OBJECTIVETo determine the feasibility and assess the validity of noncontact endocardial mapping to guide ablation of hemodynamically unstable or nonsustained ventricular tachycardia (VT).

METHODSNoncontact mapping permitted individual-beat analysis of ventricular arrhythmias. Three-dimensional electroanatomical mapping allowed detailed reconstruction of a chamber geometry and activation sequence. Eighteen hemodynamically unstable or nonsustained VTs were induced (cycle length: 336 ms +/- 58 ms) in 17 patients and mapped by noncontact mapping using an EnSite 3000 system performed for the guidance of catheter ablation.

RESULTSThree patients were mapped during premature ventricular complexes (PVCs) because sustained VT could not be induced. Analysis of the archived noncontact activation maps was performed to identify the exit site and/or the diastolic pathway of the VT reentry circuit. The endocardial exit sites 10 ms +/- 16 ms before QRS were defined in 9 right ventricular outflow tract (RVOT) and 5 ischemic VTs. The diastolic pathway was identified in 5 ischemic VTs. The earliest endocardial diastolic activity preceded the QRS onset by 60.1 ms +/- 42.6 ms. The earliest activation sites were identify in 3 patients with nonsustained VTs or PVCs. Radiofrequency current was applied around the exit site or to create a line of block across the diastolic pathway. Catheter ablation was performed in 17/18 (94%) VTs and 15/17 (88%) VTs was successfully ablated. Two (67%) of the three patients with non-sustained VTs were mapped and successfully ablated during PVCs. Catheter ablation was not performed in 1 patient (peri-Hisian VT) and was unsuccessful in 2 patients.

CONCLUSIONNoncontact endocardial mapping is able to be used to guide ablation of untolerated or nonsustained VTs.