In WPW, which PR interval finding is typical?

In WPW, which PR interval finding is typical?

• A. Prolonged PR interval
• B. Short PR interval
• C. Normal PR interval
• D. PR interval is variable

Answer: (B)

In WPW, an accessory pathway bypasses the AV node, causing preexcitation of the ventricles and shortening the time from atrial activation to ventricular activation. This manifests as a short PR interval on the ECG, often with a delta wave that widens and alters the QRS. If the preexcitation pathway isn’t conducting at that moment, the PR interval can appear normal; in intermittent preexcitation, the PR interval may also vary. A prolonged PR interval would indicate AV nodal delay or first-degree AV block, which is not characteristic of WPW.

In WPW, an accessory pathway bypasses the AV node, causing preexcitation of the ventricles and shortening the time from atrial activation to ventricular activation. This manifests as a short PR interval on the ECG, often with a delta wave that widens and alters the QRS.

If the preexcitation pathway isn’t conducting at that moment, the PR interval can appear normal; in intermittent preexcitation, the PR interval may also vary. A prolonged PR interval would indicate AV nodal delay or first-degree AV block, which is not characteristic of WPW.