This study compares two medications, *milvexian* and *apixaban*, to see which one works better at preventing *stroke* and *systemic embolism*. A stroke happens when blood flow to the brain is blocked, and systemic embolism is when a blood clot travels to another part of the body. The study focuses on people with *atrial fibrillation* (AF), which is an irregular heartbeat that can lead to blood clots.

To join, you must be at least 18 years old and have AF. You should be healthy enough to take blood-thinning medication for a long time. If you are 75 or older or have had a stroke before, you qualify. If you are between 65 and 74, you must have two other health issues like high blood pressure or diabetes. You can't join if you have serious heart valve issues or need other blood thinners for different health problems.

• The study length and number of visits will be shared with participants.
• Participants may receive compensation for their time.
• Discuss potential risks and benefits with your doctor before joining.