Septic rupture of the ascending aorta after aortocoronary bypass surgery
© Sommer et al; licensee BioMed Central Ltd. 2008
Received: 17 July 2008
Accepted: 16 December 2008
Published: 16 December 2008
We describe an exceptional case of non-fatal septic rupture of the ascending aorta in a patient with sternal dehiscence, deep sternal wound infection (DSWI) and pleural empyema after aortocoronary bypass surgery. Routine follow-up computed tomography (CT) detected a mediastinal pseudoaneurysm originating from the ascending aorta. Thereby, massive and irregular sternal bone defects and contrast-enhancing mediastinal soft tissue suggest osteomyelitis and highly-active and aggressive DSWI as initial triggers. Urgent thoracotomy 1 day later included ascending aorta reconstruction, total sternum resection and broad wound debridement. Follow-up CT 1 year later showed a regular postoperative result in a fully recovered patient.
Sternal dehiscence is a frequent complication after aortocoronary bypass surgery with an incidence estimated at 1% to 6% in a normal population . When complicated by sternum osteomyelitis and DSWI, prolonged hospitalization and increased cost of care, morbidity and mortality as high as 20% is reported . Broken wire fixations and displaced bone fragments with non-physiological sternal movement seem to be essential in its pathogenesis . Obesity, diabetes mellitus, chronic obstructive pulmonary disease and previous sternotomy make up the major risk factors . Despite antibiotic therapy and aggressive surgical interventions, the prognosis is serious . In this case report, we describe a patient developing non-fatal septic rupture of the ascending aorta with mediastinal pseudoaneurysm triggered by sternum osteomyelitis and extensive DSWI after aortocoronary bypass surgery.
Midline sternotomy is by far the most common surgical approach in cardiac surgery. One disadvantage of this technique is the relatively frequent occurence of sternal dehiscence with instability . It is described as non-physiological sternal movement after disruption of wire fixations . Because of its decreased blood supply, especially the lower sternal third is affected. Moreover, utilization of the internal mammary artery for coronary artery bypass grafting leads to additional and acute reduction of the sternal blood supply . When this situation is complicated by infection, which occurs especially in patients with immunosuppression, sternum osteomyelitis and DSWI might develop as devastating complications despite strict sterility and antibiotic prophylaxis . In case of aggressive mediastinal propagation, cardiac suture lines might be eroded with septic shock or hemorrhage as fatal complications . It is well known, that continuous bacterial spread from or within a soft tissue compartment might cause vascular infection characterized as bacterial aortitis, infected aorta, ruptured mycotic aneurysm or spontaneous non-aneurysmal suppurative vascular rupture . Sugawara et al. described a ruptured abdominal aorta secondary to klebsiella pneumonia psoas muscle abscess . The typical mechanism of aortic rupture, which is expansion of an atherosclerotic aneurysm, is virtually impossible in our patient. Neither the short period of only 9 months nor pseudoaneurysm configuration directly within the DSWI support this. Much more probable is chronic septic vascular erosion resulting in aortic rupture with pseudoaneurysm formation. Aggressive surgical interventions with broad wound debridement, plastic reconstruction, bone removal and mediastinal irrigation with antiseptic solutions in combination with intravenous antibiotic therapy seem to be the only chance to control extensive sternal osteomyelitis with DSWI and to prevent even worse complications . Accomplished in our patient, admission to a peripher hospital was possible in good clinical condition 22 days later and outpatient routine follow-up CT 1 year later documented a regular postoperative result in a fully recovered patient.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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