Hypertrophic cardiomyopathy with paroxysmal atrial fibrillation misdiagnosed as WPW syndrome

Hypertrophic cardiomyopathy (HCM) is associated with an increased incidence of Wolff–Parkinson–White (WPW) syndrome and atrial fibrillation. However, a delta-like wide QRS can be observed in the hypertrophied myocardium. When considering the rarity of the paraseptal bypass tract (BT), the normal QRS axis suggests a higher possibility of HCM origin. Otherwise, there is no known electrocardiographic clue indicating a wide QRS differentiation between HCM and WPW syndrome. Moreover, the atriofascicular, nodofascicular/ventricular or fasciculoventricular BT should be differentiated. In this case, atrioventricular conduction system incidental injury revealed a wide QRS origin from the HCM, but this method should be avoided except in some selected cases.