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Ann Thorac Surg 2002;74:S1781-S1785
© 2002 The Society of Thoracic Surgeons
a Cardiothoracic Surgery, Mount Sinai School of Medicine, New York, New York, USA
b Biomathematics, Mount Sinai School of Medicine, New York, New York, USA
* Address reprint requests to Dr Hagl, Division of Thoracic and Cardiovascular Surgery, Hanover Medical School, Carl-Neuberg-Strasse 1, Hanover 30625, Germany
e-mail: chagl{at}hotmail.com
Presented at the Aortic Surgery Symposium VIII, May 2–3, 2002, New York, NY.
Abstract
BACKGROUND: The use of prosthetic material (rather than a homograft) for ascending aorta/aortic valve replacement (Bentall procedure) in cases of acute prosthetic valve endocarditis is controversial. We report favorable results using this technique almost exclusively (a homograft was used in only 3 patients with hematological problems) during a 12-year interval.
METHODS: Twenty-eight patients (55 ± 14 years; 22 male) underwent a Bentall procedure for acute prosthetic valve endocarditis between 1988 and 2000. Twenty-five patients had undergone previous aortic valve replacement (1 with concomitant mitral valve replacement, 4 with coronary artery bypass grafting), and 3 had had a previous Bentall operation. The median interval between initial surgery and reoperation was 13 months (range, 1 to 106). Sixty-eight percent of operations were urgent or emergencies. Ninety-three percent of patients had significant aortic regurgitation; complete annuloaortic dehiscence occurred in 71%, and in 57%, an abscess was found. Causative organisms were identified in 25 of 28 patients: Staphylococcus epidermidis (9), Staphylococcus aureus (7), Streptococcus viridans (6), Pseudomonas (2), and Legionella (1).
RESULTS: Twenty-three patients had mechanical and 5 had biological valves implanted during the Bentall procedure. Hypothermic circulatory arrest was used in 64%. Hospital mortality was 11%: there was one intraoperative death, and two before discharge (one cardiac, one sepsis). Eighty-nine percent survived without stroke. During follow-up (median, 44.5 months; complete in 92%), 1 patient died of recurrent endocarditis at 4 months.
CONCLUSIONS: These results indicate that prosthetic root replacement may be superior to use of a homograft for acute aortic prosthetic valve endocarditis, with only a 4% incidence of recurrent endocarditis and reoperation.
Although advances in antimicrobial therapy and the development of better diagnostic and surgical techniques have in general reduced the morbidity and mortality of infectious endocarditis, it remains a potentially life-threatening disease. In patients with aortic prosthetic valve endocarditis, conservative medical treatment is rarely successful and reoperation is routinely required, especially when aortic regurgitation is present or when periannular tissue is destroyed. Surgical therapy involves excision of necrotic tissue, drainage of abscesses, closure of fistulas, complete removal of prosthetic material, and reconstruction or replacement of the aortic root or entire ascending aorta. Even with aggressive surgical therapy, the infection may be difficult to eradicate, and mortality and morbidity are high.
The use of biological materials (homografts [1] or even autografts [2]) in aortic prosthetic valve endocarditis is the generally accepted treatment. Reinfection rates have been reported to be low [3], and this has been attributed to improved penetration of antibiotics and the presence of viable cells [4]. But the shortage of homografts, high early calcification rates, and the favorable results of endocarditis treatment with prosthetic material [5, 6] have recently revived the controversy as to whether infectious endocarditis can be treated successfully without using biological material. The present study analyzes the outcome in 28 consecutive patients in a single institution who underwent a Bentall procedure as treatment for acute prosthetic valve endocarditis that required replacement of the aortic annulus.
Material and methods
Between August 1988 and October 2000, 28 patients with acute prosthetic valve endocarditis (biological, n = 4; mechanical, n = 24) involving the aortic root, the proximal ascending aorta, or both underwent a Bentall operation at Mount Sinai Medical Center and were reviewed retrospectively. Median age of the study patients was 57 (27 to 76) years; 22 patients (79%) were male. Twenty-five patients had undergone aortic valve replacement as their first operation: 1 in combination with mitral valve replacement due to endocarditis, and 4 in combination with coronary artery bypass grafting. Three patients had had earlier Bentall operations. The median interval between the first and second operation was 13 months, and ranged from 1 to 106 months. Sixty-eight percent of patients were operated on urgently or as emergencies. Further clinical characteristics of the cohort as a whole are given in Table 1. During the same time interval, 21 patients with prosthetic valve endocarditis underwent isolated aortic valve replacement and repair of annular destruction, and 3 patients had implantation of homografts because of contraindications to anticoagulation.
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Complete follow-up information (median, 44.5 months; range, 2 to 135 months) was available in 23 of 25 hospital survivors (92%), with a cumulative follow-up of 1,279 months. Routine late follow-up information was supplemented by calls to patients and their relatives, and conversations or correspondence with referring physicians.
Surgical technique
All patients underwent a Bentall procedure through a median sternotomy: 10 in the classic fashion, 13 using the button Bentall technique, and 5 using the Cabrol modification. A detailed description of these surgical techniques has previously been published by Midulla and associates [7].
In our cohort, a mechanical valve was used in 23 patients (82.1%). A biological valve was used in 5 (17.9%) older patients. In 18 (64%), a brief period of hypothermic circulatory arrest was used to perform an open distal anastomosis. A classic Bentall without an open distal anastomosis was primarily performed in the earlier years of the study, and the button Bentall technique, including an open distal anastomosis, was the technique of choice in the later years under scrutiny. Meticulous care was taken to remove all infected or necrotic tissue, independent of whether the conduction system was involved. All abscesses were curetted until firm tissue was encountered. Defects were closed by direct suture; care was taken to place the stitches in viable tissue away from the edge of the created defect. If direct closure of defects created by removal of necrotic tissue was not possible, inside and outside patches of pericardium or Teflon felt were used to create tension-free anastomoses. For safe anchoring of the prosthesis in ventricular muscle, interrupted pledgeted mattress sutures were used. In the patient with the accompanying ventricular septal defect, transmural sutures were taken along the septum.
Postoperative care
In all patients in whom microorganisms could be identified, antibiotic therapy was specifically directed towards the causative organism; patients with unknown organisms were treated with vancomycin and broad-spectrum gram-negative coverage. Antibiotic treatment was continued for at least 2 to 8 weeks postoperatively, and echocardiography was used to monitor the success of treatment. In general, our policy has been to base postoperative therapy on operative findings. If intraoperative cultures are positive, postoperative therapy is at least 6 weeks; if cultures are negative but organisms are seen on stain, postoperative therapy is at least 4 weeks, and if cultures and stains are negative, 2 weeks of postoperative therapy are given. Echocardiography as well as computed tomography scans with contrast were routinely performed 6 months after surgery, and then yearly to identify possible recurrent endocarditis.
Results
Surgical outcome
Complete reconstruction of the annulus was accomplished in all patients. Hospital mortality was 11%. One patient died in the operating room due to cardiac failure, and another patient succumbed several days postoperatively of cardiac causes. One patient, who was admitted with hemodynamic compromise, fever, and severe leukocytosis, died postoperatively of septic complications with renal shutdown and multiorgan failure. One patient suffered a transient stroke, but recovered fully before discharge from the hospital. There were no permanent strokes or embolic complications. In contrast, of the 21 patients with acute aortic prosthetic endocarditis who underwent the more conservative alternative of aortic valve replacement and repair of annular destruction rather than a Bentall procedure during the same interval, there was an operative mortality of 29% (6 patients).
The most common postoperative complication (22%) was complete atrioventricular block requiring pacemaker placement (present in only 1 patient preoperatively). The necessity for tracheostomy due to prolonged intubation was another frequent complication (Table 2). Three patients had a temporary renal shutdown; 2 recovered completely and 1 remained on dialysis. Median hospital stay was 28 days, with a range from 8 to 59 days.
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Another 3 patients died during follow-up. One patient suffered a hemorrhagic stroke 3 weeks after discharge. One patient had rupture of an abdominal aortic aneurysm. In 1 patient with coronary artery disease, who died at home, the cause is unknown. There were no late failures of the repair of the aortic root. Kaplan-Meier curves of actuarial survival and freedom from recurrent endocarditis and reoperation are shown in Figure 1.
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Prosthetic valve endocarditis is a dreaded complication of aortic valve replacement, and is associated with significant morbidity and mortality due to sepsis, cardiac failure, and neurologic compromise. In prosthetic valve endocarditis, extension of the infection beyond the valve annulus occurs in 56% to 100% of patients [8]. This is probably because the aortic annulus or the sewing ring are usually the primary sites of the infection [9] rather than the valve leaflets. Progression of periannular infection with creation of superficial endocardial defects can inflict substantial damage, and abscesses can create fistulas, resulting in intracardiac shunts or in ventriculo-aortic dehiscence.
It is for these reasons that surgical therapy is almost invariably required, often urgently or as an emergency, as was true in almost 70% of our patients. Because of the severity of the infective damage, a reconstruction of the aortic root is usually necessary and advisable. This approach is reinforced by our observation of a 29% mortality among the 21 patients who, during the same interval, underwent aortic valve replacement and less radical repair for prosthetic valve endocarditis. Because staphylococci were the causative microorganisms in more than 60% of our patients, the marked extent of tissue destruction was not surprising. Furthermore, coagulase-negative staphylococci are able to adhere to a variety of surfaces [10], including mechanical prostheses, and they produce an antibiotic-resistant biofilm [11].
The general consensus clearly tends toward using biological material rather than prosthetic devices for surgical repair in the presence of infection [1, 2, 12–14]. But even if one were to concede that homografts might confer a slight advantage in terms of reinfection, their use is accompanied by a number of potential drawbacks. Homografts do deteriorate progressively once implanted, assuring that reoperation will eventually be required; severe adhesions are likely to make such reoperations technically challenging. Moreover, an irregular base for the proximal suture line can distort and render insufficient a homograft. As a consequence, radical debridement may not be carried out, whereas with a prosthetic valved conduit, valvular competence is assured despite uneven tension on the proximal anastomosis. In d’Udekem’s series of 70 patients with periannular abscesses, including 36 patients with prosthetic endocarditis, a Bentall was carried out in 16 patients; in only 2 was a homograft used [15]. Furthermore, if homografts are to be used routinely in prosthetic valve endocarditis, they must be readily available in different sizes. Aagaard and Andersen [6] conclude that requirements for adequate preservation and storage of homografts are not met in many institutions, resulting in a shortage of appropriate homografts, especially in urgent situations. We also dispute the prevailing notion that implantation of biological material is technically easier than using prosthetic devices. Familiarity with either technique leads to confidence in its use, even under emergency circumstances.
We believe strongly, as do others [5, 14, 15], that radical debridement of infected and necrotic tissue is the most decisive factor for a successful outcome. Unfortunately, this aggressive approach is frequently associated with permanent complete atrioventricular block (22% in our cohort), requiring implantation of a pacemaker [14, 16]. But heart block is a minor complication compared with the potential detrimental impact of leaving infected tissue behind.
The relatively low hospital mortality seen in this study, as well as the low rate of recurrent infection, compare favorably with studies not only of prosthetic valve endocarditis but also of native aortic valve endocarditis. Watanabe and associates [17] reported an operative mortality of 32% for prosthetic valve endocarditis, and results from a Stanford meta-analysis of 30 surgical series of prosthetic valve endocarditis showed a mortality of 25%. Aargard and colleagues [6] reported a 12% early mortality in patients with native aortic or mitral valve endocarditis; in d’Udekem’s series, the early mortality was 19% in prosthetic valve endocarditis associated with periannular abscess. And in a prospective study of 138 patients who underwent aortic or mitral valve replacement with a prosthetic valve for endocarditis (in which only 11% of patients had prosthetic valve endocarditis) Bauernschmitt and associates [5] report an overall early mortality of 11.5%.
The rate of early recurrent endocarditis in this latter report (only 2.1%) is remarkable, and is similar to the 4% seen in the current study. In a study by Delay and coworkers [17], no early postoperative deaths occurred among patients with prosthetic valve endocarditis, but 59% of patients required reoperation due to recurrent endocarditis or periprosthetic leaks within the first year. We attribute the low incidence of recurrent endocarditis and reoperation in our cohort to the aggressive removal of all infected tissue at the time of the initial operation, with reconstruction of the aortic root and replacement of the ascending aorta with a durable prosthesis.
In a study with an almost identical patient cohort with complicated prosthetic valve endocarditis, Dossche and associates [18] showed that allograft aortic root replacement is a valuable technique, and is associated with a good outcome in these high-risk patients. Mortality was 9.4%. Complete heart block (as in our study) was a frequent complication (18%), and only 1 patient suffered from recurrent endocarditis. Lytle and associates report similar excellent results using cryopreserved homografts [14]. But in contrast to these findings, other studies with dismal outcomes using allografts can also be found [20]. In general, comparisons of different techniques for the treatment of prosthetic valve endocarditis are problematic because the severity of the infections and the causative microorganisms may differ in the patient cohorts. It also may be true that in some institutions, technical difficulties in securing the proximal anastomosis in the face of massive annular destruction have resulted in use of prosthetic material rather than homografts in only the most serious cases. Although familiarity with one or another technique may ordinarily predispose a surgeon to a particular surgical approach when replacement of the aortic root is required, severe annular destruction may make it difficult to place a homograft without distortion and serious risk of homograft aortic insufficiency, whereas a conduit with a prosthetic valve is more forgiving.
In general, microorganism-specific antibiotic treatment should be started as soon as possible and continued for at least 6 weeks after surgery. In cases in which no organism can be identified, general guidelines suggest empiric treatment with vancomycin and gentamicin [21]. Surgery probably should be undertaken relatively early. Moon and colleagues [22] showed that there is no difference in outcome even in patients with native endocarditis who undergo surgical intervention before completing a standard medical protocol and those who finish the full course of antibiotic treatment before operation. If possible, the organism should be identified and appropriate antibiotic treatment begun 24 to 48 hours before surgery, with the hope of eliminating distant foci of infection and reducing bacteremia. But we would not recommend waiting longer and risking progressive periannular destruction, valve dehiscence, and hemodynamic deterioration before surgical intervention once the diagnosis of prosthetic valve endocarditis has been established. Based on our results, it is hard to justify delaying operation until a suitable selection of homografts can be obtained, or transferring patients to a surgical center with a homograft bank.
We believe that our data provide convincing evidence that replacing an infected prosthetic aortic valve using a modified Bentall procedure (which involves use of prosthetic material) is the procedure of choice in treating prosthetic valve endocarditis. During the interval under study, we used homografts in only 3 patients with prosthetic valve endocarditis, all because even short-term anticoagulation after the Bentall procedure would have posed problems.
Conclusions
This study demonstrates that in the surgical treatment of acute prosthetic valve endocarditis complicated by destruction of the perivalvular apparatus, root replacement with a prosthetic conduit yields results comparable with the use of homograft root replacement. The low operative mortality and incidence of recurrent endocarditis using the Bentall procedure are probably a consequence of prompt operation, aggressive excision of all infected structures, and appropriate postoperative antibiotic therapy. ([19])
References
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 Endorsed by the European Society of Clinical Micro, Authors/Task Force Members, G. Habib, B. Hoen, P. Tornos, F. Thuny, B. Prendergast, I. Vilacosta, P. Moreillon, M. de Jesus Antunes, et al. Guidelines on the prevention, diagnosis, and treatment of infective endocarditis (new version 2009): The Task Force on the Prevention, Diagnosis, and Treatment of Infective Endocarditis of the European Society of Cardiology (ESC) Eur. Heart J., October 1, 2009; 30(19): 2369 - 2413. [Full Text] [PDF]
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