The study will test the safety and effectiveness of the EndoPhotonix™ Laser Ablation Systems to photocoagulate cardiac tissue during cardiac surgery, to create electrical isolation of the pulmonary veins and create other electrical isolation lesions in order to treat atrial fibrillation. The surgical procedure will be conducted during concomitant mitral valve repair or replacement surgery or in combination with other cardiac surgery including aortic valve surgery, tricuspid valve surgery, or coronary artery bypass surgery.