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Ann Thorac Surg 2004;78:851-852
© 2004 The Society of Thoracic Surgeons
Section of Cardiothoracic Surgery, and Section of Magnetic Resonance Imaging, Yale University School of Medicine, 333 Cedar St New Haven, CT 06510, USA
john.elefteriades{at}yale.edu
jeffrey.weinreb{at}yale.edu
There has been great difference of opinion regarding the importance of reimplanting intercostal arteries. Some aortic surgeons believe this is essential, while others, such as Griepp and colleagues [1], believe that reimplantation makes no clinical difference in paraplegia rates. This dichotomy is based on two schools of thought:
For those who believe in the reimplantation of crucial spinal arteries, the identification of the spinal artery or arteries that supply the lower spinal cord assumes critical importance. To achieve reliable, noninvasive identification of these vessels has been somewhat of a Holy Grail in aortic surgery.
Contrast angiography has been the gold standard for the identification of the spinal artery, albeit imperfect, with failures and toxicities, including iatrogenic paraplegia from the contrast media injections. This report by Kawaharada and colleagues certainly gains one's attention, because it provides apparently accurate identification of the spinal arteries in a previously unprecedented high proportion (83%) of patients studied—and does so noninvasively, by means of magnetic resonance imaging (MRI).
The main issue concerning this report is whether it will prove to be reproducible by others. We are given little information about the patients excluded from the study. Could it be that patients likely to image poorly, for example, because of obesity, were excluded a priori? Could there be physical characteristics of the Japanese population which will render these surprisingly good imaging results nonreproducible in Western environments?
We hope that these results will indeed prove reproducible, and that routine MRI imaging of the spinal artery becomes a reality. Regardless of one's school of thought, it certainly does not hurt to know the location of the intercostal arteries that provide important blood flow to the spinal cord. Such knowledge can help in many ways. The segment bearing the identified spinal vessel may be spared resection if the aorta is not severely dilated; residual mild dilatation is preferable to paraplegia. Alternatively, a bevel in the resection may preserve the crucial vessel yet still extirpate the neighboring aneurysmal tissue. Knowledge of the location of the spinal vessel may aid in intelligent placement of the lower cross-clamp, so that the vital vessel is not excluded from distal perfusion by the left atrial-femoral artery bypass set-up. And, for most surgeons who believe strongly in reimplantation, intelligent selection of implanted vessel(s) can be made—in contradistinction to the "roulette wheel" guesswork implicit without prior vessel identification.
Of course, identification of the spinal artery does not equate with good neurologic outcome. There is still the issue of duration of cross-clamping. Identifying in the surgical field the vessels numbered by the radiologist is far from trivial, and reimplantation has risks, including hemorrhage from the side-to-side anastomosis to the main aortic graft. Traction to get to bleeders in this anastomosis can easily lead to the tearing of friable tissue and necessitate the resumption of cross-clamping, with net overall harm.
The dangers inherent in the side-to-side inclusion technique have led our group [2] and others [3] to adopt a "cobra head" style of intercostal reattachment with a separate graft, which allows easy, unimpaired access to the anastomosis without jeopardizing the main graft. Kawaharada and colleagues discuss in this paper their rationale for using a similar technique for intercostal attachment. We have recently developed a prefabricated graft specifically for this purpose, which incorporates a flanged distal end for easy, secure suturing over the pertinent intercostal arteries.
We certainly hope that the results presented in this paper will prove reproducible. If this should be the case, then it is likely that the incidence of the dreaded postoperative paraplegia after aortic surgery can be reduced. If so, this paper may become a landmark clinical report in aortic surgery.
| Dr Weinreb discloses that he has a financial relationship with Berlex Laboratories.
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References
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