In regard to 3rd degree AV block, which of the following statements is true?

• A. The atrial activity is lost
• B. The ventricular pacing occurs at an independent rhythm
• C. Heart rate is always above 100 bpm
• D. Ischemia is not present

Answer: (B)

In the context of third-degree AV block, also known as complete heart block, the correct statement is that ventricular pacing occurs at an independent rhythm. This happens because the electrical signals from the atria are completely blocked from reaching the ventricles. As a result, there is dissociation between the atrial and ventricular activities; the atria may continue to beat at their normal rate, determined by the intrinsic properties of the sinoatrial node, while the ventricles rely on an escape rhythm generated by a higher pacemaker or the ventricular myocardium itself.

This independent rhythm often manifests as a lower ventricular rate, typically below 100 bpm, but it can also vary based on the location of the escape rhythm. Thus, it is crucial to understand that the ventricular response is not directly influenced by the atrial contractions due to the complete block. This condition leads to a scenario where the pacing of the ventricles does not synchronize with the atrial activity, which is a hallmark feature of third-degree AV block.

A lack of atrial activity in this situation is not accurate; the atria may still contract independently, producing P waves that are not connected to QRS complexes. The heart rate can be below 60 bpm, particularly if the escape rhythm eman