The main purpose of this project is to determine the impact of atrial fibrillation interventions (catheter ablation and exercise training) on circulating BDNF concentrations in patients with atrial fibrillation. It also seeks to determine if there is a relation between circulating BDNF concentrations and mental health (depression severity, quality of life and symptoms) among those undergoing interventions for atrial fibrillation catheter ablation or exercise training.

The main purpose of this project is to determine the impact of atrial fibrillation interventions (catheter ablation and exercise training) on circulating BDNF concentrations in patients with atrial fibrillation. It also seeks to determine if there is a relation between circulating BDNF concentrations and mental health (depression severity, quality of life and symptoms) among those undergoing interventions for atrial fibrillation catheter ablation or exercise training. Using a pre-post study design, the investigators will explore interventions in two subsets of patients at the opposite end of the atrial fibrillation clinical spectrum. Arm 1: patients with paroxysmal atrial fibrillation will undergo catheter ablation (n=100). Arm 2: patients with permanent or persistent atrial fibrillation will perform exercise training 2 times weekly for 12 weeks (n=100). Total sample size will be 200 participants. All measurements will be performed at baseline and follow-up.

Inclusion Criteria:

1. Subjects must be either currently enrolled in the OPPORTUNITY trial (NCT02602457) or have paroxysmal atrial fibrillation and be scheduled to undergo catheter ablation (for the first time) through the electrophysiology clinic at the University of Ottawa Heart Institute.
2. Subjects must be willing and able to provide a blood sample.
3. Subjects must be willing and able to provide informed consent.

Exclusion Criteria:

1. Subject is not either currently enrolled in the OPPORTUNITY trial (NCT02602457) or scheduled to undergo catheter ablation (for the first time) through the electrophysiology clinic at the University of Ottawa Heart Institute for paroxysmal atrial fibrillation.
2. Subjects with congestive heart failure with heart failure admission in the past 3 months.
3. Subjects with a cerebrovascular accident in the past 3 months
4. Subjects with severe dementia.
5. Subjects with a history of severe psychiatric illness (e.g., schizoaffective disorder, bipolar disorder, or schizophrenia).
6. Subjects with an active infection or inflammatory condition.
7. Subjects who are pregnant, lactating or planning to become pregnant during the study period.
8. Subject is unable to read or understand English or French.
9. Subject is unable to provide informed consent.

Subjects with paroxysmal atrial fibrillation that will undergo catheter ablation and subjects with permanent or persistent atrial fibrillation undergoing exercise training two times weekly for 12 weeks as part of their involvement in the OPPORTUNITY Study (NCT02602457).