Why does PAT with AV block appear as two P waves for every QRS complex on an EKG?

Why does PAT with AV block appear as two P waves for every QRS complex on an EKG?

• A. The AV node blocks conduction of every other atrial stimulus
• B. The atrial focus is firing excessively
• C. The P wave is buried in the QRS
• D. The QRS complex is abnormally wide

Answer: (A)

In the context of Paroxysmal Atrial Tachycardia (PAT) with an AV block, the scenario involves a specific relationship between the atrial and ventricular electrical activity. When there is a block in the AV node, it fails to conduct every atrial impulse generated by the atrial focus. In this case, for every other atrial impulse, the AV node successfully conducts the impulse to the ventricles, resulting in one P wave being associated with one QRS complex.

This leads to the appearance of two P waves for every QRS complex on the EKG. Essentially, while the atrial focus is firing at an increased rate, the AV block restricts the number of impulses that reach the ventricles. Hence, the consistent pattern of every two P waves correlating with a single QRS complex is a direct result of the AV node blocking conduction.

Understanding this mechanism highlights how the electrical impulses are managed within the heart and provides insight into the graphical representation on the EKG, where the relationship between atrial activity (P waves) and ventricular activity (QRS complexes) is crucial for interpreting arrhythmias.