The Characteristics of Unipolar and Bipolar Electrograms at the Origin of Ventricular Tachycardia

BACKGROUND AND OBJECTIVES: In radiofrequency catheter ablation (RFCA), it is an essential point to understand the characteristics of local electrograms at arrhythmic focus. However controversy exists as whether the unipolar or bipolar electrogram is superior in detecting arrhythmic focus.

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.