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Eur J Cardiothorac Surg 2006;29:425-426
© 2006 Elsevier Science NL
Letters to the Editor |
a University of Illinois, 614-G Laflin, Chicago, IL 60607, USA
b Department of Health Technology Assessment, ECRI, Plymouth Meeting, PA, USA
Received 9 December 2005; accepted 12 December 2005.
* Corresponding author. Tel.: +1 312 421 8508; fax: +1 312 404 8710. (Email: Jeffrey01{at}mac.com).
Key Words: Maze procedure • Atrial fibrillation • Randomized controlled trials
We thank Dr Mishra for his comments regarding our recent publication [1], which presented a statistical summary of the results of controlled trials evaluating the Cox-Maze III and its various modifications. We agree that publication bias could be another shortcoming of the maze literature. However, more randomized trials would be needed to allow testing which could determine whether publication bias was present and whether it was large enough to affect the findings of a meta-analysis.
The decision to include the various energy sources in our systematic review was based on the fundamental concept that they can produce transmural atrial lesions. These transmural lesions can ablate the atrial fibrillation pacemakers around the pulmonary vein ostia as well as interrupt the macro re-entry circuits. Although current understanding questions role of transmurality [2], it remains one of the basic foundations of arrhythmia ablation [3,4]. Sophisticated mapping techniques will be necessary to guide ablation strategies and control its efficacy in the future.
We expected that studies using radiofrequency ablation would have a lower post-operative bleeding rate than studies using surgical incisions. For this reason, we did not combine all of the studies in our meta-analysis of post-operative bleeding. Instead, we separately meta-analyzed studies using radiofrequency ablation and studies using surgical incisions for this one outcome. As expected, we found that the maze procedure had a higher rate of post-operative bleeding when using surgical incisions. However, for all other outcomes we combined studies using different procedures because we had no a priori reason to believe that the different techniques would lead to differences in these outcomes. Indeed, our meta-analyses of all other outcomes found no statistically significant heterogeneity, indicating that differences in procedure did not lead to differences in these outcomes.
An outstanding question remains: Does eradication of atrial fibrillation prevent its associated complications in the medically refractory population? This question is hard to answer at this time. The answer may depend on whether structural changes in the heart follow atrial fibrillation or whether atrial fibrillation followed the structural changes (e.g. mitral valve incompetence).
The reported success rate of the maze (conversion to sinus rhythm) is highest in patients with mitral valve incompetence, suggesting that treatment of an arrhythmia associated with structural changes has a better outcome with surgery than medical therapy. The latter may be more appropriate for lone atrial fibrillation. We await further data in this field and continue to recommend the maze procedure for conversion to sinus rhythm when operating on structural changes such as mitral valve incompetence.
The maze procedure appears to be reasonably benign when used as an adjunct in patients receiving mitral valve surgery. An important unanswered question is whether patients receiving a prosthetic valve will gain an additional benefit from maze, since, as Dr Mishra pointed out, these patients will remain on anticoagulants. The major concern from our study was the non-robust finding of a trend towards increased use of pacemakers when using the maze procedure, and a higher rate of post-operative bleeding when using surgical incisions instead of radiofrequency ablation. There was also a non-significant trend toward higher mortality with the maze procedure, although more studies will be needed to determine whether this trend is real. We patiently await further well-designed randomized trials evaluating the maze procedure to confirm and extend the findings of our study. Future trials should place particular emphasis on outcomes such as stroke, quality of life and survival, and should compare results in patients receiving mitral valve repair versus mitral valve replacement.
References
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