Asian Cardiovasc Thorac Ann 2008;16:e15-e17
© 2008 Asia Publishing EXchange Ltd
Mycotic Pseudoaneurysm of the Ascending Aorta at Site of Aortic Cannulation
Davide Gabbieri, MD,
Pascal M Dohmen, MD,
Jörg Linneweber, MD,
Alexander Lembcke, MD1,
Christian von Heymann, MD2,
Wolfgang F Konertz, MD
Department of Cardiovascular Surgery
1 Department of Radiology
2 Department of Anesthesiology and Intensive Care, Charité Hospital, Medical University Berlin, Berlin, Germany
For reprint information contact: Davide Gabbieri, MD, Tel: 49 30 450622038, Fax: 49 30 450522921, Email: dgabbieri{at}yahoo.it, Department of Cardiovascular Surgery, Charité Hospital, Medical University Berlin, Charitéplatz 1, D-10117 Berlin, Germany.
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ABSTRACT
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Reoperation for pseudoaneurysm of the ascending aorta presents a surgical challenge. Instituting femorofemoral bypass and establishing hypothermic circulatory arrest is a well-known strategy, although not free from complications. We report a case of mycotic pseudoaneurysm after coronary artery bypass in a 53-year-old man, at the site of previous aortic cannulation, and review the surgical strategies proposed to manage this pathologic entity.
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INTRODUCTION
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Pseudoaneurysm of the ascending aorta occurs in < 0.5% of cardiac surgical patients.1 After coronary artery bypass grafting (CABG), the site of aortic cannulation is most commonly involved, followed by the anastomotic suture line.2 Pseudoaneurysm of the ascending aorta is considered an urgent or emergency surgical priority, and carries high operative morbidity and mortality due to the risks associated with sternal reentry and the fact that many patients have an infectious etiology and are in a septic state at surgery.1,3 We report a case of mycotic pseudoaneurysm of the ascending aorta, which developed early after CABG.
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CASE REPORT
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A 53-year-old man developed an acute severe febrile illness 4 weeks after uneventful single CABG (left internal mammary artery to left anterior descending coronary artery) under cardiopulmonary bypass (CPB). There were laboratory signs of active infection, but blood cultures were negative, and there were no signs of sternal infection. Transthoracic echocardiography excluded heart valve endocarditis. Computed tomography revealed a 3 x 3-cm saccular aortic pseudoaneurysm, distant 2 cm from the sternotomy, with a neck located proximal to the aortic arch, probably at the site of previous aortic cannulation (Figure 1
). An emergency operation was performed. There were no signs of mediastinal infection. The pseudoaneurysm covered the distal part of the ascending aorta and adhered to the aortic arch, preventing distal aortic cannulation. The proximal aorta was cannulated just above the sinotubular junction, and repair was performed during deep hypothermic circulatory arrest (DHCA). The lumen of the pseudoaneurysm was full of a gelatinous brown material, probably infected clots. The defect causing the pseudoaneurysm, 1.5 cm in diameter, originated from the previous aortic cannulation site. Signs of infection were noted in the native aorta around the orifice. The pseudoaneurysm and infected ascending aorta were excised up to the arch, leaving only macroscopically healthy tissue. The ascending aorta was replaced with a 30-mm woven Dacron prosthesis. Systemic perfusion was restarted through the vascular prosthesis before performing the proximal anastomoses, to minimize the duration of DHCA. The patient’s postoperative recovery was uneventful. Culture of intraoperative specimens grew Staphylococcus aureus, and a 6-week course of intravenous antibiotics was started. After 1 year, he had no signs of recurrence.
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Figure 1. Preoperative contrast-enhanced computed tomography showing the origin of the pseudoaneurysm at the distal ascending aorta (arrow).
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DISCUSSION
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Surgery for ascending aortic pseudoaneurysm must be carefully planned. Major concerns are the surgical approach, control of bleeding, release of adhesions, placement of the aortic cross clamp, and myocardial protection with cardioplegia or left ventricular venting. Peripheral CPB via the femoral vessels with systemic hypothermia before reopening the sternum is a well-known strategy, permitting DHCA in the event of major bleeding due to entering the pseudoaneurysm during sternotomy or dissection of adhesions.1 However, this approach has some intrinsic risks. Retrograde aortoiliac dissection and ischemia or muscle necrosis in the cannulated leg are potential complications of femoral arterial cannulation.4 Retrograde flow through the femoral artery could be dangerous in patients with an atheromatous or dissected descending aorta, with a high risk of brain damage due to retrograde emboli or malperfusion.4 If venous drainage is inadequate, only partial CPB may be instituted, prolonging the perfusion time to reach the hypothermic state.4 Furthermore, prolonged perfusion time and hypothermia predispose to abnormal bleeding, a risk already increased by the presence of infection and in cases of reoperation.3 Moderately hypothermic (25°C–30°C) coronary perfusion can induce ventricular fibrillation, a serious complication in patients with significant aortic regurgitation. Inability to infuse cardioplegia or vent the left ventricle with severe incompetence of the aortic valve poses a risk of left ventricular dysfunction resulting from the over-stretching of myocardial fibers that occurs between the onset of ventricular fibrillation and DHCA.5
Several strategies have been developed to overcome these concerns. In patients with an atheromatous or dissected descending aorta, cannulation of the axillary artery may avoid cerebral embolization and organ malperfusion.4 To reduce hypothermic perfusion time, the degree of systemic hypothermia before repeat sternotomy can be tailored according to the distance of the pseudoaneurysm from the sternum.3 In the event of pseudoaneurysm rupture during sternal reentry or freeing of adhesions, a Foley catheter could help to control the bleeding until adhesions between the heart and the sternum are released and the distal aorta just before the innominate artery is circumscribed and cross clamped.6 The Heartport system (Heartport, Inc., Redwood City, CA, USA) has been used successfully to manage ascending aortic pseudoaneurysms.5 By permitting endoaortic clamping, left ventricular venting and cardioplegia administration before incision and DHCA, this system can avoid some drawbacks following systemic hypothermia before reopening the sternum (i.e. freeing adhesions for exposure and clamp placement at the expense of brain ischemia, and left ventricular distension before sternal entry). Good experience with port-access procedures is needed as there may be no site to place the Endo-clamp if the entry port is too high or too close to the brachiocephalic trunk, or if the dimensions of the ascending aorta exceed 40 mm which is the maximum size that can be clamped with currently available balloons. High cost also limits widespread application of this technique.5
Several techniques for mycotic ascending aortic pseudoaneurysm repair have been reported: patch repair with allograft material, Dacron, or bovine pericardium and tube replacement with a Dacron prosthesis or homograft.1,3,7 The technique chosen depends on the size of the false aneurysm lumen and overall quality of the remaining healthy aorta. In mycotic pseudoaneurysm, our policy is radical excision of all infected material. If feasible, a patch is used, and the sutures are anchored in healthy aortic tissue. As in other reports, we advise caution with conservative local repair in patients with history of aortic dissection or aortitis, because the suture-holding capacity of the native aorta could be insufficient to prevent recurrent pseudoaneurysm formation or fatal aortic rupture.3 If the aorta shows signs of infection and has a tendency to tear, we perform Dacron tube graft replacement. The best material for aortic replacement is still debated. Because homografts have proved resistant to active infection in aortic root sepsis, some surgeons prefer allograft material.3 In the absence of a homograft bank, this option is not available in urgent or emergency cases. Furthermore, satisfactory results have been reported with Dacron grafts.1,7 Recently, catheter-based interventions have been considered in patients who are poor surgical candidates. Komanapalli and colleagues8 described successful use of an Amplatzer septal occluder device (AGA Medical Corp, Golden Valley, Minn, USA) to exclude an ascending aortic pseudoaneurysm in a patient for whom repeat sternotomy and traditional open repair carried significant risk. This avoided surgical morbidity and thromboembolic complications, and had effectively treated the pseudoaneurysm at the 6-month follow-up.
We have described successful management of a mycotic ascending aortic pseudoaneurysm using an alternative strategy: cannulation of the aortic root and restarting perfusion through the prosthesis after performing the distal anastomoses. This overcomes concerns related to femoral arterial cannulation, and reduces the time of hypothermic circulatory perfusion and DHCA. This alternative strategy should be keep in mind when computed tomography shows a low risk of entering the pseudoaneurysm during repeat sternotomy and the possibility of performing arterial cannulation in the aortic root.
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REFERENCES
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ABSTRACT
INTRODUCTION
