The purpose of the BLOCk-CTI study is to evaluate the safety and effectiveness of the Blazer® Open-Irrigated Ablation Catheter for the treatment of sustained or recurrent type 1 atrial flutter. This study will compare outcomes in patients treated with the Blazer® Open-Irrigated Ablation Catheter to outcomes in patients treated with open-irrigated radiofrequency ablation catheters that have received FDA market approval for the treatment of type 1 atrial flutter.

The BLOCk-CTI study is a prospective, multicenter, single blind, 1:1 randomized study. The study is designed to demonstrate that the safety and effectiveness of the Blazer® Open-Irrigated Ablation Catheter are non-inferior to the safety and effectiveness of the control catheters. In this study, the control catheters are open-irrigated radiofrequency ablation catheters that have received FDA market approval for the treatment of type 1 atrial flutter. (Biosense Webster ThermoCool® ablation catheters (NaviStar™, EZ Steer, or SF) or St. Jude Medical ablation catheters (Therapy™ Cool Path™ or Safire BLU™).

Inclusion Criteria:

• At least 1 documented episode of type 1 atrial flutter in the 180 days (6 months) preceding enrollment documented by 12-lead ECG, Holter monitor, rhythm strip, or transtelephonic monitor
• Patients are clinically indicated for catheter ablation
• Patients receiving oral anti-arrhythmic drug therapy (class I or class III) for a tachyarrhythmia other than type 1 atrial flutter must be controlled on the anti-arrhythmic drug for a minimum of 30 days prior to enrollment. If type 1 atrial flutter was documented prior to the development of other tachyarrhythmias, this 30-day period is not required.
• Age 18 or above, or of legal age to give informed consent specific to state and national law
• Patients are competent and willing to provide written informed consent to participate in the study and agree to comply with follow-up visits and evaluation

Exclusion Criteria:

• Any prior right atrial cavo-tricuspid isthmus ablation or any cardiac ablation for non-atrial flutter arrhythmias within 90 days prior to enrollment
• Cardiac surgery within 90 days prior to enrollment
• Myocardial infarction within 60 days prior to enrollment
• Current unstable angina
• Patients who cannot have anti-arrhythmic drugs (class I and class III) prescribed for the treatment of type 1 atrial flutter stopped on the day of the procedure
• Patients regularly prescribed amiodarone within the 120 days (4 months) prior to enrollment
• Documented atrial or ventricular tumors, clots, thrombus, or have a known clotting disorder within 90 days prior to enrollment
• Implantation of permanent leads of an implantable device in or through the right atrium within 90 days prior to enrollment
• Direct remedial cause of atrial flutter (e.g. thyroid disease, pericarditis, pulmonary embolic disease)
• Atypical or scar-based flutter
• Patients with New York Heart Association Class III at the time of enrollment or New York Heart Association Class IV heart failure within 90 days prior to enrollment
• Patients with an ejection fraction less than 30% within 90 days prior to enrollment
• Clinically significant structural heart disease (including tricuspid valve regurgitation, tricuspid valve stenosis, tricuspid valve replacement, Ebstein's anomaly, or other congenital heart disease) that would preclude catheter introduction and placement, as determined by the Investigator
• Any cerebral ischemic event (including transient ischemic attacks) within 180 days prior to enrollment
• Contraindication to anticoagulation therapy based upon published guidelines
• Creatinine greater than 2.5 mg/dl or creatinine clearance less than 30 mL/min within 90 days prior to enrollment
• Any other significant uncontrolled or unstable medical condition (e.g. sepsis, acute metabolic illness)
• Enrolled in any concurrent study without BSC written approval
• Women who are pregnant or plan to become pregnant within the course of their participation in the investigation
• Life expectancy less than or equal to 2 years (730 days) per physician opinion

Subject was not told by investigator if device used was Investigational or Control. The subject could ask the investigator at end of study at 3 months if they wanted to know which device was used.