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Eur J Cardiothorac Surg 2002;21:158-159
© 2002 Elsevier Science NL
Letter to the Editor |
Divisions of Cardiothoracic Surgery and Cardiology, University of Wisconsin Hospitals and Clinics, 600 Highland Avenue, Madison, WI 53792-3236, USA
Received 30 July 2001; received in revised form 25 October 2001; accepted 5 November 2001.
* Corresponding author. Tel.: +1-317-274-7728; fax: +1-317-274-2940
e-mail: mhc1100{at}yahoo.com
Prosthetic valve endocarditis (PVE) remains a rare, although formidable complication following mechanical heart valve replacement. Attempts to inhibit bacterial invasion of the prosthetic sewing ring have been relatively unsuccessful. A new generation of mechanical heart valves have been coated with silzone, in an attempt to limit infection. We describe a case of primary mitral valve replacement using a silzone-coated mechanical valve that was complicated by acute severe PVE, resulting in valve instability. We thus add to a growing literature on efficacy of silzone valves, that has resulted in their withdrawal from the mechanical valve market.
A 63-year-old white male underwent mitral valve replacement for mitral regurgitation secondary to rheumatic heart disease. Intraoperatively, the mitral annulus was found to be dilated, and chordal shortening was present. The native valve was excised and replaced with a silzone-coated #29 St Jude mitral valve prosthesis (St. Jude Medical, S.C., Inc., One Lillehei Plaza, St. Paul, MN, 55117). There was no documented allergy to silver. The prosthetic valve was seated without complication. Intraoperative transesophageal echocardiogram, showed no perivalvular leak. Post operatively, the patient was maintained on vancomycin and ceftriaxone for 5 days.
The patient was readmitted to an outlying hospital, 3 weeks later with fever and chills. Echocardiography showed vegetations on the silzone valve. Empiric vancomycin and gentamicin therapy was commenced at this hospital. Blood cultures grew methicillin resistant staph aureus (MRSA). At the University of Wisconsin hospital, the patient, now with renal insufficiency was taken urgently to the operating room. At reoperation, the patient was found to have vegetations and inflammatory tissue on the sewing ring and leaflets of the silzone-coated valve. The valve was unstable. After explanting the valve, the annulus was thoroughly irrigated and debrided of infected inflammatory tissue. A St Jude (non-silzone-coated) prosthesis was placed in the mitral position, which on intraoperative echocardiogram was functioning normally. Postoperatively, the patient developed supraventricular tachycardia that degenerated into ventricular fibrillation. He was successfully resuscitated using advanced cardiac life support (ACLS) protocol, and was then taken emergently back to the operating room for re-exploration for bleeding. He had a difficult postoperative course from persistent septic issues. He required dialysis for his worsening renal failure, in addition to having a sudden cardio-respiratory arrest, from which he was resuscitated and reintubated. He however deteriorated into multiorgan system failure from sepsis. The family elected no further treatment and the patient expired. The mitral valve vegetation showed histological features of endocarditis but no bacterial growth.
The poor prognosis of PVE is related to the valve sewing cuff, with relatively few microorganisms being needed to initiate a serious infection. St Jude masters series valves with silzone coating were designed to prevent the development of PVE through bacteriostatic inhibition of microorganisms to the sewing cuff. There are several clinical reports that claim mixed experiences with the new generation of silzone valves. One case showed that use of the silzone valve in the aortic position was associated with PVE post operatively, requiring a homograft for definitive therapy. Despite, initial clinical experiences by other groups with the silzone valves for non-infective disease of the aortic or mitral positions, showing no subsequent PVE, and no toxic effects of the silzone valve on the patients, further studies by others have not at present upheld the treatment of PVE with the silzone valves. Probably the most definitive data could have been provided by the artificial valve endocarditis reduction trial (AVERT) trial. This multicenter randomized trial was to have assessed the efficacy of the silzoneTM coated valves in the reduction of PVE, over a 4 year period, although with the concerns regarding the valve, the trial has been interrupted. We feel that close attention should be made to the strict infection prophylaxis that accompanies valve replacements, while advances in valve biology are made. It maybe that while future coated valves are suited to resist infection, silzone at the present time is not the answer.
This article has been cited by other articles:
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  G. L. Grunkemeier and Y. Wu The Silzone effect: how to reconcile contradictory reports? Eur. J. Cardiothorac. Surg., March 1, 2004; 25(3): 371 - 375. [Abstract] [Full Text] [PDF]
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