Evaluation of Weekly Idrabiotaparinux Sodium Versus Oral Adjusted-dose Warfarin to Prevent Stroke and Systemic Thromboembolic Events in Patients With Atrial Fibrillation

The end of the study is defined by a common study end date for all participants, defined as
9 months (39 weeks) after the last participant randomized.

All participants will receive oral warfarin (or matching placebo) and weekly SC injections
of idrabiotaparinux sodium (or matching placebo) up to 6 months before the common study end
date. All participants are expected to be treated for at least 6 months.

All participants will have then an 6-month observational period after cessation of study
treatment.

Inclusion Criteria:

- Non valvular atrial fibrillation (AF)

- Indication for long-term Vitamin-K antagonist (VKA) therapy based on the presence of
previous ischemic stroke, transient ischemic attack (TIA) or systemic embolism and/or
at least two of the following risk factors: hypertension requiring drug treatment,
moderately or severely impaired left ventricular function and/or congestive heart
failure, age > or = 75 years, diabetes mellitus.

Main exclusion Criteria:

- Indication for VKA other than AF

- Stroke or TIA within previous 5 days

- Transient AF caused by a reversible disorder

- Planned major surgery/trauma or cardioversion within 30 days

- INR > 3 at baseline

- Active bleeding or high risk of bleeding

- Uncontrolled hypertension

- Pregnancy or childbearing potential without proper contraceptive measures or breast
feeding.