Risk of endocarditis in transesophageal echocardiography

Risk of endocarditis echocardiography

in transesophageal

The risk of endocarditis associated with transesophageal echocardiography was studied in 101 patients. To evaluate possible bacteremia, blood cultures were performed on samples from consecutive patients who did not have clinical or laboratory evidence of infection. The broth blood culture Signal system was used in all patients, and additionally, the lysis-centrifugation technique was performed in a subgroup of 40 patients to further ameliorate recovery of rapidly phagocytosed germs. Comprehensive criteria for differentiation between true bacteremia and possible contamination were provided by means of simultaneous blood sampling from two separate venipuncture sites and skin specimens from the venipuncture area. Orophatyngeal specimens were cultured for evaluation of possible association of oropharyngeal flora with positive blood culture findings. They revealed facultative pathogenic isolates, as well as physiologic residental flora, in 15 patients. All blood isolates that were recovered simultaneously 6 minutes after the procedure were found to be sterile. Correspondingly, clinical follow-up for 2 weeks was uneventful with regard to episodes of infection. These results indicate that the risk of bacteremia associated with transesophageal echocardiography is extremely low. Thus endocarditis prophylaxis is not required for this procedure. (AM HEART J 1993;125:190.)

Gerhard Pongratz, MD, Karl-Heinz Henneke, MD, Martin von der Griin, Bernhard Kunkel, MD, and Kurt Bachmann, MD Erlangen, Federal Republic of Germany

Transesophageal echocardiography (TEE) is performed more frequently for cardiac diagnosis even in patients with valvular heart lesions and prostheses. Because of the high risk of endocarditis in such cases the need for endocarditis prophylaxis was previously assessed.’ However, unequivocal recommendations with regard to endocarditis prophylaxis in TEE procedures have not been available until now, since markedly different bacteremia rates were found.“-8 Different study designs and different criteria for discriminating potential contaminations from significant blood stream infections may have influenced these results. This study was undertaken to reevaluate the risk of endocarditis from bacteremia associated with TEE with the aid of methods that may provide more comprehensive criteria for detection of true bacteremia. METHODS Patients.

One hundred and one patients underwent this TEE series; 45 of them were ambulatory outpatients.

From the Department of Internal Medicine, Cardiology, University of Erlangen-Nuremberg. Received for publication Apr. 17, 1992; accepted July 1, 1992. Reprint requests: G. Pongratz, MD, Med. Univ. Klinik II, &I. Stadtmauenter. 29, D-8520 Erlangen, Federal Republic of Germany. 4/l/42160

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Intraoperative caseswere not included. Informed consent wasobtained from eachpatient. Patients with any clinical or laboratory evidence of infection (especially those with signsof local inflammation of the forearms) wereexcluded; the same was true if any antimicrobial drug was given within 10 days before the examination. TEE technique. TEE was performed in the echocardiography laboratory with a 3.5 MHz or 5 MHz phased-array sectortransducer attached to a color Doppler echocardiography instrument (Toshiba SSH 65 A, Toshiba America Medical Systems, Tustin, Calif. or Siemens SI 1200, Siemens Medical Instrumentation, Inc., Iselin, N.J.). Patients abstained from food for 4 hoursbefore the examination. Dentures and all other oral prostheseswere removed, and the oropharynx was anesthetized with lidocaine aerosolto suppressthe gagreflex. No intravenous sedation was given. The patients were placed in the left lateral decubitus position, and each patient’s neck wasslightly flexed to the chest. The transducer of the endoscopewaslubricated with lidocaine jelly. A fiberoptical control was not used. After a bite guard wasplaced over the distal part of the instrument, the examiner pressedthe base of the tongue down, pulled it forward simultaneously with the middle and index fingers of one hand, and with the other hand, introduced the tip of the transducer slowly into the throat toward the esophagealorifice until resistancewasencountered. Then the patient wasrequestedto swallow,and with gentle pressurethe scopewasdirected to the upper part of the esophagus.The examination also included the transgastric view from the fornix of stomach. 0002~8703/93/$1.00

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Blood cultures. Bacteremia associated with TEE was evaluated by blood cultures, which were processed by broth culture (Signal System, Oxoid Ltd., Basingstoke, Hampshire, England) and in 40 casessimultaneously by lysiscentrifugation culture (Isolator 10ml tube, Merck, Darmstadt, Germany). Blood cultures were taken before TEE and 6 minutes after completion of the procedure. TWO blood sampleswere taken at a time through separateneedle sticks, each from a vein of the contralateral forearm. Blood sampleswere drawn by physicians and a specially trained student doctor. Preparation of the skin consistedof rubbing the anticubital fossawith benzol and wiping off the center of the venipuncture areawith sterile gauzesaturated with povidone iodine. The skin area was protected by a sterile compressand wasallowedto dry for 3 minutes. Then a skin specimenfrom the puncture areawascollected with a sterile swab (Port-A-Cul, Becton Dickinson GMBH, Heidelberg, Germany) to render possiblefurther clarification of any potential contamination of blood cultures. In addition, a pharyngeal swab (Transgerm GO, Merck) was performed. After the plastic “flip-off cap” wasremoved and after the exposedpart of the rubber stopper of the culture bottle and Isolator tube were disinfected, blood wasdrawn into a 20 ml syringe by venipuncture with a ZO-gauge needle. A new needle was attached and 10 ml of the collected blood was injected into the broth culture bottle, which had been preincubated at about 30” C, and 9 ml of the blood was injected into the Isolator tube, aseptically through the rubber stopper of the systems. Pooling of the disinfectant solution on the stopper was carefully avoided. Laboratory procedures. After the inoculated Signal bottle was shaken, the growth indicator device was fastened aseptically to the culture bottle by pushingthe needle shaft of the indicator apparatus as far as it would go through the disinfected rubber stopper. The locking sleeve waspulled downward until it wasfully locked into position. The chamberwaspresseddown to ensurefull contact with the rubber sealof the bottle. The systemwasthen shaken for 24 hours at 170 orbits/min in an orbital shaker (Certomat M Braun, Melsungen, Germany), which wasplaced in the incubator at 36’ C. Signal cultures were then grown stationary at 36” C and examined twice daily. Positive resultswere recognizedby the appearanceof the blood-broth mixture in the growth indicator chamberabove the level of the locking sleeve.If a positive signappeared,a samplewas taken aseptically for microscopicexamination and subculture by a sterile needle-syringecombination. The inoculated Isolator tubes were centrifuged at 3000g for 25 minutes; then, further specimenprocessingwasperformed in a vertical laminar air flow cabinet. After the supernatant was discarded and the pellet was homogenized with a vortex-type mixer, the concentrate wasremoved by a syringe with a long needle;equal amounts weredispersed in a straight line acrossthe middle of the agarsurface.With a loop, about sevenpasseswere made perpendicular to the original line, and contact with the edgesof the plates was avoided. The concentrates were inoculated on 5% sheep blood and chocolate agar at 36’ C in room air, in a 5% carbon dioxide atmosphereand under anaerobic conditions

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Table 1.Clinical indications for TEE in 101 cases* Indications Cardioembolic

source of TIA or stroke

Cardiacvalvedisease Prosthetic valve Congenital heart Aortic aneurysm Masses (without

dysfunction defect and/or dissection cardioembolic source)

No. of patients 59 24 6 10 1 1

‘HA, Transient ischemic attack. *No double count was performed.

for 5 days; the inoculated Sabouraud agar plates were incubated at 30° C for 6 days. Before use all plates were predried at least overnight at room temperature to enhance the absorption of the inoculum and to reduce condensationon the plate lid. The inoculated agar plates were incubated in an upright position for their first 24 hours and then in an inverted position. All plates were examineddaily. Even when growth appearedwithin 24 hours, the plates were reincubated to check for the possiblepresence of another organism,which may have grown later. If a colony appearedonly outside the inoculation streak area on agar with Isolator cultures, it was considered a plate contaminant. RESULTS The median age of the 101 examined patients (39

women and 62 men) was 52.3 years (range, 17 to 83 years). Indications for the consecutive TEES are listed in Table I. In 26 examinations insertion of the TEE probe into the esophagus was unsuccessful at the first attempt because of patient’s gagging and retching. A readjustment of the endoscope and another careful reassuring explanation of the procedure facilitated the insertion of the probe in these cases, The time needed for a TEE ranged from 3 to 16 minutes, with a mean of 7.5 minutes. No microorganisms were found in any of the blood cultures that were taken after the examination. In one broth culture sample the device chamber indicated a positive sign, but both microscopic examination and subcultures showed no evidence of growth. Staphylococcus epidermidis was grown in two preprocedure blood samples from different patients; in one case it was cultivated from the Signal system and in another, from the Isolator system. The corresponding Isolator or Signal samples were negative, and no microorganisms were found in the blood cultures that were taken simultaneously from the contralateral forearm. The corresponding skin specimens were sterile. Consequently, these isolates were considered contaminants. Thus no TEE-associated bacteremia could be detected. In a subsequent follow-up observation for 2 weeks no patient exhibited evidence of a systemic infection, though in 15 cases the oropharyngeal swab

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Table II. Transient facultative isms* isolated from 15 patients Microbial

species

American

pathogenic throat organwho underwent TEE X0. of isolates

Candida albicanst Klebsiella pneumoniae Enterobacter species

Group B streptococcit Pseudomonas aeruginosa Citrobacter Escherichia

freundii coli j

*Staphylococcus species, Candida tropicalis, and Klebsiella oxytoca considered to belong to the regional oropharyngeal flora. 7This germ was not included, if it occurred only as a trace component culture.

were in the

yielded not only normal flora but also facultative pathogenic microorganisms (Table II). DISCUSSION

In this study no bacteremia that was related to TEE was found, with the use of two blood culture methods, which have been shown to be extremely sensitive in the detection of a wide variety of pathogenic organisms. The Signal blood cuiture system indicates bacterial growth in a special detector device by visible changes that are due to bacterial metabolism. The sensitivity for initially shaken cultures is about 96 Si’,, and false positive signals are reported in the range of about 4 % . g-11 Broth medium was prewarmed to achieve cultivation of potentially perishable organisms. Since, theoretically, some microorganisms require an appropriate supplementary technique to be recovered, lysis-centrifugation technique (the Isolator system) was additionally performed in a subgroup of 40 patients. This method has been reported to enable increased recovery of intracellular microorganisms that is due to the rapid removal of organisms from the exposure to phagocytosis and microbicidal serum factor@ l3 and to provide quantification of colony forming units.14 The possibly higher contamination rate as a result of laboratory procedures was significantly decreased by processing cultures in a biologic safety cabinet with vertical laminar air flow.15 Markedly different bacterial positivity rates of up to 17% have been observed in association with TEE.2-8 However, determination of whether detected bacteria really represent true blood stream infection or contamination does not appear to be reliable in all of these studies. Because this decision is made retrospectively, the essential criteria that are usually applied for the clinical significance of isolates such as patient’s clinical data and species of detected organ-

Heart

1993 Journal

ism were supplemented in this study by an appropriate design of multiple blood collections. In this study clinical follow-up was uneventful with regard to systemic infection. These findings are in close agreement with previous observations after TEE.2-7 Bacterial species such as diphteroids or coagulase-negative staphylococci that have been isolated from blood samples have been usually considered contaminants,16-17 since these organisms belong to the physiologic skin flora. This empirical assumption could be further confirmed, if the same species are present both in the specimens that are taken from skin venipuncture areas and in the blood culture. Accordingly, subspecification of isolated corresponding organisms by serotyping or phagetyping may differentiate contamination from bacteremia. However, skin specimens were not collected in previous studies. Furthermore, the importance of obtaining sets of blood cultures taken subsequently in short time intervals by independent venipunctures has been previously emphasized. 16-18In true bacteremia the probability of positive subsequent blood cultures is about 80 %, and the same microorganisms are expected to be recovered in these cases. In contrast, when one initial blood sample is contaminated, the positivity rate of subsequent cultures is below 10% .I7 Thus the high rate of positive cultures that is reported in patients who consecutively undergo TEE* cannot be considered significant, because only in one case was the same bacterial species (S. epidermidis) found in a pair of simultaneous cultures. In addition, timing of blood sampling may affect the recovery rate of bacteria. With respect to esophagogastroduodenoscopy (EGD), in most studies peak bacteria rates occurred during examination and 5 minutes after completion of the examination.lg In comparison, bacteremias that were related to TEE were present at substantially different points of time, which ranged between 5 minutes after insertion of the probe up to 180 minutes after the end of the procedure 20-22 Time of peak incidence of bacteremia cannot’ be established in hitherto reported TEE studies. For immunologic reasons, blood sampling at intervals beyond about 20 minutes after the end of TEE does not appear to be efficient for this purpose, because a rapid elimination of microorganisms from blood by the reticuloendothelial system has to be taken into account. The main source of bacteremia associated with upper endoscopic procedures is assumed to be the oropharyngeal tract. Consequently, both throat and blood samples were taken in this study. Previous reports do not reveal a close relationship between

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throat organisms and those found in blood, even when the same isolates of simultaneous blood cultures are not required for diagnosis of bacteremia. Similarly, only two of 692 patients who were undergoing the EGD procedure have been reported to exhibit identical bacterial species in both blood and oropharyngeal samples. 22 However, both patients had undergone multiple esophageal biopsies because of endoscopically evident mucosal pathologic conditions. Neither physiologic nor transient potentially pathogenic germs that were recovered in the throat cultures could be detected in any of the subsequently performed blood cultures. The incidence of bacteremia associated with EGD is low compared with other endoscopic procedures. A review of 10 studies reporting 692 patients who underwent EGD demonstrated an overall frequency of bacteremia of 4.1% .I9 Consequently, the American Heart Association position paper on antibiotic prophylaxis categorized upper endoscopy as a low-risk procedure that does not require administration of antibiotic agents.’ In conclusion, the risk of blood stream infections associated with TEE procedures is extremely low. Even patients who are at high risk for endocarditis, such as those with prosthetic heart valves, do not generally require antibiotics for endocarditis prophylaxis. Gingival injuries caused by mechanical devices for dental care may be more harmful for these patients, as shown recently.23 We thank Christoph Schoerner, MD, Werner Solbach, MD, and the laboratory staff of the Institute of Clinical Microbiology, University of Erlangen-Nuremberg for their expert cooperation. Merck Inc., Darmstadt, Germany, generously supplied Isolator systems for blood cultures. REFERENCES

1. Dajani AS, Bisno AL, Chung JK, et al. Prevention of bacterial endocarditis: recommendations by the American Heart Association. JAMA 1990;264:2919-22. 2. GBrge G, Erbel R, Heinrichs KJ, Wenchel HM, Werner HP, Meyer J. Positive blood cultures during transesophageal echocardiography. Am J Cardiol 1990;65:1404-5. 3. Dennig K, Sedlmayr V, Seling B, Rudolph W. Bacteremia with transesophageal echocardiography [Abstract]. Circulation 1989;8O(suppl II):II-473. 4. Vijller H, Schrijder KM, Gast D, et al. Does the incidence of positive blood cultures during transesophageal echocardiography necessitate antibiotic prophylaxis? Circulation 1990; 82(suppl III):III-24.

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