The study aims to evaluate the following: 1) the incidence of new onset atrial fibrillation in patients with an atrial leadless pacemaker, 2) the need for upgrade from a standalone atrial leadless pacemaker to a dual chamber leadless pacemaker system, and 3) to compare the battery longevity of the Aveir AR at two years with the battery longevity of subjects implanted with dual chamber leadless pacemakers in the Aveir DR i2i study.

Inclusion Criteria:

1. Symptomatic sinus bradycardia
2. Sino-atrial exit block
3. Symptomatic sinus arrest with sinus pauses > 2 sec during waking hours
4. Symptomatic sinus bradycardia < 40 bpm for > 1 min during waking hours
5. PR interval ≤ 0.22 sec if aged < 70 years or PR interval ≤ 0.26 sec if aged ≥ 70 years
6. QRS width ≤ 0.12 sec
7. No prior PM implantation
8. Patients willing to receive an Assert-IQ loop recorder for research purposes

Exclusion Criteria:

1. Atrioventricular block
2. Bundle branch block
3. History of atrial fibrillation
4. Carotid sinus hypersensitivity
5. Planned cardiac surgery
6. Estimated life expectancy < 1 year
7. Presence of an existing ventricular pacemaker or implantable cardioverter defibrillator
8. Known acute deep vein thrombosis of either lower extremity
9. Unable to read or write
10. Patient with Limited English Proficiency (LEP)
11. Cognitively impaired individuals
12. Pregnant

1. 50 patients who receive an Aveir AR device as standard of care
2. Patients willing to receive an Assert-IQ loop recorder for research purposes
3. All sexes
4. Age > 18 years old
5. Able to provide written informed consent