Head-to-Head (H2H) Comparison of Ambulatory Cardiac ECG Monitors in Japan

Inclusion Criteria: 1. Participant is 18 years of age and older 2. Participant has reported symptoms that would prompt ambulatory ECG monitoring (i.e. palpitations, dizziness or lightheadedness, syncope or presyncope, shortness of breath, or asymptomatic) 3. Participant is prescribed Heartnote device as part of clinical care 4. Participant is willing and able to provide informed consent and able to complete all visits for this study Exclusion Criteria: 1. Participant has known permanent or persistent (i.e., 100% burden) atrial fibrillation (AF) 2. Participants in whom inpatient monitoring should be prescribed. 3. Participant has a known allergy to adhesives. 4. Participant has a current skin infection or injury at location for study device placement. 5. Participant has an external cardiac defibrillator or may be exposed to high frequency surgical equipment near strong magnetic fields or devices such as MRI during the wear period. 6. Participant has experienced symptomatic episodes where instance variations in cardiac performance could result in immediate danger to the participant. 7. Participant with implantable cardiac defibrillator, pacemaker, or implantable loop recorders. 8. Participant has a neuro-stimulator, as it may disrupt the quality of ECG data. 9. Participant is a member of a vulnerable population. 10. Participant is a current or prior employee of iRhythm. 11. The local Investigator deems the participant has a condition that could limit the participant's ability or willingness to participate in the study, or ability to comply with study required procedures and/or follow-up visits. 12. Participant does not have the competency to wear the device for the prescribed monitoring period. 13. Participant does not have the ability to consent for themselves (i.e., no LARs) 14. Participant is unable or unwilling to participate or comply with study protocol.