In the present study, we introduced a modified surgical ablation method for LSPAF patients who underwent MVS. Compared with the “gold standard”, CSM, the modified maze had the same efficacy in terms of maintaining normal sinus rhythm and allowing for the discontinuation of antiarrhythmic drugs. Furthermore, the modified maze procedure sped up the surgical procedure and reduced the cross-clamp and cardiopulmonary bypass times.
The underlying mechanisms of AF are less well understood, which has resulted in a wide variation in current ablation and surgical therapies for LSPAF. Pulmonary veins (PVs) may harbour one or more foci that are the trigger points for AF in 88.8–94% of cases. Therefore, pulmonary vein isolation (PVI) is the cornerstone of AF ablation.
In patients with LSPAF, the recurrence rate following PVI alone is relatively high.
 As a result, surgical approaches have emerged. The surgical CSM procedure was first introduced in 1987 by James Cox, MD. This technique was based on surgical incisions and scar creation to interrupt potential re-entrant wavelets in the atrium while “creating routes for activation of the atria and atrioventricular node (maze).” Evidence has shown maintenance of sinus rhythm to be greater than 96% at 10 years. Our results also indicated that standard CSM provides excellent results, with a high rate of absence of AF. There is no doubt that CSM is the standard criterion for the surgical treatment of LSPAF. However, the CSM has shortcomings.
First, the operation requires a relatively long period of cardiopulmonary bypass and an arrested heart.
Second, the median number of days spent in the hospital after surgery is longer. Third, a large proportion of patients required pacemakers. Fourth, left atrial dysfunction has been suggested in many patients. Finally, the complexity and apprehension about bleeding related to the CSM are considered major drawbacks. As a consequence, various energy sources used for ablation began a new era in the surgical therapy of AF (Cox maze IV procedure) based on the understanding of the anatomic substrate of AF. Using bipolar radiofrequency energy and cryoablation, the Cox maze IV replaced the CSM lesion set. Furthermore, the Cox maze IV achieves satisfactory efficacy while significantly reducing operative time and complication rates. It has been reported by Labin et al. that absence of AF without the use of AADs in patients concomitant with mitral valve procedures was approximately 70% at 2 years. The Cardiothoracic Surgical Trial Network randomized trial showed that the rate of the absence of AF at 1 year was 66% in patients who underwent the biatrial maze procedure. A meta-analysis of 7 randomized controlled trials of subjects undergoing cardiac surgery combined with surgical ablation also revealed that the average rate of the absence of AF recurrence at 12 months was 70%. However, in our group, the one-year rate of the absence of AF was 76% after bipolar radiofrequency was used to treat AF in patients concomitant with MVS. Consequently, the energy technique was less effective than the “cut-and-sew” method in LSPSAF patients concomitant with MSV. Failure to achieve complete transmural ablation lines is probably the most common cause of surgical ablation failure. Some mapping results have suggested that re-entrant and focal drivers were predominantly located in the PV antral regions and adjacent inferoposterior left atrial wall in cases of failed surgical maze. In addition, our unpublished findings support that the left atrium is the main reason for cryoablation failure. Therefore, we insisted on performing CSM in the left atrium to achieve complete transmural lines to prevent the recurrence of AF in LSPAF patients treated with our modified maze procedure. In the present study, the rate of absence of AF in both groups was nearly 90%; more importantly, most of the patients who underwent CSM and the modified maze did not require anti-arrhythmic drugs, which improved quality of life.
Our modification maze replaced the surgical incisions in the right atrium with cryoablation lines. This simplified procedure decreased the mean cross-clamp time by more than 16 minutes and the cardiopulmonary bypass time by 30 minutes. Moreover, our results clearly showed that the simplified procedure was similarly efficacious compared to traditional CSM at the two-year follow-up and did not increase complications during the operation. Except for routine cryoablation in the right atrium, additional CTI ablation was performed in our modified procedure. CTI ablation is common and extremely effective for the treatment of typical right atrial flutter because CTI remains an obligatory passage for activation in the inferior right atrium. Moreover, atrial flutter was a common finding after surgical ablation of AF in recent studies. Atrial flutter in patients who underwent CSM is a common finding. A recent study found that additional CTI ablation may reduce recurrent atrial tachyarrhythmia for persistent AF. Nevertheless, Cox et al. suggested that combining the three right atrial lesions of the maze with the CTI flutter line resulted in the development of normal sinus bradycardia., In our group, some unpublished data also indicated that patients who underwent Cox maze IV developed atrial tachycardia, including atrial flutter. Therefore, we tried to add the CTI lesion. Additionally, our study clearly suggested that none of the patients developed complete atrioventricular block or needed permanent pacemakers in our 2-year follow-up. There were several reasons for this.
First, the patients in our cohort were relatively younger with a lower incidence of sick sinus syndrome; second, if the 24-hour ECG Holter indicated a prolonged R-R interval, the patients were excluded; and last, during the operation, those with heart rates less than 60 beats per minute after electric conversion were not eligible to receive CSM or the modified maze.