What is the significance of a short PR interval with a normal QRS in tachycardia?

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Multiple Choice

What is the significance of a short PR interval with a normal QRS in tachycardia?

A short PR interval with a normal QRS during tachycardia points to preexcitation from an accessory pathway, as seen in Wolff-Parkinson-White syndrome. The accessory pathway allows atrial impulses to reach the ventricles earlier than usual, shortening the time from atrial depolarization to ventricular depolarization (PR interval). When tachycardia occurs, the ventricles can still be activated mainly through the normal His-Purkinje system (orthodromic AV reentrant tachycardia), so the QRS may remain narrow. The classic resting sign of this preexcitation is a delta wave—slurring at the start of the QRS—which supports WPW. Atrial tachycardia, sinus tachycardia, or AV block would not explain this combination of preexcitation with a tachycardic rhythm.

A short PR interval with a normal QRS during tachycardia points to preexcitation from an accessory pathway, as seen in Wolff-Parkinson-White syndrome. The accessory pathway allows atrial impulses to reach the ventricles earlier than usual, shortening the time from atrial depolarization to ventricular depolarization (PR interval). When tachycardia occurs, the ventricles can still be activated mainly through the normal His-Purkinje system (orthodromic AV reentrant tachycardia), so the QRS may remain narrow. The classic resting sign of this preexcitation is a delta wave—slurring at the start of the QRS—which supports WPW. Atrial tachycardia, sinus tachycardia, or AV block would not explain this combination of preexcitation with a tachycardic rhythm.

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