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Ann Thorac Surg 2005;79:389
© 2005 The Society of Thoracic Surgeons
Department of Cardiothoracic Surgery, National Heart Center, 17 Third Hospital Ave, Mistri Wing, Singapore 168 752, Singapore
vslad{at}rediffmail.com
vidlad{at}yahoo.com
To the Editor:
I read with interest the article on the atrial compartment operation by Lo and associates [1] and congratulate them on their excellent work. The biggest virtues of this operation are its simplicity, its conservative nature, and its good control of arrhythmias.
Isolation of the atrium has been achieved by the "corridor" procedure [2] and by the left atrial (LA) isolation procedure [3]. Atrial compartment operations, in most instances, allow connection between the right and left atria [4]. The perplexing issue is "why in the rest, the left atrium, gets isolated?" I believe that extending the posterior end of the LA incision to the mitral annulus occasionally amounts to overzealous dissection of the fat pad in the posterior left atrioventricular groove, thereby uncovering the terminal end of the coronary sinus. A cryolesion at this end, in effect, leads to a cryolesion of an empty coronary sinus, which may ablate fibers behind the sinus. Furthermore, this injury can perpetuate fibrosis in the terminal portion of the sinus and lead to complete LA isolation in some instances over time. In their maze III modification, Cox and associates [5] ensure complete LA isolation and interruption of the fibers around the coronary sinus in a similar manner. Therefore, I believe that limiting the posterior end of the LA incision by 1.5 to 2 cm and using a cryolesion on the endocardial surface to complete the LA incision would prevent the above.
In the study by Lo and co-workers, 87.5% of the patients had attained sinus rhythm at the 1-year follow-up, and in most instances, the connections between the atria were preserved. I believe complete atrial isolation, as achieved in the corridor procedure or LA isolation, is not essential for restoring sinus rhythm. In fact, maintaining the connections between the atria contributes to the preservation of atrial mechanical function, and this, in turn, might translate into a low risk of thromboembolism. The issue of concern, however, is the high incidence of postoperative recurrent atrial fibrillation and flutter and the associated risk of thromboembolism. On the basis of the experience of my colleagues and myself [6] with 84 patients who underwent a modified maze procedure using radiofrequency coagulation and cryoablation, I believe it is prudent to administer amiodarone hydrochloride for 3 weeks postoperatively to prevent early recurrence of these arrhythmias, which can be caused by mechanisms other than chronic atrial fibrillation. Reentry around the superior vena cava [7] and a trigger stimulus from the isthmus between the inferior vena cava and the posterior tricuspid annulus [3] are two important mechanisms for atrial flutter. A modified right atrial incision that blocks these two pathways may prevent this problem.
The optimal lesion set has not yet been defined, although there appears little difference in outcome produced by minor variations. In the near future it is likely that new probes and thoracoscopic staplers will facilitate off-pump epicardial ablation through thoracoscopy. Procedures such as the atrial compartment operation, which involve simpler and fewer incisions, provide a necessary impetus for developing these techniques.
References
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