This study will evaluate the correlation between the respiratory rate derived from the Reveal Insertable Cardiac Monitor (ICM) electrocardiogram (ECG) with the respiratory rate obtained from an external respiratory band in patients previously implanted with a Reveal for unexplained syncope or suspected arrhythmia.

Inclusion Criteria:

• Subject is implanted with a Reveal ICM or Reveal XT ICM for unexplained syncope or suspected arrhythmia
• Subject (or the legal representative) is willing to sign informed consent form
• Subject is 18 years or older or as specified minimal age per local law/regulation

Exclusion Criteria:

• Significant respiratory diseases such as COPD or pulmonary hypertension.
• Patients with frequent arrhythmias, including PVC's.
• Patients with known heart failure.
• Body conditions that would complicate accurate measurement of respiratory rate with the respiration device.
• Patients which are not able to take the postures as necessary for the study protocol and which cannot walk continuously for a period of 6 minutes.
• Pregnant or breastfeeding women, or women of child bearing potential and who are not on a reliable form of birth control.
• Subject is enrolled in one or more concurrent studies that would confound the results of this study