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(November 10, 2006). doi:10.1510/mmcts.2006.001941 Copyright © 2006 European Association for Cardio-thoracic Surgery Procedure The Quick simple clamping technique for the repair of descending aortic aneurysmDepartment of Cardiovascular Surgery, Centro Cardiologico Monzino IRCCS, University of Milan, Via Parea 4, 20138 Milan, Italy * Corresponding author: * Tel.: +39 02 58002321; fax: +39 02 58011194 E-mail: paolo.biglioli{at}unimi.it and paolo.biglioli{at}ccfm.it
The surgical treatment for thoracic and thoraco-abdominal aortic aneurysms still remains a challenge for the surgeon, as it can be complicated by paraplegia. Several techniques were developed in order to decrease the risk of paraplegia. We describe a surgical variation of the ‘clamp and sew’ technique, named ‘Quick simple clamping’ technique, that we adopted starting in 1995. In our experience, it has allowed us to eliminate paraplegia. This technique was developed on the basis of anatomical, patho-physiological and fluid-dynamic studies which demonstrated that the anterior spinal artery (ASA) is not interrupted, the arteria radicularis magna is not a terminal artery and the sacrifice of intercostal arteries does not lead to an increasing risk of spinal cord ischemia.
Key Words: Descending thoracic aorta • Aortic aneurysm • Surgery • Paraplegia
The treatment for descending aortic aneurysms still remains a challenge for the cardiovascular surgeon. Despite the standardization of surgical techniques and the important advances in technology, this surgery is still characterized by a high rate of complications during the perioperative period. Paraplegia remains the main complication of surgical procedures on the thoracic aorta [1, 2]. The risk of paraplegia after surgical procedures on the thoracic aorta is determined by the interaction of several factors, namely the aortic cross-clamping time, the extension of the replaced aortic segment and the exclusion of critical intercostal arteries [3, 4]. Different protective techniques were proposed to reduce the risk of spinal cord injury, including short aortic cross-clamping time, intercostal artery reimplantation, distal aortic perfusion, cerebrospinal fluid drainage, drugs and cardiopulmonary bypass with or without hypothermia [5]. From the beginning of the 1980s, we developed an integrated research–clinical program with the aim of understanding the anatomical features of the spinal cord circulation and the patho-physiological mechanisms on the basis of paraplegia. Starting from this evolving experience we developed a variation of the ‘clamp and sew’ technique [1], named ‘Quick simple clamping’ technique [6]. Its peculiar characteristics are:
The anatomical bases of the ‘Quick simple clamping’ technique: the continuity of the anterior spinal artery This open debate leads to clinical consequences as it can influence the surgical strategies that should be adopted to prevent paraplegia in patients who undergo descending aortic replacement. The hypothesis that the ASA is a non-continuous vessel, and the ARM is a terminal artery, led to the development of several surgical techniques such as intercostal and lumbar vessel reimplantation and distal aortic perfusion. Our anatomical studies pointed out that ASA is constantly an uninterrupted vessel receiving blood supply from the vertebral arteries, the ARM and other anterior radiculo-medullary arteries. All these vessels are interconnected in a collateral network over the entire vertebral column [7, 8]. The continuity of the ASA makes the ARM not a terminal artery per se. The prevalent origin of the ARM is from lumbar arteries. Anatomical evidence of an extensive collateral network along the spinal cord may justify the sacrifice of intercostal arteries during descending thoracic aortic aneurysm repair without increasing the risk of paraplegia. The same conclusions were reported by Griepp et al., who confirmed that spinal cord blood supply is unlikely to depend on a single artery or even on a small number of critical intersegmental vessels [11] (Schematics 1 and 2).
These anatomical features (the continuity of the ASA, the non-terminality of the ARM and the extensive collateral network along the spinal cord) can justify the systematic sacrifice of the posterior intercostal arteries during isolated repair of the descending thoracic aorta. The presence of this network guarantees the spinal cord blood flow even after resection of the intercostal arteries (Video 1).
After the induction of general anesthesia, a catheter is inserted between the third and fourth lumbar vertebral space to measure the cerebrospinal pressure and for drainage, if necessary. The strict monitoring of systemic pressure, venous pressure and cerebrospinal pressure represents one of the main topics of the technique. With the patient positioned in a right lateral decubitus position, a left posterolateral thoracotomy is performed. We generally perform a double thoracotomy (third intercostal space and sixth intercostal space) with a single cutaneous incision. It permits to clearly expose the aortic aneurysm and the proximal and distal neck. When the aneurysm's extension is limited, we perform a single thoracotomy (third space). We adopted two different surgical techniques depending on the aneurysm's characteristics.
Technique adopted when aneurysm is easy to isolate The aneurysm is isolated in its proximal and ventral portion. All intercostal vessels are occluded with large clips and sectioned. Starting from the anatomical findings exposed above, the intercostal vessels are not reimplanted in order to decrease the aortic cross-clamping time, decrease bleeding and increase collateral blood flow (Video 2).
After the second thoracotomy, the distal part of the aneurysm is isolated progressively in the same fashion. Following this, the aneurysm is completely mobilized, all intercostal arteries are sectioned and the proximal and distal necks are isolated for the aortic cross-clamping (Video 3).
The aorta is cross-clamped, the aneurysm is removed and a right-size prosthesis is anastomosed to the aorta with a continuous suture. During suturing, it is important that the graft is positioned inside the aorta. The anastomoses are generally wrapped and reinforced by means of biological glue (Videos 4 and 5).
Technique adopted when aneurysm is difficult to isolate or involves a large extent of the thoracic aorta In these cases, only the proximal and distal necks of the aneurysm are isolated, while the aneurysm is not removed after aortic cross-clamping (Video 6).
After the thoracotomy in the third intercostal space, the superior lobe of the left lung is separated from the anterior part of the aneurysm and the proximal part of the aneurysm is mobilized (Video 7).
The second thoracotomy is performed and the distal neck is isolated in the same fashion, occluding and sectioning the intercostal arteries with large clips. The central part of the aneurysm is not isolated (Video 8).
The aneurysm's proximal neck is cross-clamped with two clamps. The proximal anastomosis is performed between two clamps. The distal neck of the aneurysm is not clamped at this time (Video 9).
The aneurysm's distal neck is cross-clamped in the same fashion in order to exclude the aneurysm and avoid bleeding from the intercostal arteries which originated from the non-isolated part of the aneurysm. The proximal and distal anastomoses are performed between two clamps (Video 10).
After the circulation is restored, the aneurysm is opened and the intercostal arteries are sutured from the inside of the aneurysm. Finally, the anastomoses are wrapped and reinforced with biological glue. Even the prosthesis is wrapped with the aneurysmatic wall (Video 11).
Our first experience was previously described [6]. No patients developed perioperative paraplegia or paraparesis. Long-term survival was significantly higher in patients treated with the ‘Quick simple clamping’ technique. At multivariate logistic regression analysis, aortic cross-clamping time was found to be an independent predictor of in-hospital mortality [6]. These data have been confirmed by our following experiences. By December 2005, the ‘Quick simple clamping’ technique was globally adopted in 181 patients with descending thoracic aortic aneurysm. Perioperative (30-days) mortality was 3.9% (7 patients). The cause of death was multi-organ failure in 4 patients, surgical infection in 1, stroke in 2. Perioperative morbidity was 11.0% (20 patients). No one experienced paraplegia, while transient paraparesis was observed in 4 cases (2.2%). Eight patients had acute renal failure, 5 had acute respiratory failure and 3 requested reoperation for bleeding.
The ‘Quick simple clamping’ technique is a variation to the ‘clamp and sew’ technique that we adopted, starting in 1995, for the treatment of descending thoracic aneurysms. It was developed on the basis of anatomical studies and biological considerations. The demonstration that the ASA is not interrupted and the ARM is not a terminal artery led us to consider unnecessary the reimplantation of the intercostal vessels. We need to underline that it would be prudent to preserve the lumbar arteries when an extensive thoracoabdominal aortic aneurysm is planned. Previous or concomitant abdominal aortic repair increases the risk of paraplegia in the case of descending thoracic aortic repair. We can hypothesize that systematic occlusion of all intercostal and lumbar arteries leads to a marginal spinal cord circulation and ischemia [8]. For the same reason, in our opinion the reimplantation of intercostal arteries can be useful only if a previous abdominal aortic repair was performed [8]. The cross-clamping time is an important factor influencing the risk of paraplegia [12,13,14]. It could be related to the steal phenomenon in the excluded part of the aorta during the cross-clamping time. Stating that ASA is a continuous artery and ARM is not a terminal artery, during the cross-clamping time the blood circulation can be rerouted from the ASA to the distal part of the aorta, worsening the spinal cord ischemia [8] if ischemia time is longer than 20–30 min.
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