A COMPARISON OF UNIPOLAR AND BIPOLAR ELECTRODES DURING CARDIAC MAPPING STUDIES

Controversy exists as to whether the unipolar or bipolar electrode con figuration is superior in detecting local activations during cardiac m apping studies. However, the strengths and weaknesses of each mode sug gest that they may provide complementary information. To examine the r elative merits of unipolar and bipolar electrode configurations, recor dings by each were simultaneously acquired during episodes of ventricu lar tachycardia in eight consecutive patients undergoing map guided ar rhythmia surgery. Unipolar electrograms were classified as either unam biguous or ambiguous according to whether or not they were polyphasic in nature. The activation times from the unambiguous electrograms were compared with activation times from the corresponding bipolar signals where local activation was measured both at the signal's peak amplitu de (BI-PK), and at the point at which the waveform's first major, rapi d transient crossed baseline (BI-TRN). Occurrences of discrete diastol ic activations were also quantified from the unipolar and bipolar trac ings. From a total of 415 unipolar electrograms, 301 unambiguous signa ls were identified as suitable for comparison with the bipolar signals . Both BI-PK and BI-TRN criteria for the determination of local activa tion were highly correlated with and not significantly different from the local activation from the unipolar electrogram. From 85 ambiguous unipolar electrograms, it was possible to determine local activation f rom the corresponding bipolar signal in 33% of the occurrences. From t he eight patients, 64 diastolic potentials were recorded of which 42 w ere seen only in bipolar mode, 7 in only unipolar mode, and 15 were ev ident in both tracings. The prevalence of diastolic potentials was sig nificantly greater in recordings made using bipolar mode. The results demonstrate that complementary information regarding local activations and diastolic potentials can be derived from unipolar and bipolar rec ordings and suggest that both electrode configurations should be used in multichannel cardiac mapping systems.