Funding

Catheter ablation is a first-line treatment for patients with cavotricuspid isthmus (CTI) dependent atrial flutter (AFL; also known as typical AFL), a common arrhythmia. This is done using radiofrequency (RF) catheters and single-procedure success is approximately 95%. Ablation is often done using one of three methods:

1. fluoroscopically, using X-rays to guide the operator to visualise catheter position within the heart. This method involves the most radiation exposure to patient and operator. Ablation is generally performed for a set time-period (eg. 30-60secs) to ensure each ablation lesion is successful.
2. using a 3-dimensional mapping system which allows the catheters to be magnetically located and visualised on a monitor without X-rays, and using "contact force" (CF) sensing catheters. This requires minimal X-ray use, and by ensuring a minimum degree of force between catheter tip and the heart before applying RF for a set time-period (eg. 30 seconds), operators can be more confident of successful lesions.
3. using an ultra-high density mapping system which uses magnetic tracking as above, but allows higher resolution visualisation of the cardiac electrical system with potential for improving procedure success; this has not yet been formally evaluated for AFL. Catheters using this method use "local impedance" (LI) instead of CF. This is a direct measure of heart tissue impedance with real-time changes during ablation. A minimum drop or plateau in the LI value during ablation allows confidence of lesion success, without the need to ablate for a pre-defined time-period. This could potentially reduce ablation time and subsequent complications, but has also not yet been formally compared to the above for this indication.

This prospective randomised study aims to compare these three standard of care procedures to determine if differences in ablation metrics, efficacy and safety exist.

Inclusion Criteria:

• Patients under the care of the NHS
• Aged 18-80 years
• Symptoms and 12-lead ECG suggestive of typical (cavotricuspid isthmus dependent) atrial flutter
• Due to undergo first-time cavotricuspid isthmus ablation (including as part of a combined ablation if also having pulmonary vein isolation for atrial fibrillation) on clinical grounds

Exclusion Criteria:

Pre-procedure:

• Inability to given informed consent / lack of mental capacity
• Obesity (BMI >40)
• Congenital heart disease or tricuspid valve abnormalities likely to prolong procedure time, including Ebstein anomaly, atrial septal defects, tricuspid valve repair or replacement, severe tricuspid valve regurgitation
• Inability or unwillingness to receive oral anticoagulation with a vitamin K antagonist (VKA) or non-VKA oral anticoagulant (NOAC)
• Previous cavotricuspid isthmus ablation procedure
• Known infiltrative cardiomyopathy
• Pregnancy
• Age < 18 or >80
• Inability to speak adequate English/need for an interpreter for study consent process

Post procedure:

- arrhythmia mechanism found not to be cavotricuspid isthmus dependent atrial flutter