Ann Thorac Surg 1998;66:1818-1819
© 1998 The Society of Thoracic Surgeons
Case Reports
Homograft failure in mycotic aortic aneurysm caused by streptococcus pneumoniae
Pascal A. Berdat, MDa,
Raffaele Malinverni, MDb,
Beat Kipfer, MDa,
Thierry P. Carrel, MDa
a Clinic for Thoracic and Cardiovascular Surgery, University Hospital of Berne (Inselspital), Berne, Switzerland
b Medical Policlinic, University Hospital of Berne (Inselspital), Berne, Switzerland
Accepted for publication May 8, 1998.
Address reprint requests to Dr Berdat, Clinic for Thoracic and Cardiovascular Surgery, Inselspital, 3010 Berne, Switzerland
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Abstract
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Treatment of a rare Streptococcus pneumoniae mycotic aneurysm by homograft replacement failed in a 59-year-old patient because of persistent lobar pneumonia. Despite reoperation with replacement of the infected homograft by a fresh one, he finally died of septicemia. This case illustrates that homograft tissue may be infected per continuum and that extensive debridement of periaortic tissue—including major lung resection—and the use of muscle flaps may be necessary in certain circumstances.
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Introduction
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A 59-year-old man was admitted to our hospital with a large mycotic aneurysm of the proximal descending aorta. He had previously been treated with oral azithromycin (Zithromax; Pfizer Co, Zurich, Switzerland), 500 mg/day during 10 days, for a pneumonia of the left upper lobe. Several weeks later hospitalization became necessary because of severe chest pain, weight loss, and onset of hoarseness and hemoptysis. At this time, a bronchoscopy was normal and neither bronchial lavage nor blood cultures showed any pathogens. Diagnosis of the mycotic aneurysm was established soon after admission by computed tomography (Fig 1).
An operation was performed through a left posterolateral thoracotomy and with femorofemoral bypass. A short period of deep hypothermic circulatory arrest was necessary to control the distal aortic arch. Dense adhesions between the left lung and the descending aorta were found. The mycotic aneurysm was excluded by interposition of a cryopreserved aortic homograft (Fig 2) with the proximal and distal suture line being made with healthy-looking aortic tissue. Biopsy specimens of the wall of the aneurysm showed necrotic aortitis, and cultures of the excised tissue identified Streptococcus pneumoniae.
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Fig 2. Intraoperative view of the homograft in situ (arrow = proximal suture line; asterisk = homograft.)
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The initial recovery was uneventful, but 3 weeks later hemoptysis and fever reappeared despite postoperative continuous intravenous ceftriaxone (Rocephin; Roche Pharma Co, Reinach, Switzerland), 2 g/day. Repeated computed tomography showed bleeding, most probably at the level of the distal anastomosis. At reoperation, the left lung was completely necrotic and a dehiscence of the distal homograft anastomosis was found. Therefore, left pneumonectomy was performed and the infected homograft was replaced by a fresh, vancomycin-soaked (Vancocin CG; Lilly SA, Vernier, Switzerland) homograft, covered by a diaphragmatic and serratus muscle flap. Through a small thoracic window, daily rinses with povidone iodine (Betadine; Mundipharma Pharmaceutical Co, Hamilton, Bermuda) were applied. Histologic examination of the excised homograft showed an acute infection with pneumococci and Candida. Fluconazol (Diflucan; Pfizer Co, Zurich, Switzerland) was therefore added to ceftriaxone. After isolation of coagulase-negative staphylococci inside the wound, the antibiotic regimen was adjusted with vancomycin and imipenem/cilastatin (Tienam; MSD, Glattbrugg, Switzerland). Despite the broad antibiotic treatment, pneumonia of the right lung developed, and the patient died of septicemia 17 days later. At autopsy, the homograft was completely healed and there were no signs of persistent infection in the left pleural cavity.
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Comment
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Treatment of mycotic aneurysms, which account for 0.8% of aneurysms operated on [1], requires an aggressive approach including adequate antimicrobial therapy and immediate surgical repair. To deal with the difficult problem of infected aorta or aortic prosthetic material, many surgeons prefer homograft material, which seems to be advantageous theoretically, experimentally [2], and clinically [3–6]. Isolation of Streptococcus pneumoniae in mycotic aneurysms seems to be very rare [7], and the role of this pathogen in cardiovascular infections remains unclear.
Considering the promising results obtained with cryopreserved homografts in the treatment of aortobronchial fistulas [5, 8], we decided to treat our patient with this modality. Although several authors suggest that homografts may be more resistant to infection, because of mechanisms that are still poorly understood [2, 4, 5], the cryopreserved homograft in our patient failed. The finding at reoperation was consistant with infection per continuum of the homograft caused by the persistent purulent pneumonia. We therefore think that a concomitant upper lobectomy at the time of initial repair or coverage of the homograft by a muscle flap might have protected the homograft and its anastomosis from recurrent infection. Recurrent or persistent infection with septicemia is the leading cause of death in these patients, with mortality rates ranging from 8.3% to 25%. However, death caused by homograft-related problems seems to be remarkably rare, as only 1 case of late death was reported in two series of 8 and 19 patients, respectively [4, 6]. Our patient as well did not die of a homograft-related complication, because at autopsy the operative site presented no signs of persisting infection and the second homograft was perfectly healed. We think that the local healing was primarily the result of the eradication of the infection focus by pneumonectomy and the use of muscle flaps to cover the homograft. It remains speculative if the fresh, antibiotic-soaked homograft was more resistent to infection than the cryopreserved one. The patient most probably succumbed to contralateral pneumonia persisting despite adjusted antibiotic and antifungal treatment. Because no immunologic deficiency could be demonstrated, the reason for this intractable infection with Streptococcus pneumoniae remains unclear.
From this observation we have learned that local debridement of infected periaortic tissue alone might be insufficient for safe healing and that in some circumstances much more aggressive resection of periaortic structures—including lung tissue—or protection of the homograft by a muscle or omental flap is probably required even when fresh or cryopreserved homografts are used to replace the diseased aortic segment.
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References
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- Svensson L.G., Crawford E.S. Cardiovascular and vascular disease of the aorta. Philadelphia: Saunders, 1996:126-152.
- Koskas F., Goeau-Brissonnière O., Nicolas M.H., Bacourt F., Kieffer E. Arteries from human beings are less infectible by Staphylococcus aureus than polytetrafluoroethylene in an aortic dog model. J Vasc Surg 1996;23:472-476.[Medline]
- Cordero J.A., Jr, Darling R.C., III, Chang B.B., Shah D.M., Paty P.S., Leather R.P. In situ prosthetic graft replacement for mycotic thoracoabdominal aneurysms. Am J Surg 1996;62:35-39.
- Knosalla C., Weng Y., Yankah A.C., Hofmeister J., Hetzer R. Using aortic allograft material to treat mycotic aneurysms of the thoracic aorta. Ann Thorac Surg 1996;61:1146-1152.[Abstract/Free Full Text]
- Vogt P.R., Pfammatter T., Schlumpf R., et al. In situ repair of aortobronchial, aortoesophageal, and aortoenteric fistulae with cryopreserved aortic homografts. J Vasc Surg 1997;26:11-17.[Medline]
- Vogt P.R., von Segesser L.K., Goffin Y., et al. Eradication of aortic infections with the use of cryopreserved arterial homografts. Ann Thorac Surg 1996;62:640-645.[Abstract/Free Full Text]
- Gelabert H.A., Quinones-Baldrich W.J. Mycotic aneurysm of the suprarenal aorta secondary to Streptococcus pneumoniae: an unusual pathogen. Ann Vasc Surg 1991;5:529-532.[Medline]
- Abad C., Hurle A., Feijoo J., Gomez-Marrero J., Abdallah A. Total aortic arch replacement by a cryopreserved aortic homograft. Eur J Cardiothorac Surg 1995;9:531-533.[Abstract]
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