Diagnostic yield of FDG positron-emission tomography/computed tomography in patients with CEID infection: a pilot study

Role of radionuclide imaging for diagnosis of device and prosthetic valve infections

Cardiovascular implantable electronic device (CIED) infection and prosthetic valve endocarditis (PVE) remain a diagnostic challenge. Cardiac imaging plays an important role in the diagnosis and management of patients with CIED infection or PVE. Over the past few years, cardiac radionuclide imaging has gained a key role in the diagnosis of these patients, and in assessing the need for surgery, mainly in the most difficult cases. Both ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) and radiolabelled white blood cell single-photon emission computed tomography/computed tomography (WBC SPECT/CT) have been studied in these situations. In their 2015 guidelines for the management of infective endocarditis, the European Society of Cardiology incorporated cardiac nuclear imaging as part of their diagnostic algorithm for PVE, but not CIED infection since the data were judged insufficient at the moment. This article reviews the actual knowledge and recent studies on the use of ¹⁸F-FDG PET/CT and WBC SPECT/CT in the context of CIED infection and PVE, and describes the technical aspects of cardiac radionuclide imaging. It also discusses their accepted and potential indications for the diagnosis and management of CIED infection and PVE, the limitations of these tests, and potential areas of future research.

Management of bacteremia in patients living with cardiovascular implantable electronic devices

Cardiovascular implantable electronic devices (CIEDs) have become a critical component in management of patients with cardiac rhythm disturbances, heart failure, and prevention of sudden cardiac death. However, infection remains a major complication of CIED implantation and is associated with significant morbidity and mortality for device recipients. Early-onset CIED infections frequently originate from the generator pocket, secondary to device or pocket contamination at the time of implantation, and may progress to involve device leads or cardiac valves. However, hematogenous seeding of the device leads from a remote source of bacteremia is not infrequent in patients with late-onset CIED infections. Whereas CIED pocket infection can be diagnosed in the majority of cases based on physical findings at the pulse generator site, device lead infection may only manifest with fever and positive blood cultures. However, not every patient with a CIED and positive blood cultures has underlying CIED lead infection. Consequently, management of bacteremia in a CIED recipient without local signs of infection presents a significant challenge. The risk of underlying CIED lead infection in patients presenting with bacteremia depends on several factors, including the type of microorganism isolated in blood cultures, duration and source of bacteremia, type of CIED, and number of device-related procedures. These risk factors must be considered when making decisions regarding the need for further diagnostic imaging and whether to retain or remove the device. In this article, we review the published data regarding risk of CIED infection in patients presenting with bacteremia and propose an algorithm for appropriate evaluation and management.

Accuracy of Positron Emission Tomography as a Diagnostic Tool for Lead Endocarditis: Design of the Prospective Multicentre ENDOTEP Study

Background: Rates of pacemaker implantation are steadily increasing and as patients are living longer, endovenous leads remain implanted for an extended period of time thereby increasing the risk of cardiac implantable electronic device (CIED) infection. Investigating fever of unknown origin in patients with implanted pacemakers can be challenging. Recently, ¹⁸F-fluorodeoxyglucose positron emission tomography/computerised tomography (¹⁸F-FDG-PET/CT) scanning has been used as a diagnostic tool for lead endocarditis in small studies. Objectives: ENDOTEP is a prospective and multicentre study designed to evaluate the accuracy of ¹⁸F-FDG-PET/CT scanning in the diagnosis of lead endocarditis. Methods: A total of 250 patients referred for pacemaker extraction due to suspicion of an infected device will be prospectively enrolled in six French regional centres for investigation and treatment of CIED infection. ¹⁸F-FDG-PET/CT scanning (index test) will be performed in each patient in the 48 hours preceding lead extraction. Bacteriological cultures (reference standard) will assess the presence of lead endocarditis, blind to ¹⁸F-FDG-PET/CT results. Enrolment started in June 2015 and is expected to end by June 2017. The primary objective will be to establish the sensitivity of the ¹⁸F-FDG-PET/CT scan for lead endocarditis. Secondary objectives will include other accuracy parameters, inter-observer agreement in the interpretation of ¹⁸F-FDG-PET/CT scanning, the influence of previous antibiotic therapy on ¹⁸F-FDG-PET/CT diagnostic accuracy and assessment of septic emboli associated to lead endocarditis. Conclusion: The ENDOTEP study will examine the ability of ¹⁸F-FDG-PET/CT scanning to avoid possible false-positive results, as is common using the current usual diagnostic strategy and may lead to unnecessary extraction of implants in patients with suspected lead infection.

Radionuclide Imaging of Cardiovascular Infection

Owing to expanding clinical indications, cardiac implantable electronic devices (CIEDs) are being increasingly used. Despite improved surgical techniques and the use of prophylactic antimicrobial therapy, the rate of CIED-related infection is also increasing. Infection is a potentially serious complication, with clinical manifestations ranging from surgical site infection and local symptoms in the region of the generator pocket to fulminant endocarditis. The utility of radionuclide imaging as a stand-alone noninvasive diagnostic imaging test in patients with suspected endocarditis has been less frequently examined. This article summarizes the recent advances in radionuclide imaging for evaluation of patients with suspected cardiovascular infections.

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.

Early diagnosis of cardiac implantable electronic device generator pocket infection using ¹⁸F-FDG-PET/CT

AIMS

To examine the utility of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) in the early diagnosis of cardiac implantable electronic device (CIED) generator pocket infection.

METHODS AND RESULTS

A total of 86 patients with CIEDs were evaluated with (18)F-FDG PET/CT imaging: 46 with suspected generator pocket infection and 40 without any history of infection. (18)F-FDG activity in the region of the generator pocket was expressed as a semi-quantitative ratio (SQR)-defined as the maximum count rate around the CIED divided by the mean count rate between normal right and left lung parenchyma. All patients underwent standard clinical management, independent of the PET/CT result. Patients with suspected generator pocket infection that required CIED extraction (n = 32) had significantly higher (18)F-FDG activity compared with those that did not (n = 14), and compared with controls (n = 40) [SQR: 4.80 (3.18-7.05) vs. 1.40 (0.88-1.73) vs. 1.10 (0.98-1.40), respectively; P < 0.001]. On receiver operator characteristic analysis, SQR had a high diagnostic accuracy (area under curve = 0.98) for the early identification of patients with confirmed infection (i.e. those ultimately needing extraction)-with an optimal SQR cut-off value of >2.0 (sensitivity = 97%; specificity = 98%).

CONCLUSION

This study highlights the potential benefits of evaluating patients with suspected CIED generator pocket infection using (18)F-FDG PET/CT. In this study, (18)F-FDG PET/CT had a high diagnostic accuracy in the early diagnosis of CIED generator pocket infection, even where initial clinical signs were underwhelming.

Management of Cardiac Implantable Electronic Device Infection

Despite improved preventive measures, infection associated with the use of cardiac implantable electronic devices (CIEDs) to treat often life-threatening conditions is rising at an average annual rate of almost 5 %. This rise is being driven by the increasing complexity of CIED technology and by the advancing age and co-morbidities of the patients. Although CIED infection is usually suspected based on local signs at the generator pocket site, diagnosis can be challenging in patients presenting no local manifestations or symptoms. Diagnostic methods include microbiological testing and echocardiography, and may be completed by positron emission tomography (PET)/computed tomography (CT) scan in selected cases. CIED infection requires a multidisciplinary approach in view of hardware extraction, targeted antibiotic therapy and reimplantation on an as-needed basis. Antibiotic prophylaxis targeting staphylococcal flora is recommended but the relation of these infections to medical care exposes patients to multi-resistant bacteria. New preventive measures utilising an antibacterial sleeve look promising. Treatment can be started on an empirical basis using an antistaphylococcal agent but must be continued using targeted antibiotic therapy. Crucial questions remain as to the best prevention strategy, optimal duration and timing of antibiotic therapy, and the most effective reimplantation technique.

The characteristics and outcome of infective endocarditis involving implantable cardiac devices

Infection of implantable cardiac electronic devices in particular lead endocarditis (cardiac device infective endocarditis (CDIE)) is an emerging problem with significant morbidity, mortality and health care costs. The epidemiology is characterised with advanced age and health care association in cases presenting within 6 months of implantation. Risk factors include those of the patient, the procedure and the device. Staphylococcal species predominate as the causative organisms. Diagnosis is reliably made by blood cultures and transesophageal echocardiography. Complications include pulmonary and systemic emboli, persistent bacteremia and concomitant valvular involvement. Management includes complete device removal and prolonged antimicrobial therapy. With long-term follow-up to 1 year, the mortality of CDIE is as high as 23 %. It is associated with patient co-morbidities and concomitant valvular involvement and may be prevented by device removal during index admission.

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.

FDG-PET in cardiac infections

Cardiac infections include a group of conditions involving the heart muscle, the pericardium, or the endocardial surface of the heart. Infections can extend to prosthetic material or the leads in case of the implantation of devices. Despite their relative low incidence, these conditions that are associated with high morbidity and mortality involve a relevant burden of diagnostic workup. Early diagnosis is crucial for adequate management of patient, as early treatment improves the prognosis; unfortunately, the clinical manifestations are often nonspecific. Accurate and timely diagnosis typically requires the correlation of imaging findings with laboratory data. (18)F-FDG-PET is a well-established imaging modality for the diagnosis and management of malignancies, and evidence is also increasing regarding its value for assessing infectious and inflammatory diseases. This article summarizes published evidence on the usefulness of (18)F-FDG-PET for the diagnosis of cardiac infections, mainly focused on endocarditis and cardiovascular device infections. Nevertheless, the diagnostic potential of (18)F-FDG-PET in patients with pericarditis and myocarditis is also briefly reviewed, considering the most likely future advances and new perspectives that the use of PET/magnetic resonance would open in the diagnosis of such conditions.