Extremely rare cardiac conduction disorder presenting with short PR interval and normal QRS complex on surface electrocardiogram. A type of ventricular pre-excitation in which the atrial impulse conducts via accessory pathways, shortening time to the ventricles (short PR interval), while ventricular activation follows the normal His Purkinje conduction pathway (normal QRS complex). Common signs and symptoms include dyspnea, palpitations, presyncope, increased heart rate, atrial flutter, and episodic tachyarrhythmias. Management may involve radiofrequency ablation and medication to lower risk of atrial fibrillation.