Catheter ablation of incessant irregular ventricular tachycardia originating from the right bundle branch.

Case presentation A 32-year-old woman presented with a history of palpitations over the prior 7 days. Twelve-lead ECG indicated an irregular, wide QRS complex tachycardia with a left bundle branch block (LBBB) morphology and a late precordial R/S transition (Panel A). Echocardiography and cardiac magnetic resonance imaging demonstrated no evidence of structural heart disease. This arrhythmia did not respond to verapamil or metoprolol administration. Two attempts of electrical cardioversion of 200 J failed to restore sinus rhythm, and the administration of intravenous amiodarone slowed but failed to terminate the arrhythmia. As the tachycardia rate become slower and regular, closer inspection of ECG showed P waves of probable sinus rhythm with atrioventricular dissociation (Panel B, red arrows) indicative of ventricular tachycardia (VT). Because the tachycardia was incessant, urgent catheter ablation was planned. Using a three-dimensional electroanatomic mapping system (CARTO 3), the site of the earliest local ventricular activation was found in mid-anteroseptal region