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J Thorac Cardiovasc Surg 2005;129:1207-1208
© 2005 The American Association for Thoracic Surgery
Letters to the Editor |
First Department of Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan
To the Editor:
We read with great interest the article by Kouchoukos and Masetti1 titled "Total Aortic Arch Replacement With a Branched Graft and Limited Circulatory Arrest of the Brain," published in the August 2004 issue of the Journal. The article describes the authors’ experience with total arch replacement (TAR) for various pathologic conditions of the aortic arch (except acute type A dissection) with branched aortic prostheses and unilateral antegrade cerebral perfusion through the right axillary artery. The article generally attests to the appropriateness of the use of branched aortic prosthesis and antegrade brain perfusion for TAR surgery. Since 1986, we have been routinely using antegrade selective cerebral perfusion and a branched aortic graft for TAR procedures.2 The results we have achieved through the years give us reason to be convinced that the use of the branched grafts rather than tube prostheses and antegrade brain perfusion for cerebral protection represent the optimum surgical strategy for this complex surgery.3 The branched aortic graft allows easier bleeding control at arch-vessel anastomotic sites and has been found to be associated with a lower incidence of postoperative strokes, making it a better option than tube graft. Similarly, selective cerebral perfusion, when used to its full potential, basically relieves the surgeon from the psychologic burden of a limited brain protection time and thus allows meticulous arch repair. It is good to see that more and more aortic surgeons all over the world are realizing the advantages of these techniques, which once were thought to be cumbersome.
Concerns have been expressed by some authorities, including Kouchoukos and Masetti,1 regarding the potential hazards of direct cannulation of the arch vessels in the form of cerebral embolization of air or debris. In our experience, such concerns are mostly unwarranted. Our arch vessel cannulation technique involves transecting the arch vessels distant from their origins, at sites where they are free from atherosclerotic debris or dissection, and then cannulating them under direct vision. Blood flow through the arch vessels is continued until just before the cannulation with the patient in a Trendelenburg position. These measures help to avoid air embolism.4
For patients with acute type A aortic dissection and degenerative arch aneurysm requiring TAR in whom the ascending aorta is not suitable for arterial inflow because of atheromas, we first cannulate the right axillary artery through an 8-mm graft attached to it in an end-to-side fashion. Then, after cooling of the patient with cardiopulmonary bypass and initiation of circulatory arrest, the left common carotid artery is also cannulated, ensuring bihemispheric antegrade brain perfusion during the arch repair. Although some authors have advocated the use of unilateral cerebral perfusion for aortic arch replacement surgery,5 our experience with that technique is limited to cases requiring a less radical aortic repair, such as ascending aortic replacement with open distal anastomosis or hemiarch replacement. In 10 patients (acute type A dissection n = 7, chronic type A dissection n = 1, degenerative arch aneurysm n = 1, and mycotic arch aneurysm n = 1), hemiarch replacement was carried out with right axillary artery perfusion as the only brain protection method under moderate hypothermic circulatory arrest (mean rectal and tympanic temperatures 22.3°C ± 1.6°C and 16.9°C ± 2.4°C, respectively). Mean perfusion flow rate and pressure were 5.1 ± 1.9 mL/(kg·min) and 27.8 ± 9.4 mm Hg, respectively. Mean selective cerebral perfusion time was 35.8 ± 14.1 minutes. There was 1 postoperative death from an unrelated cause, and no temporary or permanent neurologic deficits were seen. Although this represents a satisfactory outcome, routine adoption of unilateral brain perfusion for TAR, which usually requires a longer brain protection, may not always be equally successful. If it has to be done, however, a more substantial lowering of core body temperature might be helpful.
The arch-first strategy described by Kouchoukos and Masetti1 may not always be advantageous. This is because it makes the distal aortic anastomosis more difficult, with the bulky aortic prosthesis coming to obscure much of the operative field. Moreover, deep hypothermia still needs to be continued during the distal anastomosis. As Kouchoukos and Masetti1 say, a bilateral anterior thoracotomy will facilitate the distal anastomosis in these situations.
Finally, we think that despite the small number of patients studied, Kouchoukos and Masetti1 deserve credit for the results they obtained with unilateral brain perfusion for TAR. However, preoperative assessment of the cerebral circulation as well as careful selection of cases should always be considered before deciding on a brain protection strategy.
References
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