Comparison of unipolar versus bipolar ablation and single electrode control versus simultaneous multielectrode temperature control.

BACKGROUND: Creation of linear lesions using multielectrode catheters may be effective at treating cardiac arrhythmias.
OBJECTIVE: We compared unipolar versus bipolar ablation, evaluated the effects of varying effective electrode areas, and compared single electrode versus multielectrode temperature control during multielectrode radiofrequency ablation.
METHODS: Intramural radiofrequency ablation was performed on five greyhounds at thoracotomy, from an epicardial approach using a 0.8 mm diameter bipolar electrode needle. Fifteen left ventricular ablations were performed per animal. Intramural ablation was performed to maintain a constant electrode-tissue interface. The distal and proximal electrodes measured 1.5 and 1.0 mm in length respectively with an interelectrode distance of 4 mm. Radiofrequency energy was applied to both electrodes simultaneously for 60 s using a target temperature of 80 degrees C. During bipolar ablation, the temperature was regulated from either the distal (BPA1.5) or proximal (BPA1.0) electrode only. During unipolar ablation (UPA), the temperature at both electrodes were simultaneously controlled. Lesions were assessed histologically.
RESULTS: During UPA, consistent target temperatures were achieved at both electrodes. In comparison to UPA, the temperature at both electrodes were significantly decreased during BPA1.0. During BPA1.5 a significant (p < 0.001) temperature increase (94.7 +/- 2.1 degrees C) was observed at the 1.0 mm electrode. BPA1.0 resulted in reduced (p = 0.008) lesion width at the 1.5 mm electrode and no change in lesion depth (p = 0.064) at both electrodes compared to UPA. Conversely, lesion dimensions increase significantly at both electrodes during BPA1.5.
CONCLUSION: Unipolar multielectrode ablation with simultaneous temperature control at both electrodes is more predictable and hence likely to be safer than bipolar ablation.