Ann Thorac Surg 2003;75:1660-1661
© 2003 The Society of Thoracic Surgeons
How to do it
A method for descending thoracic aortic replacement retaining a posterior strip bearing intercostal vessels
James C. Halstead, MA, MRCSa*,
Max Baghai, MRCSa,
Eric Lim, MRCSa,
John J. Dunning, FRCSa,
Stephen R. Large, FRCP, FRCSa
a Department of Cardiothoracic Surgery, Papworth Hospital, Papworth Everard, Cambridge, United Kingdom
Accepted for publication October 17, 2002.
* Address reprint requests to Mr Halstead, 27 Longridge Road, Earl’s Court, London, SW5 9SD, United Kingdom
e-mail: jameschalstead{at}hotmail.com
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Abstract
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Operations for aneurysms of the descending thoracic aorta are still fraught with danger. Spinal cord injury remains a major cause of morbidity. Many therapeutic strategies have been suggested to reduce the incidence of this devastating complication, including reimplantation of intercostal vessels. However, reimplantation of intercostal vessels, both individually or in groups, is time consuming and compounded by the absence of a reliable means of identifying which vessels actually supply the cord. We present a technique that allowed inclusion of all potentially important descending aortic branching vessels into the repair leading to a favorable outcome in a series of patients.
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Introduction
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Intrathoracic aortic aneurysms most commonly form secondary to arteriosclerosis, chronic dissection, or connective tissue disease. Aneurysms affecting the descending aorta present with local symptoms, dissection, distal embolization, or rupture. A significant proportion of such aneurysms are detected on incidental investigations. Although the incidence and natural history of these aneurysms is not as well documented as for infrarenal aortic aneurysms, most surgeons advocate surgical intervention for dilatation greater than twice normal size or 5 cm in diameter. Spinal cord morbidity is a feared surgical complication occurring in approximately 10% of operations involving the distal descending thoracic aorta, increasing to 30% for thoracoabdominal aneurysm repair [1]. Failure to restore spinal cord blood supply, reperfusion injury, and the duration of ischemia are established risk factors [2]. Reimplantation of critical intercostal vessels is important in avoiding spinal cord ischemia. The variability in the level of essential blood supply has led some to advocate total intercostal reimplanation [3]. We present a technique that allows complete replacement of the aneurysmal portion of the aorta with preservation of a large number of intercostal vessels. This surgical technique has been used in descending thoracic aortic replacement for both atherosclerotic aneurysms and chronic dissections.
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Technique
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The anesthetized patient is positioned in the right lateral position with the patient intubated with a double-lumen endotracheal tube. First, the left femoral artery is exposed and prepared for cannulation. All aneurysms of the descending thoracic aorta that involve its proximal portion are approached through a left posterolateral thoracotomy in the fifth intercostal space. The aneurysm undergoes minimal manipulation before the institution of cardiopulmonary bypass, which is accomplished through pulmonary arterial drainage and ascending aortic return. Cooling to 30°C is undertaken while the aneurysm is mobilized and adherent lung is released. The proximal and distal cross-clamps are placed simultaneously to normal-caliber aorta. Once clamped, lower body perfusion is provided, through a Y-line from the main arterial perfusion catheter into the left femoral artery. Next, the aorta is incised, and any thrombus or dissection flaps are excised. A posterior strip of aorta containing the intercostal artery ostia is fashioned (Fig 1).
Its proximal extent reaches above all potentially significant vessels. An appropriately sized prosthetic tube graft is selected and, after being cut to length, a longitudinal strip is removed so that the graft conforms to the residual aortic tissue. The graft is placed with a single continuous suture line (Fig 2).
We have not needed to use circulatory arrest during anastomosis of the graft to the proximal neck of the aneurysm. We have not routinely used cerebrospinal fluid pressure monitoring or drainage during these procedures.
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Fig 1. The aneurysm has been resected showing the prepared posterior strip of aorta bearing intercostal vessel ostia.
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From January 1996 to June 2001, 7 patients with symptomatic atherosclerotic or dissection-related aneurysms were treated using this technique. We completely resected the aneurysmal portion of the descending thoracic aorta without any operative deaths or spinal complications. Although this technique does involve the construction of a long continuous anastomosis, in all cases we were able to restore spinal cord perfusion within 30 minutes of the application of the aortic clamps (mean, 23 minutes; range, 17 to 28 minutes).
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Comment
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Many therapeutic options and surgical strategies have been attempted to reduce the rate of spinal cord damage in operations on the descending thoracic aorta. In addition to intercostal artery reimplantation, these have included the use of hypothermic cardiopulmonary bypass, drainage of cerebrospinal fluid, distal aortic perfusion, local cooling of the spinal cord, pharmacologic agents, and the monitoring of somatosensory evoked potentials [4–6].
Intercostal reimplantation is important, because in the lower thoracic and upper lumbar regions those arteries give rise to radicular arteries large enough to reach the anterior median sulcus of the spinal cord, where they anastomose with the anterior spinal artery. The largest of these, the so-called arteria radicularis magna, is inconsistent in its position and importance, but typically arises from the lower thoracic or upper lumbar aorta and may be essential for the lower two thirds of the cord. The central rami of the anterior spinal artery supply the ventral gray column, part of the dorsal column, and neighboring white matter, including long motor tracts. The posterior spinal arteries are paired and have a richer collateral supply. This provides relative protection to the posterior third of the cord.
In the clinical setting, several authors have advocated the reimplantation of intercostals to preserve this source of spinal cord blood supply. Obviously, if they are individually anastomosed to the replacement aortic graft this would prolong cross-clamp time, which is correlated with adverse neurologic outcome. Excellent results have been obtained with no reimplantation in a large series, although distal suture lines were fashioned obliquely in attempts to retain more intercostal vessels [7]. The technique reported provides an opportunity to decrease the metabolic requirements of the ischemic cord through cooling and to permanently preserve the blood supply through the retention of all intercostal vessels. This is achieved without having to anastomose them separately, and so the anastomosis can be completed in an acceptable time frame. Moreover, the posteromedial aortic tissue between the ostia at any given level is never aneurysmal, because of the relative fixity to surrounding tissues, and so its retention should not expose the patient to a higher risk of subsequent aneurysm formation.
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References
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- Estrera A.L., Miller C.C., 3rd, Huynh T.T., Porat E., Safi H.J. Neurological outcome after thoracic and thoracoabdominal aortic aneurysm repair. Ann Thorac Surg 2001;72(4):1225-1230.[Abstract/Free Full Text]
- Wan I.Y., Angelini G.D., Bryan A.J., Ryder I., Underwood M.J. Prevention of spinal cord ischaemia during descending thoracic and thoracoabdominal aortic surgery. Eur J Cardiothorac Surg 2001;19(2):203-213.[Abstract/Free Full Text]
- Usui A., Hosokawa H., Kawamura M., Hibi M. Total intercostal artery reimplantation for descending thoracic aortic replacement. Ann Thorac Surg 1996;62(5):1523-1525.[Abstract/Free Full Text]
- Kouchoukos N.T., Rokkas C.K. Hypothermic cardiopulmonary bypass for spinal cord protection: rationale and clinical results. Ann Thorac Surg 1999;67(6):1940-1942.[Abstract/Free Full Text]
- Estrera A.L., Rubenstein F.S., Miller C.C., 3rd, Huynh T.T., Letsou G.V., Safi H.J. Descending thoracic aortic aneurysm: surgical approach and treatment using the adjuncts cerebrospinal fluid drainage and distal aortic perfusion. Ann Thorac Surg 2001;72(2):481-486.[Abstract/Free Full Text]
- Guerit J.M., Witdoeckt C., Verhelst R., Matta A.J., Jacquet L.M., Dion R.A. Sensitivity, specificity and surgical impact of somatosensory evoked potentials in descending aortic surgery. Ann Thorac Surg 1999;67(6):1943-1946.[Abstract/Free Full Text]
- Cooley D.A., Golino A., Frazier O.H. Single-clamp technique for aneurysms of the descending thoracic aorta: report of 132 consecutive cases. Eur J Cardiothorac Surg 2000;18(2):162-167.[Abstract/Free Full Text]
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