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Cryoablation as Standard Treatment of Atrial Flutter (CASTAF)

This study has been completed.
Information provided by (Responsible Party):
Mats Jensen-Urstad, Karolinska University Hospital Identifier:
First received: May 21, 2012
Last updated: October 5, 2016
Last verified: October 2016

The hypothesis of the present study is to evaluate cryoablation(cooling of the tissue) as standard therapy of common atrial flutter,focusing on efficacy, feasibility, procedure time, and patient content.

The purpose of this study is to determine whether cryoablation, performed only by operators experienced in cryothermic ablation is effective and safe in the treatment of atrial flutter.

Condition Intervention
Atrial Flutter Procedure: Medtronic Freezor Max Cardiac Cryoablation Catheter

Study Type: Interventional
Study Design: Intervention Model: Single Group Assignment
Masking: None (Open Label)
Primary Purpose: Treatment
Official Title: Cryoablation as Standard Treatment of Atrial Flutter - Long Term Efficacy and Patient Content

Further study details as provided by Mats Jensen-Urstad, Karolinska University Hospital:

Primary Outcome Measures:
  • Efficacy [ Time Frame: One year after intervention ]
    Clinical success defined as the freedom from atrial flutter evaluated at the 12-month follow-up.

Secondary Outcome Measures:
  • Safety [ Time Frame: During and up to one year after intervention ]
    The secondary endpoints will be acute ablation success defined as bidirectional CTI-block, safety assessed by the rate of periprocedural complications, procedure and fluoroscopy times and the level of pain experienced by the patient during the ablation procedure.

Enrollment: 193
Study Start Date: June 2012
Study Completion Date: June 2016
Primary Completion Date: June 2016 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: Cryoablation Procedure: Medtronic Freezor Max Cardiac Cryoablation Catheter
Cryoablation is performed using a sequential application technique point-by-point from the tricuspid annulus to the inferior vena cava. Ablation is performed at a target temperature of -80 ºC. Each application will last for 240 seconds.
Other Names:
  • Cryoablation
  • CTI ablation

Detailed Description:

Atrial flutter (AFL), a common atrial tachyarrhythmia may cause significant symptoms and serious adverse effects including embolic stroke, myocardial ischemia and congestive heart failure. Currently, radiofrequency (RF) catheter ablation of the cavotricuspid isthmus (CTI) is considered first-line therapy for treatment of CTI-dependent AFL. However, RF ablation of the CTI is associated with significant pain during lesion delivery. Furthermore, RF ablation can potentially injure cardiac structures adjacent to the CTI such as the AV node, tricuspid valve and right coronary artery. RF ablation can also lead to steam pops, cardiac tamponade and fatal complications have also been reported in association with CTI-ablation. Ablation using cryothermal energy (Cryo) has several potential advantages over RF ablation including greater catheter stability due to adherence to myocardial tissue during applications, reduced risk of thrombus formation, systemic embolization, and lower risk of myocardial perforation due to preservation of tissue architecture.

The investigators have in a prospective randomized, single centre study (CRAFT) investigated efficacy and safety of RF versus Cryo for atrial flutter, and showed that cryoablation is as effective as RF ablation in the short and long term. The patients perceived significantly less pain and required significantly lower doses of analgesia and sedation during cryoablation compared to RF ablation. The study was powered for non-inferiority with 75 patients in each group.

The objective of the present study is to expand the findings from the CRAFT study in a larger cohort of patients, letting only operators experienced in cryothermic CTI ablation use Cryo as standard therapy focusing on efficacy, feasibility, procedure time, and patient content.

To perform an ablation within the study, the electrophysiologist must have a previous experience of a minimum of 25 cryoablations of atrial flutter.


Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Consecutive patients referred to our institution for ablation therapy of ECG-documented, typical CTI dependent AFL.
  • Patients above the age of 18 having symptomatic CTI-dependent AFL documented on a 12-lead ECG with typical ECG appearance of negative saw tooth waves in the inferior limb leads and positive deflections in V1 or positive saw tooth waves in the inferior limb leads and negative deflections in V1.
  • Patients with a history of atrial fibrillation will only be included if they have predominant atrial flutter under chronic treatment with class I or III antiarrhythmic agents.

Exclusion Criteria:

  1. prior ablation for AFL;
  2. atrial flutter related to recently undergone surgery, hyperthyroidism or other severe disease;
  3. inability to adhere with the study protocol;
  4. pregnancy;
  5. predominant atrial fibrillation; and
  6. for patients with persistent atrial flutter contraindication to warfarin
  Contacts and Locations
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Please refer to this study by its identifier: NCT01604369

Karolinska University Hospital
Stockholm, Sweden, SE-14186
Sponsors and Collaborators
Karolinska University Hospital
Principal Investigator: Mats Jensen-Urstad, Professor Karolinska University Hospital
  More Information

Responsible Party: Mats Jensen-Urstad, Professor, Karolinska University Hospital Identifier: NCT01604369     History of Changes
Other Study ID Numbers: KS1
Study First Received: May 21, 2012
Last Updated: October 5, 2016

Keywords provided by Mats Jensen-Urstad, Karolinska University Hospital:
Atrial flutter
Cavotricuspid isthmus
Visual analogue scale

Additional relevant MeSH terms:
Atrial Flutter
Arrhythmias, Cardiac
Heart Diseases
Cardiovascular Diseases
Pathologic Processes processed this record on September 18, 2017