Asian Cardiovasc Thorac Ann 2002;10:346-348
© 2002 Asia Publishing EXchange Pte Ltd
False Aneurysm Due to Suture Loosening After Aortic Arch Replacement
Keita Tanaka, MD,
Haruo Makuuchi, MD,
Yoshihiro Naruse, MD,
Toshiya Kobayashi, MD,
Ichiro Hayashi, MD,
Takehiko Takayama, MD,
Yusuke Namifusa, MD
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Division of Cardiovascular Surgery Toranomon Hospital Tokyo, Japan
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For reprint information contact: Keita Tanaka, MD Tel: 81 436 62 1211 Fax: 81 436 61 3961 email: kyky-tanaka{at}mvc.biglobe.ne.jp Division of Cardiovascular Surgery, Teikyo University School of Medicine, Ichihara Hospital, 3426-3 Anesaki, Ichihara City, Chiba 299-0111, Japan.
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ABSTRACT
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We describe a case of false aneurysm due to loosening of the anastomotic sutures 5 years after graft replacement for subacute type A aortic dissection. Leakage from the graft was controlled by tightening the suture slack indicating that suture loosening was the cause of the aneurysm. The mechanism was probably the progressive thinning of the edematous swollen aortic wall over the years causing the sutures to loosen.
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INTRODUCTION
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Although advances in surgical techniques and perioperative management have improved the results of surgery for acute aortic dissection, the incidence of reoperation has risen. We report a case of false aneurysm due to loosening of the anastomotic sutures 5 years after the ascending aorta and aortic arch were replaced because of subacute type A aortic dissection.
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CASE REPORT
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A 65-year-old man receiving medication for hypertension was referred to our hospital because of abrupt severe back pain. Thorough examination revealed moderate aortic regurgitation and aortic dissection of type A according to the Stanford classification. A month earlier, he had received medical treatment for acute myocardial infarction at another hospital after complaining of severe epigastric pain. We suspected that dissection had started at that time. The patient underwent surgery on the 4th day of admission. The initial intimal tear was located on the lesser curvature of the aortic arch near the origin of the left subclavian artery, while no tear was observed on the intimal wall of the ascending aorta. The ascending aorta and aortic arch were replaced by a 27.5-mm woven Dacron tube graft (Ube Industries, Ube, Yamaguchi, Japan) with 4 prefabricated branches, and the aortic commissures were resuspended. Both the proximal and distal anastomoses were made with continuous 3/0 Surgilene suture (Davis & Geck, Danbury, CT, USA) using an open technique. Teflon felt strips were placed inside the intima and outside the adventitia of both aortic cuffs to buttress the aortic wall. Because the interposed graft was very close to the parasternum, it was covered with a prosthetic material, Gore-Tex sheet. Hemostasis was easily achieved during surgery, and the patient made an uneventful recovery. Careful follow-up by computed tomography (CT) continued after discharge because postoperative angiography showed persistent patency of the false lumen in the descending aorta.
Five years after the operation, follow-up CT scan disclosed leakage and thrombi between the prosthetic graft and the sternum (Figure 1 
), which were not observed 6 months earlier. On readmission, the patient’s blood pressure was 150/90 mm Hg in both arms and body temperature was 36.5ºC. Blood analysis, including white blood cell count and C-reactive protein levels, was normal. Aortography showed opacification around the tube graft, and a diagnosis of false aneurysm was made. The site of dehiscence was seen at both the proximal and distal anastomoses by magnetic resonance angiography (Figure 2 ). The chronic dissecting aneurysm of the descending aorta measured 50 mm in diameter on the CT scan, and mild aortic regurgitation was observed by echocardiography.
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Figure 1. Preoperative computed tomographic scan showing leakage and thrombi between the prosthetic graft and the sternum and persistent patency of the false lumen in the descending aorta.
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The right axillary artery and right femoral vessels were exposed and encircled to provide access routes for cannulation, followed by sternal reentry using an oscillating saw. During dissection of the retrosternal adhesions of the Gore-Tex sheet, profuse bleeding occurred, indicating that the sheet had formed part of the false aneurysmal wall. Cardiopulmonary bypass (CPB) was started immediately with right axillary arterial and right femoral venous cannulation. While systemic temperature was slowly lowered, the remaining adhesions were dissected and the right atrium cannulated to improve venous drainage. This allowed perfusion from the right femoral artery to be started, leading to full flow. The left atrial vent cannula was inserted from the right upper pulmonary vein to avoid ventricular overdistention due to aortic regurgitation. Finally, deep hypothermia was established and cardioplegic arrest obtained.
Gross observation revealed major leakage mainly from the posterior wall of the distal anastomotic suture line and leakage from the anterior wall of the proximal anastomotic suture line. There were no signs of infection around the prosthetic graft. Although neither laceration of the aortic wall nor fraying of the prosthetic graft was identified at the bilateral anastomotic sites, there was 3-cm slack in the sutures (Figure 3 ). The leakage stopped almost completely after the slack was tightened, indicating that suture loosening was the cause of the false aneurysm. Complete hemostasis was achieved by making additional sutures. There was no evidence of infection or mediastinal abscess. The patient was weaned uneventfully from CPB.
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DISCUSSION
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Mediastinal false aneurysm remains one of the main lifethreatening complications after aortic surgery. Because of the risk of rupture, cardiac tamponade due to the mass effect, and cerebral embolism from thrombus in the aneurysm,1 surgical repair is mandatory. Once false aneurysm is diagnosed, it should be repaired before it enlarges, adheres to the parasternum, or erodes into the cardiac chambers, significantly increasing surgical risk.2
The usual causes of false aneurysm are graft infection and laceration of the native aortic wall. The latter is due to suture line tension and persistent bleeding into the space between the graft and the wrapped aortic wall.3 Accumulation of blood within the aneurysmal wrap of the graft creates tension in the suture lines.4 Large "bites" can probably reduce the tension, but complete surgical hemostasis at the suture lines is the most important measure to prevent false aneurysm formation. In the present case, however, hemostasis was easily achieved and the graft-aortic wall was not wrapped during the initial surgery. Slack in the sutures was observed at both the proximal and distal anastomoses. The cause of suture loosening 5 years after the initial operation is unclear. One possibility is mechanical failure of the suture material: it has been reported that 3/0 Surgilene may elongate by 43.7 ± 6.2%.5 However, we believe that the edematous and swollen aortic wall gradually became thinner over the years following surgery since the operation was performed at the subacute phase of aortic dissection. Through this experience, we recommend adding several simple sutures to buttress the anastomotic sites to avoid false aneurysm formation, especially in the case of aortic dissection.
One of the key elements to successful reoperation on the ascending aorta or aortic root is a safe reentry into the mediastinum.6 If the false aneurysm is situated close to the sternum, CPB preferably should be started with systemic cooling before reopening so that the sternum can be divided and any retrosternal adhesions dissected safely. However, if aortic regurgitation exists concomitantly, as in this case, care must be taken to avoid ventricular fibrillation and left ventricular distention.7 In such a situation, lower partial division of the sternum and placement of a vent cannula through the apex is a useful procedure.8 In the present case, right axillary arterial cannulation provided safe perfusion.
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REFERENCES
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ABSTRACT
INTRODUCTION
