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Ann Thorac Surg 2001;72:758-762
© 2001 The Society of Thoracic Surgeons
a Department of Thoracic and Cardiovascular Surgery, University Hospital RWTH, Aachen, Germany
b Medical Clinic I, University Hospital RWTH, Aachen, Germany
Accepted for publication April 5, 2001.
Address reprint requests to Dr Seipelt, Department of Thoracic and Cardiovascular Surgery, Universitätsklinikum RWTH Aachen, Pauwelsstr 30, G-52074 Aachen, Germany
e-mail: rseipelt{at}post.klinikum.rwth-aachen.de
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Abstract |
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Methods. From January 1998 to December 1999, the SJM "Silzone" valve was implanted in 40 consecutive patients with active endocarditis (20 aortic, 14 mitral, and 6 both valves). Late transesophageal echocardiography was performed in 87% of survivors, and transthoracic echocardiography in the remaining 13%. Follow-up was 100%.
Results. Hospital mortality was 17.5%. Early PVE occurred in 2 of 40 patients (5%). There were two late deaths without signs of recurrent PVE. A hemodynamic relevant paravalvular leak necessitating reoperation was seen in 2 patients within 6 months after operation. The rate of a minor paravalvular leak was 13% (4 of 31 patients).
Conclusions. The SJM "Silzone" valve when implanted for active bacterial endocarditis does not give better results than other mechanical prostheses with regard to early recurrence of endocarditis. The rate of a hemodynamic relevant paravalvular leak requiring reoperation seems rather high during the early postoperative period, whereas the occurrence of minor paravalvular leaks is comparable with that of other mechanical prostheses. Routine observation, recommended for all patients with mechanical heart valves, is also sufficient for patients with the SJM "Silzone" valve.
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Introduction |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Patients with preoperatively active native or prosthetic valve endocarditis are at increased risk for postoperative PVE [1, 2]. Particularly in this group of patients, the SJM "Silzone" valve is expected to reduce recurrent endocarditis. The aim of the present study was to examine prospectively the efficiency of the "Silzone" valve to avoid recurrent PVE in cases of heart valve replacement for active bacterial endocarditis and retrospectively to detect the frequency of paravalvular leakage.
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Material and methods |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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The diagnosis of bacterial endocarditis was based on the clinical signs of infection together with typical abnormalities in laboratory findings, echocardiography, and positive blood cultures, as well as the intraoperative aspects of the valve itself.
Preoperative examinations
Fifteen patients (37.5%) were in New York Heart Association (NYHA) functional class III and 25 (62.5%) in NYHA functional class IV. Mechanical ventilation was necessary in 9 patients (22.5%) preoperatively. The indications for operation are summarized in Table 1. Among the 17 patients who suffered systemic embolization, 9 had emboli to the central nervous system, 3 to the spleen, and 5 had multiple emboli.
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Before surgery, all but 2 patients were on a regimen of intravenous antibiotics for various periods of time (mean 17 ± 15 days, range 0 to 59 days). The 2 patients without antibiotic treatment presented with subfebrile temperatures only, and the diagnosis of active infection was based on the intraoperative appearance of the valve and the presence of acute inflammatory changes in the histological examination of the removed tissue, positive in culture.
Transesophageal echocardiography was done in all patients before operation. It revealed vegetations on 14 (13 native and one mechanical valve) of 26 aortic valves and on 14 (12 native and two mechanical valves) of 20 mitral valves. Abscess cavities could be identified in 13 patients (6 patients with prosthetic valve endocarditis). Four patients had an endocarditis-related ventricular septal defect.
Coronary angiography was performed in 27 patients at a median time of 5.5 days before operation (range 0 to 70 days). Two patients with early PVE had had coronary angiography before the first heart valve procedure. Significant coronary artery disease was detected in 5 of the 29 studied patients (17.2%).
Operative technique
All patients were operated on cardiopulmonary bypass under moderate hypothermia (28°C) and cardioplegic arrest with either antegrade cold crystalloid cardioplegia (4°C; Bretschneider HTK, Dr Franz Koehler Chemie, Alsbach-Hählein, Germany) or intermittent antegrade and retrograde cold blood cardioplegia, depending upon the surgeons’ preference.
Patients with infection limited to the valve leaflets were treated by valve replacement only. If the infection had extended into or beyond the annulus, an aggressive debridement of all infected tissue and reconstruction of the left ventricular outflow or inflow tract was performed with autologous pericardium. In 4 patients, an endocarditis-related ventricular septal defect was closed by an autologous pericardium patch with a running 4-0 polypropylene suture. The Silzone-coated St. Jude Medical prosthesis was implanted in mitral position with Teflon patch-armed 2-0 Ticron mattress sutures. In aortic position, single 2-0 Ticron sutures were used, when the infection was confined to the valve tissue only. In cases with involvement of the annulus and aortic root, the prosthesis was fixed with Teflon-armed 2-0 Ticron mattress sutures, which were placed in part across the aortic root with the patch on the outside. Special attention has to be given to the nearby coronaries. Simultaneous coronary artery bypass grafting was necessary in 5 patients. The different operations are summarized in Table 2.
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Postoperatively, patients received intravenous antibiotics for an average of 24 ± 13 days. Afterwards, all antibiotic treatment was continued for 3 to 4 months in patients with positive cultures from the tissue excised at operation, but for 1 month only, when the specimens were sterile.
All hospital survivors underwent transthoracic echocardiography (TTE) before discharge, 3 months later, and afterwards every year. All 31 patients who were alive in June 2000 attended the outpatient clinic for clinical and echocardiographic evaluation. In 27 of 31 patients (87%), a transesophageal echocardiography (TEE; Sonos 5500; Hewlett-Packard, Palo Alto, CA) was performed, and in 4 patients, a TTE was performed. A high-velocity, eccentric turbulent jet with its origin beyond the edge of the sewing ring in the Doppler color flow was considered as paravalvular regurgitation and as mild, moderate, and severe as described previously [7]. Moderate to severe paravalvular regurgitation was considered as a hemodynamically relevant leak in need of surgical reintervention.
Statistical analysis
Statistical analysis was performed with the Statistical Package for Social Sciences (Version 9.0; SPSS Institute, Chicago, IL). Statistical differences between nominally and ordinally scaled variables were determined with 
2 test. Continuous variables were compared with Wilcoxon two-sample test; p values less than 0.05 were considered significant. Variables with p values less than 0.10 by univariate testing were entered into a multivariate logistic regression model. The Kaplan-Meier method was used to estimate event-free survival probabilities.
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Results |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Three patients (7.5%) required reexploration for excessive bleeding. Prolonged mechanical ventilation (
48 hours) was necessary in 8 patients (20%). Eight patients required dialysis for either preexisting (5) or new occurrence (3) of renal failure. The median stay on the intensive care unit was 3.5 days (range 1 to 34 days). One patient required a permanent transvenous pacemaker because of postoperative complete heart block. Twenty patients (50%) had an uneventful postoperative course.
Late follow-up
Follow-up information was available in all 33 hospital survivors. Mean follow-up was 17 ± 8.5 months (range 3 to 28 months). There were two late deaths. One patient died 3 months after surgery due to persistence of preoperative cerebral damage, the other patient died 9 months after surgery due to progressive congestive heart failure, but without signs of recurrent endocarditis.
Thirty-one patients (77.5%) were alive at follow-up, with 29 patients in NYHA functional classes I and II and 2 patients (6.5%) in class III. One patient suffered a subdural hemorrhage 2 months after operation but recovered without residual deficits. Other anticoagulant-related complications or thromboembolic events were not observed.
Recurrent endocarditis and paravalvular leak
Early PVE occurred in 2 of 40 patients (5%). One patient with Staphylococcus epidermidis native valve endocarditis and an abscess died in septic shock with early PVE 18 days after operation. In the second patient with Streptococcus mitis mitral valve endocarditis, early PVE (Staphylococcus epidermidis) with hemodynamic relevant paravalvular leak occurred 7 weeks after operation (Fig 1). This patient underwent reoperation (re-replacement with a SJM "Silzone" valve), but the endocarditis recurred again after 2 months, and a third operation was necessary (re-re-replacement with SJM Masters Series). In the echocardiographic examination 3 months after the last operation, a relevant paravalvular leak was detected again.
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The overall rate of a clinically irrelevant paravalvular leak was 13% (4 of 31) with regard to the number of patients and 11% (4 of 36) with regard to the implanted valves, all in aortic position. These patients were doing well without signs of hemolysis, infection, or congestive heart failure. There was no late PVE, and the endocarditis-free survival rate was 94.6% at 2 years (Fig 2).
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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In the present study, the SJM "Silzone" valve was implanted in 40 patients with proven active bacterial endocarditis, and therefore only in patients for whom the prosthesis was originally intended. The hospital mortality of 17.5% in these critically ill patients is comparable with data from other reports in the literature [8–12]. Most reports describe a substantially higher hospital mortality in patients operated upon for prosthetic than for native valve endocarditis [8–10, 13]. However, due to the small number of patients, this difference does not reach statistic significance in our series. Independent predictors of hospital mortality in our group were the presence of an abscess cavity as a sign of advanced infective destruction and severe congestive heart failure paired with ongoing septicemia.
In spite of strict preoperative and postoperative antibiotic therapy, recurrence of endocarditis after valve replacement is quite high and ranges between 2.5% and 11.4% [8, 10–12, 14]. The wide range reflects the different definitions used for early PVE (ie, PVE within 60 days, within 3 months, or within 4 months) as well as the differences in inclusion criteria. In this regard, the 5% recurrence rate of the present series is rather favorable.
With regard to early PVE, the antimicrobial benefit of the silver coating in the SJM "Silzone" valve, even though proven in animal experiments [3], seems to be uncertain in the clinical setting. This is in accordance with a recent animal study, which showed better prevention of bacterial infection, colonization, and abscess formation in sewing ring fabrics coated with antibiotics than with silver [15]. Therefore, the antibiotic-coated sewing ring could be a more promising approach to reduce PVE. However, further studies are necessary to find an appropriate agent effective for the whole variety of microorganisms responsible for endocarditis.
Late PVE did not appear in the present series, but the study is limited to a relatively short-term follow-up, and longer follow-up will be necessary to confirm the efficiency of the SJM "Silzone" valve with regard to reduction of late PVE.
Little information is available about the frequency of paravalvular leaks in the literature. In a recent study by Rallidis and associates [16], the incidence of mild paravalvular leakage for mechanical valves was 44% after aortic valve replacement. Two other reports found rates of 14% and 24%, respectively [17, 18], but none of the studies deals solely with valve replacement for active endocarditis. Therefore, the overall rate of mild paravalvular leakage of 11% with regard to the implanted valves and 13% with regard to the number of patients in our series compares favorably with others. One reason for the appearance of mild paravalvular leakage without recurrent endocarditis could be the silzone coating of the sewing cuff, which might impair tissue ingrowth into the cuff and pannus formation on its surface [5]. While a mild paravalvular leak without signs of recurrent endocarditis or significant hemolysis does not need reoperation, a moderate or severe paravalvular leak, as found in 2 patients in our series, needs reoperation irrespective of the presence of early PVE or not. The 5% significant early paravalvular leakage with the "Silzone" valve in our patients is slightly higher but not much different from the proportion reported in the literature, which ranges between 1% and 4.2% [14, 19, 20].
Over time, relevant paravalvular leaks are reported in 4% to 16% [11, 14, 19, 20]. A possible reason for such wide range and the fact that we did not see significant paravalvular leaks in our series may be the difference in mean follow-up time, which is 17 months in our series and ranges from 38 to 148 months in the above-mentioned studies. Even though we did not find but minor paravalvular leaks with the "Silzone" prosthesis, in the long term, careful observation of the patient population is mandatory. However, patient monitoring does not need to be more extended than it is for all patients with an implanted prosthetic heart valve. According to our results, an elective exchange of a normally functioning SJM "Silzone" prosthesis is not justified until now.
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References |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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