The atrioventricular (AV) bridge is vulnerable to many circumstances that depress conduction. Abnormal impulse transmission may be caused by drugs, autonomic effects, or destructive processes. Type 1 (Wenckebach) AV block is owing to depressed AV nodal conduction and is recognized by a prolonging PR interval ending in a "dropped beat." Type II (Mobitz) AV block is owing to abnormal infranodal conduction, and is usually accompanied by bundle branch block. Second-degree AV block with 2:1 conduction can be a difficult problem. Third-degree (complete) AV block is a diagnosis too often rendered and too often incorrect.
Keywords: Atrioventricular block; Complete AV block; Mobitz block; Wenckebach block.
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