MATERIAL AND METHODS
This was a single-center cohort study in which all data were collected
prospectively for surgery occurring between January 2011 and December
2017. Patients with pre-operative AF, who were above 70 years and
underwent 2 cardiac procedures with or without additional AF procedures
were included in the study. Patients were divided into two groups based
on how the AF was addressed: (1) Cox-maze IV procedure (2) Nil surgical
AF treatment group. Patients undergoing redo procedures or who had
isolated Pulmonary vein isolation (PVI) or left atrial appendage
occlusion (LAAO) to address their AF were excluded from the study.
History of preoperative atrial fibrillation was determined through our
local database and type of atrial fibrillation was determined according
to Heart Rhythm Society guidelines. The database was also used to gain
additional preoperative characteristics and perioperative outcomes.
Detailed follow-up data was collected for patients through telephone
consultations and medical record review. In addition, reports from
primary care physicians and cardiologists from referring centres were
obtained if required. Rhythm status for patients who underwent a
surgical ablation procedure was determined according to the Heart Rhythm
Society guidelines and verified by electrocardiogram and Holter monitor.
The Heart Rhythm Society definition of success (ie, all documented
atrial Arrhythmias > 30 seconds are considered a
failure) was used to determine the return to sinus rhythm rate at first
follow (usually 6 weeks), annual follow and long-term follow-up
[15]. Anticoagulation status was also collected at the follow-up
time points. Operative mortality was defined as death occurring within
30 days of operation or at any time point during the index
hospitalization.
Operative Approach
Multiple surgeons performed the complete Cox-maze IV lesion set in a
standard fashion as described previously. This consisted of a bilateral
PVI, roof and connecting lesions between the right and left pulmonary
veins, lesion to the left atrial appendage, mitral isthmus lesion, right
intercaval lesion, right appendage lesion, right free wall lesion to the
tricuspid annulus lesion and the coronary sinus lesion. The energy
source used was cryothermia and bipolar radiofrequency (Medtronic,
Minneapolis, Minn; AtriCure Inc, West Chester, Ohio). The left atrial
appendage was occluded in all patients who had Cox-Maze IV. This was
performed using the Atriclip device (AtriCure Inc, West Chester, Ohio).
The patients in the “Nil procedure” group only had two cardiac
procedures and served as our primary control group. The decision of
whether to add the Cox Maze procedure to a specific surgical procedure
was left to the discretion of the surgeon.
Statistical Analysis
Continuous data are presented as mean +/- standard deviation or Median
+/- Interquartile range. Categorical data is presented as frequency
(+/-percent) unless otherwise noted. Patient groups were compared usingc 2 or Fisher exact test for preoperative and postoperative
categorical variables and student independent samples t test or
Mann-Whitney U test for continuous measures as appropriate based on
parametric test assumptions. Statistical significance was considered p
< 0.05, 2-tailed. Kaplan-Meier analysis was used to compare
the groups on cumulative survival, freedom from AF, NYHA 1 status,
freedom from permanent pacemaker insertion and freedom from stroke.
Gehan-Behan-Wilcoxon test was used to assess significance of these
survival analyses. All analyses were conducted using SPSS version 17.0
(SPSS Inc, Chicago, Ill) or GraphPad Prism, Version 6.00 for Mac
(GraphPad Software, La Jolla, CA, USA).