Inclusion Criteria:
1. Patients with clinically documented recurrent atypical AFL (based on ECG findings or electrophysiological study findings) after previous ablation for pulmonary vein isolation or atypical AFL within 5 years. The use of oral anticoagulation will follow current guidelines before and after the ablation procedure. In brief, oral anticoagulation will be administered for at least 4 weeks before the procedure.
2. Patients undergoing elective AFL ablation using point-by-point PFA (BWI PFA/RFA ablation system), for any of the following types of atypical AFL: gap reentrant, perimetral, roof-dependent, bi-atrial, or scar-related atypical AFL.
3. Patients aged ≥18 and \<80.
4. Patient is willing and capable of providing informed consent.
5. Patient is willing and capable of participating in all follow-up assessments and testing associated with this clinical investigation at an approved clinical investigation center.
Exclusion Criteria:
1. those with AFL due to reversible conditions (e.g., thyroid disorders, acute alcohol intoxication, or recent major surgeries),
2. those who had acute coronary syndrome, underwent percutaneous coronary intervention, or had valve or coronary bypass grafting surgery in the 90 days preceding the procedure, or receiving surgical interventions with mechanical valve implants, and
3. those with documented cardiac thrombus before the procedure, a history of cardiac thrombus, stroke, or transient ischemic attack in the previous 90 days.
4. Categorized as vulnerable population and requires special treatment with respect to safeguards of well being.
5. Any of the following atrial conditions:
1. Left atrial anteroposterior diameter ≥ 5.5 cm, or if LA diameter not available, non-indexed volume \>100 ml (physician note or imaging)
2. Current atrial myxoma
3. Any PV abnormality, stenosis, or stenting (common and middle PVs are admissible)
6. Any of the following CV conditions:
1. History of sustained ventricular tachycardia or any ventricular fibrillation
2. Current or anticipated pacemaker, implantable cardioverter defibrillator or cardiac resynchronization therapy devices, or implantable loop recorder.
3. Prior interatrial baffle, atrial septal patch, atrial septal defect closure device, patent foramen ovale occluder, Amulet devices, or other left atrial appendage closure device if implanted within 90 days of enrollment
7. Presence of any of the following:
1. Moderate to severe mitral valve stenosis
2. More than moderate mitral regurgitation (\>3+)；
3. Moderate to severe aortic stenosis
8. Hypertrophic cardiomyopathy
9. Any IVC filter, known inability to obtain vascular access or other contraindication to femoral access
10. Awaiting cardiac transplantation or other cardiac surgery within the next 12 months
11. Severe right ventricular dysfunction with documented echocardiography and/or hemodynamic data within 6 months.
12. Any of the following conditions at baseline:
1. Heart failure associated with NYHA Class III or IV
2. Documented LVEF \< 40% as documented within the previous 12 months
3. Any of the following events within 90 Days of the Consent Date:
i. Heart failure hospitalization: Heart failure hospitalization ii. Pericardium: Pericarditis or symptomatic pericardial effusion iii. GI bleeding: Gastrointestinal bleeding iv. Neurovascular event: Stroke, TIA, or intracranial bleeding v. Thromboembolism: Any active non-neurologic thrombus and/or thromboembolic event vi. Carotid intervention: Carotid stenting or endarterectomy vii. Diabetes: Uncontrolled diabetes mellitus or a recorded HgbA1c \> 8.0%
13. Any of the following congenital conditions:
1. Congenital heart disease: Congenital heart disease with any clinically significant residual anatomic or conduction abnormality
2. Methemoglobinemia: History of known congenital methemoglobinemia
3. G6PD deficiency: History of known G6PD deficiency
14. Any of the following known pre-existing conditions:
1. Transplantation: Solid organ or hematologic transplant, or currently being evaluated for a transplant
2. Diaphragmatic abnormality: Any prior history or current evidence of hemi-diaphragmatic paralysis or paresis
3. Pulmonary: Severe lung disease, severe pulmonary hypertension, or any lung disease involving abnormal blood gases or requiring supplemental oxygen
4. Renal: Renal insufficiency if an estimated glomerular filtration rate (eGFR) is \< 30 mL / min / 1.73 m2, or with any history of renal dialysis or renal transplant
5. Malignancy: Active malignancy at enrolment (other than squamous cell carcinoma)
6. Gastrointestinal: Clinically significant gastrointestinal problems involving the esophagus or stomach including severe or erosive esophagitis, uncontrolled gastric reflux, gastroparesis, esophageal candidiasis or active gastroduodenal ulceration
7. Infections: Active systemic infection
8. Sleep apnea: Untreated diagnosed obstructive sleep apnea with apnea hypopnea index classification of severe (\>30 pauses per hour)
9. Hematologic condition: Known coagulopathy or bleeding disorder (e.g. von Willebrand disease, hemophilia)
10. Contraindication to anticoagulation: Contraindication to, or unwillingness to use, systemic anticoagulation, or acceptable alternatives, pre-, intra- and post-procedure to achieve adequate anticoagulation.
11. Pregnancy: Women of childbearing potential who are pregnant, lactating, not using medical birth control or who are planning to become pregnant during the anticipated study period
12. General health conditions: Health conditions that in the investigator's medical opinion would prevent participation in the study, interfere with assessment or therapy, significantly raise the risk of study participation, or modify outcome data or its interpretation.
13. Participation in another trial: Subjects who are currently enrolled in another investigational study or registry that would directly interfere with the current study, except when the subject is participating in a mandatory governmental registry, or a purely observational registry with no associated treatments; each instance must be brought to the attention of the Sponsor to determine eligibility.
14. Life expectancy: Predicted life expectancy less than three years
15. A subject that is ineligible for participation for any other reason as determined by the investigator.
