
* Pediatric Cardiology
Infectious Disease, Department of Pediatrics, University Childrens Hospital, Geneva, Switzerland
| ABSTRACT |
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Study Design. Retrospective case study in a tertiary pediatric hospital.
Methods and Results. Between 1985 and 2001, 41 episodes of IE were documented in 40 children (median: 7 years old; range: 1 week to 18 years). The diagnosis was based on echocardiographic and microbiologic or pathologic findings. The initial echocardiogram suggested IE in 95% of the cases. Main findings were vegetations in 36, perivalvular abscess in 4, and/or new valvular leaks in 6 cases. In 31 (76%) of the 41 episodes, the causative organisms were identified directly by specimen bacteriology or blood cultures (BCs) or indirectly by polymerase chain reaction or serology. Sensitivities of the von Reyn, Duke, and modified Duke criteria in diagnosing IE were 63%, 81%, and 88%, respectively. In 10 cases (22%), the diagnosis of IE was "rejected" by the von Reyn criteria but was "definite or possible" by the Duke and modified Duke criteria. In 3 cases, the diagnosis of IE was "possible" by the Duke but "definite" by the modified Duke criteria: 2 of the 3 cases had 1 major and
3 minor symptoms, and 1 had Q fever. Five episodes (12%) were classified as "possible" IE by the modified Duke criteria: although major findings were present on echocardiography, no organism was identified on repeat BCs. Positive BC was the only criterion that differentiated "definite" from "possible" IE.
Conclusions. The modified Duke classification was more sensitive in diagnosing IE in children than the von Reyn and Duke criteria. Still, 12% failed to be classified as "definite" IE by the modified Duke criteria. This illustrates the importance of positive BCs as a major IE criterion while significant echocardiographic findings are less considered by the presently used criteria.
Key Words: endocarditis pediatric diagnosis infection
Abbreviations: IE, infective endocarditis BC, blood culture PCR, polymerase chain reaction TTE, transthoracic echocardiography TEE, transesophageal echocardiography
The clinical diagnosis of infective endocarditis (IE) may be challenging, which explains the need for a precise and uniform diagnostic approach. The initial classification elaborated by von Reyn and colleagues1 was based primarily on clinical and pathologic findings including demonstration of the infection by histopathology or positive blood cultures (BCs). The von Reyn classification, invented before the introduction of two-dimensional and Doppler ultrasonography, does not consider characteristic echocardiographic findings related to endocardial infection, which may explain its limited value in diagnosing IE when BCs remained negative.2,3 In 1994, Durack et al4 proposed a new classification, the Duke criteria, which includes echocardiographic anomalies as major findings. The Duke criteria have been shown to be more sensitive in diagnosing IE in adults and children when compared with the von Reyn criteria.46 Nonetheless, Habib et al7 found that in some pathologically proven cases of IE, the definite diagnosis had been missed either because BCs remained negative or the endocarditis had been caused by Q fever. To increase the diagnostic sensitivity, the Duke criteria were modified recently and tested in a heterogeneous adult population.8 The modified Duke criteria utility in children is not known. This study aimed to assess the value of the von Reyn, Duke, and modified Duke classification in children who had been diagnosed to have IE since the introduction of high-resolution two-dimensional and Doppler ultrasound techniques at our center.
| PATIENTS AND METHODS |
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Diagnostic Criteria (Tables 1 and 2)
von Reyn, Duke, and modified Duke classifications were applied according to their original descriptions.1,4,8 According to the von Reyn criteria, patients were classified as "definite," "probable," "possible," or "rejected" IE. Based on the Duke and modified Duke criteria the diagnosis of IE was "definite," "possible," or "rejected."
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Echocardiography
All children underwent complete transthoracic two-dimensional and Doppler transthoracic echocardiography (TTE) studies at diagnosis and follow-up by using Vingmed Diasonics CFM 700 or System Five ultrasound systems mainly with 5- to 7-MHz phased-array transducers. Six patients underwent additional transesophageal echocardiography (TEE) with 5-MHz multiplane probes. Unlike in adults, TTE and TEE are considered equally accurate for the diagnosis of IE in children, in particular for the detection of vegetations.11,12 Potential sources for false-negative studies may include vegetations that are smaller than the lower limit of ultrasound resolution (<2 mm), previous embolization of vegetations, and inaccurate imaging to detect small abscesses.4 Echocardiographic examinations were read by 2 observers. All ultrasound studies were videotaped and available for off-line analyses. Detected anomalies were classified either as major or minor findings according to the Duke and the modified Duke classification.4,8
Statistical Analysis
To determine the sensitivities of the 3 analyzed criteria, only patients with probable IE by von Reyn and definite IE by von Reyn, Duke, or modified Duke were considered to have true IE. Patients with only possible or rejected diagnosis of IE were considered to be "uncertain" or "false-negative" results. A 2-tailed Fishers exact test was performed to analyze differences in major and minor modified Duke criteria between cases with definite and possible IE diagnosis. A P value of <0.05 was considered to be significant.
| RESULTS |
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Echocardiography
Findings compatible with endocardial infection were found in 39 (95%) of the 41 episodes on initial TTE examination. TEE to confirm the IE diagnosis was done in 6 patients. IE lesions failed to be detected in 2 cases by ultrasound imaging, although the diagnosis was established in both cases by histologic examination of tricuspid valve that was obtained during surgery. This included the only patient in our series with concomitant glomerulonephritis, which was confirmed by renal biopsy. Of the detected anomalies, 36 vegetations, 4 perivalvular abscesses, and 6 new valvular regurgitations were found in 39 cases. Vegetations were right-sided in 17 (tricuspid valve: n = 9; pulmonary valve: n = 4; patch: n = 3; atrium: n = 1) and left-sided in 19 (mitral valve: n = 8; aortic valve: n = 8; left atrium: n = 1; patch: n = 2) cases. Valvular regurgitation related to infectious lesions was initially an infrequent finding, present in only 15% of the cases. On follow-up, it emerged in another 14 cases, affecting a total of 49% of the cases.
Microbiology
BCs (16 cases with
2 positive BC and 5 cases with 1 positive BC) or tissue specimen and serologic testing were found positive in 31 of the 41 (75.6%) IE episodes. Gram-positive microorganisms (n = 17 [41%]: Staphylococcus aureus and Staphylococcus epidermidis, Staphylococcus mitis, Staphylococcus mileri, and Staphylococcus sanguis, Corynebacterium diphtheriae, Enterococcus faecalis, Propionibacterium acnes, and Actinomyces odontolyticus) and fungi (n = 9 [22%]: Candida albicans, Candida guillermondi, and Hansenula anomala) predominated. Less common causes of IE were from the HACEK group (n = 3 [7%]: Haemophilus paraprophilus, Haemophilus influenzae, and Haemophilus aphrophilus), Gram-negative bacteria (n = 3 [7%]: Pseudomonas aeruginosa, Bartonella quintana, and Salmonella typhi), and Q fever (n = 1 [2%]: Coxiella burnetti). One episode had multiple isolates. Ten episodes (24%) remained culture-negative (Table 3).
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| DISCUSSION |
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In the 1980s, high-resolution two-dimensional and Doppler echocardiography emerged as the primary cardiovascular imaging modality. Typical lesions, resulting from bacterial or fungal infection of the native endocardium and implanted patches and mechanical devices, had suddenly become detectable noninvasively. The inclusion of vegetations, perivalvar abscesses, and valvar leaks as major diagnostic findings in the Duke and modified Duke criteria has improved the accuracy in diagnosing IE significantly.13 Similar to previously published data,7 there was a high detection rate of vegetations (85%) with TTE in our series. The demonstration of vegetations is most helpful if BCs are inaccurately withdrawn and are slowly or not growing. The American Heart Association recommends that the search for the causing microorganism ideally should include "3 BCs, obtained by separate venipunctures on the first day, followed by 2 more if there is no growth by the 2nd day of incubation."14 In our experience, this is not always practical, particularly in the small neonate with restricted vascular access, whereas it is of limited value in the patient who is already receiving antimicrobial therapy. By using conventional BC procedures, no causing microorganism was demonstrated in a quarter of our patients. PCR on tissue samples and serologic techniques may help in this situation: 2 BC-negative cases in our series were diagnosed as having Bartonella endocarditis and Q fever, respectively.10 Although PCR-based testing may prove beneficial for the identification of certain organisms,8 the use of this new technology to find major criteria should be deferred until it can be validated.
Our analysis of the diagnostic value of 3 different criteria in children demonstrates that the modified Duke criteria is most helpful in diagnosing IE. The inclusion of echocardiographic findings has contributed significantly to the improved diagnostic accuracy, whereas positive BCs remain the mainstay in IE diagnosis. Still, 12% of our cases were classified only as having possible IE. All 5 cases had endocardial involvement, and most had 2 minor criteria. Most children with IE do have predisposing cardiac anomalies and present with unspecific clinical symptoms such as fever and anorexia. Nevertheless, striking vascular or immunologic abnormalities are unusual in the pediatric age group.13,14 Data issued from some series demonstrated elevated inflammatory markers (elevated erythrocyte sedimentation rate or C-reactive protein) and new clinical findings (new clubbing, splenomegaly, and microscopic hematuria) in patients with IE.15,16 Increased sensitivity of the elevated erythrocyte sedimentation rate in cases of IE seems to be even more relevant in patients who did not undergo surgery.17 In our series, of the 5 possible IE, 4 had an elevated erythrocyte sedimentation rate. Therefore, further modifications with a refinement of the present minor IE criteria may help to improve the diagnostic accuracy, in particular in children with negative BC and echocardiographic criteria for IE.
Limitations
Most of our patients originated from Africa and had been referred for cardiovascular surgery of sometimes long-standing acquired or congenital heart disease in combination with malnutrition. This may have influenced the spectrum of encountered microorganisms and the clinical and echocardiographic findings of IE in some of our patients. Our study did demonstrate a higher sensitivity in diagnosing IE with the modified Duke criteria, but, because of the retrospective study design, we were not able to assess the specificity and positive predictive values of the various criteria. This is of clinical importance, because a false-positive or false-negative diagnosis may have an impact on the management and outcome of children with IE. Although there was no "gold standard" for IE diagnosis, misclassification may have occurred to the few patients with possible IE. Considering the rarity of endocardial infection, a prospective multicenter study is needed, probably with the inclusion of new minor diagnostic findings.
| FOOTNOTES |
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Address correspondence to Pierre Tissières, MD, Department of Pediatrics, University Hospitals of Geneva, Unit of Cardiology, 6 Rue Willy-Donzé 1211 Geneva 14, Switzerland. E-mail: pierre.tissieres{at}hcuge.ch
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