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Ralph J. Damiano, Jr., MD, John M. Shoenberg Professor of Surgery and Chief of Cardiac Surgery
Washington University School of Medicine
The incidence of atrial fibrillation varies between 30-50% in patients who present for surgery with valvular heart disease. At our institution, 35% of patients who presented for mitral surgery between 1997 and 2002 had chronic atrial fibrillation (AF). Curative surgery for atrial fibrillation at the time of valve surgery can eliminate the need for postoperative anticoagulation by restoring sinus rhythm. This is particularly important in patients having a valve repair or a bioprosthetic valve. Bleeding rates with mitral bioprostheses average between 0.6-2.1 episodes/patient year, in part due to the need for anticoagulation in patients with chronic atrial fibrillation. The Cox-Maze procedure has been shown to improve survival and late cardiac function and reduce the incidence of late stroke following mitral valve surgery.1 Atrial fibrillation surgery has been shown to decrease the risk of late stroke, even in patients who had mechanical valves and required anticoagulation.2
In patients who present with AF, the duration of the arrhythmia has a significant impact on the choice of therapy. In a study from the Mayo Clinic, patients who presented in normal sinus rhythm for valve surgery had only a 5% incidence of late AF.3 Thus, prophylactic AF surgery is not recommended. In patients who had AF less than three months, all patients were cured of their arrhythmia with mitral valve repair alone. However, in patients who presented with chronic AF of greater than six months duration, 80% of patients remained in AF after surgery. It is in this group that AF surgery has its most significant role.
The effectiveness of the full Cox-Maze lesion set in patients with mitral valve disease has been well established.4 At Washington University, we have performed a full Cox-Maze procedure in 98 consecutive patients undergoing mitral valve surgery between January, 1988 and March, 2004. Mean followup in this series has been 4.5 years. The average duration of atrial fibrillation was 5.2 years, with a range of 6 months to 28 years. 41% of the patients were in paroxysmal atrial fibrillation (AF), and the rest of the patients were in either persistent or permanent AF. The operative mortality in this series was 2%. The freedom from atrial fibrillation at 10 years in this cohort of patients was 97%, and there have been no late strokes.
Unfortunately, the traditional cut and sew Maze procedure is time-consuming and technically demanding, and most surgeons did not feel comfortable adding this operation to a mitral valve procedure. In order to simplify the operation, many groups around the world have proposed replacing the surgical incisions with linear lines of ablation. Various energy sources have been used for this purpose, including radiofrequency energy, microwave, laser, ultrasound and cryoablation. Other groups have also proposed simplifying the lesion set, and some have advocated performing only a pulmonary vein isolation.
Recently, we have modified the Cox-Maze III and replaced most of the incisions with bipolar radiofrequency ablation.5,6 This new procedure, the Cox-Maze IV, greatly simplifies the operation, and results in only two atriotomies, one on the right and one on the left atrium. It has decreased the average cross-clamp time by over 30 minutes and now adds only 10-15 minutes to the entire procedure. The freedom from AF with this modified procedure is 92% at 12 months. In contrast, our results in this patient population with a more limited lesion set, pulmonary vein isolation alone, have been poor. In patients with chronic atrial fibrillation, our freedom from atrial fibrillation at late followup in 16 patients has been 40% with a success rate of only 50% in paroxysmal AF, and 33% in permanent AF. It is our feeling that this operation has a minimal role in patients undergoing concomitant valve surgery.
In conclusion, with the use of alternative ablation technology, the Cox-Maze procedure can be safely performed in conjunction with mitral valve surgery. In our present practice, all patients with chronic atrial fibrillation coming for valve surgery are considered for an ablation-assisted Cox-Maze procedure. The role of more limited lesion sets remains to be defined.
References:
1. Bando K, Kasegawa H, Okada Y, Kobayashi J, et al. Impact of preoperative and postoperative atrial fibrillation on outcome after mitral valvuloplasty for nonischemic mitral regurgitation. J Thorac Cardiovasc Surg, 2005, in press.
2. Bando K. Kobayashi J, Hirata M, Satoh T, et al. Early and late stroke after mitral valve replacement with a mechanical prosthesis: Risk factor analysis of a 24-year experience. J Thorac Cardiovasc Surg 2003; 126:358-364.
3. Chua YL, Schaff HV, Orszulak TA, Morris JJ: Outcome of mitral valve repair in patients with preoperative atrial fibrillation. Should the maze procedure be combined with mitral valvuloplasty - J Thorac Cardiovasc Surg 1994;107:408-415.
4. Prasad SM, Maniar HS, Camillo CJ, Schuessler RB, Boineau JR, Sundt TM III, Cox JL, Damiano RJ Jr. The Cox-Maze III procedure for atrial fibrillation: Long-term efficacy in patients undergoing lone versus concomitant procedure. J Thorac Cardiovasc Surg 126:1822-1828, 2003.
5. Damiano RJ Jr, Gaynor SL: Atrial fibrillation ablation during mitral valve surgery using the Atricure device. Operative Techniques in Thoracic and Cardiovascular Surgery. Op Tech Thorac Cardiovasc Surg 9:24-33, 2004.
6. Gaynor SL, Diodato MD, Prasad SM, Ishii Y, Schuessler RB, Bailey MS, Damiano NR, Bloch JB, Damiano RJ Jr.: A prospective, single center clinical trial of a modified Cox-Maze procedure using bipolar radiofrequency ablation. J Thorac Cardiovasc Surg 128:535-542, 2004.
