Diastolic potentials observed in idiopathic left ventricular tachycardia

Radiofrequency catheter ablation (RF-CA) has demonstrated a high success ra te in eliminating idiopathic left ventricular tachycardia (ILVT), and the t arget site is determined by the score of pace mapping or the Purkinje poten tial (PP) preceding the onset of the ventricular activation, which is consi dered to indicate the exit site of the reentrant circuit. However, only a f ew reports have described the potential obtained from the slow conduction z one. RF-CA was successfully performed in 8 patients with ILVT. Careful mapp ing of the left ventricle during tachycardia was carried out to find the di astolic potential (DP). A DP was obtained in 4 patients (group 1), but not in 4 others (group 2). The local electrogram was recorded from the distal t ip of the ablation catheter during the RF current application in order to i nvestigate the pattern of termination of ILVT. A DP was recorded at the poi nt where the catheter was slightly pulled back to a site proximal to the ex it site of the reentrant circuit at the left interventricular basal septum. In group 1, conduction block between the DP and PP eliminated ILVT in 3 ou t of 4 cases, and 1 case showed conduction block between the DP and ventric ular potential. In 2 out of 4 patients in group 2, the local electrogram sh owed conduction block between PP and the ventricular potential when VT term inated, The ablation site in group 1 was located relatively more basal than that in group 2 in anatomy. A DP was obtained in a half of the cases with ILVT and RF-CA at this site could eliminate ILVT. A DP was obtained at a si te relatively basal to the exit of the reentrant circuit and it is consider ed that this is a useful marker in terms of the successful ablation of ILVT .