What are the telemetry features of third-degree (complete) AV block?

What are the telemetry features of third-degree (complete) AV block?

• A. Atria and ventricles beat independently; P and QRS have no fixed relationship; usually an escape rhythm with wide QRS
• B. Prolonged PR interval with every P conducted
• C. Progressive PR prolongation with dropped QRS
• D. Intermittent dropped QRS with normal PR

Answer: (A)

Complete heart block means there is no conduction from the atria to the ventricles, so the two chambers beat independently. On telemetry you’ll see P waves at a regular rate and QRS complexes at a slower rate, with no fixed relationship between the P wave and the following QRS (AV dissociation). The ventricle then relies on an escape pacemaker below the block to generate its rhythm, which is why you see an escape rhythm. If that escape focus is in the ventricular tissue, the QRS complexes appear wide because ventricular conduction is slow and abnormal; junctional escape (higher up) would produce a narrower QRS. This combination—AV dissociation with independent atrial and ventricular rhythms and an escape rhythm—is the hallmark of third-degree (complete) AV block. The other descriptions fit different AV block types: prolonged PR with P waves conducted describes first-degree block; progressive PR prolongation with dropped QRS is Mobitz type I; intermittent dropped QRS with normal PR is Mobitz type II.

Complete heart block means there is no conduction from the atria to the ventricles, so the two chambers beat independently. On telemetry you’ll see P waves at a regular rate and QRS complexes at a slower rate, with no fixed relationship between the P wave and the following QRS (AV dissociation). The ventricle then relies on an escape pacemaker below the block to generate its rhythm, which is why you see an escape rhythm. If that escape focus is in the ventricular tissue, the QRS complexes appear wide because ventricular conduction is slow and abnormal; junctional escape (higher up) would produce a narrower QRS. This combination—AV dissociation with independent atrial and ventricular rhythms and an escape rhythm—is the hallmark of third-degree (complete) AV block. The other descriptions fit different AV block types: prolonged PR with P waves conducted describes first-degree block; progressive PR prolongation with dropped QRS is Mobitz type I; intermittent dropped QRS with normal PR is Mobitz type II.