When second-degree AV block progresses to third-degree AV block, in type I it is an AV junctional escape rhythm with a narrow QRS at a rate of 40-50/minute, and it is reversible; whereas in type ...

The diagnosis is NSR, Mobitz type I second-degree atrioventricular (AV) block (Wenckebach), nonconducted (blocked) PACs, and early transition (counterclockwise rotation). (Enlarge Image) Figure 2 .

Third-degree sinoatrial exit block occurs when no SA nodal action potentials are able to leave the SA node. No P waves are seen on the ECG. When a junctional escape ensues, the rhythm may be ...