Single site study: The goal of the study is to determine the incidence of new onset atrial fibrillation (AF) in patients with severe obstructive sleep apnea (OSA) syndrome through the use of a Medtronic Reveal XT implantable Loop recorder (ILR). The ILR device is approved for use in Canada, for the assessment of atrial fibrillation.

Inclusion Criteria:

1. Patients with severe OSA defined as Apnea Hypopnea Index (AHI) > 30.
2. Age > 18 years.

Exclusion Criteria:

1. Previous history of clinical AF defined as documented lone, paroxysmal, persistent or permanent, according to standard definitions.
2. Patient with anticipated requirement of MRI.
3. Patient with well-know allergy to any component of the Medtronic Reveal XT.
4. Patients with implantable cardiac rhythm device [pacemakers or internal cardiac device (ICDs)].
5. Women of child bearing potential.
6. Unable or unwilling to provide written informed consent.
7. Unable or unwilling to complete the study follow-up schedule (eg. intention to leave the Kingston area over the next 3 years.
8. Previously enrolled in this trial.
9. Enrolled in another study that would confound the results of this trial.
10. Documented history of heart failure
11. Diagnosed with severe obstructive sleep apnea greater than 1 year from screening date