A rhythm described as a 'Regular rhythm block' corresponds to which block type?

• A. 3rd Degree Block
• B. 2nd Degree Type 2
• C. 1st Degree
• D. 2nd Degree Type 1

Answer: (A)

Understanding AV block types hinges on whether conduction from the atria to the ventricles is preserved and whether the rhythm remains regular. A “Regular rhythm block” describes a situation where the ventricular rhythm stays steady even though there is no conduction from the atria to the ventricles—the atria and ventricles beat independently. This is the hallmark of complete heart block, where the AV node fails to conduct any atrial impulses and an escape pacemaker below the block drives a slow, regular ventricular rhythm. Because the escape rhythm is stable, you see a consistent, regular rhythm despite the atrial activity marching to its own rate.

This is not the pattern seen with first-degree block, where every P is conducted to a QRS and there’s no true block. It also doesn’t fit Mobitz type I, which shows progressively lengthening PR intervals with occasional dropped beats and an irregular rhythm, nor Mobitz type II, which has dropped beats as well but without progressive PR changes and often an irregular rhythm. So the description aligns with a third-degree (complete) AV block.