Relation of high-pass filtered unipolar electrograms to bipolar electrograms during ventricular mapping

A filtered bipolar electrogram (EG) amplitude <1.5 mV is a robust indicator of relatively dense scar, but is influenced by the wavefront direction. Unipolar recordings are not subject to directional influence. We hypothesized that high-pass filtered unipolar EGs would provide similar information to bipolar EGs, without potential errors related to wavefront direction.

Simultaneous bipolar filtered at 30-500 Hz and unipolar (high-pass filtered at 30 Hz) signals were recorded during ventricular voltage maps in 24 patients (group A). In five subsequent patients, low voltage surface areas were compared in electroanatomic maps (group B).

Of 2,789 mapping points in group A, filtered unipolar EG amplitude correlated well with bipolar EG amplitude. Agreement of filtered unipolar recordings in classifying sites as >1.5 mV or <1.5 mV with bipolar EG amplitude was 83%. Discordance was due to unipolar > bipolar amplitude at 83% of the discordant sites, consistent with possible reduction of bipolar amplitude due to direction dependence. Discordance was more frequent during epicardial than endocardial mapping. Double potentials were more frequently observed in bipolar than in unipolar recordings (3.2% vs 1.8%, P < 0.0001). In group B, the mean low-voltage surface area (<1.5 mV) was 70.1 ± 48.9 cm(2) for bipolar and 61.3 ± 52.2 cm(2) for filtered unipolar EG maps.

Direction dependent effects on bipolar EG amplitude may influence the identification of substrate for arrhythmias. High-pass filtered unipolar EGs might be a reasonable alternative to bipolar recordings for creation of voltage maps.