How Certain is a Negative Echocardiogram for Excluding Infective Endocarditis?
April 15, 2022 4 minutes read
By Michael H. Crawford, MD
Professor of Medicine, Lucy Stern Chair in Cardiology, University of California, San Francisco
SYNOPSIS: Applying the proposed strict negative criteria for infective endocarditis (IE) on the first echocardiogram indicated this approach largely prevented unnecessary repeat tests unless clinically indicated for continued suspicion of IE.
SOURCE: Marcos-Garces V, Gabaldon-Perez A, Merenciano-Gonzalez H, et al. Applicability of echocardiographic strict negative criteria for suspected infective endocarditis. Am J Cardiol 2022;162:156-162.
Since a negative echocardiogram carries a high negative predictive value, efforts have been made to define strict negative criteria for infective endocarditis (IE) detection to prevent unnecessary follow-up tests. Researchers from a single center in Valencia, Spain, retrospectively reviewed every echocardiogram requested for suspected IE between 2014 and 2018 in their database.
From 32,572 echocardiograms, 1,251 were requested to rule out IE. The authors excluded 346 tests that were initial transesophageal echocardiograms (TEE) or follow-up echocardiograms, leaving a final study population of 905 patients. Clinical data and six years of follow-up were extracted from electronic medical records. The diagnosis of IE was made by investigators blinded to the echocardiogram results. The strict negative criteria of Sivak were applied to the tests: at least moderate quality; normal anatomy; no valvular stenosis or sclerosis; less than mild valvular regurgitation; less than moderate simple pericardial effusion; absence of pacemaker/defibrillator leads or central venous catheters; absence of prosthetic valves; and absence of typical or suggestive signs of IE, such as valve masses or ring abscesses.1
Patients were divided into three groups: strict negative criteria fulfilled, so no follow-up echocardiogram indicated; strict negative criteria unfulfilled, but no signs of IE, so follow-up echocardiogram may be reasonable depending on other clinical data; and strict negative criteria unfulfilled and typical or suggestive signs of IE were evident, so another echocardiogram generally would be indicated. The primary endpoint was the percentage of echocardiograms to rule out IE that fulfilled the strict negative criteria for IE, the number of follow-up tests conducted, and the final diagnosis of IE in each group. Secondary analyses included the echocardiogram predictors of a repeat study and the outcome of patients. The mean age of the patients was 65 years, and the majority were men (61%). Follow-up echocardiograms were performed more frequently in those with valvular disease detected or a prosthetic valve (P < 0.001). There was a trend toward more follow-up echocardiograms in those with a history of parenteral drug use (P = 0.084), but this was a small group (n = 16). At least one positive blood culture was found in 31%, and follow-up echocardiograms were conducted more frequently in these patients, especially if typical IE organisms were found (Enterococcus, Staphylococcus, Streptococcus).
Group 1 included 50% of all patients. The main reason for not fulfilling strict negative criteria was more than mild valvular regurgitation (30%), followed by poor echocardiogram quality (12%), and signs of IE (13%). Overall, 15% underwent follow-up echocardiograms, most of which were TEEs. In group 1, only 5% underwent a follow-up echocardiogram. For group 2, it was only 14%, but 59% of patients in group 3 underwent a follow-up (P < 0.001). The strongest predictors of a subsequent echocardiogram were signs of IE, valvular disease, or typical organisms on blood culture. A definitive diagnosis of IE was made in 8% of patients; most in group 3 (67%), followed by group 2 (28%), and group 1 (5.5%). During a median follow-up of three years, no group 1 or 3 patients and only one group 2 patient was admitted to the hospital with a diagnosis of new IE.
The authors concluded that in daily clinical practice, echocardiography is overused in patients with suspected IE. Only 13% of patients showed any signs suggestive of IE, and only 8% received an IE diagnosis. Strict negative criteria on echocardiograms were present in half the population suspected of IE, which was associated with a low probability of a request for a follow-up study and of an IE diagnosis.
COMMENTARY
Marcos-Garces et al used the Duke criteria for diagnosing IE. Echocardiography results heavily influence these criteria. Since blood cultures are nonspecific regarding source, it is not surprising echocardiograms are the foundation of IE diagnosis and prone to overuse. Also, an echocardiogram usually can be obtained before the results of blood cultures are available.
The aim of this relatively large observational study was to evaluate whether the systematic application of the proposed strict negative echo criteria (SNC) on the first transthoracic echo ordered could safely deter unnecessary subsequent echocardiogram requests. The authors found that despite the lack of systematically applying the SNC or even knowledge of them, clinicians intuitively used the characteristics of the first echocardiogram to determine the request for subsequent echocardiograms. In patients later found to meet the SNC (group 1), only 5% underwent subsequent echocardiograms. In those who did not meet SNC, but showed no signs of IE on echocardiogram (group 2), only 14% did. Usually, these patients tested positive on blood cultures for organisms often associated with IE.
The results of this study are unlikely to change clinical practice. To codify this, the authors recommend that if the first echocardiogram meets the SNC and blood cultures are negative, no follow-up echocardiogram is necessary unless clinical suspicion remains. In the latter case, the second echocardiogram probably should be a TEE.
REFERENCE
- Sivak JA, Vora AN, Navar AM, et al. An approach to improve the negative predictive value and clinical utility of transthoracic echocardiography in suspected native valve infective endocarditis. J Am Soc Echocardiogr 2016;29:315-322.
Applying the proposed strict negative criteria for infective endocarditis (IE) on the first echocardiogram indicated this approach largely prevented unnecessary repeat tests unless clinically indicated for continued suspicion of IE.
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