A Clinical Trial to Evaluate the Detection of Atrial Fibrillation for an One Day Versus More Than or Equal to Eight Days Using MEMO Patch PLUS in Individuals Aged ≥ 75 Years, or Those at High Risk of Stroke

\[Inclusion criteria\] A participant will be eligible for inclusion in the study if the participant: 1. Has provided documented informed consent for the study. 2. Is adult at least 19 years of age on the day of providing documented informed consent 3. Is the high risk group for stroke, i.e. adult at least 75 years of age or CHA2DS2-VASc score more than 2 4. Is life expectancy more than 6 months 5. Has no Atrial fibrillation or Atrial flutter as a result of 12-lead ECG 6. Has symptoms associated with Atrial fibrillation \*symptoms associated with Atrial fibrillation: palpitation, dizziness, dyspnea, syncope, stroke/transient ischemic accident, systemic embolism etc. \[Exclusion criteria\] The participant must be excluded from the study if the participant: 1. Has had prior history of Atrial fibrillation or Atrial flutter 2. Has received prior or ongoing anticoagulant or antiplatelet therapy 3. Has inserted Pacemaker or Defibrillator that can diagnose Atrial fibrillation or Atrial flutter 4. Has plan of Carotid endarterectomy or inserting Stent\* within 90 days on the day of providing document informed consent \*Stent insertion: means when stent-related interventions have been performed on the carotid arteyr or coronary arteries.