Asian Cardiovasc Thorac Ann 2003;11:77-79
© 2003 Asia Publishing EXchange Ltd
Ruptured Mycotic Thoracic Aortic Aneurysm: Lobectomy and Dacron Graft Repair
Sin Yoong Kong, FRCS,
Chua Yeow Leng, FRCS
Department of Cardiothoracic Surgery, National Heart Centre, Singapore, Republic of Singapore
For reprint information contact: Chua Yeow Leng, FRCS Tel: 65 6436 7598 Fax: 65 6224 3632 email: Chua_Yeow_Leng{at}nhc.com.sg Department of Cardiothoracic Surgery, Mistri Wing, National Heart Centre, 17 Third Hospital Avenue, Singapore 168752, Republic of Singapore.
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ABSTRACT
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A 57-year-old man presenting with hemoptysis and chest pain was diagnosed to have a Staphylococcus aureus mycotic aneurysm of the descending thoracic aorta, which subsequently ruptured into the left lower lobe of the lungs. He underwent successful repair with lung resection and Dacron graft replacement under hypothermic circulatory arrest, followed by long-term antibiotic therapy.
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INTRODUCTION
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Infected thoracic aortic aneurysm is an uncommon entity and presents difficult management problems. The standard therapy includes exclusion with extraanatomic bypass or in-situ graft replacement with an infection-resistant prosthesis. A ruptured mycotic aneurysm limits the treatment options to emergency repair and reconstruction with a commonly available off-the-shelf prosthesis, followed by long-term antibiotic therapy. We report successful management of such a catastrophic event.
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CASE REPORT
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A 57-year-old man with no significant past medical history complained of coughing blood-streaked sputum and chest discomfort for a week. Chest radiography showed a widened mediastinum (Figure 1
), and computed tomography of the thorax demonstrated a pseudoaneurysm of the descending thoracic aorta 5 cm in diameter (Figure 2) extending from the level of the pulmonary artery bifurcation down to the 12th thoracic vertebra. The patient was febrile with a total white blood cell count of 25,000 x 106 L-1.
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Figure 2. Computed tomographic scan of the thorax showing the pseudoaneurysm surrounded by an extensive hematoma.
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On the way to the operating room for urgent surgery, the patient developed acute massive hemoptysis and hypotension. Volume resuscitation was commenced and emergency cardiopulmonary bypass instituted via femoral cannulation. A posterolateral thoracotomy was performed, and the aneurysm was found to have ruptured into the left lower lobe of the lungs, which was tense and distended. During mobilization of the lungs, there was spontaneous rupture with loss of blood. Proximal and distal control of the thoracic aorta was obtained, and the proximal descending thoracic aorta was cannulated for upper body perfusion with additional cannulation of the pulmonary artery for optimal venous return. The patient was then cooled to 18°C before hypothermic circulatory arrest was instituted. The lower lobe of the lung was rapidly resected together with an area of edematous inflamed aorta and its surrounding inflammatory tissue. A Dacron prosthesis was then sewn to healthy margins of the descending thoracic aorta before circulation was restarted.
Postoperatively, the patient recovered with no evidence of neurological deficit. Blood and tissue cultures grew Staphylococcus aureus. He was treated with cloxacillin for 6 weeks intravenously before converting to an oral dose for a total of 9 months. He was afebrile immediately after surgery and throughout his 6-week hospital stay. However, his total white cell count did not return to normal until 3 weeks after the operation. Computed tomography 5 months postoperatively showed a resolving hematoma around the graft (Figure 3). At the 2-year follow-up, he remained well with no evidence of graft infection or pseudoaneurysm formation at the anastomotic site.
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Figure 3. Computed tomographic scan of the thorax 5 months after repair showing the Dacron graft surrounded by a resolving hematoma.
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DISCUSSION
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"Mycotic" aneurysm was first described in 1885. It has been described in association with coarctation and can occur in the normal or atherosclerotic aorta. Organisms most commonly isolated include salmonellae, Staphylococcus aureus, and streptococci.1,2
A ruptured mycotic aneurysm is an uncommon emergency that presents an enormous challenge to the surgeon faced with the problems of firstly obtaining hemodynamic control and subsequently reconstruction with an infection-resistant prosthesis. There is often insufficient time to plan and execute an exclusion procedure combined with extraanatomical bypass.
In patients with an adequate margin of healthy aorta to effect proximal and distal control, distal aortic perfusion utilizing partial left heart bypass without heparinization is the ideal.3 Where no control is likely to be obtained, a useful strategy, utilized in this case, is to proceed to hypothermic circulatory arrest. This obviates the need for a space-consuming clamp, allows optimum graft-to-aorta anastomosis with minimum distortion, and provides a degree of spinal cord protection. The disadvantage is the ensuing coagulopathy on completion of the procedure, which necessitates the use of multiple thrombostatic agents.
The prosthesis of choice is a homograft,4,5 if available. Alternatives include a superficial femoral vein6 and a silver-impregnated Dacron graft. In the absence of these, a biological patch such as a xenopericardium7 can be contemplated if the aneurysm is amenable to localized repair. Otherwise, a Dacron graft is the default choice of prosthesis, and the anastomosis should be performed to a healthy segment of the aorta after extensive debridement of the infected tissue.8 Long-term antibiotic treatment and graft surveillance are mandatory postoperatively.
Fortuitously for this patient, the rupture was initially contained within the left lower lobe of the lungs. This is the first reported case of concomitant lung resection and interposition graft repair for the treatment of ruptured mycotic aneurysm. Aggressive debridement, anastomosis of the graft to healthy portions of the aorta, and long-term antibiotic therapy contributed to the successful clinical outcome.
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REFERENCES
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ABSTRACT
INTRODUCTION
