The goal of this study is to compare OTW balloon with microcatheter in the Marshall vein alcohol ablation study. The main questions it aims to answer are: • Is there a difference in the effectiveness and safety of OTW balloon and microcatheter in Marshall vein alcohol ablation? Participants will be asked to:

Undergo treatment with OTW balloon Undergo treatment with microcatheter If there is a comparison group: Researchers will compare the OTW balloon group and the microcatheter group to see different effects.

Inclusion Criteria:

1. Age range: 18-80 years.
2. Persistent atrial fibrillation or atrial flutter dependent on the mitral isthmus.
3. Inadequate response to antiarrhythmic drug therapy, or intolerance to antiarrhythmic drugs.
4. New York Heart Association functional class ≤ IV,with left ventricular ejection fraction (LVEF) ≥ 35%

Exclusion Criteria:

1. Patients with known allergies to alcohol.
2. Participants with a history of serious cardiovascular events such as myocardial infarction or stroke within the past three months will be excluded from the study