A randomized controlled trial will be conducted to evaluate the efficacy of Ablation Index-guided high power - short duration (HPSD) ablation compared to conventional power settings in Cavotricuspid Isthmus (CTI) dependent atrial flutter. Participants will be randomized to receive either AI-guided HPSD ablation at 50 Watts or conventional power settings at 30 Watts. Both arms will use the Carto 3D mapping system and the QDOT MICRO ablation catheter (Biosense Webster). An anatomically contiguous line will be created with <6mm inter-lesion distance. After a standardized wait time of 30 minutes, ablation success will be assessed. The primary outcome is total radiofrequency ablation time. Secondary outcomes include procedural time, fluoroscopy time, safety outcomes, and 3-month freedom from recurrence. It is our expectation that HPSD will result in a shorter primary outcome.

Title: A Randomized Trial of Ablation Index Guided High vs Standard Power Radiofrequency Ablation for Typical Atrial Flutter

Design: Prospective, two-arm, single center, superiority study with comparison of standard 30W power settings vs 50W high power settings

Purpose: To evaluate the superiority of high-power ablation settings over standard power settings in achieving block across the CTI for typical flutter

Enrollment: A minimum of 25 subjects in each arm. Enrollment over a period of 12 months.

Subjects: Subjects referred by a cardiac electrophysiologist for standalone radiofrequency ablation of typical atrial flutter

Clinical site: Foothills Medical Center, University of Calgary, Calgary, Alberta, Canada

Endpoints: Primary endpoint: total radiofrequency time per procedure

Secondary endpoints:

RF time to initial CTI block Total procedure time Time from procedure start to procedure end Incidence of early reconnections during wait period Incidence of dormant conduction during adenosine testing Total number of ablation lesions required to achieve durable CTI block Total analgesia and sedation usage, e.g. midazolam, fentanyl and propofol in mg and/or mL Post-procedure patient perception of a) pain and b) nausea on a scale of 1 (none) to 10 (maximum possible)

Secondary safety endpoints:

Steam pops Pericardial effusions Pericardial tamponade

Secondary follow-up outcomes:

The presence of durable CTI block if a subsequent EP study is performed within 3 months of the initial procedure (e.g. AF ablation) Recurrence of documented AFL within 3 months by available ECGs, telemetry, wearable monitors, or Holters Holter at 2 months for incidence and burden of atrial arrhythmias

Materials: 3-D electro-anatomical mapping system: CARTO, Biosense Webster Diagnostic catheters: 20-pole halo catheter, 10 pole coronary sinus catheter Ablation catheter: QDOT MICRO, BiosenseWebster

Sponsors: None, fellow initiated research

Despite the existing observational data, there have been no randomized controlled trials (RCTs) investigating HPSD in CTI ablation to validate its effectiveness. Furthermore, the applicability of AI to CTI ablation has not been tested. It's important to note that CTI ablation, performed under conscious sedation, introduces respiratory movement, leading to increased CF variability, which may affect precise energy delivery.

We propose conducting the first RCT, to our knowledge, investigating the use of High-Power Short-Duration Ablation (HPSD) in the treatment of CTI-dependent flutter.

Inclusion Criteria:

1. Clinically determined by a cardiac electrophysiologist to have had at least one episode of CTI dependent atrial flutter
2. Clinically determined by a cardiac electrophysiologist likely to benefit from standalone CTI ablation
3. For this to be their first CTI ablation attempt
4. Able and willing to comply with all protocol requirements
5. Agree to and sign patient Informed Consent Form (ICF)
6. Be 18 years of age or older

Exclusion Criteria:

1. Previous CTI ablation
2. Adult congenital heart disease, including Ebstein's anomaly
3. Previous surgery involving the tricuspid valve and atrium including cannulation scars for cardiopulmonary bypass
4. Pediatric population age <18
5. Women who are pregnant or breastfeeding.
6. Active enrollment in another investigational study involving a drug or device.
7. A requirement for additional procedures in the same setting. Such as EP study and ablation of other induced arrhythmias since these prolong secondary endpoints such as procedure time and RF time
8. Patients on anti-arrhythmic drugs (AADs) such as flecainide, sotalol, or amiodarone should have their AAD stopped 3 days prior, and not be restarted after the procedure
9. Patients under General Anesthetic (GA)
10. Patients with sufficient baseline cognitive impairment to be unable to answer a post-procedure survey or consent Previous ablations, other than for CTI flutter, are acceptable.

Single-blinded. Investigator will know study arm, patients/participants will not. The outcomes assessor will be blinded.