The purpose of this study is to evaluate the benefits in the atrial fibrillation detection rate of the continuous ECG monitoring group for more than 8 days by contrasting with one-day ECG monitoring using MEMO Patch PLUS in 1000 patients with atrial fibrillation-related symptoms in the high risk group of stroke. The participant is allocated randomly to One-day ECG monitoring group or the continuous ECG monitoring group for more than 8 days in ratio of 1:1, only if the participant provides informed consent and eligible for all the inclusion/exclusion criteria. The investigator confirms the results of MEMO Patch PLUS monitoring at 1 month from the date of MEMO Patch PLUS attachment. The participation of the subject is terminated on the 1 year from the date of MEMO Patch PLUS attachment. On that day, investigator evaluates incidence of the event associated with atrial fibrillation, the event is included ischemic stroke/transient ischemic accident, hemorrhagic stroke, systemic embolism, etc.

[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 inserted Pacemaker or Defibrillator that can diagnose Atrial fibrillation or Atrial flutter
3. 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.