Additional Study Information: Atrial fibrillation (AFib) is an arrhythmia (abnormal heart rhythm) that causes the heart's upper chambers (the atria) to beat very fast and irregularly. The purpose of this study is to determine if early study treatment with the medicine dronedarone is more effective than usual care alone for the prevention of unplanned cardiovascular hospitalization. A computer will randomly assign you (like the flip of a coin) to receive either the study intervention or usual care. Both you and your study doctors will know to which group you have been assigned. The study intervention is the oral (by mouth) medication dronedarone. Dronedarone is a heart rhythm medicine. The usual care group will be prescribed medicines that they would receive as part of their usual car.