In A fib RVR, what is the status of the PR interval?

In atrial fibrillation with rapid ventricular response (A fib RVR), the PR interval is considered not applicable (N/A) because there is no consistent P wave associated with each QRS complex. In normal sinus rhythm, the PR interval represents the time from the onset of atrial depolarization to the onset of ventricular depolarization, measured from the beginning of the P wave to the beginning of the QRS complex.

However, in atrial fibrillation, the P waves are typically absent due to the chaotic electrical activity in the atria. As a result, the measurement of a PR interval becomes irrelevant, as there is no defined P wave to measure from. This lack of organization in the atrial depolarization means that the PR interval cannot be determined, thus making it N/A in this scenario.