Chad: A republic in central Africa, east of NIGER, west of SUDAN and south of LIBYA. Its capital is N'Djamena.Adenoviruses, Simian: Species of the genus MASTADENOVIRUS associated with respiratory and enteric infections in primate hosts.Atrial Fibrillation: Abnormal cardiac rhythm that is characterized by rapid, uncoordinated firing of electrical impulses in the upper chambers of the heart (HEART ATRIA). In such case, blood cannot be effectively pumped into the lower chambers of the heart (HEART VENTRICLES). It is caused by abnormal impulse generation.Atrial Appendage: Ear-shaped appendage of either atrium of the heart. (Dorland, 28th ed)Anticoagulants: Agents that prevent clotting.