Conducting randomized trials in the electrophysiology laboratory: lessons from a randomized comparison of recording methods during pulmonary vein isolation by segmental ostial ablation.

Accurate identification of pulmonary vein (PV) potentials during segmental ostial ablation for PV isolation is very important to completely isolate the PVs and also to avoid unnecessary applications of radiofrequency energy. A prior post hoc analysis of unipolar and bipolar electrograms recorded from successful and unsuccessful ablation sites demonstrated that unipolar electrograms recorded at successful sites were more likely to have a rapid intrinsic deflection, larger amplitude, and earlier activation than electrograms recorded at unsuccessful sites. Moreover, unipolar electrograms recorded from the ablation and circular ostial mapping catheters were almost identical at successful sites. Based on these observations, a prospective, randomized study was conducted to test whether unipolar and bipolar electrograms would facilitate the ablation procedure when compared to bipolar electrograms alone during PV isolation in patients with atrial fibrillation (AF). In 44 consecutive patients with paroxysmal AF, 114 PVs were randomized to segmental ostial ablation guided by unipolar and bipolar electrograms (61) or by bipolar electrograms only (53). Segmental ostial ablation guided by unipolar and bipolar electrograms was associated with a approximately 20-30% decrease in the procedure and fluoroscopy times necessary for isolation of a PV and also in the duration of radiofrequency energy application required for complete isolation of a PV. Although the sample size was not sufficient to detect a 5% change, the success rate for complete electrical isolation and the risk of symptomatic PV stenosis were similar between the 2 groups. Online analysis of unipolar electrograms facilitated the PV isolation procedure and was incremental to the analysis of bipolar electrograms alone. However, because segmental ostial ablation has only modest efficacy in achieving long-term freedom from recurrent AF, alternative ablation strategies that may or may not target PVs will eventually evolve. The role of unipolar electrograms in these new methods remains to be determined.