AV Blocks – Progressive Conduction Failure: 1. First-Degree AV Block: Consistent delay at the AV node. Prolonged PR interval (>200 ms). Every impulse eventually reaches the ventricles. 2. Mobitz I (Wenckebach): Progressive PR interval lengthening until a P wave is blocked (a QRS is dropped). Typically at the AV node. Usually benign. 3. Mobitz II: Intermittent, sudden failure of conduction without preceding PR prolongation. Block typically infranodal (Bundle of His or below). Carries significant