Assess impact of Tart Cherry Concentrate in cardiac surgical patients on POAF and related clinical and economic outcomes. Measure inflammation gene transcripts in cardiac tissue.

Inclusion Criteria:

1. Males and female patients (age 50-79) at the Mitral Valve Clinic/CVC undergoing elective cardiac surgery for mitral valve repair without the Cox MAZE procedure (MVR patients also undergoing CABG and/or tricuspid valve repair are also eligible)
2. In sinus rhythm (no pre-operative atrial fibrillation, no hx of AF)

Exclusion Criteria:

1. Age ≥ 80 years
2. Diagnosed pre-operative chronic or paroxysmal AF
3. Prior ablation procedure for AF
4. Previous cardiac surgery
5. Implanted pacemaker
6. Active smoker
7. Comorbidities such as congenital or cardiac re-operation
8. Use of antiarrhythmic agents
9. Active inflammatory or infectious disease or malignancy
10. Diagnosed autoimmune disease
11. Corticosteroid or other immunomodulatory or immunosuppressive medication
12. Known sensitivity to sorbitol
13. Known gastric sensitivity to acidic juices like orange juice