SUBJECTS AND METHODS: We evaluated the characteristics of unipolar and bipolar electrograms at ventricular tachycardia (VT) origin. Electroanatomical mapping and RFCA were performed in 6 patients with idiopathic VT. 22 sites were enrolled and 6 of them were successful sites. We analyzed the relationship between surface and local electrograms in accordance with success or failure. We also analyzed the morphology of local electrograms.

RESULTS: At successful sites of RFCA, point of unipolar onset (22.86±10.82 msec vs 5.47±26.31 msec, p<0.05) and maximal negative slope (16.57±17.46 msec vs -4.00±22.77 msec, p<0.05) were recorded earlier than unsuccessful sites. R wave amplitude (0.11±0.19 mm vs 0.64±0.57 mm, p<0.05) and R/S ratio (0.02±0.30 vs 0.18±0.26, p<0.05) of unipolar electrograms were smaller at successful sites. R wave duration was shorter at successful sites (6.29±8.49 msec vs 11.33±6.26 msec) but there was no statistical significance. QRS duration of bipolar electrograms was longer at successful sites (66.14±17.93 msec vs 49.07±13.11 msec, p<0.05).

CONCLUSION: In electranatomical mapping for VT, point of unipolar onset and maximal negative slope could predict local activation time more precisely Unipolar electrograms showed shorter R wave duration and smaller R/S ratio at successful sites of RFCA. We can estimate the focus of VT by using these chracteristics of unipolar and bipolar electrogram.