The Elephant Trunk Technique

Abstract

We describe a complication that occurred during the 2nd stage of an “elephant trunk” aortic replacement. The patient was a 58-year-old woman who had undergone graft replacement of the ascending aorta and aortic arch with the elephant trunk technique for an acute, Stanford type-A aortic dissection.

The “elephant trunk” is a technique whereby excess tubular graft material is inserted during ascending aortic and arch repair to facilitate the subsequent treatment of distal aortic aneurysms. ¹ The method has improved the results of complex replacement of the ascending aorta, aortic arch, and distal aorta, and has resulted in better survival rates than those of traditional approaches. ² There are few types of complications related to the technique and their incidence is low. ¹

We describe herein a complication that occurred during the 2nd stage of a staged elephant trunk operation.

Case Report

In January 2000, a 58-year-old hypertensive woman was admitted to our institution with severe dyspnea and chest pain. In October 1997, at another institution, she had undergone replacement of the ascending and transverse aorta, with use of the elephant trunk technique, for an acute, Stanford type-A aortic dissection. In November 1998, she had an episode of acute thoracic pain, followed by progressive dyspnea and recurrent episodes of respiratory infection.

At the January 2000 hospital admission, her physical examination revealed a blood pressure of 170/85 mmHg with an irregular pulse of 108 beats/min. She was peripherally cyanotic with a respiratory rate of 32 breaths/min. Auscultation of the thorax indicated the absence of left lung ventilation. Arterial blood gas analysis showed severe hypoxia (oxygen concentration [PaO₂], 42 mmHg) and respiratory acidosis (carbon dioxide concentration [PaCO₂], 59 mmHg). Chest radiography revealed complete atelectasis of the left lung (Fig. 1). A contrast-enhanced computed tomographic (CT) scan showed a giant pseudoaneurysm at the distal anastomotic site of the aortic arch graft (Fig. 2), occupying the entire left thorax and compressing the left pulmonary artery and main bronchus. The descending thoracic and abdominal aorta was of normal diameter, with no sign of dissection at any level.

Fig. 1 Chest film showing complete atelectasis of the left lung.

Fig. 2 Contrast-enhanced computed tomographic scan reveal-ing a giant pseudoaneurysm at the distal anastomotic site of the aortic arch graft.

The patient was scheduled for emergency surgery. The chest was entered through an anterolateral thoracotomy at the 5th intercostal space. The left femoral and left axillary arteries were cannulated for arterial inflow. The false aneurysm was opened after the institution of hypothermic (24°C) cardiopulmonary bypass (CPB). A short period (4 min) of circulatory arrest allowed time for us to open the lesion and cross-clamp the elephant trunk graft and distal aorta. The proximal part of the graft (Meadox™ woven Hemashield®, Meadox-Boston Scientific Corporation; Oakland, NJ), upstream from the original distal anastomosis, had completely healed and was surrounded by dense scar tissue. However, the distal part of the graft was floating in the false aneurysm, and no intimal or adventitial lining was present. Reconstruction of the thoracic aorta consisted of the interposition of a Dacron double-velour prosthesis (Intervascular SA; La Ciotat, France) between the unresected elephant trunk graft and the mid-thoracic aorta. Weaning of the patient from CPB was uneventful.

After heparin neutralization, no coagulopathy was indicated by the hemostasis laboratory measurements; however, there was severe bleeding through the interstices of the elephant trunk graft wall. The new graft remained impermeable. Despite all attempts to control the bleeding, including the topical application of fibrin glue, collagen fleece, hemostatic mesh, and external wrapping, the bleeding continued: 4900 cc of blood was processed by the cell saver and an additional 1500 cc from the blood bank was required. Correction of developing coagulation defects required the administration of 12 units of fresh frozen plasma, 12 units of platelets, and quantities of antithrombin-III (AT III) concentrates, aprotinin, and coagulation factors. Apparent control of the bleeding was achieved 6 hours after discontinuation of CPB, and the patient was transferred to the intensive care unit. Correction measures for coagulation disorders were continued, but further bleeding necessitated a return of the patient to surgery. Again, persistent and extensive seepage of blood through the elephant trunk graft was found. After another 5 hours of unsuccessful attempts to control the bleeding, we decided to replace the old graft up to the healed portion. We used the BioMed-icus centrifugal pump (Medtronic BioMedicus; Eden Prairie, Minn) for arterial (axillary–femoral) bypass with limited systemic heparinization. Access to the proximal aorta was difficult because of tenacious adhesions. The bleeding ceased completely after resection and replacement of the old graft.

The patient's postoperative course was character-ized by prolonged mechanical ventilatory support (20 days), which required a tracheostomy. She was discharged from the hospital on postoperative day 45. At her 6- and 12-month follow-up visits, she was in good physical condition.

Microscopic examination of the explanted prosthesis revealed that neither fibroblasts nor capillary blood vessels had infiltrated the graft; however, numerous plasma cells, lymphocytes, and macrophages were found. Although the Dacron fabric did not exhibit major structural abnormalities, the impregnated collagen of the graft had been absorbed completely.

Discussion

By presenting this case, we hope to focus attention on a complication that compromised the results of an otherwise satisfactory operation. To our knowledge, this complication has not been described previously.

Few complications related to the elephant trunk technique have been reported in the literature; ¹ these include 1) entrapment of the trunk in the smaller dissected aortic lumen downstream without an adequate distal reentry, 2) paraplegia, most likely caused by thrombosis of the Adamkiewicz artery, 3) thromboembolic complications resulting from old clot in the blind aortic pocket surrounding the trunk, and 4) splitting of the anastomosis due to enlargement of the false lumen.

Our experience with the treatment of a chronic aneurysm by use of the elephant trunk technique is limited. We have performed 2nd-stage procedures on the descending aorta in 6 other patients and have not encountered any such bleeding complication. However, in all of these patients, some degree of neointima was present, probably because of a larger contact zone between the graft and the aneurysmal wall.

Some questions about this case remain unanswer-ed, including these:

• Should we have expected severe bleeding from the graft since neointimal formation was absent?

• Should we have resected the old graft earlier, despite the risk of difficult proximal control due to the extensive scarring?

• Should we have anticipated the possibility of graft failure when we found the prosthesis floating in the dilated aorta?

• Was graft failure (seepage) due to a normal process of gelatin readsorption or due to other factors, such as poor quality of the prosthesis or even subclinical infection?

From a practical viewpoint, we recommend careful attention to the degree of healing of the elephant trunk graft at the time of the 2nd stage of the elephant trunk procedure. In order to avoid serious bleeding complications, resection of the old prosthesis should be considered when neointimal lining is absent, and when difficulties with hemostasis are experienced.