THE USE OF HALF NORMAL SALINE TO SHORTEN TIME REQUIRED TO ACHIEVE BIDIRECTIONAL BLOCK FOR THE CATHETER ABLATION OF TYPICAL ATRIAL FLUTTER

Abstract

Complete bidirectional block (BB) of the cavotricuspid isthmus (CTI) during catheter ablation of atrial flutter (AFL) is an established endpoint. Standard irrigated radiofrequency ablation is performed using normal saline (NS, 0.9%), yet the use of lower ionic concentration with half normal saline (HNS, 0.45%) has previously led to the creation of wider and deeper lesions ex vivo. It has yet to be elucidated as to whether these results could be used to alter ablation outcomes in human subjects. We compared the use of HNS to NS for catheter ablation of typical AFL with respect to the time taken to achieve BB, radiofrequency time, and recurrence of conduction within 30 minutes. The incidence of intraoperative complications, including steam pops and pericardial effusions, was also recorded. Patients were randomized to catheter ablation with either NS or HNS using a 4mm irrigated catheter at a power setting of 30W. Ablation was performed with the aim of restoring sinus rhythm in patients who were in AFL. BB was confirmed by double potentials separated by an isoelectric line measuring >= 110ms and evidence of conduction block using differential pacing. A total of 30 patients underwent catheter ablation for typical AFL (14 HNS, 16 NS). Sinus rhythm and bidirectional block were achieved in all patients. The two groups were comparable with respect to patient age (69±10 years HNS vs. 71±15 years NS) and duration of AFL (7±6 months HNS vs. 8±5 months NS). The mean time to achieve BB using RF was 10.4±2.6 mins using HNS compared with 14.5±3.8 mins using NS (p=0.01). There were slightly more steam pops amongst patients in the HNS arm (2 HNS vs. 0 NS). Conversely, recurrences of conduction were higher for patients in the NS group as compared to HNS, 3 vs. 0 respectively. Overall, there were no significant adverse events observed in either arm. The time taken to achieve BB was shorter when HNS was used as compared to NS. This was not associated with any major complications in either group, but with an increased frequency of recurrences of conduction in patients undergoing catheter ablation with NS.