Spontaneous automaticity of an atriofascicular accessory pathway

In a 12-year-old girt with history of recurrent palpitation, an ambulatory 24 h Hotter electrocardiogram showed a wide QRS complex rhythm with atrioventricular dissociation. During an electrophysiology study, an atriofascicular pathway was diagnosed with an inducible antidromic atrioventricutar re-entrant tachycardia. At slower heart rates, the patient had a wide QRS complex escape rhythm similar to the tachycardia and the pre-excited QRS complex morphology. This indicates the presence of pacemaker-like cells in the atriofascicular accessory pathway giving rise to the wide QRS complex escape rhythm at a slower heart rate.