What role does the AV node play in the EKG appearance of PAT with AV block?

What role does the AV node play in the EKG appearance of PAT with AV block?

• A. It sends rapid impulses to the ventricles
• B. It blocks every other atrial stimulus
• C. It enhances the conduction of P waves
• D. It causes atrial fibrillation

Answer: (B)

The atrioventricular (AV) node is crucial in managing the conduction between the atria and the ventricles. In the context of paroxysmal atrial tachycardia (PAT) with AV block, the AV node acts as a filter for the rapid atrial impulses generated during tachycardia.

When there is an AV block, particularly when it is of the second or third degree, the AV node does not conduct every atrial impulse to the ventricles. Instead, it selectively blocks some of these impulses, which is why the choice stating that it blocks every other atrial stimulus is accurate. In this situation, the atria are firing rapidly, but not all of these impulses are transmitted to the ventricles, leading to a characteristic EKG pattern where there may be P waves that are not followed by QRS complexes. This results in the distinctive appearance of PAT with variable ventricular response, where some P waves are dropped or missed entirely due to the block.

This mechanism is essential in understanding the dynamics of the EKG in the presence of AV block during episodes of PAT, highlighting the role of the AV node in managing atrial impulses rather than amplifying or enhancing them or leading to other arrhythmias like atr