This study is a post-market clinical follow-up (PMCF) study to identify and evaluate residual risks associated with the use of the BIOMONITOR III and BIOMONITOR IIIm that are discovered or remain even after risk analysis, risk mitigation and successful conformity assessment. Furthermore, this study will also provide additional data as required by regulatory authorities outside of the CE-region.

Inclusion Criteria:

• Patient is at high risk of developing a clinically important cardiac arrhythmia; or
• Patient is undergoing investigation for symptoms such as palpitations, pre- syncope or syncope, that are suggestive of an underlying cardiac arrhythmia; or
• Patient is undergoing investigation for the detection of atrial fibrillation following cryptogenic stroke; or
• Patient is planned for AF ablative procedure or has already undergone an AF ablative procedure.
• Patient is able to understand the nature of the study and able to provide written informed consent.
• Patient is willing and able to perform all follow-up visits at the investigational site.
• Patient is willing and able to use the CardioMessenger and accepts the BIOTRONIK Home Monitoring concept.

Exclusion Criteria:

• Patient is implanted with an ICD or pacemaker.
• Patient is pregnant or breast-feeding.
• Patient is less than 18 years old.
• Patient's life-expectancy is less than 12 months.
• Patient is participating in another interventional clinical investigation.