Diagnostic and Prognostic Implications of Surface Recordings from Patients with Atrioventricular Block.

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.