A Randomized Trial of Contact Force in Atrial Flutter Ablation

Atrial flutter (AFL) is a macro-reentry tachycardia in the right atrium [1,2]. AFL is seen in 0,4 -1,2% of ECG´s in the hospital[3]. Prevalence is higher in patients with structural heart disease, as hypertension, coronary heart disease and cardiomyopathy and also in patients with chronic obstructive lung disease. AFL occurs frequently among patients operated for congenital heart disease.

Cavotricuspid isthmus ablation (CTIA) using radiofrequency (RF) energy is a well-established first line therapy of typical AFL.

The most common arrhythmia requiring treatment is atrial fibrillation (AF). When performing catheter ablation for AF, contact force (CF) applied during radiofrequency energy delivery is a powerful predictor of the electrical isolation of the pulmonary veins and of the clinical response. However, prospective data documenting the superiority of ablation guided by the real time CF monitoring over the standard procedure both for AF and for AFL, are missing. In this regard, showing superiority of ablation guided by the real time CF monitoring over the standard procedure in the simple lesion model of CTIA can serve as a proof of concept for more complex lesion sets, as in AF ablation. The Lesion Size Index (LSI) estimates the size of the lesion created by ablation. It takes account for the nonlinear relationship between the size of the lesion and its three main determinants (CF, power and duration [4,5]), and may therefore be an effective mean to precisely dose the amount of the delivered radiofrequency energy. This may prevent both insufficient lesion creation and complications due to excessive energy delivery. The aim of the present study is to evaluate if CF guided ablation targeting a specific value of LSI is superior to standard radiofrequency catheter ablation (RFCA).

Hypothesis:

CF guided ablation targeting a specific value of LSI is superior to standard RFCA with respect to creating lasting ablation lesions in the cavo-tricuspid isthmus region.

Purpose:

The present study is designed to determine if CF guided ablation targeting a specific value of LSI is superior to standard RFCA with respect to creating lasting ablation lesions in the cavo-tricuspid isthmus region.

Inclusion criteria:

Patients with typical AFL undergoing first CTIA are included.

Exclusion criteria:

Congenital heart disease AF is the dominant arrhythmia Prior right atrial atriotomy Significant mitral valve disease New York Heart Association (NYHA) class IV Secondary AFL (e.g. post-surgery, infections, hyperthyroidism) Age < 40 years Patient does not want to participate.

Study size:

156 patients.

Study design:

Randomized controlled double-blinded study

Inclusion and randomization:

Consecutive patients referred to Department of Cardiology, Aarhus University Hospital, Skejby for ablation of AFL will be screened. All pts without documented AF will undergo a 5 day ambulatory ECG before the scheduled ablation procedure.

Pts with AF documented either on a 12-lead ECG or during ambulatory ECG will be informed about pulmonary vein isolation, if suitable and in the case of accept will be referred for such.

Pts without documented AF fulfilling the inclusion criteria and pts who are not candidates for or not wanting Pulmonary Vein Isolation (PVI) will be invited to an interview with the daily contact person. They will here be informed about the study both orally and written. The interview will take place in a room specially selected for this interview to ensure there will be no interruptions. At the end of the interview pts will be asked to sign a written consent form. Subsequently patients are randomized (computer-based) to two Groups:

1. In group 1, the ablation will be guided by real time CF monitoring and LSI, with a target LSI of 7,0 with a target range 6,8-7.2 . The aim will be a stable contact, and CF 10-30 g. Intermittent contact will be avoided.
2. In group 2, the operator is blinded to the real-time CF.

Randomization Study data are recorded in a web-based case record form (CRF) with loggin of all data entries. The CRF is also used for randomization using computerized permuted blocks of different sizes. Randomization is stratified according to gender. An external data manager is responsible for the CRF and has programmed the random-number generator used.

Follow-up

4 weeks after ablation, a 5 day ambulatory ECG will be performed. 3 months after ablation an Electro Physiological study (EP) will be performed along with administration of adenosine to check the completeness of Bidirectional Isthmus Block (BDIB). In case of reconduction BDIB will be completed. Recurrent isthmus conduction will be classified as located in the anterior half of the isthmus, the posterior half of the isthmus or both.

The follow-up will be 12 months. Patients will be seen at the outpatient clinic 12 month after the ablation, where a 12-lead ECG will be performed. Before this 12 months' visit, a 5 day ambulatory ECG will be performed.