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Ann Thorac Surg 1995;60:364
© 1995 The Society of Thoracic Surgeons

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Invited Commentary

Invited Commentary

Department of Thoracic and Cardiovascular Surgery, The Cleveland Clinic Foundation, One Clinic Center, 9500 Euclid Ave, F-25, Cleveland, OH 44195-5066

See also page 361.

Cox's maze procedure is being applied more frequently by cardiac surgeons, in particular for patients undergoing operations for mitral valve disease. Although the operation initially was used in patients with only atrial fibrillation, referrals for operative treatment in this patient group are unusual due to the alternative use of radiofrequency modification of the atrioventricular node with insertion of a permanent pacemaker by the electrophysiologist. Also encouraging early attempts to recreate the maze incisions using catheter-based radiofrequency ablation have given many electrophysiologists a ``wait and see'' attitude before referring patients for open heart operation. Because some patients referred for mitral valve operation have chronic atrial fibrillation with dilated atria (and, therefore, are unlikely to return to sinus rhythm despite a successful mitral valve operation), and because the left atrial incisions to expose the mitral valve are similar to some of the atrial incisions used in the maze operation (and therefore part of the maze operation already is started), it is appropriate to combine mitral valve operations with the maze procedure in a select patient group.

The report by Gregori and associates reports on the treatment of 20 patients who underwent mitral valve operation with the original ``maze I'' procedure but with the technical modification of omitting the cryolesions that typically are placed at the coronary sinus and the mitral and tricuspid valve annuli. At first, Gregori and associates omitted this step because the special equipment and cryoprobe were not available in their institution. They continued with this approach because of the good early results they had obtained. Theoretically, microscopic bundles of atrial fibers adjacent to these structures can sustain reentry circuits if they are not either surgically interrupted (by cutting), or destroyed with cryolesions [1]. However, persistent atrial fibrillation developed in only 1 of the 20 patients after their procedure without the use of cryoablation, attesting to the general success of this approach. These results are encouraging and indicate that for those institutions without the capability of creating cryolesions wide surgical dissection around these structures will still provide good results. Also, Gregori and associates' results are similar to ours in that the addition of the maze procedure adds approximately 30 minutes of cross-clamp time and 60 minutes of cardiopulmonary bypass time to what would otherwise be expected with just a mitral valve operation. Morbidity from adding the maze procedure has been low, especially for patients who undergo the ``maze III'' procedure and who have an earlier return of sinus node function [2].

More important than the electrocardiographic appearance of sinus rhythm is the functional return of atrial contraction. Atrial systole should improve hemodynamic function (via restoration of ``atrial kick'') and reduce the risk of atrial stasis with thrombus formation and embolization. Return of atrial contraction has been shown in most maze patients, albeit not to normal levels, and is more pronounced in the right than left atria [3--5]. Itoh and colleagues found that after the maze operation (I and II) with mitral valve operation left atrial contraction ``was detectable but incomplete in the elderly.'' With only 10 patients, and a maximum age of 67 years, it is difficult to draw conclusions from Itoh and associates' report. In addition, the methodology of comparing the maze/mitral valve operation patients with 7 ``control'' patients having had coronary bypass can provide many errors. Eight patients had prosthetic mitral valve replacements and therefore are expected to have higher E waves (from higher transmitral gradients, which are not reported in the article); therefore, calculated A/E ratios and atrial filling fraction will appear lower than for patients with native valves (the control group). Therefore, comparisons with age-matched post--coronary artery bypass grafting controls are meaningless. The most important information in this report is that ``evidence of left atrial active contraction was detected in 9 of 10 patients in the maze group.'' Other published and ongoing studies indicate that the quantity of atrial contraction may not be normal but it is most likely better for the maze patients than the alternative: chronic atrial fibrillation without atrial contraction.

References

1. Cox JL. The surgical treatment of atrial fibrillation. J Thorac Cardiovasc Surg 1991;101:584–92.[Abstract]
2. Cox JL, Boineau JP, Schuessler RB, Kater KM, Lappas DG. From fisherman to fibrillation: an unbroken line of progress. Ann Thorac Surg 1994;58:1269–73.[Abstract]
3. Feinberg MS, Waggoner AD, Kater KM, Cox JL, Lindsay BD, Perez JE. Restoration of atrial function after the maze procedure for patients with atrial fibrillation. Assessment by Doppler echocardiography. Circulation 1994;90(Suppl 2):285–92.
4. Feinberg MS, Waggoner AD, Kater KM, Cox JL, Perez JE. Echocardiographic automatic boundary detection to measure left atrial function after the maze procedure. J Am Soc Echocardiogr 1995;8:139–48.[Medline]
5. Klein AL, Albirini A, Garcia M, et al. Left and right atrial systolic function after the maze procedure: a long-term echo-Doppler follow-up study. J Am Coll Cardiol 1995;25(Suppl):351A.

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Patrick M. McCarthy Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by McCarthy, P. M. Articles by Scalia, G. M. Search for Related Content PubMed Articles by McCarthy, P. M. Articles by Scalia, G. M. Related Collections Related Article