Ann Thorac Surg 1999;67:1664-1668
© 1999 The Society of Thoracic Surgeons
Original Articles
Extended aortic replacement in acute dissection by the separated elephant trunk technique
Toshio Konishi, MDa,
Kazuhiko Higuchi, MDa,
Mutumu Fukata, MDa,
Makoto Takeda, MDa,
Shinji Akisima, MDa,
Shoji Fukuda, MDa
a Department of Cardiovascular Surgery, Yokohama Rosai Hospital, Yokohama, Japan
Accepted for publication December 15, 1998.
Address reprint requests to Dr Konishi, Department of Cardiovascular Surgery, Yokohama Rosai Hospital, 3211, Kozukue, Kohoku-Ku, Yokohama 222-0036, Japan
e-mail: konix{at}muf.biglobe.ne.jp
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Abstract
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Background. Extensive aortic replacement in acute dissection is currently not a widely accepted method of treatment.
Methods. We developed a safe method for extended aortic repair including the aortic arch in type A acute dissection, and describe here its application in 5 cases. This method was based on a modification of the elephant trunk method and several other strategies. Most of the procedures were carried out under simple hypothermic circulatory arrest.
Results. All patients recovered within 2 days without recurrent nerve injury. One patient suffered from unilateral upper arm palsy due to severe innominate dissection. Patients were all discharged and early postoperative computed tomography (CT) showed thrombotic obliteration around the elephant trunk. Follow-up CT after 4 to 18 months confirmed that thromboexclusion proceeded down to the distal end of the elephant graft in 1 patient and to the diaphragmatic level in 3 patients. Total obliteration was observed in the remaining 1 patient.
Conclusions. This technique enables extended aortic repair in acute dissection with no increase in morbidity, and effectively promotes thromboexclusion of the dissected lumen to a wider extent than conventional methods.
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Introduction
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Replacement of the ascending portion of the aorta is the conventional method for treatment of acute type A aortic dissection. If the dissection involves the entire aorta, replacement of the ascending aorta and aortic arch may also be warranted. However, this more extensive procedure may also result in a significant increase in morbidity. When the surgical procedure is extended deeply into the thoracic cavity, there is a risk of uncontrollable bleeding from the distal aortic anastomosis, possible recurrent nerve injury, or subsequent respiratory failure. After surgical treatment, residual pathology of the downstream aorta plays an essential role in determination of prognosis. As long as the false lumen remains patent, the chances of survival may remain in hazard. Therefore, a method that can extensively replace the aorta with minimal morbidity and that can eliminate the need for additional surgery is required.
In this viewpoint, we developed a new method integrating a number of strategies. Using this method, it is possible to extensively replace the aorta and effectively enhance thrombotic closure in the pseudo lumen. This method features the use of a modified "elephant trunk" technique with compact composite grafting and is performed under simple hypothermic circulatory arrest. We have treated 5 patients using this method on an emergent basis with successful results.
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Material and methods
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Patient profile
Between December 1996 and January 1998, 5 patients with acute type A aortic dissection were treated in our institute by extensive aortic replacement using our modified elephant trunk technique (Table 1). Computed tomographic (CT) scanning showed that the dissections in these patients involved the entire aorta and extended into the cervical tributaries. The intimal flaps were clearly identified in all sections with patent dissected lumens. Mild to moderate aortic regurgitation was confirmed by echocardiography in all of these patients. None of the subjects showed either Marfan syndrome or significant organ failure. All patients were operated upon within 8 to 36 hours from the onset of chest pain.
Technique
Cardiopulmonary bypass was started with a midline sternal incision by subclavian or femoral arterial cannulation. The aorta was opened from the ascending portion to the arch under the deep hypothermic circulatory arrest. Antegrade cardioplegic infusion was performed only once under hypothermic arrest. The aortic arch was completely resected between the origins of the left carotid and the left subclavian artery, so that the anastomotic line of the distal aorta remained proximal to the recurrent nerve (Fig 1A). Gelatin-resorcin-formalin (GRF) glue was applied to the dissected space of the distal aorta. While GRF glue would attain its stiffness, the innominate, the left carotid, and the left subclavian arteries were reconstructed at first. These three arteries were all separated away from the aortic arch and anastomosed separately to the branched grafts that trifurcated from the arch graft (Fig 1B). This specially designed arch graft, which was intended to save space during the procedure, was fabricated before performing cardiopulmonary bypass. The residual stump of the left subclavian artery on the distal aorta was closed by suturing. Even if the circulatory arrest time limit had been reached at this point, cerebral perfusion could be commenced any time either antegradely though the arch graft by clamping the both ends, or retrogradely through the superior caval vein.
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Fig 1. Operative technique. (A) The aortic arch and the major cervical arteries were completely resected. (B) The cervical arteries were first connected to the composite arch graft, into which the elephant trunk was inserted and the distal aorta was anastomosed. The root of the left subclavian artery was closed by suturing. r = recurrent nerve of vagus.
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This step was followed by our modified elephant trunk technique to reconstruct the distal aortic arch. A simple straight graft 10 to 15 cm in length (separated elephant trunk), the caliber of which corresponded to the inner diameter of the distal aorta, was inserted into the true lumen of the distal aortic arch. The arch graft was anastomosed to this distal aortic arch incorporating the separated elephant trunk inside by simple running suture. Teflon felt was also wrapped around the distal aortic arch with this suturing. Thus, the elephant trunk method was completed, then the cardiopulmonary bypass was resumed by antegrade arterial perfusion through the arch graft. Finally, reconstruction of the aortic root was completed during the rewarming period. The aortic valve annulus was repaired by glue and suspension.
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Results
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Three patients were cannulated through femoral artery and two were cannulated through the left subclavian artery. Intimal tears were found at ascending or arch portion in all except 1 patient. Circulatory arrest time was 48 to 64 min, and the lowest rectal temperature was 16.4°C to 22.9°C (Table 2). In the first case, it took 64 min for completion of anastomoses of the three cervical branches. Therefore, the incorporating suture of the separated elephant trunk graft was followed by an antegrade cerebral perfusion through the arch graft by clamping both ends. In the next 2 cases, the cerebral perfusion was not supplemented at all. However, in the last 2 cases, retrograde cerebral perfusion was performed during the elephant trunk-incorporating suture without clamping the arch graft. The purpose of this retrograde cerebral perfusion was not only to secure brain protection, but also to flush out debris from the cerebral arteries. Aortic cross-clamping time was 122 to 188 minutes, and cardiopulmonary bypass time was 159 to 266 minutes.
Most of the patients woke the next day, but one patient woke on the second day. This patient had amnesia that lasted a week. No recurrent nerve injury was observed except in 1 case of tracheal edema that required airway management. Left upper extremity palsy was found in 1 case, which was a sequela by the localized cerebral infarction of the right temporal region. In this case, the dissection of her innominate artery extended so distally that thromboembolic fragmentation might have been generated. Aortography and CT were carried out in all cases postoperatively. The ends of the elephant trunk grafts were identified in all cases reaching down to the proximal or mid portion of the descending thoracic aorta (Fig 2). Thrombotic closure around the elephant trunk graft was also confirmed in all cases from the level of distal aortic arch to the upper portion of descending thoracic aorta by CT. In one of the patients (case 3), thromboexclusion of the false lumen had already proceeded down to the level of the diaphragm, but in the remaining patients, the false lumen was still patent below the distal thoracic aorta (Fig 3).
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Fig 2. Postoperative aortography. The crimp of elephant trunk graft was identified in the thoracic aorta. The distal end of the graft had reached down to the thoracic aorta at the back of aortic valve (case 5).
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Fig 3. Early postoperative computed tomogram. Note the elephant trunk graft inside the true lumen of the thoracic aorta. Perigraft clotting remained incomplete and the false lumen was still patent (case 5).
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All patients were discharged and followed up by CT 4 to 18 months later. Consequently, further thromboexclusions had been demonstrated, down to the distal end of the elephant trunk graft in 1 patient, to the level of diaphragm in three patients (Fig 4), and completely over the entire extent of the false lumen in 1 patient (case 1). They were alive 6 to 21 months after the operation without events.
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Fig 4. Late follow-up computed tomogram. Note that the false lumen had been thromboexcluded in the thoracic aorta (case 5).
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Comment
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In acute dissection, surgical replacement is generally confined to the ascending aorta or proximal aortic arch, whereas it could be also extended to the total aortic arch. However, there has been some debate concerning how the prognosis differs between these two forms of treatment. Crawford and associates [1] reported that operative mortality was 3% for the confined procedure and 16% for the extended procedure. Therefore, they could not simply accept that the extensive replacement policy would benefit in spite of the possible increased prevalence of reoperation after the confined procedure. Massimo and associates [2] had extendedly replaced the aortic arch totally, but the early mortality accounted for approximately 20%. On the other hand, Kazui and associates [3] demonstrated a lower mortality of 8.7% with a 4-year survival rate of 87% by replacing both the ascending aorta and the total arch, as long as there were no accompanying preoperative risk factors. The distal false lumen after the surgical repair appears to often remain patent. Ergin and associates [4] emphasized a lower patency of 47.3% in comparison with other studies due to their policy of resecting tears with a sutureless technique. They confirmed that the 5-year event-free rate in their patients with closed distal false lumen seemed superior to that in cases in which the false lumen remained patent. If the operative risk of extensive replacement is comparable with that of confined replacement, extensive repair may be beneficial as an initial treatment regimen. These viewpoints motivated us to search another approach carrying out an extensive aortic replacement based on the concept below.
We delineated a kind of a watershed on the aortic arch between the left carotid and the left subclavian bifurcation, which we assumed to demarcate the territory of surgical risk. As long as the procedures were limited to this line, the operative risk would not increase. Bleeding from the suture line would be relatively easy to control because it would lie within the surgeon’s field of view similarly to replacement of the ascending aorta. In addition, the recurrent nerve would never be injured during this procedure. We believe the area beyond this line should remain untouched at least in acute situations. However, some measures should be adopted to reduce the patency of dissected channel downstream to this line. Our resolution for this was the use of intraluminal approach by the elephant trunk method [5], which we expected to eliminate the need for further correction for the remaining portion of the aorta. Since the dissected false lumen tends to dilate and gain its wall thickness in chronic phase, the chances of thrombotic obliteration by the elephant trunk graft might be higher in acute phase. In addition, the roots of the major cervical arteries are often involved in the dissection. Therefore, independent graft replacement of these arteries would represent a curative procedure. The orifice of the left subclavian artery will be sealed by the elephant graft. To minimize the physical demands placed on the patients, each process should be simplified as much as possible. All procedures should be performed under hypothermic circulatory arrest. In addition, the elephant trunk technique should be further modified and the arch graft should be designed to have compactly branching grafts to save space.
The selective antegrade cerebral perfusion method requires cannulation or clamping of each cervical artery, and these procedures themselves may result in further injury or require sophisticated perfusion circuits. Whereas open anastomosis under hypothermic circulatory arrest is generally used in such cases [6], the period of cerebral ischemia is always a major concern during the arrest. We must emphasize that procedural arrangement has a major contribution to management of the time limitation under circulatory arrest. Bachet and associates [7] reported that GRF-treated aorta gains durability that leads to the timesaving during suturing, but fixing occurs too gradually to be completed under circulatory arrest. Therefore, GRF glue should be applied in advance of other procedure, and sufficient time should be allowed for fixation before proceeding. The major cervical arteries should be connected to the arch graft before anastomosing the distal aortic arch. Even if the period of circulatory arrest was prolonged, cerebral perfusion could be commenced through the arch graft clamping both ends. Retrograde cerebral perfusion is also available. Okita and associates [8] reported that prolonged hypothermic circulatory arrest plus retrograde cerebral perfusion over 60 min was not associated with mortality rate or stroke. In this situation, retrograde cerebral perfusion apparently serves as a suitable modality because it obviates the need for clamping. The circulatory arrest times of the herein-reported cases reached around 60 minutes, which might threaten the safe limit. From the prudent standpoint, antegrade cerebral perfusion through the arch graft could be the safer choice, especially in such a case whose circulatory arrest time would be prolonged.
The original elephant trunk technique [4] was cumbersome due to the need for handling the acutely dissected fragile aorta. Modifications were, however, developed by Borst and associates [9], Svensson [10], and Emery and associates [11] to facilitate the anastomotic procedure. Their concept of the modification involves invagination of the elephant trunk graft. Our separated elephant trunk technique offers a greater enhancement particularly in acute dissection. As a result of the separation, insertion of the elephant graft into the aorta is a simple matter and grafts of different sizes can be used. Suturing the arch graft altogether with the elephant trunk-inserted distal aorta is a simple procedure, irrespective of whatever complex composites the arch graft might contain. We prepared a special arch graft with trifurcated branch grafts to save space around the crowded aortic area, although a multiple composite graft might be commercially obtainable.
The depth to which the elephant trunk graft should be extended into the downstream aorta could generate some debate. To thromboexclude the dissected false channel, the trunk should be as long as possible. In contrast, this might result in an increased risk of thrombotic complications, such as dreadful paraplegia or paraparesis [9]. Heinemann and associates [12] from the Hannover group reported a few acute cases among a total of 50 dissections, and the proper length of the elephant trunk graft is still unclear in an acute situation as well. In our cases, the trunk could reach the upper half of the thoracic aorta at the longest reach by our separated method. To further extend the trunk, some kind of delivery system would be needed. However, thromboexclusion of the false lumen proceeded beyond or at least to the upper half of the thoracic aorta. Therefore, we could not find a rationale for using excessively long elephant trunk graft, which should be retained within the upper half of the thoracic aorta at the longest reach.
We have developed not only a safe and secure method for extensive aortic replacement as a substitute for total arch replacement, but we have also established a possibly curative treatment regimen that may provide a better prognosis. In this series of 5 cases, their aortae was severely dissected with completely patent false lumen, and the major cervical branches were also involved. Preoperative organ failure was not complicated and their life longevity was good, as expected. In such cases, we place a rationale to also treat the aortic arch because the operative mortality or morbidity would not be increased. We integrated conventional techniques and resources into a systematic treatment strategy. Therefore, we referred to this as an integrated method for extended aortic replacement in acute dissection. In conclusion, this method provides an additional choice for the treatment of acute aortic dissection and may reduce the incidence of sequelae in the long term.
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References
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Abstract
Introduction
