Paroxysmal fascicular tachycardia: electrophysiologic characteristics and treatment by catheter ablation.

A 69 year old man with ischemic heart disease underwent electrophysiologic evaluation for paroxysmal wide QRS tachycardia, the configuration of which was identical to that recorded during sinus rhythm, that is, right bundle branch block, left anterior fascicular block and anterior myocardial infarction. Electrocardiographic recordings during tachycardia showed atrioventricular dissociation and His bundle activation occurring 5 ms after the onset of the QRS complex recorded on the surface electrocardiogram, consistent with a left posterior fascicular tachycardia. All traditional therapeutic attempts failed to prevent frequent recurrences of tachycardia, which was finally ablated by three 300 J shocks delivered through an electrode catheter positioned in the posterobasal region of the left ventricular septum.