Patients
The study included a total of 157 AF patients from two inpatient wards in the First Affiliated Hospital, School of Medicine, Zhejiang University. The minimally invasive MAZE group(mi-MAZE group) included 42 patients who underwent modified minimally invasive MAZE with monopolar radiofrequency ablation and mitral valve surgery from January 1, 2014 to May 31, 2018 (18 male: 42.9%, 24 female: 57.1%; age range: 27–70 years old), the open surgery MAZE group (os-MAZE group) includes 115 patients underwent traditional bipolar radiofrequency ablation and mitral valve surgery from January 1, 2014 to May 31, 2018 (78 male: 67.8%, 37 female: 32.2%; age range: 29–83 years old). Patients with a history of atrial fibrillation less than 2 years and a left atrial diameter < 60 mm with mitral valve disease were selected. Eventually 107 AF patients [42 patients in mi-MAZE group (100%), 65 patients in os-MAZE group (56.5%)] were included. All patients were diagnosed as AF by conventional 12-lead ECG (electrocardiogram) or 24-h Holter ECG. And echocardiography was used to diagnose mitral valve disease. The primary outcome is the atrial fibrillation ablation rate evaluated by ECG 3 months, 6 months, 12 months after operation. And secondary outcome is the postoperative quality of life, which is assessed by the SF-36 scale [18,19,20].
Surgical technique
The mi-MAZE group: Our hospital used an original surgery technique for the mi-MAZE group—— After general anesthesia, incision was made in the fourth intercostal space of the right chest. After heparinization, peripheral extracorporeal circulation was established through the femoral artery and vein. Blunt dissection and monopolar ablation of the right superior and inferior pulmonary veins were done during extracorporeal circulation. The left upper and lower pulmonary veins are bluntly separated after heart arrest. The Medtronic Cardioblate flushing radiofrequency system which is connected to the monopolar ablation pen was used for ablation. Left atrial ablation path includes: left and right pulmonary vein ring, the line which connects right superior pulmonary vein and left superior pulmonary vein, the line which connects right lower pulmonary vein and left lower pulmonary vein, the line which connects the incision on interatrial groove and mitral annulus, the line which connects left lower pulmonary vein and mitral annulus, and the line which connects left atrial appendage and left superior pulmonary vein. After the ablation is completed, the valve is replaced or repaired and the left atrial appendage is ligated. The epicardial temporary pacing leads are placed routinely.
The os-MAZE group: After general anesthesia, traditional sternotomy was made in the midline. After heparinization, extracorporeal circulation was established through ascending aorta and right atrium. Blunt dissection and bipolar ablation of the right superior and inferior pulmonary veins were done during extracorporeal circulation and the Marshall ligament was cut off. The left upper and lower pulmonary veins are bluntly separated after heart arrest. The Medtronic Cardioblate flushing radiofrequency system which is connected to the bipolar and the monopolar ablation pen was used for ablation. Left atrial ablation lines were the same as in mi-MAZE group. The right atrium ablation lines include: the line which connects superior vena cava and inferior vena cava, the line which connects right atrial anterior wall incision, coronary sinus and tricuspid posterolateral annulus, the line which connects right atrial anterior wall incision and atrial septal fossa, the line which connects the tricuspid anterior leaflet and the right atrial appendage, and the line which connects the tricuspid posterior valve annulus and the incision on right atrial anterior wall. After the ablation is completed, the valve is replaced or repaired and the left atrial appendage is ligated. The epicardial temporary pacing leads were placed routinely.
The patients’ surgical approaches were determined by the surgeon.
Follow up
All patients were treated with oral anticoagulation for 3 months. If the mitral valve replacement was not performed and the patient was in normal sinus rhythm, the oral anticoagulant was discontinued the fourth month after surgery.
Prevention of arrhythmia is one of the routine treatments. Amiodarone is used as the first choice: intravenous bolus injection of 300 mg, followed by continuous infusion of 1200 mg / 24 h until the first day after surgery. If the patients have no first degree AV (atrioventricular) block, oral administration of amiodarone of 200 mg is given three times a day until discharge. A maintenance regime of 200 mg / day is given for 3 to 6 months. In patients with contraindications to amiodarone, metoprolol or propranolol is administered. Diuretics and isosorbide mononitrate are also routinely used during hospitalization.
After their discharge, we followed up the patients by telephone, letter, and outpatient visiting. The effectiveness of the radiofrequency ablation was evaluated by the electrocardiogram and echocardiography 3 months, 6 months and 12 months after surgery. The postoperative quality of life was assessed by the SF-36 (short form 36 questionnaire) scale.
Statistical analysis
Data were analyzed using SPSS (Statistical Package for Social Sciences, Microsoft) 22.0, using Shapiro-Wilk to test normally distribution. Differences between the mi-MAZE and the os-MAZE group were analyzed using Fisher’s exact test, Pearson’s test, continuous correction test for categorical variables and Student t test and Kolmogorov-Smirnov test for continuous variables. A P value < 0.05 was considered statistically significant for all analyses.
Medical ethics
The study has been approved by the Ethics Committee of the First Affiliated Hospital, School of Medicine, Zhejiang University.