A 16-year-old female patient was hospitalized due to narrow QRS tachycardia suggestive of fascicular ventricular tachycardia. Initially, the differential diagnosis with supraventricular tachycardia can be challenging. The tachyarrhythmia is well controlled with medication, but electrophysiological study and ablation may be necessary in patients who remain symptomatic.

Pulmonary veins electrical isolation as an invasive treatment of atrial fibrillation has been widely used in electrophysiology laboratories. This case report presents a rare and transient complication, during transseptal puncture for atrial fibrillation ablation. ST-segment elevation, hypotension and bradyarrhythmia related to catheterization were observed despite cineangiocoronariography without obstructive lesions. Clinical stability was achieved after administration of intravenous atropine and saline solution. It is speculated that the phenomenon is attributed to an increased vagal tone after the mechanical effect of transseptal puncture in the interatrial vagal network. The procedure was completed despite the phenomenon.