Asian Cardiovasc Thorac Ann 2000;8:241-244
© 2000 Asia Publishing EXchange Pte Ltd
Surgical Management of Infective Endocarditis
Sin Yoong Kong, FRCS,
Tan Yong Seng, FRCS,
Sriram Shankar, FRCS,
Chua Yeow Leng, FRCS
Department of Cardiothoracic Surgery
National Heart Centre
Singapore, Republic of Singapore
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For reprint information contact: Sin Yoong Kong, FRCS Tel: 65 436 7598 Fax: 65 224 3632 email: sin_yoong_kong{at}nhc.com.sg Department of Cardiothoracic Surgery, National Heart Centre, 17 Third Hospital Avenue, Mistri Wing, Singapore 168752, Republic of Singapore.
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Abstract
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Despite advances in diagnostic and pharmaceutical therapy, a significant subset of patients with infective endocarditis require surgical intervention. Details of 44 consecutive patients operated upon for infective endocarditis from December 1990 to January 1996 were analyzed retrospectively. Patient characteristics, presentation, risk factors and microbiological epidemiology are described. The mitral valve was most commonly affected. Nearly 70% of patients had an underlying cardiac abnormality. Early mortality was 11%. Streptococcus was most frequently isolated (40% of cases), Staphylococcus aureus was found in 28% of patients and it was associated with significantly higher mortality. Prosthetic valve endocarditis accounted for 14% of cases and it was associated with significantly earlier intervention as well as a high mortality. Overall survival at 5 years was 84% with an event-free survival of 79%. Surgical intervention when valve failure develops or medical therapy is unsuccessful, is lifesaving and can be associated with acceptable morbidity and mortality. Patients with Staphylococcus aureus infection and those with prosthetic valve endocarditis require aggressive therapy including early referral for surgery.
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Introduction
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Infective endocarditis is a complex disease process associated with a high mortality. While the advent of antimicrobial therapy has significantly reduced what used to be a near total mortality, the issues of valvular dys-function and progressive heart failure were not addressed until valve replacement began in the 1960s.1 Current management strategies are evolving in parallel with advances in diagnosis as well as medical and surgical therapy. However, controversies exist regarding the timing and aggressiveness of surgical intervention.2,3 We under-took a retrospective review of our experience with endo-carditis over a recent 5-year period.
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Patients and Methods
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Between December 1990 and January 1996, 49 con-secutive patients who underwent surgery for infective endocarditis were retrospectively reviewed. Forty-four fulfilled the modified Von Reyn criteria for the diagnosis of endocarditis.4 All had clinical evidence of infection with positive echocardiographic evidence of vegetations and significant valvular dysfunction. The diagnosis was corroborated by the gross pathological appearance of the valve at the time of surgery or by subsequent histologic examination. The 5 patients excluded from this study had been operated upon for hemodynamic reasons and endocarditis was excluded on both gross pathologic and histologic grounds.
Follow-up was obtained from the last review in the medical records or by direct telephone contact. The follow-up time was calculated as the period from diagnosis to last contact or death. For definitions of mortality and morbidity, standard guidelines were used.5 An early event referred to any event within the first 30 postoperative days or during the entire hospital stay. Data are summarized by mean and range for continuous variables, and by percent-ages for categorical variables. Late postoperative (> 30 days) complications were expressed as linearized rates (% per year). Statistical differences between subgroups of patients were determined by chi-squared analysis or analysis of variance (means comparison). A p value of < 0.05 was considered significant.
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Results
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The male to female ratio was 2.7 with a mean age at diagnosis of 38 years (range, 13 to 70 years). Total cumulative follow-up was 85 patient-years, with a mean of 23 months; no patient was lost to follow-up and it was 100% complete. Clinical presentation and risk factors are summarized in Tables 1 and 2
. Fever was the most common presentation, followed by embolic phenomena, especially in the extremities. Potential anatomical risk factors for the development of endocarditis varied widely, most patients had previous rheumatic heart disease or an open heart procedure. Fourteen patients (32%) had no history of an underlying cardiac abnormality. Of these 14 patients, 6 had a significant source of potential bacteremia: 2 had undergone a recent dental procedure; 2 were habitual intravenous drug users; 1 was recovering from surgery for bowel infarction; and 1 suffered from chronic renal failure requiring hemodialysis, leaving 8 patients (18%) with no risk factors. Some patients had more than one risk factor.
Streptococcal species (17 patients) and Staphylococcus aureus (12 patients) were the most common organisms recovered by blood culture (Figure 1). Of the 12 patients with positive blood cultures for Staphylococcus aureus, 3 perished in the early postoperative period and 2 died after a late recurrence, giving rise to a significant 42% mortality (p < 0.01) and a 17% recurrence rate associated with Staphylococcus aureus endocarditis. While Strepto-coccal and Staphylococcal species were mostly responsible for native valve endocarditis (27 patients; 72%), the organisms isolated in prosthetic valve endocarditis varied widely with no single predominant organism (Table 3). Recovery of the organisms from tissue cultures was possible in only 5 patients (11%).
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Figure 1. Microorganisms recovered by blood culture. "Others" category includes Enterococcus species, Pseudomonas aeruginosa, Acinetobacter species, Xanthomonas maltophilia, and nonfermentative gram-negative bacteria.
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The site of involvement was determined by echocardio-graphy and confirmed at surgery (Figure 2). Left heart valvular endocarditis predominated in the study population with only 3 patients (7%) having tricuspid involvement, 2 were intravenous drug abusers and 1 had endocarditis associated with a ruptured sinus of Valsalva. There were 6 patients with prosthetic valve endocarditis, 3 with mechanical valves, and 3 with bioprosthetic implants. The indication for surgery was failed medical therapy in 3 of these patients, whereas recurrent embolism, valve dehiscence, and cardiac failure were the indications in the other 3. The mean interval from diagnosis to surgery was 15 days compared to 85 days in the entire cohort (p = 0.036). Mortality was higher with 2 deaths in this subgroup. Twenty-eight patients (64%) were operated upon for valvular dysfunction and cardiac failure. Ten patients (23%) had failed medical therapy, 4 (9%) developed recurrent embolism, and 2 (5%) had vegetations deemed large on echocardiography.
Most procedures were performed electively except in 9 patients (20%) who underwent surgery on an emergency basis. Eight of these 9 were either in acute cardiac decompensation (6) or septic shock (1) or both (1). The remaining patient had a large vegetation protruding into the left ventricular outflow tract. The most common procedure was mitral valve replacement (46%) reflecting the predominance of mitral valve disease. Other procedures varied from simple valve debridement to triple valve procedures (Table 4). A bioprosthetic or mechanical valve was used where replacement was indicated, although this practice will likely alter with the use of homografts in severe infections if time allows for procurement.
Early morbidity was 11% (5 patients) with the majority due to reexploration for excessive postoperative bleeding (4). One patient developed a postoperative stroke giving a total early stroke rate of 2%. Two patients developed recurrent endocarditis on follow-up with 1 requiring reoperation, yielding a linearized prosthetic endocarditis rate of 2.4% per year and a reoperation rate of 1.2% per year. There were no episodes of thromboembolism, anticoagulant-related hemorrhage, or valve thrombosis.
There were 5 early deaths (11%). Four died from nonvalve cardiac causes while the other patient, a habitual intra-venous drug abuser, succumbed to overwhelming sepsis from multiple lung abscesses that had seeded from the infected native tricuspid valve. Two of those who died early had undergone surgery on an emergency basis. There were 2 late deaths (5%) both resulting from recurrent Staphylococcus aureus endocarditis. One patient under-went reoperation but died of multiorgan failure post-operatively. Overall survival at 5 years was 84%, while event-free survival was 79%.
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Discussion
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Infective endocarditis occurs most commonly in patients who have an underlying anatomical abnormality. In combination with patients who had high risk factors but normal hearts, the total at risk in this series was a formidable 82% (34 patients). It is of interest that there was 1 patient who developed endocarditis in association with an atrial septal defect, despite evidence that such a defect is associated with a low or negligible risk.6
Presentation can be innocuous with the majority initially complaining of fever or vague constitutional symptoms. Evidence of embolic phenomena, found in nearly 50% of patients in this series, coupled with a history of an anatomical abnormality or risk factor, necessitates urgent investigation and treatment. Microbiology is important not only from the therapeutic viewpoint, but also for prognosis. Staphylococcus infections are tenacious and are consistently reported to have a higher mortality.7 Staphylococcus and fungal infections, especially involving the aortic valve or in the presence of a prosthesis, are well known to require aggressive antibiotic therapy and earlier surgical intervention for complete eradication.8 The presence of an abscess also warrants a surgical approach.9
The predominance of mitral valve involvement in this series is in contrast to most other studies reporting a greater proportion of surgery involving the aortic valve.9,10 Aortic valve endocarditis and resulting incompetence is more frequently associated with heart failure and is less effectively managed medically compared to mitral valve disease, hence the tendency towards surgery. In this series, the predominance of rheumatic disease (33%) with its known predilection for the mitral valve, and a younger age group (mean age, 38 years) with a lower incidence of degenerative aortic disease, most likely explains the apparent anomaly. Patients with prosthetic endocarditis are a subgroup that benefits from surgery. Mortality is higher in those treated medically compared with those managed by combined medical and surgical therapy.10,11 Despite a significantly shorter interval from diagnosis to surgery compared to patients with native valve endo-carditis, mortality was high with 2 deaths among the 6 patients in this subgroup. These patients should be referred early for surgery and the threshold for intervention should be lower.
The morbidity and mortality rate in this series is com-parable to current literature.3,10,11 Most of the morbidity was due to reexploration for excessive bleeding against a background of patients who are likely to have coagulation deficits, either sepsis-related or from residual anticoagulant therapy preoperatively, usually with heparin or warfarin. Of the 5 early deaths, 2 had acute decompensation pre-operatively and underwent emergency surgery and 1 succumbed to multiple Staphylococcus aureus pulmonary abscesses secondary to an infected tricuspid valve.
While the mainstay of treatment for infective endocarditis is medical therapy, surgery should not be regarded as a treatment of last resort. There is no doubt that a com-bination of medical and surgical therapy enhances survival.10,12,13 In selected subgroups, early surgery is the preferred option for optimal results.8,14 Close cooperation between physicians and surgeons is essential and their roles are complementary as far as the need for surgical intervention and optimal timing are concerned. The increasing availability of antibiotic-preserved homografts with inherent resistance to infection attributed to the method of preservation and absence of prosthetic materials, adds to the surgeon's armamentarium when faced with the complex task of reconstruction in an infected field.11,15 Surgical results will continue to improve in tandem with advances in diagnostic capabilities and medical treatment. The current challenge remains to further define patients who would benefit from surgery, and the optimal timing. This study reinforces the need to recognize subgroups of patients who require surgery despite current best medical therapy, and to refer these patients early.
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References
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Abstract
Introduction
