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Table of Contents
CASE REPORT
Year : 2020  |  Volume : 10  |  Issue : 4  |  Page : 187-189

Localization of focus by 18 F-fludeoxyglucose positron emission tomography computed tomography in the definitive diagnosis of infective endocarditis


1 Department of Cardiology, Apollo Main Hospitals, Chennai, Tamil Nadu, India
2 Department of Infectious Diseases, Apollo Main Hospitals, Chennai, Tamil Nadu, India
3 Department of Nuclear Medicine, Apollo Main Hospitals, Chennai, Tamil Nadu, India

Date of Submission20-Jan-2020
Date of Decision04-May-2020
Date of Acceptance20-Jun-2020
Date of Web Publication21-Jan-2021

Correspondence Address:
Dr. Sathyamurthy Immaneni
Department of Cardiology, Apollo Main Hospitals, Chennai-6, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JICC.JICC_3_20

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  Abstract 


18 F-fludeoxyglucose positron-emission tomography computed tomography scans are helpful in making definitive diagnosis of infective endocarditis (IE) in some selected cases. We are reporting two cases of IE, in one case, the infective focus was in the organized left ventricular mural thrombus and the second case the infective focus was found in the aortic root and annulus and the prosthetic valve was spared. This being a noninvasive test can be repeated to ascertain the adequacy of treatment during follow-up.

Keywords: 18 F-fludeoxyglucose positron-emission tomography computed tomography scans, computed tomography scan, infective endocarditis


How to cite this article:
Immaneni S, Ramasubramanian V, Indirani M, Shelley S. Localization of focus by 18 F-fludeoxyglucose positron emission tomography computed tomography in the definitive diagnosis of infective endocarditis. J Indian coll cardiol 2020;10:187-9

How to cite this URL:
Immaneni S, Ramasubramanian V, Indirani M, Shelley S. Localization of focus by 18 F-fludeoxyglucose positron emission tomography computed tomography in the definitive diagnosis of infective endocarditis. J Indian coll cardiol [serial online] 2020 [cited 2022 Dec 7];10:187-9. Available from: https://www.joicc.org/text.asp?2020/10/4/187/307614




  Introduction Top


18 F-fludeoxyglucose positron-emission tomography computed tomography (FDG PET/CT) is being used routinely as a diagnostic modality in oncology (tumor-specific imaging), sarcoidosis and in conditions like vasculitis. This imaging is also used to confirm or rule out the diagnosis of infective endocarditis (IE). It is particularly helpful in culture-negative IE and those with prior healed vegetations when they present with fever of unknown etiology. FDG PET/CT is also helpful to localize the site of infection, in the follow-up of such cases to assess the adequacy of treatment and in predicting prognosis. We are reporting two cases of suspected IE, in whom PET scans helped in localizing the site and extent of the infection, in making definitive diagnosis of IE and also in assessing response to therapy.


  Case Report Top


Case I

Forty-two-year-old male who suffered anterior wall myocardial infarction in the past with severe left ventricular (LV) dysfunction had undergone percutaneous coronary intervention to left anterior descending. Due to the recurrence of symptoms, he has undergone Dorr's aneurysmoraphy and bypass surgery. Three months follow-up revealed LV apical thrombus, which was treated with oral anticoagulants. Subsequent follow-ups revealed that LV mural thrombus was well organized. Eight years later, he presented with high-grade fever, and blood cultures grew methicillin-resistant staph aureus. Transthoracic echocardiogram (TTE) and transoesophageal echocardiogram (TEE) did not reveal any evidence of native valve vegetations. FDG PET/CT revealed hypermetabolic uptake in the organized thrombus and patch was free from infective foci, and the patient was treated with appropriate antibiotics for 8 weeks, and he remained asymptomatic during follow-up [Figure 1]. Follow-up PET/CT revealed clearance of infective focus.
Figure 1: (a and b) Axial and coronal sections of computed tomography: Ill-defined lesion is noted in the LV with soft tissue thickening in the pericardium abutting left ventricular apex. (c and 1) axial and coronal sections of positron-emission tomography computed tomography images showing increased fludeoxyglucose uptake in the ill-defined lesion and soft-tissue thickening

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Case II

A 46-year-old male underwent Bentall's procedure in 2008 for Type A aortic dissection. In Jan 2018, he was admitted with high-grade fever of 10 days duration with splenic and renal infarcts. Blood cultures grew Streptococcus mitis. TTE and TEE did not show any evidence of ring abscess or vegetations. FDG PET/CT revealed hypermetabolic inflammatory activity in the aortic root and aortic ring. He was treated with suitable antibiotics for 3 months. Repeat PET/CT revealed complete clearance of the hypermetabolic uptake [Figure 2].
Figure 2: (a and b) Axial and coronal sections of fused positron emission tomography computed tomography chest in baseline scan: Patchy increased fludeoxyglucose uptake is seen around the prosthetic aortic valve (January 2018). (c and d) Corresponding axial and coronal sections of fused positron-emission tomography computed tomography in follow-up scan (April 2018) showing resolution of fludeoxyglucose uptake post treatment

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  Discussion Top


Metabolic imaging with 18F–FDG PET/CT has been shown to improve diagnostic accuracy when used in conjunctions with Duke's criteria. Many cases of probable IE can result in a definitive diagnosis. In one study[1] of 30 patients, echocardiogram and FDG–PET/CT confirmed the diagnosis in only half of them. In the remaining half, focally increased FDG uptake was observed in the valve area without vegetations suggesting that the disease could be diagnosed even in the early stages. Conversely, absence of abnormal FDG can rule out IE. They suggested that FDG-PET/CT should be included as a major criterion for the diagnosis of IE. In the study by Ricciardi et al.[2] in 27 patients with prosthetic valve endocarditis (PVE), they demonstrated diagnostic accuracy can be increased by including FDG-PET/CT to Duke's criteria and echocardiography.

In one large study[3] of 92 patients of the prosthetic valve and device-related IE, all were evaluated with Duke's criteria and echocardiography. The diagnostic accuracy was 54% by Duke's criteria alone, and the accuracy raised to 95% by adding FDG-PET/CT. Duke's criteria and PET/CT substantially reduced the rate of doubtful cases of IE from 20% to 8%, and it helped in rejecting the diagnosis in 12% of cases [Table 1]. However, there are certain limitations in FDG PET/CT as a diagnostic modality, like low intensity of radiotracer activity may be observed relative to background activity and increased radiotracer uptake in noninfected structures adjacent to prosthetic valves, particularly in cases of recent surgery due to reactive tissue inflammation. However, in both of our cases, there was a long gap after the surgery. The adequacy of antibiotic therapy was assessed by repeat scans, as was done in both of our cases.
Table 1: Improving the diagnostic accuracy with fludeoxyglucose-positron emission tomography/computed tomography

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In cases of culture-negative PVE in whom TEE failed, FDG PET/CT has been found to be confirmatory.[4],[5] In one pooled analysis[6] of FDG-PET/CT where 13 studies were included involving 537 patients from Jan 90 to April 2017 in the diagnosis of IE, pooled sensitivity was 76.8%, specificity 77.9% for native valves and for the diagnosis of PVE sensitivity of 80.5% and specificity of 73.1%. The site of infection in our cases could be located in the LV mural thrombus and aortic root. The absence of infective focus by FDG–PET/CT can rule out the possibility of endocarditis.


  Conclusion Top


18 F–FDG PET/CT is helpful in the diagnostic workup of IE. Because of the lack of large studies, routine use of 18F-FDG PET/CT has not been included in the guidelines. This modality of imaging is not readily possible, expertise is not widely available; it is expensive. However, in future, it may find a place in the diagnostic armamentarium of IE in selected cases to make a definitive diagnosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Saby L, Laas O, Habib G, Cammilleri S, Mancini J, Tessonnier L, et al. Positron emission tomography/computed tomography for diagnosis of prosthetic valve endocarditis: increased valvular 18Ffluorodeoxyglucose uptake as a novel major criterion. J Am Coll Cardiol 2013;61:2374-82.  Back to cited text no. 1
    
2.
Ricciardi A, Sordillo P, Ceccarelli L, Maffongelli G1, Calisti G2, Di Pietro B, et al. 18-fluoro-2-deoxyglucose positron emission tomography-computed tomography: An additional tool in the diagnosis of prosthetic valve endocarditis. Int J Infect Dis 2014;28:219-24.  Back to cited text no. 2
    
3.
Pizzi MN, Roque A, Fernández-Hidalgo N, Cuellar-Calabria H, Ferreira- Gonzalez I, Gonzalez-Alujas MT, et al. Improving the diagnosis of infective endocarditis in prosthetic valves and intracardiac devices with 18F fluordeoxyglucose positron emission tomography/computed tomography angiography: Initial results at an infective endocarditis referral center. Circulation 2015;132:113.  Back to cited text no. 3
    
4.
Tamis W, Scholter A, Habets J, van den Brink RB, van Herwerden LA, Chamuleau SA , et al. Fusion of cardiac computed tomography and 18F – Fluorodeoxy glucose positron emission tomography for the detection of prosthetic heart valve endocarditis. JACC Cardiovasc Imaging 2013;6:1008.  Back to cited text no. 4
    
5.
Dilsizian V, Achenbach S, Nasula J. On adding-selecting imaging modalities for incremental diagnosis. A case study of F –Fluorodeoxy glucose PET/CT in prosthetic valve endocarditis. JACC Cardiovasc Imaging 2013;6:1020.  Back to cited text no. 5
    
6.
Mahmood M, Kendi AT, Ajmal S, Farid S, O'Horo JC, Chareonthaitawee P, et al. Meta-analysis of 18F-FDG PET/CT in the diagnosis of infective endocarditis. J Nucl Cardiol 2019;26:922-35.  Back to cited text no. 6
    


    Figures

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    Tables

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