Idiopathic left ventricular tachycardia with left and right bundle branch block configurations.

Background: Idiopathic left ventricular tachycardia typically has a right bundle branch block configuration. The purpose of this case report is to demonstrate that idiopathic ventricular tachycardia arising in or near the left posterior fascicle also may have a left bundle branch block configuration.

Results: A 27-year-old woman underwent an electrophysiologic procedure because of recurrent, verapamil-responsive, wide QRS complex tachycardia. Two types of ventricular tachycardia (cycle lengths 330 to 340 msec) were reproducibly inducible, one with a right bundle branch block configuration and left-axis deviation that had been documented clinically, and the other with a left bundle branch block configuration and axis of zero. A Purkinje potential recorded at the junction of the left ventricular mid-septum and inferior wall preceded the ventricular complex by 40 msec in both tachycardias. A single application of radiofrequency energy at this site successfully ablated both ventricular tachycardias.

Conclusions: The findings of this case report demonstrate that idiopathic ventricular tachycardia arising in or near the left posterior fascicle may have a left bundle branch block configuration.