PLUG Dementia Trial and MRI PLUG Dementia Sub-Study

Inclusion Criteria: 1. Male or female \>65 years of age 2. Atrial fibrillation documented by electrocardiogram, ambulatory event monitor, or telemetry within 6 months of enrollment 3. Moderate risk of thromboembolism based upon a CHADS2 score or CHADS2 Vasc score of ≥2. 4. Recipient of a left atrial appendage closure device within 3 months of enrollment (within 6 months, for patients considered for the MRI PLUG Dementia Sub-Study) 5. Have the ability to complete a mini-mental status evaluation 6. Have the ability to independently comprehend and complete a quality of life and dementia questionnaires. 7. Ability to provide informed consent for study participation 8. Willing and able to comply with the prescribed follow-up tests and schedule of evaluations. Exclusion Criteria: 1. Have a history of any form of dementia 2. Have a life expectancy less than 24 months 3. Are unable to comply with the follow-up schedule 4. An upper age limit not to be used if participation inclusion criteria are met. 5. Participation in any other clinical trials involving an investigational or marketed drug within 30 days prior to entry in this study; 6. Other conditions that in the opinion of the Principal Investigator may increase risk to the subject and/or compromise the quality of the clinical trial 7. The Principal Investigator(s) determine(s) that the subject is not eligible for participation in this research study. In addition to the above exclusion criteria, patients considered for the MRI PLUG Dementia Sub-Study will be excluded if the patient - 1. Does not receive a left atrial appendage closure device 2. Has contraindication towards the MRI scan (presence of a nonconditional cardiac implantable device, a history of metallic implants, shrapnel, neurosurgical clip placement) 3. Has conditional cardiac MRI cardiac implantable device, joint replacements, coronary stents, ASD/PFO closure devices, sternal wires or most prosthetic heart valves 4. Has severe renal dysfunction, defined as a creatinine clearance \<15 mL/min (documented within the last 3 months)