Elsevier

PET Clinics

Volume 14, Issue 2, April 2019, Pages 251-269
PET Clinics

PET/Computed Tomography Evaluation of Infection of the Heart

https://doi.org/10.1016/j.cpet.2018.12.006Get rights and content

Section snippets

Key points

  • Background relating to cardiac infections, current diagnosis and limitations, international guidelines.

  • The role of 18F-fluorodeoxyglucose (18F-FDG)-PET/computed tomography (CT) in the diagnosis and monitoring of secondary complications associated with infective endocarditis, cardiac implantable device infection, left ventricular assist device infection and graft infection.

  • Current limitations in the use of 18F-FDG-PET/CT to diagnose and monitor cardiac infection.

  • Current best-practice protocols.

Infective endocarditis: current diagnostic approaches

Because of the underlying risk factors, varied causative infectious agents, and associated secondary complications of IE, the diagnosis, clinical management, and monitoring of IE require a multidisciplinary approach.4, 5 The initial diagnosis is a challenge, because of a myriad of clinical presentations, many of which are nonspecific to IE. The Modified Duke Criteria have offered guidance and have become an international diagnostic cornerstone, with major criteria focusing on microbiological

Prosthetic valve endocarditis

The application of 18F-FDG-PET/CT in relation to IE is most recognized and accepted in the diagnostic work-up of prosthetic valve endocarditis (PVE), as shown by its inclusion in the ESC guidelines, where there is a high level of clinical suspicion in patients with prosthetic valves and when the diagnosis is classified as possible or rejected, even following repeat microbiology and TTE4 (Fig. 1). Subsequently, this was supported by the findings of a best-evidence analysis of observational

Native valve endocarditis

In contrast with PVE, a review analysis of several small-scale studies14, 15 and 2 recent large retrospective studies12, 16 has suggested a low-sensitivity diagnostic value relating to 18F-FDG-PET/CT when used alone, in terms of uptake of tracer in native valves in which infection has been proved (sensitivity, specificity, positive and negative predictive values: 18%, 100%, 100%, and 66%, respectively).12 Possible reasons for the limited sensitivity have been attributed to (1) continuous

Cardiac implantable electronic device infection

CIED therapy is continuing to grow, with expanding implications for use including bradycardia, tachycardia, and heart failure, resulting in 1.2 million to 1.4 million CIEDs implanted annually worldwide.17 Associated infections are significant, not only in terms of morbidity and mortality but also with respect to health care financial implications, in terms of both hospitalization and surgical procedures. CIEDs in an increasing aging population with concomitant comorbidities, such as diabetes

Left ventricular assist device infection

LVADs are increasingly used to provide temporary circulatory support to patients with end-stage heart failure, both acute and chronic, that is unmanageable by medical therapy, and as such act as a bridge to transplant or destination therapy, when the patient does not meet the criteria for a transplant.27 Other indications for use include reversible causes of heart failure (bridge to recovery) or patients who may meet the criteria for transplant in the future (bridge to candidacy).27 LVADs have

Infective endocarditis complications

Secondary complications following IE and CIED infection are primarily associated with septic embolic events, occurring in 22% to 43% of patients, generally within the first 2 weeks of therapy, with pulmonary emboli being the most frequent.38 Complications of IE include metastatic infection, septic arthritis, spondylodiscitis, osteomyelitis, pericarditis, and metastatic soft tissue abscess. Analyses of recent prospective and retrospective studies38, 39, 40, 41, 42 have shown 18F-FDG-PET/CT to be

Graft infection

Prosthetic graft infections can be associated with prosthetic valves, aortic vascular stent prostheses, or hybrid prostheses. Early superficial wound infection occurs in 3.2% of cases and endocarditis occurs as a late complication in 1.4% of cases.43 Such infections are potentially life threatening and treatment may involve repeat surgery, which is associated with a high morbidity and mortality; however, currently there are no specific diagnostic criteria available to ensure the optimum

Monitoring of antimicrobial therapy

It is recognized that the duration of antimicrobial therapy in the treatment of IE infection varies depending on the site of infection (NVE, PVE, or CIED infection) and the causative organism. Treatment durations are based either on randomized studies conducted in the 1990s or on expert opinion, with a lack of recent comparative data on treatment duration with respect to IE.47 The promising role of 18F-FDG-PET/CT in the monitoring of antimicrobial therapy in IE has been suggested by small

Other cardiac infections

There have been several interesting case reports in which 18F-FDG-PET has been reported to be beneficial in the detection other cardiac-related infections and unusual localizations of IE, such as endarteritis of the descending aorta,50 myocardial tuberculoma,51 mural endocarditis,52 myocarditis,53, 54 infected left ventricular pseudoaneurysm,55 and infected pulmonary conduit.56, 57

Limitations and suggested improvements

A major limitation to the application 18F-FDG-PET/CT in the diagnosis of cardiac infection is the current lack of standardized protocols in relation to both patient preparation and image interpretation, which may have contributed to the variation of findings in the published literature. A recent extensive analysis of current protocols has been conducted in an attempt to construct an evidence-based practice in order to improve the diagnostic potential of 18F-FDG-PET/CT in relation to PVE and

False findings

False-negative findings have been attributed to low inflammatory activity at the time of imaging, possibly caused by prolonged antibiotic therapy.13 On assessment of inflammatory activity and 18F-FDG-PET/CT in the diagnosis of PVE, it was reported that a C-reactive protein level of less than 4 times the upper normal limit (<40 mg/L) was a significant and major predictor of false-negative interpretations.13 False-positive findings in areas where surgical adhesives had been applied have been

Image interpretation

Most studies to date have focused on visual interpretation of images, to differentiate between normal physiologic and pathologic uptake. Such visual assessment of 18F-FDG-PET/CT has been reported as having a sensitivity, specificity, positive predictive value, and negative predictive value for PVE of 74%, 91%, 89%, and 78%, respectively, although this was significantly improved when patients were excluded because of significant confounders, as outlined earlier (91%, 95%, 95%, and 91%).13

A

Limitations and challenges related to imaging the infected heart

Over the past 5 decades, significant advances have been made in assessing structural and functional abnormalities that are associated with various diseases and disorders.65, 66, 67, 68, 69, 70, 71, 72, 73 In particular, the introduction of CT and PET-MRI has substantially improved the ability to visualize anatomic structures with great detail in health and disease. Although early instruments had the disadvantage of low spatial resolution and required image acquisition over a long period of

Summary

The role of 18F-FDG-PET/CT in the diagnostic algorithm for cardiac infections should be acknowledged, particularly when used in conjunction with the Modified Duke Criteria in relation to PVE, because it is a useful adjuvant in classifying cases. 18F-FDG-PET/CT should be restricted to cases of NVE with a strong suspicion of IE, but inconclusive by conventional approaches, because inclusion with the Modified Duke Criteria improves specificity in such cases. In relation to LVAD, 18F-FDG-PET/CT is

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  • Cited by (13)

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      The potential for additional value of other imaging techniques is high, and in recent years both the interest in and the evidence for 18F-fluorodeoxyglucose (FDG) PET/computed tomography (CT) in this complex diagnosis has expanded significantly. The role of FDG-PET/CT in infections of the heart has been reviewed in detail by Millar and colleagues1 in a recent edition of PET Clinics; in the current article, the general concepts and available evidence are reviewed with a focus on recent publications, and recommendations for image acquisition and interpretation are given. As described in more detail in the article by Søren Hess and colleagues, “Patient Preparation and Patient Related Challenges in Infectious and Inflammatory Disease,” in this issue, patient preparation for FDG-PET/CT is especially important when evaluating the heart and its surrounding tissues.

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