To assess the acute and long-term efficacy of half-normal saline compared to normal saline for irrigation of open-irrigated catheters during catheter ablation for the treatment of cavotricuspid isthmus dependent atrial flutter.

It is unclear whether ionic strength affects energy delivery and ablation lesion size during radiofrequency ablation for atrial flutter. Given that saline contains ionic sodium and chloride in the solution, it has conductive properties that may disperse radiofrequency energy away from the tip-tissue interface, thereby reducing current density and lesion size compared to ablation with nonionic solutions. The efficacy of half-normal saline will be measured by the time taken to create bidirectional block across the cavotricuspid isthmus as well as the acute recurrence rate within 30 minutes of the initial occurrence of bidirectional block and the 1 year freedom from flutter recurrence.

Inclusion Criteria:

• Patients > 18 years of age at the time of enrollment
• Patients presenting for right sided typical atrial flutter ablation who have a clinical indication to undergo catheter ablation
• Fully informed written informed consent by either the subject or subject's legal representative and ability for subject to comply with study responsibilities

Exclusion Criteria:

• The presence of thrombus within the left atrial appendage
• Prior catheter ablation of the cavotricuspid isthmus for right sided atrial flutter
• The inability to provide consent or comply with study requirements
• A predicted life expectancy of < 12 months

Multicentre study, patient data deidentified for post-enrolment analysis