title: Restoration of sinus rhythm and atrial transport function after the maze procedure: U lesion set versus box lesion set.
abstract: OBJECTIVE
  In a U lesion set, the left atrium (LA) roof between the right and left superior pulmonary veins is not ablated, to allow activation to propagate across the posterior LA and to recruit this segment as a contractile atrial component. In contrast, the box lesion set isolates the entire posterior LA.
  
  
  METHODS
  To compare the two lesion sets, postoperative freedom from atrial fibrillation (AF) and LA transport function were examined in 402 patients who underwent surgery for AF with a U lesion (n = 329) or box lesion (n = 73) set. Patients who underwent pulmonary vein isolation alone or other simplified procedures were excluded from the study. LA transport function was quantified at 20 ± 33 months postoperatively by the ratio of peak velocity of the A wave to the E wave (peak A/E) of the transmitral Doppler flow.
  
  
  RESULTS
  In patients with long-standing persistent AF, freedom from AF was 85% with the U lesion set and 77% with the box lesion set at 5 years after the maze procedure, and 82% and 77%, respectively, at 10 years after the procedure. There was no significant difference between the U lesion set and box lesion set in patients with long-standing persistent AF (P = .30) and those with paroxysmal or persistent AF (P = .90). Proportional hazards analysis identified increased LA diameter (P = .003) and long-standing persistent AF (P = .03), but not the type of lesion set (P = .51), as predictive of postoperative AF recurrence. The postoperative peak A/E was significantly greater after the U lesion set than after the box lesion set (0.42 ± 0.22 vs 0.23 ± 0.17), and multiple regression analysis demonstrated that the type of lesion set and preoperative LA diameter significantly affected postoperative A/E.
  
  
  CONCLUSIONS
  The U lesion set restores sinus rhythm frequently as the box lesion set and provides better LA transport function. A dilated LA is a risk factor for postoperative recurrence of AF and poor postoperative LA transport function.
authors.affiliation: Department of Cardiovascular Surgery, Nippon Medical School, Tokyo, Japan. Electronic address: nitta@nms.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nitta
authors.affiliation: Department of Cardiovascular Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Ishii
authors.affiliation: Department of Cardiovascular Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Fujii
authors.affiliation: Department of Cardiovascular Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Miyagi
authors.affiliation: Department of Cardiovascular Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Shun-Ichiro
authors.initials: S
authors.lastname: Sakamoto
authors.affiliation: Department of Cardiovascular Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hiromoto
authors.affiliation: Department of Cardiovascular Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Imura
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology / Q000601:surgery*; D016279:Atrial Function, Left; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods* / Q000401:mortality; D016009:Chi-Square Distribution; D018572:Disease-Free Survival; D015150:Echocardiography, Doppler; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011667:Pulmonary Veins / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome
keywords: lesion set; posterior LA; transport function