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* From the Departments of Infectious Diseases (Drs. Martín-Dávila, Fortún, Navas, Cobo, and Moreno) and Cardiology (Drs. Jiménez-Mena and Moya), Hospital Ramón y Cajal, Madrid, Spain.
| Abstract |
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Material and methods: Cases included were those classified as "probable" or "definite" by the IE diagnostic criteria of Durack. Nosocomial acquisition was considered if diagnosis was made > 72 h after hospital admission and there was no evidence that IE was present at the time of admission. Patients receiving a diagnosis within 60 days of a previous hospital admission were also classified as nosocomial, when a risk procedure for bacteremia was performed, or when any predisposing factor for IE was present during hospitalization. Early prosthetic valve endocarditis (PVE) cases (< 1 year) were excluded from the analysis. Clinical characteristics, etiology, predisposing cardiac condition, source of infection, and outcome were analyzed. Results were compared with those obtained in community-acquired cases.
Results: Of 493 cases of IE diagnosed over 15 years, 38 were considered to be hospital acquired. Twenty-eight cases were native valve endocarditis (NVE) in non-IV drug user patients, and 10 cases were late PVE. Overall, the most frequent microorganisms involved were staphylococci (58%). The main sources of infection were intravascular procedures or catheter-related infections (55%). When nosocomial NVE cases were compared with community-acquired cases, mortality was greater (29% vs 9.7%) in hospital-acquired endocarditis. Analysis of time trends showed an increased rate of nosocomial cases in NVE throughout the years of the study.
Conclusions: In NVE, the number of cases that are hospital acquired has been increasing during the last 15 years. These cases are frequently associated with invasive intravascular procedures or IV catheter-related infections. Most patients have a previous valvulopathy that predisposes to IE. The spectrum of microorganisms involved is different from the community-acquired cases. Also, the outcome of endocarditis is worse in nosocomial NVE patients.
Key Words: native valve nosocomial endocarditis prosthetic valve
| Introduction |
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| Materials and Methods |
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The acquisition of IE was considered nosocomial if the diagnosis was made > 72 h after hospital admission and if there was no evidence that IE was present at the time of admission. Diagnoses made within 60 days of a previous hospital admission were also classified as nosocomial, or when a risk procedure for bacteremia was performed, or when any predisposing factor for IE was present during hospitalization. Cases of early prosthetic valve endocarditis (PVE) occurring in the first year after implantation as well as pacemaker lead endocarditis were excluded from the analysis.
A predisposing factor for IE was defined as any invasive procedure known to induce bacteremia that had been performed within 60 days prior to IE diagnosis, and the following categories were considered: dental manipulation, gynecology procedures, GI manipulation, urologic manipulation, invasive intravascular techniques (cardiac catheterization, pacemaker insertion, intravascular devices), and previous bacteremia or uncontrolled infection. Cardiac conditions associated with IE were those considered of moderate or high risk for IE included in the recommendations of prevention of bacterial endocarditis elaborated by the American College of Cardiology and the American Heart Association.14
Microbiology
Blood samples for culture were drawn under sterile conditions and processed with an automated monitoring system (BACTEC NR660, BACTEC 9240; Becton, Dickinson and Company; Franklin Lakes, NJ). Isolates were identified with standard microbiological tests and automated methods (PASCO; Difco; Detroit, MI) from 1987 to 2000. Before 1987, species were identified using enzymatic or biochemical tests based on the Manual of Clinical Microbiology.15 Antibiotic susceptibility tests were performed using methods recommended by the National Committee for Clinical Laboratory Standards.
Echocardiography
Patients underwent the transthoracic modality of echocardiographic imaging and transesophagic echocardiography. The echocardiographic studies were done with commercially available instruments (Ultramark 2 and HDI 5000; Advanced Technology Laboratories; Bothell, WA). Two-dimensional, Doppler transthoracic echocardiography was performed with 2- to 4-MHz phase-array transducers. Valvular vegetation was defined as a localized mass of shaggy echoes adherent to a valve leaflet. Nonspecific valvular thickening was not interpreted as vegetation (minor criteria). The vegetative mass was measured in various planes. Size was measured by maximal length and width during freeze-frame analysis. Valvular regurgitation and its severity were graded by color Doppler imaging, using semiquantitative standard criteria. A perivalvular abscess was defined as a circular echo density, without flow in its interior.
Statistical Analysis
The association between categorical variables was performed with the
2 test with the Yates correction or the Fisher Exact Test (two-tailed) as needed. Continuous variable association was analyzed with the Mann-Whitney U test. For time trends, analysis for linear proportions was performed with a
linear trend (
LT) test. Statistical analysis was performed using statistical software (SPSS version 9.0; SPSS; Chicago, IL; and EpiInfo 6.0; Centers for Disease Control and Prevention; Atlanta, GA). Statistical significance was defined as p < 0.05.
| Results |
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Microbiology:
Coagulase-negative staphylococci were the most frequent microorganisms involved in nosocomial NVE (n = 9 cases, 32%), followed by S aureus (n = 8, 28.5%) and by Enterococcus sp (n = 4, 14.2%). There were some differences in the etiologic agents when nosocomial-acquired cases were compared to those acquired in the community. In community-acquired cases, the most frequent etiologic agents were viridans group streptococci (36%); however, these microorganisms only caused 4% of the hospital-acquired NVE cases (p < 0.001; odds ratio [OR], 0.10; 95% confidence interval [CI], 0.01 to 0.69). Coagulase-negative staphylococci were the most frequent microorganisms in nosocomial cases (32%), although they were an uncommon etiology in community-acquired cases (4%) [OR, 12.4; 95% CI, 3.2 to 48.6; p < 0.001]. NVE cases due to fungal etiology were all nosocomially acquired, and no cases were found in the community-acquired NVE group (p = 0.005) [Table 2
].
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Cardiac Involvement:
Twenty-three cases (82%) were left-sided endocarditis. The valves involved were the mitral valve (50%), aortic valve (11%), tricuspid valve (11%), aortic and mitral valves (11%), and mural endocarditis (7%).
Outcome:
Nineteen cases (68%) had a complication associated with endocarditis. Systemic embolisms occurred in 36% of the nosocomial NVE cases. Six cases had neurologic events (21%). Fifty percent (14 cases) underwent surgical therapy. The frequency of mortality in patients with nosocomial NVE was 29% (n = 8). The frequency of mortality in patients with community-acquired NVE was 10% (n = 13) [OR, 3.7; 95% CI, 1.4 to 10; p = 0.012]. Etiologies of the eight cases with a fatal outcome were caused by S aureus (n = 3), Staphylococcus epidermidis (n = 4), and polymicrobial etiology (n = 1). Two of these patients died due to causes not related to endocarditis.
Time Trend:
Analysis of the time trends of the frequency of nosocomial NVE cases revealed that the number of cases with hospital acquisition has increased during the 15 years of the study. During the period from 1985 to 1987, the frequency of nosocomial NVE was 3.4% of the NVE cases diagnosed. The frequency of nosocomial NVE during the last period analyzed, 1997 to 1999, was 31% (nine cases). The change in the number of NVE cases nosocomially acquired was statistically significant when linear trend of proportions was used (
LT = 9.7; p = 0.001) [Fig 2
].
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Patient Characteristics:
Five patients were male, and five were female. Mean age was 43 years (range, 1 to 74 years). Mean time from valve prosthesis replacement to endocarditis diagnosis was 3,094 days (range, 880 to 5,400 days; median, 3,172 days).
Microbiology:
The most frequent etiologic agents were staphylococci causing 50% of the cases: coagulase-negative staphylococci (three cases), followed by S aureus (two cases). Fungal etiology caused two cases. Microorganisms causing endocarditis were similar in patients with late hospital-acquired PVE and community-acquired PVE, but cases caused by Candida sp were only nosocomial (p = 0.032) [Table 3
].
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Cardiac Involvement:
Seven cases affected mitral prosthesis (70%), and there was also one case each of aortic, aortic and mitral, and patch involvement.
Outcome:
Two patients underwent valve surgery (20%). Forty percent of cases had no complications associated with endocarditis. The mortality rate of the nosocomial late PVE cases was 20%, and the mortality rate of the community-acquired late PVE cases was 14% (not significant [NS], p = 0.63).
Time Trend:
In the analysis of the time trend of late PVE according to the type of acquisition, the frequency of hospital-acquired cases did not change significantly. Analysis for linear proportions (
LT) could not be calculated because the expected frequency was < 1 in one of the period of time considered (1985 to 1987) [Fig 3
].
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| Discussion |
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The major changes in the epidemiology of IE in developed countries include the older age of the patients, the occurrence of new predisposing factors for IE, and the increased rate of hospital-acquired cases, which is especially associated with the more frequent use of intravascular devices and intravascular procedures.146 These changes are associated with a concomitant switch in the etiologic microorganisms that cause IE. In some series of NVE,591011 S aureus is more frequent than viridans group streptococci, the main group of microorganisms causing IE during the 1970s and 1980s.
Hospital-acquired endocarditis reported in other series6101617 represent 10 to 30% of all the IE cases. Ferrnandez-Guerrero et al6 reported a rate of 9.3% of nosocomial endocarditis not related to cardiac surgery in their series, which included 248 episodes of endocarditis diagnosed from 1978 to 1992. They found a 10-fold increase in the number of hospital-acquired cases diagnosed during 1980s compared with their historical series.6
Although the proportion of hospital-acquired cases in our study is similar to that found in other series, we have observed that the frequency of nosocomial-acquired cases has experienced an increase during the 15 years of the study. In the first period of the study (1985 to 1987), nosocomial NVE cases represented 3.4% of the NVE cases diagnosed during these years, but the frequency of hospital acquired cases reached 31% of the NVE cases in the last period (1997 to 1999). This change in the number of nosocomial NVE cases was statistically significant (
LT = 9.7; p < 0,01).
This finding could be explained by the increase in the number of nosocomial bloodstream infections, the number of patients admitted to ICUs, the increase in the number of invasive vascular procedures, and the higher incidence of degenerative valve disease in our aging population. Although in the study of Fernandez-Guerrero et al6 only 23% of nosocomial cases had previous valvulopathy, and 32% in the series of Lamas and Eykyn,18 in our series 72% of nosocomial-acquired NVE cases had any predisposing cardiac condition; rheumatic disease was the most frequent heart condition (36%). Although rheumatic fever is considered eradicated in our country, due to the high incidence of rheumatic fever in those previous decades (until the 1960s), we now have a population aged 50 to 80 years that suffered valvular disease as a sequelae of the episode in the childhood, and rheumatic valvulopathy is still the most frequent underlying heart disease in our study. However, it should be noted that this might not be the case in another context. Chronic rheumatic disease is now rare in industrialized countries, although this group of patients has been replaced by new at-risk groups including elderly people with degenerative valve disease, patient with intravascular prostheses, and patients with intravascular devices.19
The source of infection determines the profile of microorganisms causing endocarditis. When the source was intravascular devices or procedures, staphylococci were the most frequent etiologic agents; when the source was the genitourinary tract, Enterococcus sp was the predominant microorganism.6 Fernandez-Guerrero et al6 found that the source of infection was IV catheterization in 56.5% of cases, genitourinary tract instrumentation in 30%, total parenteral nutrition in 8.6%, and with liver biopsy in 4.3%. In our study, the most frequent predisposing factors were IV catheter-related infections (32%) and intravascular invasive procedures (25%).
The first cases of endocarditis due to S aureus associated with IV catheters were reported by Watanakunakorn and Baird.20 After this article, other investigators691217 reported cases of IE related to intravascular catheters, with S aureus being the most frequent microorganism. Fowler et al 21 reported that intravascular devices were the most common source of infection (50.8%) in 59 cases of endocarditis caused by S aureus diagnosed in their institution from 1994 to 1998. Half of them were long-term venous access or hemodialysis catheters, and 14% were peripheral catheters.
The risk of endocarditis developing after an episode of S aureus bacteremia in patients with intravascular devices remains controversial. In a prospective study by Fowler et al22 in this group of patients, 23% had endocarditis evident on transesophagic echocardiography. In a study published by Chang et al,9 the rate of endocarditis due to S aureus with intravascular devices as source of bacteremia was 11%. The need to perform echocardiography in all patients with bacteremia due to S aureus is debated by some authors. Pigrau et al23 considered that echocardiography did not need to be performed in patients with uncomplicated bacteremia (no predisposing valvulopathy, persistent fever, metastatic foci).
Other series6818 of nosocomial endocarditis reported the frequent association with intravascular devices and S aureus as the most frequent etiologic agent. Gouello et al8 reported 22 hospital-acquired endocarditis cases occurred in an ICU. Forty-one percent of these patients had previous valvulopathy. The source of infection was identified in 54.5% of cases, and 90% of these cases were associated with intravascular devices. S aureus was the most frequent microorganism (77.2%).8 Lamas and Eykyn18 reported 22 nosocomial NVE cases diagnosed over 11 years (1985 to 1996). The incidence of hospital-acquired cases was 14%. Seventy-seven percent were caused by staphylococci, and the main source of infection was an intravascular device.18
In an article by Muñoz et al,24 aimed at defining the incidence, risk factors, and characteristics of the bacteremias occurring during the first 72 h after nonsurgical cardiologic invasive procedures, the incidence of bacteremia was 0.11% after these procedures. Only 16% of the patients with bacteremia had a previous valvulopathy, and none had endocarditis.24 In our study, all the cases related to cardiac catheterization were in patients with previous valvulopathy, and endocarditis was always left sided. The diagnosis of endocarditis was performed a mean of 28 days after cardiac catheterization.
In our study, the most frequent etiologic agent causing nosocomial endocarditis was coagulase-negative staphylococci, in 32% of the cases. In other series,6161825 the frequency of nosocomial endocarditis caused by coagulase-negative staphylococci was lower (1 to 7%).
The frequency of mortality of nosocomial-acquired cases in our study was 29% higher than the mortality frequency of community-acquired-acquired NVE cases (9.7%). This high mortality rate has been reported also by other authors. Fernandez-Guerrero et al6 reported a mortality rate of 48% in their nosocomial cases. Gouello et al8 had a mortality rate directly related with nosocomial endocarditis of 36%. Lamas and Eykyn et al18 reported a mortality rate of 50% in patients with nosocomial NVE. In a series by Mouly et al,10 analyzing the mortality of patients with IE diagnosed in their institution, the hospital acquisition was identified as an independent risk factor associated with mortality.
In conclusion, the number of hospital-acquired cases of NVE has increased during the last years. These cases are frequently associated with invasive intravascular procedures or IV catheter-related infection. Most patients have a previous valvulopathy that predisposes to IE. The spectrum of microorganisms involved is different than that of the community-acquired cases. These data should be considered when empiric therapy for suspected nosocomial IE is initiated. Noteworthy, the outcome of endocarditis is worse in patients with nosocomial NVE. Physicians must be aware of the risk of endocarditis developing during hospitalization in patients who undergo invasive procedures that potentially cause bacteremia. Patients with a previous valvulopathy subjected to these procedures may benefit from anticipated or prophylactic antimicrobial therapy; and in any case, prompt echocardiography and empiric therapy are compelling if patients become febrile or bacteremic.
| Footnotes |
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LT =
linear trend; CI = confidence interval; IE = infective endocarditis; NS = not significant; NVE = native valve endocarditis; OR = odds ratio; PVE = prosthetic valve endocarditis Received for publication January 12, 2005. Accepted for publication February 10, 2005.
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E Cecchi, M Imazio, and R Trinchero The changing face of infective endocarditis. Heart, October 1, 2006; 92(10): 1365 - 1366. [Abstract] [Full Text] [PDF] |
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