Ann Thorac Surg 2006;82:1687
© 2006 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Invited commentary
Mirko Doss, MD
Department of Thoracic and Cardiovascular Surgery, J.W. Goethe University Frankfurt am Main, Theodor Stern Kai 7, Frankfurt am Main, 60599 Germany
(Email: mirkodoss{at}aol.com).
In this report [1], the authors describe their experience with spinal cord protective measures, known from conventional aortic surgery, in the setting of thoracoabdominal aortic stent grafting. The incidence of spinal cord ischemia, resulting in paraplegia, after stent graft placement in the descending thoracic aorta is a rare event. However, patients who had previous abdominal aortic aneurysm repair followed by endovascular stent graft placement in the thoracic aorta are at an increased risk of having paraplegia develop. The same holds true for patients that have combined stent grafting of the thoracic and abdominal aorta. It seems that in this subset of patients, neurophysiologic monitoring and spinal cord protective measures as implemented by the authors are valuable tools to reduce the risk of paraplegia. There are two aspects of this report that merit detailed comment as they affect perioperative paraplegia in different ways.
The use of intraoperative neurophysiologic monitoring, using somatosensory and motor evoked potentials to detect spinal cord ischemia and help prevent paraplegia, has been successfully implemented in open thoracoabdominal aortic surgery. Both types of evoked potentials target different spinal cord structures with a different blood supply. Therefore many groups use a combination of both methods as the authors have done in their report. Interestingly they have shown that spinal cord ischemia occurs during endovascular stent grafting, which is not a surprising finding, considering that a significant number of intercostal and lumbar arteries are covered by the stent graft. It would have been intriguing to know, if in patients that received two stent grafts, spinal cord ischemia occurred after placement of the first or second stent graft and whether it was more common when an abdominal stent graft was placed in combination with a thoracic one.
The second important concept in this report is the implementation of spinal cord protective measures. Cerebrospinal fluid drainage is being used by many centers to prevent perioperative and delayed paraplegia. With regard to ensuring adequate spinal cord perfusion, endovascular stent grafting is distinctly different from open repair in that it always leaves segmental arteries to the spinal cord uncovered in the region of the visceral arteries. Therefore a collateral blood supply is always preserved, unless previous surgery of the abdominal aorta has occurred. Second, it is our experience that during stent graft procedures, hypotension rarely presents a problem. Usually we have to counteract hypertension to enable safe stent graft placement.
As an additional treatment option in type B dissections, fenestration of the false lumen can restore blood flow to selected malperfused segments and should be considered. In summary, both neurophysiologic monitoring and spinal cord protective measures positively impact neurologic outcome after open aortic surgery and are thus attractive concepts for thoracoabdominal stent grafting as well. The authors' contention that these steps offer an effective prevention of adverse events with minimal complications, although based on a small patient group, certainly merits further evaluation in a larger cohort.
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References
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- Weigang E, Hartert M, Siegenthaler MP, et al. Perioperative management to improve neurologic outcome in thoracic or thoracoabdominal aortic stent-grafting Ann Thorac Surg 2006;82:1679-1687.[Abstract/Free Full Text]
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