Asian Cardiovasc Thorac Ann 2003;11:332-336
© 2003 Asia Publishing EXchange Ltd
Surgical Repair of a Distal Arch Aneurysm with a Stent-graft
Kazuhiko Higuchi, MD,
Kenzi Koseni, MD,
Motoyuki Hisaki, MD,
Yutaka Kotsuka, MD,
Shinichi Takamoto, MD
Department of Cardiac Surgery, Asahi General Hospital, Chiba, Japan, Department of Cardiac Surgery, University of Tokyo, Tokyo, Japan
For reprint information contact: Kazuhiko Higuchi, MD Tel: 81 479 63 8111 Fax: 81 479 63 8580 email: higux{at}blue.ocn.ne.jp Department of Cardiac Surgery, Asahi General Hospital, I-1236 Asahi, Chiba 289-2511, Japan.
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ABSTRACT
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This study evaluates the effectiveness and potential complications of stent-grafting for the treatment of distal arch aneurysms using profound hypothermia and circulatory arrest with retrograde cerebral perfusion. Between December 1998 and December 2001, 9 consecutive patients with a distal arch aneurysm (6 men and 3 women, mean age 71 years) underwent surgical repair using a stent-graft. Profound hypothermic circulatory arrest and retrograde cerebral perfusion were performed in all patients. Endovascular leakage was screened postoperatively using three-dimensional computerized tomography. The mean follow-up period was 27.4 months. Thirty day mortality was 0%. One patient died 3 months after stent-grafting due to proximal leakage into her aneurysm. The mean postoperative extubation period was 2.1 days. No patients suffered cerebral infarction or paraplegia. Although preliminary outcomes using this technique were good, endovascular leakage is a concern. We suggest that, if major proximal leakage is recognized postoperatively, re-intervention should be performed as soon as possible. Endovascular stent-grafting appears to be a good alternative treatment for distal arch aneurysms, although longer follow-up is necessary to more comprehensively evaluate this procedure.
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INTRODUCTION
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Surgical repair of a distal arch aneurysm is generally conducted using left thoracotomy. However, this procedure is associated with a high risk of pulmonary injury that can require prolonged ventilatory support. End-luminal insertion of a stent-graft via a median sternotomy is an alternative treatment that may be attractive, since it results in less morbidity and mortality.1,2 In this study, we report our initial clinical results using a stent-graft in the treatment of distal arch aneurysms including the effectiveness and potential complications of the procedure.
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MATERIAL AND METHODS
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Between December 1998 and December 2001, 9 consecutive patients (6 men and 3 women) with a distal arch aneurysm underwent surgical repair using a stent-graft at the Asahi General Hospital. In this period the procedure was performed for all patients with a distal arch aneurysm. The average age of the patients was 71 years (ranging from 64 to 84 years). All patients had an aneurysm caused by degeneration of the distal part of their aortic arch. The maximal diameter of these aneurysms ranged from 47 to 73 mm (mean diameter, 60 mm). Our surgical indication for a distal arch aneurysmectomy is usually over 5 cm in diameter. Coronary artery bypass grafting (CABG) was performed concomitantly in one patient with an aneurysm of 47 mm in diameter, so that, for the patient’s well being, a second operation could be avoided. Patients were evaluated preoperatively with chest radiographs, contrast-enhanced spiral computerized tomography, and coronary angiography before their scheduled operation. Coronary angiography and aortic angiography were carried out routinely to evaluate stenosis or occlusion of the coronary arteries and to identify the anatomic and functional characteristics of the aneurysm and the neck vessels.
All procedures were performed under general anesthesia. All patients were placed in a supine position. A Swan-Ganz catheter and a transesophageal echocardiography probe were inserted preoperatively for monitoring. The surgical approach was through a median sternotomy. After systemic heparinization (200 IU•kg-1 body weight), the ascending aorta was cannulated and venous cannulas were inserted into the superior and inferior venae cavae through the right atrium, and a cardiopulmonary bypass was established. After each patient was cooled to a rectal temperature of 20°C, the ascending aorta was clamped, and cold blood cardioplegia was induced with the simultaneous application of ice slush to the surface of the heart. Each patient’s head was surrounded by ice bags and 1,000 mg methylpredonisolone was administered. Circulatory arrest was then established, and 1,000 to 1,500 ml of blood was drained into the reservoir of the pump system. During circulatory arrest, retrograde cerebral perfusion was used to increase the tolerance of the central nervous system. The superior vena cava was snared and was perfused with an arterial line from the extracorporeal circuit, which was connected to the cannula of the superior vena cava. The central venous pressure was kept under 20 mm Hg for retrograde cerebral perfusion.
The aortic arch was transected at the distal end of the left subclavian artery. A 24 French Curved Sheath (Cook Inc, Bloomington, IN, USA) had been prepared and loaded with a stent-graft. This stent-graft was made of woven polyester graft (Ube Inc, Ube, Japan) and a stainless steel Z-stent (Gianturco, Self-Expandable: Cook Inc, Bloomington, IN, USA). A stent was inserted inside the distal portion of the woven graft and sutured to the graft by interrupted 4-0 Prolene (Ethicon, Somerville, NJ, USA). The sheath was fitted with a stent-graft and was then inserted through the aortic incision and placed across the aneurysm. Once the pushing rod was advanced and in contact with the stent-graft, the latter was deployed by holding the pushing rod (Cook Inc, Bloomington, IN, USA) in the same place and withdrawing the sheath. The anchoring length in the distal end of the stent-graft was intended to be at least 3 to 4 cm. The diameter of the graft was selected so as to be the mean of the diameter just proximal to the anastomosis and that just distal to the anchoring position. After the stent-graft was deployed, a balloon catheter was inserted and inflated to attach the stent-graft to the wall of the descending aorta. An endoscopic camera was inserted inside the stent-graft to verify that the graft was open and not twisted or kinked (Figure 1
). The proximal anastomosis was made carefully onto the posterior wall with continuous 3-0 suture (Surgilene: Sherwood Med, St. Louis, MO, USA), and was completed anteriorly using Teflon felt for reinforcement.
When the anastomosis was completed, air was removed from the cerebral arteries with retrograde cerebral perfusion (RCP) and from the aorta by femoral perfusion connected to the arterial line of the cardio-pulmonary bypass (CPB). After an air vent was placed in the ascending aorta, CPB was resumed, and rewarming was initiated. During rewarming, CABG was performed in one patient and the left subclavian artery was reconstructed. CPB was terminated when the patient’s rectal temperature reached 36°C.
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RESULTS
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Table 1 summarizes the patients’ demographics and outcomes. All nine patients survived the early postoperative period. Patient No. 7 died 3 months postoperatively from a rupture of the descending thoracic aorta, following an emergency repair operation. After the initial stent-graft insertion, three-dimensional computerized tomography (3D-CT) revealed that this patient had suffered major leakage from the proximal end of the stent. A Z-stent was then deployed from the femoral artery to repair the major leakage. The leakage was reduced to a minor leakage, which was expected to become occluded in the future, but which could not immediately be stopped completely. The patient was then followed in the outpatient clinic. Patient No. 2 had minor leakage at the proximal end of the stent, and this leak was occluded 6 months after operation. Patient No. 5 had a minor leakage at the distal end of the stent. Because this was not occluded until 17 months after the initial operation, the patient became symptomatic. A Z-stent was successfully employed to occlude the leakage, and the patient became asymptomatic. No neurologic complications, including cerebral infarction and paraplegia, occurred in our patients. The graft sizes were either 28 mm or 30 mm. The mean circulatory arrest time was 67 minutes (ranging from 44 to 90 minutes). The mean postoperative extubation period was 2.1 days (ranging from 1 to 6 days). The follow-up period ranged from 3 to 47 months (mean: 24.7 months). Left subclavian arterial reconstruction was performed in 4 patients. CABG was performed in one patient. Figure 2 shows a typical preoperative distal aneurysm and Figure 3 shows successful stenting of an aortic aneurysm following stent-graft replacement.
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Figure 3. A postoperative 3D-CT demonstrates successful treatment of an aneurysm using the stent-graft procedure. (Patient No. 9)
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DISCUSSION
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Distal arch aneurysms can be treated by the implantation of a stent-graft, as originally reported by Kato et al.3 This treatment is less invasive than that performed through a left thoracotomy. Stent-graft implantation has several advantages over the left thoracotomy procedure:
- hemostasis is easier to maintain;
- there is less chance of damage to the left recurrent nerve and to the lung;4
- it requires only a large sheath catheter, a pushing rod and a Gianturco Z-stent with a graft.
Our initial results using stent-graft insertion in the distal aortic arch demonstrate the feasibility of this method for repairing atherosclerotic distal arch aortic aneurysms. We used an endoscope to check for kinking or torturing of the stent-graft and to make sure that the distal end of the stent-graft was correctly positioned on the descending aorta. Determination of the proximal and distal positions of the stent-graft is essential to ensure that both sides are anchored tightly. However, in almost all cases, the diameter of the proximal landing zone was slightly different from that of the distal landing zone. We therefore used a stent-graft with a diameter that was the mean of the diameters of the aorta at the proximal and distal ends of the stent. The proximal end of the stent-graft was cut to fit to the shape of the site of the proximal anastomosis, and was then tightly sutured to the aorta.
The most important consideration in this procedure is the quality of the aortic wall at the site of proximal anastomosis. If the proximal anastomosis is inadequate, major or minor proximal leakage can occur; and minor leakage can produce an occlusion, while major leakage can be lethal. We attribute our success rate of 0% hospital mortality to our postoperative screening for potential leakage using 3D-CT. Using this screening technique, we were able successfully to identify major leakage in one patient (Patient No. 7). We were able to substantially reduce the leakage by inserting a stent into the stent-graft through femoral the artery. By reinforcing the original stent-graft, we were able to temporarily reduce the proximal leakage to a minimum, and intended to occlude the leakage completely in the future. This is illustrated in Figure 4. The leakage could not be stopped without re-operation, and so we decided to follow the patient up in the outpatient clinic. She unfortunately died from perforation of the aneurysm 3 months later despite undergoing emergency surgery.
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Figure 4. A postoperative 3D-CT demonstrates residual endovascular leakage from the site of proximal anastomosis to the distal end of the stent-graft through an aneurysm. (Patient No. 7, following Z-stent repair)
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Recognizing the presence of any unfavorable anastomosis of proximal end of the stent-graft to a sclerotic aortic wall greatly reduces the incidence of leakage.5,6 The operative procedure for endoluminal stent-grafting involves only a small incision in the aortic arch. The proximal end of the stent-graft is then sutured onto the wall of the aortic arch just distal to the left subclavian artery. However, if the aortic wall is too fragile to withstand such suturing, we favor the selection of a more proximal site. This allows a better fit for suturing, although reconstruction of the neck vessels is needed. If major leakage at proximal anastomosis cannot be arrested by the stent insertion, we recommend either a repetition of this procedure or performance of the procedure through a left thoracotomy as soon as possible.
No neurologic complications, such as paraplegia or cerebral infarction, were observed in our patients. The possible reasons are as follows. Paraplegia is relatively rare in the repair of a distal aortic arch aneurysm. Moreover, many intercostal branches were already occluded at atherosclerotic aneurysms, and collaterals supplied blood to the spinal cord. Even the sudden deployment of the stent does not lead to the steal phenomenon in perfusion of the spinal cord.7 Svensson et al. suggested that the risk of stroke increases when cerebral ischemia time exceeds 45 minutes.8 In our study, circulatory arrest time exceeded this threshold, with a mean of 67 minutes (ranging from 44 to 90 minutes), and yet, no strokes occurred in our patients.9 These results indicate that hypothermic circulatory arrest with RCP is effective for cerebral protection and preserves neurologic integrity. This finding corroborates the results reported by Ergin et al.10 One beneficial effect of RCP may be reduction of the risk of cerebral embolism.11,12 In this procedure, the extubation period was shorter than it is for conventional distal arch replacement. This suggests that the incidence of respiratory complications arising from the stent-graft technique may be lower than that arising from conventional surgery through left thoracotomy. Avoidance of left thoracotomy had additional benefits, including preservation of respiratory function and less postoperative pain.
In conclusion, our findings indicate that the stent-graft procedure is both feasible and safe, and has minimal neurological complications. Profound hypothermia and circulatory arrest with assisted retrograde cerebral perfusion appear to be effective in maintaining cerebral protection. The median sternotomy approach used in this procedure reduces the risk of respiratory complications and reduces postoperative pain management. Because we can so far report only early results in a limited number of patients, a longer follow-up and a larger patient population are warranted to assess the long-term effectiveness of this procedure.
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REFERENCES
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ABSTRACT
INTRODUCTION
