Daniel Juneau

Positron Emission Tomography and Single-Photon Emission Computed Tomography Imaging in the Diagnosis of Cardiac Implantable Electronic Device InfectionCLINICAL PERSPECTIVE: A Systematic Review and Meta-Analysis

Background— The use of cardiac implantable electronic devices (CIED) is increasing, and their associated infections result in significant morbidity and mortality. The introduction of better cardiac imaging techniques could be useful for diagnosing this condition and guiding therapy. Our objective was to systematically assess the diagnostic accuracy of Fluor-18-fluorodeoxyglucose positron emission tomography and computed tomography, labeled leukocyte scintigraphy (LS), and Gallium-67 citrate scintigraphy for the diagnosis of CIED infection. Methods and Results— A systematic review of the literature and meta-analysis on the use of all 3 modalities in CIED infection were conducted. Pooled sensitivity, specificity, and summary receiver operating characteristic curves of each imaging modalities were determined. The literature search identified 2493 articles. A total of 13 articles (11 studies for 18F-FDG PET-CT and 2 for LS), met the inclusion criteria. No studies for 67Ga citrate scintigraphy met the inclusion criteria. The pooled sensitivity of 18F-FDG PET-CT for the diagnosis of CIED infection was 87% (95% CI, 82%–91%) and pooled specificity was 94% (95% CI, 88%–98%). The summary receiver operating characteristic curve analysis demonstrated good overall accuracy, with an area under the curve of 0.935. There were insufficient data to do a meta-analysis for LS, but both studies reported sensitivity above 90% and specificity of 100%. Conclusions— Both 18F-FDG PET-CT and LS yield high sensitivity, specificity, and accuracy, and thus seem to be useful for the diagnosis of CIED infection, based on robust data for 18F-FDG PET-CT but limited data for LS. When available,18F-FDG PET-CT may be preferred.

Clinical PET Myocardial Perfusion Imaging and Flow Quantification

Cardiac PET imaging is a powerful tool for the assessment of coronary artery disease. Many tracers with different advantages and disadvantages are available. It has several advantages over single photon emission computed tomography, including superior accuracy and lower radiation exposure. It provides powerful prognostic information, which can help to stratify patients and guide clinicians. The addition of flow quantification enables better detection of multivessel disease while providing incremental prognostic information. Flow quantification provides important physiologic information, which may be useful to individualize patient therapy. This approach is being applied in some centers, but requires standardization before it is more widely applied.

Inter- and Intra- observer agreement of FDG-PET/CT image interpretation in patients referred for assessment of Cardiac Sarcoidosis

Recent studies have reported the usefulness of 18F-FDG PET in aiding with the diagnosis and management of patients with cardiac sarcoidosis (CS). However, image interpretation of 18F-FDG PET for CS is sometimes challenging. We sought to investigate the inter- and intraobserver agreement and explore factors that led to important discrepancies between readers. Methods: We studied consecutive patients with no significant coronary artery disease who were referred for assessment of CS. Two experienced readers masked to clinical information, imaging reports, independently reviewed 18F-FDG PET/CT images. 18F-FDG PET/CT images were interpreted according to a predefined standard operating procedure, with cardiac 18F-FDG uptake patterns categorized into 5 patterns: none, focal, focal on diffuse, diffuse, and isolated lateral wall or basal uptake. Overall image assessment was classified as either consistent with active CS or not. Results: One hundred scans were included from 71 patients. Of these, 46 underwent 18F-FDG PET/CT with a no-restriction diet (no-restriction group), and 54 underwent 18F-FDG PET/CT with a low-carbohydrate, high-fat and protein-permitted diet (low-carb group). There was agreement of the interpretation category in 74 of 100 scans. The κ-value of agreement among all 5 categories was 0.64, indicating moderate agreement. For overall clinical interpretation, there was agreement in 93 of 100 scans (κ = 0.85). When scans were divided into the preparation groups, there was a trend toward higher agreement in the low-carb group versus the no-restriction group (80% vs. 67%, P = 0.08). Regarding the overall clinical interpretation, there was also a trend toward greater agreement in the low-carb group versus the no-restriction group (96% vs. 89%, P = 0.08). Conclusion: The interobserver agreement of cardiac 18F-FDG uptake image patterns was moderate. However, agreement was better regarding overall interpretation of CS. Detailed prescan dietary preparation seemed to improve interobserver agreement.

Molecular Imaging for the diagnosis of infective endocarditis: A systematic literature review and meta-analysis

BACKGROUND Infective endocarditis (IE) is a serious, potentially life-threatening condition. Currently, the modified Duke criteria is used to assist with the diagnosis of IE, but it can still remain difficult. Growing data supports the potential use of molecular imaging to assist in the diagnosis of IE. Our objective was to understand the potential utility of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT), 67Ga citrate and radiolabeled white blood cell (WBC) scintigraphy in the diagnosis of IE. METHODS AND RESULTS A systematic review of the literature and meta-analysis on the use of all 3 modalities in IE was conducted. The literature search identified 2753 articles. A total of 14 studies met the inclusion criteria (10 for 18F-FDG, 3 for WBC and 1 for both modalities). No 67Ga citrate study met the inclusion criteria. Pooled sensitivity of 18F-FDG studies with adequate cardiac preparation for the diagnosis of IE was 81% (95% CI, 73%-86%) and pooled specificity was 85% (95% CI, 78%-91%). There was good overall accuracy with an area under the curve (AUC) of 0.897. Pooled sensitivity of WBC for the diagnosis of IE was 86% (95% CI, 77%-92%) and pooled specificity was 97% (95% CI, 92%-99%). The overall accuracy of WBC was excellent with an AUC of 0.957. CONCLUSIONS Both 18F-FDG and WBC have good sensitivity, specificity and accuracy for the diagnosis of IE. Both modalities are useful in the investigation of IE, and should be considered in cases where the diagnosis is uncertain.

The role of nuclear cardiac imaging in risk stratification of sudden cardiac death

Sudden cardiac death (SCD) represents a significant portion of all cardiac deaths. Current guidelines focus mainly on left ventricular ejection fraction (LVEF) as the main criterion for SCD risk stratification and management. However, LVEF alone lacks both sensitivity and specificity in stratifying patients. Recent research has provided interesting data which supports a greater role for advanced cardiac imaging in risk stratification and patient management. In this article, we will focus on nuclear cardiac imaging, including left ventricular function assessment, myocardial perfusion imaging, myocardial blood flow quantification, metabolic imaging, and neurohormonal imaging. We will discuss how these can be used to better understand SCD and better stratify patient with both ischemic and non-ischemic cardiomyopathy.

How common is isolated cardiac sarcoidosis? Extra-cardiac and cardiac findings on clinical examination and whole-body 18F–fluorodeoxyglucose positron emission tomography

BACKGROUND Sarcoidosis is a systemic inflammatory disease which can involve nearly any organ. Clinically manifest cardiac involvement occurs in perhaps 5% of patients with sarcoidosis. The reported prevalence of isolated cardiac sarcoidosis (CS) varies widely with reported rates of 27-54%. The explanation for this variability is likely multi-factorial but perhaps mostly related to the diagnostic method(s) for assessing extra-cardiac involvement. The primary aim of this study was to assess the rate of isolated CS in a homogeneous, prospectively recruited cohort of patients with clinically manifest CS, using whole body FDG PET-CT imaging as a gold standard. A secondary aim was to describe the extent and distribution of extra-cardiac sarcoidosis at the time of first presentation of clinically manifest CS. METHODS Patients were prospectively recruited at the time of first presentation with cardiac symptoms. All patients underwent whole-body and cardiac 18F-FDG PET-CT. All patients were examined for presence of skin sarcoidosis and were assessed by an ophthalmologist. RESULTS 31 patients were included (mean age 56±8years, 17 female, 100% Caucasian). Patients had limited extra-cardiac involvement (mean of 2.2 organs) however using the most precise definition, only 1/31 (3.2%) patients had isolated CS. There were marked differences in right ventricular (RV) and atrial involvement between patients presenting with CS as first presentation compared to patients presenting initially with extra-cardiac disease. CONCLUSIONS Most patients had limited extra-cardiac involvement at the time of presentation of manifest CS however, isolated CS, using the proposed gold standard, was only observed in one patient.

Cardiac involvement in rheumatoid arthritis mimicking sarcoidosis on FDG PET-CT and MR imaging

A 37-year-old male developed sudden shortness of breath, chest pain, and palpitations. He presented to the emergency department with monomorphic ventricular tachycardia (VT), which was successfully cardioverted. Echocardiography and coronary angiographywere normal. F-FDG PET-CT demonstrated abnormal uptake within the myocardium and thoracic lymph nodes (Figure 1), and was interpreted as highly suggestive of active cardiac and extra-cardiac sarcoidosis. Cardiacmagnetic resonance also revealed abnormal areas of late gadolinium enhancement (Figure 2) and was reported as compatible with nonspecific myocarditis versus sarcoidosis. Endomyocardial biopsy showed non-specific chronic inflammation. Transbronchial and mediastinal lymph node biopsies were negative. At this stage, the findings were felt to be most suggestive of cardiac sarcoidosis. An implantable cardioverter-defibrillator was implanted. Over the next year, 4 episodes of non-sustained VT were recorded, and one appropriate shock was delivered for VT. The patient developed progressive incapacitating episodes of polyarthritis, an exudative left-sided pleural effusion, and pleural thickening. Prior laboratory investigations had revealed a positive rheumatoid factor, a positive anti-cyclic citrullinated peptide, and an elevated C-reactive protein. Thoracoscopic pleural biopsy and serologic markers were consistent with the final diagnosis of rheumatoid arthritis (RA). Considering this, cardiac findings were considered consistent with myocarditis secondary to rheumatoid arthritis. The patient began treatment for RA. His arthritis and pleural effusion improved significantly and after 4 years of follow-up on appropriate therapy, he has had no recurrence of ventricular arrhythmias. A repeat whole-body F-FDG PET-CT demonstrated complete resolution of abnormal FDG myocardial uptake (Figure 3).

False-positive 13N-ammonia positron emission tomography perfusion scan caused by misalignment of adjacent lung activity during attenuation correction

Myocardial perfusion imaging (MPI) with positron emission tomography-computed tomography (PET-CT) is a powerful tool for the assessment of coronary artery disease. It has many advantages over single-photon emission computed tomography MPI, including more accurate attenuation correction. However, extracardiac activity can complicate the proper alignment of the PET and CT images, leading to attenuation correction artifacts.

Role of 18F-Fluorodeoxyglucose/Positron Emission Tomography Imaging to Demonstrate Resolution of Acute Myocarditis

A young woman experienced complete heart block, leading to Torsades de pointes. Cardiac 18F-fluorodeoxyglucose/positron emission tomography was used to confirm the resolution of her acute myocarditis and was critical to the decision-making process that prevented unnecessary pacemaker insertion.