or 2:1.