Imaging for infected cardiac implantable electronic devices: a new trick for your pet

The performance of quantitation methods in the evaluation of cardiac implantable electronic device (CIED) infection: A technical review

BACKGROUND

Quantitative assessment of [18F]-FDG PET/CT images has been shown to be useful in the diagnosis of cardiac implantable electronic device (CIED) infection. This study aimed to compare the accuracy of various quantitative methods, using the same patient cohort and to assess the utility of dual time point imaging.

METHODS

The study comprised a retrospective review of 80 [18F]-FDG PET/CT studies. Of these, 41 were oncological patients with an asymptomatic CIED in situ (Group 1), and 39 were studies performed in patients with symptomatic devices. Of these, 14 were subsequently deemed on follow-up to be non-infected (Group 2), and 25 confirmed as infected post-device extraction (Group 3). Ratios of maximal uptake around the CIED in both the attenuation corrected and non-attenuation corrected images were calculated to regions of normal physiological uptake, along with the maximal standardized uptake value (SUVmax) alone. Receiver operating characteristic analysis was performed for all methods at both time points. Measurement reliability was assessed using the intraclass correlation coefficient (ICC).

RESULTS

Using Group 1 as a reference, all methods gave an area under the curve (AUC) greater than 0.93. Using Group 2 as reference, the accuracy varied greatly, with AUC values ranging from 0.71 to 0.97. The hepatic blood pool (HBP) ratio gave the highest AUC values. The calculated ICC values for each method showed the SUVmax and HBP measurement to have the greatest reliability, with values of 1.0 and 0.97, respectively.

CONCLUSIONS

Quantitation of [18F] FDG uptake was found to have a high degree of accuracy in confirming the diagnosis of CIED infection. Normalization to HBP uptake was found to give the greatest AUC and demonstrated excellent reliability. Inconsistencies from published data indicate that individual imaging centers should only use published data for guidance.

High performances of (18)F-fluorodeoxyglucose PET-CT in cardiac implantable device infections: A study of 40 patients

BACKGROUND

Cardiovascular implantable electronic devices (CIED) infections are life-threatening complications. The diagnosis can be difficult to establish. Our purpose is to evaluate the diagnostic value of (18)F-FDG PET.

METHODS

Forty patients who received work-up for suspected CIED infection were retrospectively included (group 1) and compared with 40 controls (group 2); CIED patients were referred for oncologic PET. PET-CT data were blindly assessed. Interpretation was based on visual analysis of both attenuation-corrected and non-corrected images and a semi-quantitative analysis was performed. The gold standard was bacteriological data of explanted devices or clinical follow-up for at least 1 year.

RESULTS

Infection was present in 18 out of 40 patients of group 1. Sensitivity, specificity, positive predictive value, and negative predictive value of PET-CT were 83%, 95%, 94%, and 88%, respectively. Accuracy was 90%. PET-CT revealed the presence of additional pathological hypermetabolic foci in 28% of cases. PET-CT was negative at implanted devices in all patients of group 2.

CONCLUSION

(18)F-FDG PET-CT is helpful in the work-up of suspected CIED infections. It is a potential tool to make the accurate diagnosis of CIED infection and to assess the extent of infection. The promising results in this indication need to be validated in a prospective multicenter study.

18-Fluoro-2-deoxyglucose positron emission tomography-computed tomography: an additional tool in the diagnosis of prosthetic valve endocarditis

OBJECTIVES

To evaluate the role of 18-fluoro-2-deoxyglucose positron emission tomography-computed tomography ((18)F-FDG-PET-CT) in the diagnosis of infectious endocarditis (IE).

METHODS

We retrospectively examined 27 consecutive patients who were admitted to the Infectious Diseases Department of Tor Vergata University Hospital between 2009 and 2013 with a suspicion of IE. The final IE diagnosis was defined according to the modified Duke criteria, and the microbiological and diagnostic results were collected for each patient.

RESULTS

Twenty out of 27 patients had a suspected prosthetic valve endocarditis (PVE) and seven had a suspected native valve endocarditis (NVE). Twenty-five out of 27 patients (92%) had a confirmed diagnosis of IE (18/25 PVE and 7/25 NVE); 16 had a positive echocardiography evaluation and 16 had positive (18)F-FDG-PET-CT findings. Echocardiography showed a higher sensitivity as a diagnostic tool for the detection of IE compared to (18)F-FDG-PET-CT (80% vs. 55%). However, a greater number of PVE had positive (18)F-FDG-PET-CT results compared to those with positive echocardiography findings (11/13 vs. 9/13), and overall 89% (16/18) of confirmed PVE resulted (18)F-FDG-PET-CT positive. Analyzing only the cases who underwent transoesophageal echocardiography, (18)F-FDG-PET-CT showed a sensitivity of 85% in PVE (vs. 69% for echocardiography and 77% for the Duke criteria). All seven patients with NVE had a positive echocardiography and negative (18)F-FDG-PET-CT findings (p<0.001).

CONCLUSIONS

The results of this study further highlight the limitations of echocardiography in the diagnosis of PVE and the potential advantages of (18)F-FDG-PET-CT in these cases.

Cardiovascular implantable electronic device infection: delayed vs standard FDG PET-CT imaging

BACKGROUND

Positron emission tomography-computed tomography (PET-CT) with (18)F-fluorodeoxyglucose (FDG) has emerged as a rapidly evolving diagnostic tool for infectious diseases. However, the optimal imaging time in this clinical setting is not clear yet. The aim of this study is to investigate whether delayed (3 hours) FDG PET-CT could increase the diagnostic accuracy of this technique compared to standard (1 hour) imaging in the detection of septic foci involving the pocket and/or pacing leads in patients with suspected cardiovascular implantable electronic device (CIED) infection scheduled for device removal.

METHODS AND RESULTS

Twenty-seven patients underwent standard and delayed imaging. PET-CT results were compared to bacteriological cultures after CIED removal. Fifteen controls free of infection underwent PET-CT imaging as part of investigation of malignancy. The diagnostic accuracy of delayed imaging was significantly higher than 1-hour scan for lead infection (70% vs 51%, P = .024). No significant difference was found between standard and delayed diagnostic accuracy for pocket or device infection. Semi-quantitative analysis showed that mean pocket and lead target-to-background ratio were significantly higher on delayed compared to standard imaging (3.7 ± 1.9 vs 1.6 ± 1.1, P = .0002; 3.0 ± 1.3 vs 0.7 ± 1.0, P = .01).

CONCLUSIONS

Delayed FDG PET-CT imaging should be considered at least in patients with negative 1-hour scan and founded suspicion of pacing lead infection.

Analysis of extracted cardiac device leads for bacteria type: clinical impact

The use of cardiac implantable electronic devices (CIED) increased over time, followed by rise of CIED-related complications, mainly infections and malfunctions. A clear diagnosis of CIED infection is of pivotal importance. When infection is confirmed, transvenous lead extraction (TLE) becomes mandatory, with associated risks and mortality. Local lesions at the device pocket often return negative swabs and tissue specimens, but conservative interventions are inconclusive, raising risks of systemic dissemination of infection and difficulties of subsequent TLE any more. When local bacteriological analyses are positive, once again, a contamination effect cannot be excluded. So traditional local swabs and tissue specimens exhibit low sensitivity and specificity for diagnosis of CIED infection. On the contrary, in cases sepsis, blood samples show high specificity, while the sensibility remains low, due to possible negative results in patients on antibiotics. In this scenario, the analysis of extracted device leads seems more appropriate for diagnostic purposes.