F. Hyafil

Respective Performance of 18F-FDG-PET and Radiolabeled Leukocyte Scintigraphy for the Diagnosis of Prosthetic Valve Endocarditis

Echocardiography plays a key role in the diagnosis of infective endocarditis (IE) but can be inconclusive in patients in whom prosthetic valve endocarditis (PVE) is suspected. The incremental diagnostic value of 18F-FDG PET and radiolabeled leukocyte scintigraphy in IE patients has already been reported. The aim of this study was to compare the respective performance of 18F-FDG PET and leukocyte scintigraphy for the diagnosis of PVE in 39 patients. Methods: 18F-FDG PET and leukocyte scintigraphy were performed on 39 consecutive patients admitted because of clinically suspected PVE and inconclusive echocardiography results. The results of 18F-FDG PET and leukocyte scintigraphy were analyzed separately and retrospectively by experienced physicians masked to the results of the other imaging technique and to patient outcome. The final Duke–Li IE classification was made after a 3-mo follow-up. Results: Of the 39 patients, 14 were classified as having definite IE, 4 as having possible IE, and 21 as not having IE. The average interval between 18F-FDG PET and leukocyte scintigraphy was 7 ± 7 d. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 93%, 71%, 68%, 94%, and 80%, respectively, for 18F-FDG PET and 64%, 100%, 100%, 81%, and 86%, respectively, for leukocyte scintigraphy. Discrepancies between the results of 18F-FDG PET and leukocyte scintigraphy occurred in 12 patients (31%). In patients with definite IE, 5 had true-positive 18F-FDG PET results but false-negative leukocyte scintigraphy results. Of these 5 patients, 3 had nonpyogenic microorganism IE (Coxiella or Candida). Of patients for whom endocarditis had been excluded, 6 had true-negative leukocyte scintigraphy results but false-positive 18F-FDG PET results. These 6 patients had been imaged in the first 2 mo after the last cardiac surgery. The last patient with a discrepancy between 18F-FDG PET and leukocyte scintigraphy was classified as having possible endocarditis and had positive 18F-FDG PET results and negative leukocyte scintigraphy results. Conclusion: 18F-FDG PET offers high sensitivity for the detection of active infection in patients with suspected PVE and inconclusive echocardiography results. Leukocyte scintigraphy offers a higher specificity, however, than 18F-FDG PET for diagnosis of IE and should be considered in cases of inconclusive 18F-FDG PET findings or in the first 2 mo after cardiac surgery.

Role of radiolabelled leucocyte scintigraphy in patients with a suspicion of prosthetic valve endocarditis and inconclusive echocardiography

AIMS In patients with a suspicion of prosthetic valve endocarditis (PVE), detection of perivalvular infection can be difficult based only on echocardiography. The aim of this retrospective study was to test the interest of radiolabelled leucocyte scintigraphy (LS) for the detection of perivalvular infection in patients with a suspicion of PVE and inconclusive transoesophageal echocardiography (TEE). METHODS AND RESULTS LS was performed in 42 patients. The results of LS were classified as positive in the cardiac area (intense or mild), or negative. Macroscopical aspects and bacteriology were obtained from patients who underwent cardiac surgery (n = 10). Clinical outcome was collected in patients treated medically (n = 32). Among patients with intense signal with LS who underwent surgery (n = 6), five had an abscess confirmed during intervention and one, post-operatively. Patients with intense accumulation of radiolabelled leucocytes with scintigraphy and treated medically (n = 3) had a poor outcome: death (n = 1); prosthetic valve dehiscence (n = 1); and recurrent endocarditis (n = 1). Among patients with mild activity with LS (n = 5), one patient developed a large prosthetic valve dehiscence during the follow-up. The remaining four patients were treated medically and did not present any recurrent endocarditis after a median follow-up of 14 months. No abscess was detected in patients with negative LS who underwent surgery (n = 4). Among the patients with negative LS treated medically (n = 24), none presented recurrent endocarditis after a mean follow-up of 15 ± 16 months. Patient management was influenced by the results of LS in 12 out of 42 patients (29%). CONCLUSION This study suggests that LS is useful for the identification of perivalvular infection in patients with a suspicion of PVE and inconclusive TEE.

Upregulated myocardial CXCR4-expression after myocardial infarction assessed by simultaneous GA-68 pentixafor PET/MRI.

Just recently, inflammatoryprocesses aftermyocardial infarction (MI) as an important additional factor for cardiac remodeling have come to the fore. As a consequence, there is an urgent unmet clinical need for tracers targeting specifically non-pathogen-driven, inflammatory processes in the heart. Here, we present the potential of a novel PET tracer targeting the expression of the chemokine receptor 4 (CXCR4) on inflammatory cells after acute MI. CXCR4 belongs to the family of G-protein-coupled receptors and is involved in biological processes such as the entry ofHIV-1, the development of metastasis and several inflammatory conditions. The CXCR4 receptor is expressed only at low levels on the surface of circulating lymphocytes, macrophages, and neutrophils, but is highly upregulated when these cells infiltrate inflamed tissues. In addition, CXCR4 expression is strongly increased on the cell surface under hypoxic conditions via the stimulation of HIF (hypoxiainducible factor). Therefore, the CXCR4 receptor represents an attractive molecular target to identify the presence of activated inflammatorycells located in the post-ischemic myocardium. Recently, Ga-68 pentixafor, a ligand with high affinity and selectivity to hCXCR4-receptors (IC50 = 5 nM) that exhibits excellent pharmacokinetics and dosimetry in humans has been introduced and successfully tested in first human studies. Due to its rapid blood and renal clearance, pentixafor might also be useful for the detection of inflammatory cells both in atherosclerotic plaques and in the myocardium (Figure 1). To the best of our knowledge, we describe here for the first time the successful use of Ga-68 pentixafor for the assessment of inflammatory processes in the myocardium in a human by simultaneous PET/MRI.

Detection of 18fluoride sodium accumulation by positron emission tomography in calcified stenotic aortic valves.

Aortic valve stenosis progression rate is highly variable among patients and to date remains unpredictable. Evaluation of osteoblastic activity inside aortic valves may help identify patients with fast aortic stenosis progression rates and worse prognoses. Fluoride-18 sodium (FNa) is a clinically approved positron emission tomographic (PET) radiotracer with high and rapid bone uptake. The aim of this study was to test whether FNa accumulates in degenerative aortic valves and can be detected with PET imaging. Five patients with severe aortic stenosis and 10 patients free of aortic valvular calcium on computed tomography underwent PET imaging 40 minutes after the injection of 4 MBq/kg of FNa for oncologic or rheumatologic purposes. Maximal standard uptake values (SUVs) were measured retrospectively in aortic valves using PET imaging. Tissue-to-background ratios were calculated for each patient by dividing the maximal SUV measured in aortic valves by the mean SUV of blood. In patients with severe aortic stenosis, an intense accumulation of FNa was detected in aortic valve region on PET imaging, whereas only low activity was found in patients free of valvular calcification (median maximal SUV 2.6 g/ml/kg [interquartile range (IQR) 2.3 to 3.6] vs 2.0 g/ml/kg [IQR 1.7 to 2.2] and median tissue-to-background ratio 2.2 [IQR 2.0 to 2.7] vs 1.5 [IQR 1.5 to 1.7], respectively, p = 0.008 for both). Intraobserver variability for maximal SUV and tissue-to-background ratio in aortic valves was measured at 0.99 and interobserver variability at 0.98 and 0.97, respectively. In conclusion, in this pilot study, FNa accumulated in patients with severe aortic stenosis and could be quantified on PET imaging with good reproducibility. FNa PET imaging represents a promising imaging modality to evaluate osteoblastic activity inside calcified aortic valves.

A joint procedural position statement on imaging in cardiac sarcoidosis: from the Cardiovascular and Inflammation & Infection Committees of the European Association of Nuclear Medicine, the European Association of Cardiovascular Imaging, and the American Society of Nuclear Cardiology

This joint position paper illustrates the role and the correct use of echocardiography, radionuclide imaging with 18F-fluorodeoxyglucose positron emission tomography, radionuclide myocardial perfusion imaging and cardiovascular magnetic resonance imaging for the evaluation and management of patients with known or suspected cardiac sarcoidosis. This position paper will aid in standardizing imaging for cardiac sarcoidosis and may facilitate clinical trials and pooling of multi-centre data on cardiac sarcoidosis. Proposed flow charts for the work up and management of cardiac sarcoidosis are included.

Rupture of Nonstenotic Carotid Plaque as a Cause of Ischemic Stroke Evidenced by Multimodality Imaging

A 34-year-old woman was admitted for sudden onset of left-sided hemiparesis. Diffusion-weighted magnetic resonance imaging (MRI) 12 hours after symptom onset was positive, with hypersignal in the territory of the right middle cerebral artery consistent with acute cerebral infarction. Magnetic resonance angiography confirmed occlusion of the right middle cerebral artery and found a 30% stenosis (North American Symptomatic Carotid Endarterectomy Trial criteria) of the origin of the right internal carotid artery. Carotid ultrasound (Figure, A–D) evidenced the presence of a noncalcified plaque of the right carotid causing a stenosis of the origin of the internal carotid artery evaluated at 40% (North American Symptomatic Carotid Endarterectomy Trial criteria). Results of electrocardiography, Holter monitoring, transthoracic and transesophageal echocardiography, and laboratory investigations were all normal. Figure. A–D , Carotid ultrasound of the right carotid showed the presence of a noncalcified plaque with gray-scale 2-dimensional imaging (white arrow; A , longitudinal view; C , axial view) that caused a …

Systematic review of cost-effectiveness of myocardial perfusion scintigraphy in patients with ischaemic heart disease

Coronary artery disease (CAD) is a major cause of death and disability. Several diagnostic tests, such as myocardial perfusion scintigraphy (MPS), are accurate for the detection of CAD, as well as having prognostic value for the prediction of cardiovascular events. Nevertheless, the diagnostic and prognostic value of these tests should be cost-effective and should lead to improved clinical outcome. We have reviewed the literature on the cost-effectiveness of MPS in different circumstances: (i) the diagnosis and management of CAD; (ii) comparison with exercise electrocardiography (ECG) and other imaging tests; (iii) as gatekeeper to invasive coronary angiography (ICA), (iv) the impact of appropriate use criteria; (v) acute chest pain, and (vi) screening of asymptomatic patients with type-2 diabetes. In total 57 reports were included. Although most non-invasive imaging tests are cost-effective compared with alternatives, the data conflict on which non-invasive strategy is the most cost-effective. Different definitions of cost-effectiveness further confound the subject. Computer simulations of clinical diagnosis and management are influenced by the assumptions made. For instance, diagnostic accuracy is often defined against an anatomical standard that is wrongly assumed to be perfect. Conflicting data arise most commonly from these incorrect or differing assumptions.

Quoi de neuf en cardiologie nucléaire

Depuis deux a trois ans, des progres technologiques tres importants sont survenus en cardiologie nucleaire. Ces innovations concernent a la fois l’imagerie en coupe monophotonique (SPECT), avec l’apparition d’un nouveau type de detecteurs bouleversant les performances des gamma-cameras conventionnelles (ou cameras d’Anger), et la tomographie par emission de positons (TEP-CT), avec l’arrivee tres prochaine en France de nouveaux traceurs de perfusion, associee a des cameras TEP ultrasensibles (« temps de vol »). Pour les deux techniques, l’association de la scintigraphie de perfusion et du coroscanner dans une imagerie « hybride » est egalement une donnee recente. Enfin, l’imagerie moleculaire se developpe en cardiologie, avec de nouveaux traceurs dont l’evaluation est deja tres avancee, actuellement en phase II ou III, tels que l’annexine V marquee au 99mtechnetium pour l’imagerie de la necrose et de l’apoptose myocytaire et l’activation plaquettaire, ou le 18FML10 (Earlytest®), nouveau radio-traceur pour la tomographie par emission de positons (TEP) se fixant dans les cellules apoptotiques. Nous envisagerons successivement ces differentes avancees.