Venet M, Jalal Z, Ly R, Malekzadeh-Milani S, Hascoët S, Fournier E, Ovaert C, Casalta AC, Karsenty C, Baruteau AE, Le Gloan L, Selegny M, Douchin S, Bouvaist H, Belaroussi Y, Camou F, Tlili G, Thambo JB.
JACC Cardiovasc Imaging. 2022 Feb;15(2):299-308. doi: 10.1016/j.jcmg.2021.07.015. Epub 2021 Sep 15.
PMID: 453863
Study Summary and Take-Home Points:
- In this retrospective study that included 66 patients with suspected endocarditis of a prosthetic pulmonary valve or right sided conduit, 44 patients had definite diagnosis of endocarditis, 10 had possible and 12 a rejected diagnosis. The most frequent pathogens were staphylococcus and streptococcus, both accounting for 68% of overall microbiological findings.
- The median interval between the initial endocarditis suspicion date and a 18F-Fluorodeoxyglucose Positron Emission Tomography Computed Tomography (18 F-FDG-PET/CT) was 7.5 days. Appropriate antibiotics were started before PET/CT for 83.3% of the patients. Among them, the median delay between antibiotics onset and PET/CT was 7 days. Sufficient myocardial suppression was obtained in 92.5% of the cases.
- The sensitivity, specificity, positive, and negative predictive values of 18F-FDG PET/CT for diagnosis of PPVE were as follows: 79.1% (95% CI: 68.4%-91.4%), 72.7% (95% CI: 60.4%-85.0%), 91.9% (95% CI: 79.6%-100.0%), and 47.1% (95% CI: 34.8%-59.4%), respectively.
- The median time between antibiotics starting and PET/CT in the false negative cases was 2.5 days and median CRP level was 56 mg/L, whereas in true positive cases, this delay was 7.0 days and median CRP level was 67.0 mg/L.
- More atypical causing bacteria were grown in the false negative group. The type of prosthesis was not associated with higher false positives or negatives PET/CT results.
- Among the 44 cases of definite endocarditis, 27 patients exhibited both positive imaging studies (i.e. TTE/TEE or cardiac CT) and PET/CT, and 13 patients presented a positive PET/CT despite a negative imaging study. PET/CT appeared to provide better diagnostic capabilities when more common causing organisms were involved: when streptococcus or staphylococcus were identified as the causative agent, 80% PET/CTs were positive, whereas when less common microorganisms were involved, PET/CT was positive in 66.7%. Notably, four definite endocarditis patients had both negative PET/CT and imaging studies. In these patients, the causing organisms were atypical (Streptococcus sanguinis, Aggregatibacter actinomycetemcomitans, Candida parapsilosis, and Coxiella burnetii)
- Embolic and distant lesions were identified by PET/CT in 31 patients. Pulmonary septic emboli were identified by chest CT and PET/CT in 14 patients, 13 of which had definite and 1 had possible endocarditis.
- During a median follow up period of 26.6 months in the endocarditis group, 75% of the patients required surgery and one 50 year old patient with tetralogy of Fallot and other “severe comorbidities” passed away from the infection.
Commentary from Dr. Yonatan Buber (Seattle, USA), section editor of ACHD Journal Watch:
The overall incidence of endocarditis in congenital heart disease patients is estimated at 1.33 per 1,000 person-years, and 50% to 60% of the cases involve right-sided valves with a high proportion of pulmonary prosthetic valve or conduit endocarditis. Both transcatheter and surgically implanted valve can be affected. Although the integration of 18F-FDG positron emission PET/CT increased the diagnostic sensitivity by 52%-70% to 91%-97% for endocarditis involving left-sided valve, the data on its applicability for right-sided on endocarditis remains limited.
This was a retrospective study conducted between 2010-2020 in 8 centers in France aimed to evaluate the diagnostic performance of 18F-FDG PET/CT in the diagnosis of prosthetic pulmonary valve or conduit endocarditis in CHD patients. Sixty-six suspected pulmonary prosthetic valve or conduit endocarditis episodes involving 59 patients were included, all of which underwent an 18F-Fluorodeoxyglucose Positron Emission Tomography Computed Tomography (18F-FDG PET/CT) study . Median age was 23.4 years, 10 patients were below 15 years of age, the youngest was 5 years old, and 72.7% were men. The involved RVOT prosthetic substrates included percutaneous pulmonary valved stents (Melody, Medtronic Inc; and Sapien, Edwards Lifesciences devices), surgical pulmonary bioprostheses, right ventricle to pulmonary artery prosthetic conduits, and pulmonary homografts.
Similar to other studies reporting the diagnostic performance of 18F-FDG-PET/CT in left-sided endocarditis, the main strength appears to be its strong positive predictive value, which in this study was 92%, whereas its main limitation remains the very low negative predictive value, which in this study was only 47%. Sensitivity (79%) and specificity (72%) were in the moderate-high range. Noteworthy observations that are of considerable clinical implications are that the diagnostic capabilities of 18F-FDG-PET/CT were lower when the causative organisms were atypical, when the inflammatory markers were lower and when the studies were performed <3 months from the time of the valve or conduit implantation.
The authors provide additional theoretical explanations to the low negative predictive performance, including the fact that many nuclear physicians are less familiar with RVOT features than left-sided valve prostheses, and the potential lower difference between pathological and nonpathological 18F-FDG uptake with some biological tissues such as bovine jugular vein materials or pulmonary homografts.
Notably, the gold standard used for the diagnosis of endocarditis in this study was an expert consensus obtained by an endocarditis group, while only 4 explanted valves or conduits showed evidence of infection. An important limitation is the lack of intracardiac echo studies in this series, a tool that is commonly used in contemporary practice for suspected pulmonary valve endocarditis patients.
18-F FDG PET/CT can thus be a useful tool in the workup of patients with suspected prosthetic pulmonary valve endocarditis. It appears that is should be performed early in the inflammation phase but not in the first 2-3 months after the valve implantation, and that CRP levels could help guide the timing. Negative results should not be used to rule out the diagnosis of endocarditis in this clinical setting.
