Structure of the reentrant circuit of idiopathic left ventricular tachycardia: New insights into the role of the Purkinje network

In idiopathic left ventricular tachycardia (ILVT), the reentrant circuit is considered to involve the Purkinje system, and the Purkinje potential (P-p otential) appears to be a marker for successful ablation. However, the char acteristics of the reentrant circuit in ILVT have not yet been defined. In 2 cases of ILVT, we performed detailed mapping along the left ventricular s eptum during VT and sinus rhythm. ILVTs were successfully ablated at the po steroapical area of the left ventricular septum where the high frequency P- potential was recorded and this portion was considered to be the exit site of the reentrant circuit. A small P-potential was also recorded at the port ion proximal to the exit site, and it preceded the P-potential at the exit site. However, the local ventricular electrogram at the exit site preceded that at the proximal site during VT. Moreover, the small P-potential was or thodromically entrained by ventricular pacing from the proximal site. These findings suggest that the reentry circuit of ILVT appeared to have conside rable size.