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Ann Thorac Surg 1995;60:2-6
© 1995 The Society of Thoracic Surgeons
Division of Thoracic and Cardiovascular Surgery, Surgical Center, Hannover Medical School, Hannover, Germany
Abstract
Background. In aortic replacement, the ``elephant trunk technique'' uses surplus intravascular graft length to facilitate subsequent operations on the downstream aorta. This study investigates the experience with the technique since its conception by our group.
Methods. Between 1982 and 1994, 80 elephant trunks were implanted in 72 patients. In 40 cases the primary position was in the proximal descending thoracic aorta, extending an aortic arch graft. In 32 instances the elephant trunk was placed in the distal descending thoracic aorta, extending descending aortic replacement. Aortic pathology comprised aneurysms in 22 cases, chronic dissection in 47, and acute dissection in 3. Fourteen patients had Marfan's syndrome.
Results. There was a total of 10 early deaths, 7 of which occurred during the early experience. Subsequent downstream aortic operation was undertaken in 24 patients after a mean interval of 14 months, replacing the descending thoracic aorta in 17 cases and the thoracoabdominal portion in 7 cases. Six patients underwent third-stage procedures. Several technical modifications were developed, helping to ease placement and unfolding of the trunk.
Conclusions. The elephant trunk technique greatly facilitates and at the same time reduces the risk of multiple-stage aortic replacement.
The ``elephant trunk technique'' was first described by our group in 1983 [1]. It was developed to facilitate staged aortic replacement using surplus intravascular graft length. An elephant trunk can be placed within the proximal descending aorta as an extension of a total arch graft (``proximal'' elephant trunk) or in the distal vessel as an extension of a descending thoracic aortic graft (``distal'' elephant trunk). This study reports the experience with and the modifications of the technique over the past 12 years.
Patients and Methods
Operative Technique (Proximal)
There are three modes of inserting an elephant trunk extension of an aortic arch graft. Initially, the end of the arch graft was inserted distally, and the side of the fabric tube then was anastomosed to the origin of the descending aorta with a circular tangential suture [1]. As this was found to be cumbersome with the graft in the way during suturing, we subsequently switched to the technique of invaginating the future trunk part retrogradely into the arch graft. The resulting fold was anastomosed to the aortic wall and the trunk extended antegradely into the descending thoracic aorta immediately before completion of this anastomosis [2] (Fig 1
).
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). From that point the operation proceeds like conventional aortic arch replacement. After thorough deairing of the downstream aorta by resuming retrograde flow, perfusion must be switched to the antegrade direction via a cannula inserted high in the arch graft. This is connected to a Y-piece in the arterial line, which is part of our routine pump circuitry for aortic operations.
Operative Technique (Distal)
When grafting the descending thoracic aorta in anticipation of a subsequent downstream operation, a distal elephant trunk likewise can be inserted. This approach is applicable to any graft-to-descending aortic anastomosis except those made in an oblique fashion to preserve intercostal arteries. Either one or two grafts may be used. In the first variant, a prosthesis is connected to the proximal descending aorta. The downstream end of the graft then is invaginated proximally over the desired trunk length. The distal anastomosis is created between the resulting fold and the transected aorta (Fig 2). Before its completion, extracorporeal circulation is terminated, and the trunk part is extracted and manipulated downstream with forceps. Antegrade flow to the lower part of the body is restored after the final stitches are placed.
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Patients
Between February 1982 and December 1994 a total of 80 elephant trunk procedures was performed in 72 patients. The primary position of the trunk was proximal as an extension of an arch graft in 40 patients. A distal elephant trunk as an extension of a descending aortic prosthesis was inserted in 32 cases. The underlying aortic pathology comprised a megaaorta syndrome in 22 patients, chronic aortic dissection in 47, and acute aortic dissection in 3. Fourteen patients had Marfan's syndrome. In 18 instances an emergency operation on the ascending aorta had preceded the first trunk placement because of acute proximal aortic dissection.
In 24 patients, the elephant trunk procedure was followed by subsequent aortic replacement. A proximal elephant trunk was extended in 17 patients; in 8 cases a second elephant trunk was inserted distally. Thoracoabdominal aortic replacement after distal trunk placement was carried out in 7 patients. Six patients underwent third-stage aortic replacement further downstream. Thus, a total of 120 aortic operations was performed in 72 patients.
Results
There were ten early deaths in the 72 patients operated on (13.8%). Three of these ten early deaths (33.3%) followed a reoperation. If analyzed by aortic pathology, there was a 100% operative mortality rate for the 3 patients operated on as an emergency with acute dissection. All succumbed to neurologic sequelae of their disease, and there was no mortality associated with the trunk technique as such. Four of the 22 patients with aneurysm died early (18.1%), 3 during the period between 1983 and 1987. Two of these patients succumbed to cerebral damage after total arch replacement. Operative mortality was lowest in the large group with chronic dissection, with three deaths in 47 patients (8.5%). All 3 patients had been operated on between 1984 and 1986. Early mortality according to pathology and its development over time are shown in Table 1.
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Operative complications associated with the elephant trunk procedure were encountered in 3 patients. All had undergone total arch replacement for chronic dissection and had development of a significant pressure gradient between the radial and femoral arteries after reestablishment of antegrade perfusion. The underlying problem was entrapment of the trunk in the dissected smaller downstream aortic lumen with lack of an adequate distal reentry, leading to kinking or flattening of the graft. This phenomenon was relieved in all three instances by immediate descending aortic replacement via a lateral thoracotomy, using the elephant trunk.
Although a moderate amount of densely adherent clot frequently is seen during reoperation in the blind aneurysmal pocket surrounding the trunk, no thromboembolic complications have been documented so far by us. In one instance we actually inserted a long elephant trunk into the descending aorta with the intention to thromboexclude an aneurysm. This patient suffered from both unstable angina and a symptomatic descending aortic aneurysm. After quadruple coronary bypass the circulation was arrested and the distal arch opened. A long graft was anastomosed to the proximal descending aorta and allowed to float downstream. Subsequently clot formation around the prosthesis completely obliterated the aneurysm [2].
The time course for staged aortic replacement covered a wide range from 1 hour to 92 months. Apart from the three emergency procedures for trunk entrapment in dissection, 21 elective continuations of an elephant trunk were performed. The mean interval until reoperation for these procedures was 14.7 months (range, 1 to 92 months). In 14 patients a descending aortic replacement using a proximal trunk was done after a mean interval of 9.6 months (range, 1 to 58 months). There was no operative mortality or morbidity including the three emergency completions. Seven additional patients underwent thoracoabdominal aortic replacement as a completion of a distal trunk after a mean interval of 25 months (range, 3 to 92 months). Again, there was no operative mortality, but 1 of these patients became paraplegic. Of the 6 individuals who underwent third-stage downstream replacement, 3 patients with Marfan's syndrome required an infrarenal Y graft because of progressive dilatation of the aorta or the iliac arteries. Three other patients underwent thoracoabdominal replacement, 1 becoming paraplegic. These results are summarized in Table 2.
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Comment
Since its introduction in 1983, the elephant trunk technique has been used widely for staged aortic replacement by our own group as well as that of the late Dr Crawford [1–4]. The main advantages of the technique are that it saves the proximal graft-to-aorta anastomosis, at the same time avoiding dangerous complications at the previous anastomotic site. As conjoining two grafts is a matter of only a few minutes, the extension of an elephant trunk basically reduces the time of aortic occlusion in simple clamping to that needed for the distal anastomosis.
At second-stage replacement the aorta usually is surrounded by densely adherent tissue. The danger of lacerating the vessel and of damaging the recurrent laryngeal or vagus nerve during dissection were the main reasons why the elephant trunk technique was developed. With a trunk dangling within the proximal part of the segment to be replaced, the surgeon can stay away from the indurated zone and free the vessel further downstream where a cross-clamp can be applied easily. Svensson [4] has suggested opening the aorta, simply grabbing the stump of the trunk and placing the cross-clamp on it.
Over time the elephant trunk technique has undergone several technical variations. For insertion of a proximal trunk into the descending aorta, the modification as originated by Crawford and associates [3] and Svensson [4] and described above is preferable in our view. Apart from simplifying the approach to the origin of the descending aorta, this technique has the theoretical advantage of increasing the contact zone between graft and aortic wall.
Marking the distal end of the trunk with metal clips eases its identification on plain chest roentgenograms or other radiographic modes such as computed tomographic scanning (Figs 3, 4). Knowledge of this level is essential when planning the next operative stage. The markers are applied before the graft is invaginated.
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In aortic dissection an elephant trunk may become entrapped in the smaller lumen. Insufficient communication between both lumens then may lead to its obstruction resulting in a pressure gradient. This was seen in 3 cases of proximal elephant trunk insertion and was relieved immediately by descending aortic replacement via a left-sided thoracotomy. Since then we have taken great care to excise a generous portion of the dissecting membrane which in length should exceed that of the elephant trunk. This ascertains equal perfusion of both distal lumina. In case of doubt intraoperative transesophageal echocardiography is helpful.
Some old clot is often found in the blind aortic pocket surrounding the trunk. We have not encountered any thromboembolic complications resulting therefrom, although we do not anticoagulate patients for the reason of trunk insertion alone. One has to bear in mind, however, that a considerable proportion of patients are on a warfarin regimen anyway because of prosthetic aortic valve replacement.
We suggest a trunk extension of about 6 to 8 cm in length (Fig 5). This suffices for convenient subsequent grafting in most of the cases. Conversely, the concept of purposefully inserting a long trunk into the descending aorta with the aim of thromboexcluding it, as first suggested by us [2], has been followed by Buffolo and colleagues [7] for treating acute distal dissection. Through a midline sternotomy and under circulatory arrest a long prosthesis is anastomosed to the junction of the arch and descending aorta, thereby excluding the tear. Clot formation in the dead space then leads to obliteration of the aortic lumen similar to a patient of ours treated in this way [2]. In Buffolo and colleagues' series a complication rate of 60% was reported, including paraplegia presumably due to thrombosis of the artery of Adamkiewicz. This makes us hesitant to recommend this approach for acute dissection.
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The time interval for extension of a proximal elephant trunk must be expected to be considerably shorter than that of a distal trunk. Probably because of its sharp curve and relatively loose support in the mediastinum the proximal descending part of the aorta is the one most likely to dilate early in dissection [8]. The thoracoabdominal aorta is closely impacted by the diaphragmatic crura and tends to expand only slowly.
As is customary with surgical methods, the elephant trunk technique has matured and undergone several refinements over time. Twelve years after its conception we consider it a reliable, safe, and reproducible approach. It has become a routine in our surgical armamentarium for treating extensive aortic disease.
Footnotes
Presented at the Thirty-first Annual Meeting of The Society of Thoracic Surgeons, Palm Springs, CA, Jan 30–Feb 1, 1995.
Address reprint requests to Dr Heinemann, Department of Thoracic and Cardiovascular Surgery, University Hospital, Hoppe-Seyler-St3, D 72076 Tuebingen, Germany.
References
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