• Composite incidence of -
  
• Stroke
  
• Transient Ischemic Attack
  
• Peripheral Embolism
  
• Major hemorrhagic bleeding
  

• Prevalence of thrombi or spontaneous contrast detected by ICE,
  
• Time to cardioversion following randomization
  
• Minor bleeding events
  
• Death and major procedure related complications (other than the primary endpoints)
  
• Number of hospitalizations.
  
• Quality of life
  

Inclusion Criteria:

Inclusion Criteria for the Phase I Component

1. Patients with spontaneous AF
2. Patients with or without structural Heart Disease.
3. Men or Women aged 18 years or older.
4. Patients undergoing an invasive catheterization procedure including right heart catheterization.
5. Patients who give an informed consent for participation in the study.
6. Patients who have undergone a trans-thoracic echocardiogram within the last 14 days showing absence of intracardiac thrombi.
7. Patients who have undergone a trans-esophageal echocardiogram within the last 48 hours.

Inclusion Criteria for the Phase II Component

1. Patients with spontaneous AF
2. Patients with or without structural Heart Disease.
3. Men or Women aged 18 years or older.
4. Patients undergoing an invasive catheterization procedure including right heart catheterization.
5. Patients who give an informed consent for participation in the study.
6. Patients who have undergone a trans-thoracic echocardiogram within the last 14 days showing absence of intracardiac thrombi.

Exclusion Criteria:

Exclusion Criteria for the Phase I Component

1. Patients in whom placement of an ICE catheter for adequate atrial visualization is technically not feasible.
2. Women of child bearing potential, in whom pregnancy cannot be excluded.
3. Patients with any medical condition or social circumstance, which in the opinion of the investigator, would make the patient’s successful completion of the study doubtful

Exclusion Criteria for the Phase II Component 1. Patients anticoagulated for > 7 days. 2. Patients who have had a cardioembolic event within the last 1-month. 3. Patients requiring urgent cardioversion due to hemodynamic instability. 4. Patients in whom placement of an ICE catheter for adequate atrial visualization is technically not feasible. 5. Patients with contraindications for Warfarin. 6. Women of child bearing potential, in whom pregnancy cannot be excluded. 7. Patients who need anticoagulation withdrawn due to an elective procedure 8. Patients with any medical condition or social circumstance, which in the opinion of the investigator would make the patient’s successful completion of the study doubtful.

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