DEMONSTRATION OF PURKINJE POTENTIAL DURING IDIOPATHIC LEFT-VENTRICULAR TACHYCARDIA - A MARKER FOR ABLATION SITE BY TRANSIENT ENTRAINMENT

During VT of QRS morphology with right bundle branch block and left ax is deviation in a patient without obvious structural heart disease, en trainment by pacing from the right ventricular outflow tract and high right atrium was demonstrated. During entrainment of VT, a Purkinje po tential preceding the QRS and recorded at the left ventricular mid-sep tum was activated by orthodromic impulses in the reentry circuit. The interval between the Purkinje potential and the earliest left ventricu lar activation was decrementally prolonged with shortening of pacing c ycle length. Radiofrequency energy was applied to this site, resulting in successful elimination of VT. Therefore, the Purkinje potential re presented activation by an orthodromic wavefront in the reentry circui t, while the orthodromically distal site to this potential showed an a rea of slow conduction with decremental property.