Amyloidosis, Familial; Atrial Fibrillation; Black or African American/genetics; Heart Failure; Ischemic Stroke; Prealbumin/genetics; Amyloidogenic Proteins/genetics; Amyloidosis, Familial/complications; Amyloidosis, Familial/ethnology; Amyloidosis, Familial/genetics; Atrial Fibrillation/diagnosis; Atrial Fibrillation/etiology; Atrial Fibrillation/prevention & control; Female; Follow-Up Studies; Genetic Testing; Heart Failure/diagnosis; Heart Failure/etiology; Heart Failure/prevention & control; Humans; Ischemic Stroke/diagnosis; Ischemic Stroke/etiology; Ischemic Stroke/prevention & control; Male; Middle Aged; Polymorphism, Single Nucleotide; Preventive Health Services/methods; Risk Factors; United States/epidemiology