aMAZE Study: LAA Ligation Adjunctive to PVI for Persistent or Longstanding Persistent Atrial Fibrillation

This study is a prospective, multicenter, randomized (2:1) controlled study to evaluate the safety and effectiveness of the LARIAT System to percutaneously isolate and ligate the Left Atrial Appendage from the left atrium as an adjunct to planned pulmonary vein isolation (PVI) catheter ablation in the treatment of subjects with symptomatic persistent or longstanding persistent atrial fibrillation. This study will be conducted in two stages: * Limited Early Stage (Stage 1): up to 250 subjects at up to 65 sites. (COMPLETED, transitioned to Stage 2) * Pivotal Stage/ Phase III (Stage 2): up to 600 subjects at up to 65 sites. (COMPLETED) All subjects from both stages will be included in the primary analysis.