In a case of tachycardia with a wide QRS and short PR interval, what diagnosis should be considered?

When evaluating tachycardia characterized by a wide QRS complex and a short PR interval, the possibility of antidromic Wolff-Parkinson-White (WPW) syndrome becomes significant. In antidromic WPW, there is a reentrant circuit involving an accessory pathway, which leads to ventricular pre-excitation and results in a wide QRS complex. The accessory pathway allows for conduction that bypasses the normal AV node conduction, contributing to the short PR interval.

In this scenario, the wide QRS arises because the electrical impulse travels through the ventricle rather than the usual conduction pathway through the AV node, leading to a more chaotic and prolonged depolarization of the ventricular myocardium. The short PR interval signifies that the atrial impulse is conducted to the ventricles via the accessory pathway rather than the AV node. These features collectively point towards antidromic WPW as a likely diagnosis.

By recognizing this pattern, clinicians can differentiate antidromic WPW from other causes of wide QRS tachycardia, such as ventricular tachycardia or other supraventricular tachycardias, which often have different QRS morphologies and conduction characteristics.