Normal imaging findings after aortic valve implantation on 18F-Fluorodeoxyglucose positron emission tomography with computed tomography.

BACKGROUND: To determine the normal perivalvular 18F-Fluorodeoxyglucose (18F-FDG) uptake on positron emission tomography (PET) with computed tomography (CT) within one year after aortic prosthetic heart valve (PHV) implantation. METHODS: Patients with uncomplicated aortic PHV implantation were prospectively included and underwent 18F-FDG PET/CT at either 5 (± 1) weeks (group 1), 12 (± 2) weeks (group 2) or 52 (± 8) weeks (group 3) after implantation. 18F-FDG uptake around the PHV was scored qualitatively (none/low/intermediate/high) and quantitatively by measuring the maximum Standardized Uptake Value (SUVmax) and target to background ratio (SUVratio). RESULTS: In total, 37 patients (group 1: n = 12, group 2: n = 12, group 3: n = 13) (mean age 66 ± 8 years) were prospectively included. Perivalvular 18F-FDG uptake was low (8/12 (67%)) and intermediate (4/12 (33%)) in group 1, low (7/12 (58%)) and intermediate (5/12 (42%)) in group 2, and low (8/13 (62%)) and intermediate (5/13 (38%)) in group 3 (P = 0.91). SUVmax was 4.1 ± 0.7, 4.6 ± 0.9 and 3.8 ± 0.7 (mean ± SD, P = 0.08), and SUVratio was 2.0 [1.9 to 2.2], 2.0 [1.8 to 2.6], and 1.9 [1.7 to 2.0] (median [IQR], P = 0.81) for groups 1, 2, and 3, respectively. CONCLUSION: Non-infected aortic PHV have similar low to intermediate perivalvular 18F-FDG uptake with similar SUVmax and SUVratio at 5, 12, and 52 weeks after implantation.

Added value of 18F-FDG-PET/CT and cardiac CTA in suspected transcatheter aortic valve endocarditis.

BACKGROUNDS: Transcatheter-implanted aortic valve infective endocarditis (TAVI-IE) is difficult to diagnose when relying on the Duke Criteria. Our aim was to assess the additional diagnostic value of 18F-fluorodeoxyglucose (18F-FDG) positron emission/computed tomography (PET/CT) and cardiac computed tomography angiography (CTA) in suspected TAVI-IE. METHODS: A multicenter retrospective analysis was performed in all patients who underwent 18F-FDG-PET/CT and/or CTA with suspected TAVI-IE. Patients were first classified with Duke Criteria and after adding 18F-FDG-PET/CT and CTA, they were classified with European Society of Cardiology (ESC) criteria. The final diagnosis was determined by our Endocarditis Team based on ESC guideline recommendations. RESULTS: Thirty patients with suspected TAVI-IE were included. 18F-FDG-PET/CT was performed in all patients and Cardiac CTA in 14/30. Using the Modified Duke Criteria, patients were classified as 3% rejected (1/30), 73% possible (22/30), and 23% definite (7/30) TAVI-IE. Adding 18F-FDG-PET/CT and CTA supported the reclassification of 10 of the 22 possible cases as "definite TAVI-IE" (5/22) or "rejected TAVI-IE" (5/22). This changed the final diagnosis to 20% rejected (6/30), 40% possible (12/30), and 40% definite (12/30) TAVI-IE. CONCLUSIONS: Addition of 18F-FDG-PET/CT and/or CTA changed the final diagnosis in 33% of patients and proved to be a valuable diagnostic tool in patients with suspected TAVI-IE.

Improving the Diagnostic Performance of 18F-Fluorodeoxyglucose Positron-Emission Tomography/Computed Tomography in Prosthetic Heart Valve Endocarditis.

BACKGROUND: 18F-Fluorodeoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT) was recently introduced as a new tool for the diagnosis of prosthetic heart valve endocarditis (PVE). Previous studies reporting a modest diagnostic accuracy may have been hampered by unstandardized image acquisition and assessment, and several confounders, as well. The aim of this study was to improve the diagnostic performance of FDG PET/CT in patients in whom PVE was suspected by identifying and excluding possible confounders, using both visual and standardized quantitative assessments. METHODS: In this multicenter study, 160 patients with a prosthetic heart valve (median age, 62 years [43-73]; 68% male; 82 mechanical valves; 62 biological; 9 transcatheter aortic valve replacements; 7 other) who underwent FDG PET/CT for suspicion of PVE, and 77 patients with a PV (median age, 73 years [65-77]; 71% male; 26 mechanical valves; 45 biological; 6 transcatheter aortic valve replacements) who underwent FDG PET/CT for other indications (negative control group), were retrospectively included. Their scans were reassessed by 2 independent observers blinded to all clinical data, both visually and quantitatively on available European Association of Nuclear Medicine Research Ltd-standardized reconstructions. Confounders were identified by use of a logistic regression model and subsequently excluded. RESULTS: Visual assessment of FDG PET/CT had a sensitivity/specificity/positive predictive value/negative predictive value for PVE of 74%/91%/89%/78%, respectively. Low inflammatory activity (C-reactive protein <40 mg/L) at the time of imaging and use of surgical adhesives during prosthetic heart valve implantation were significant confounders, whereas recent valve implantation was not. After the exclusion of patients with significant confounders, diagnostic performance values of the visual assessment increased to 91%/95%/95%/91%. As a semiquantitative measure of FDG uptake, a European Association of Nuclear Medicine Research Ltd-standardized uptake value ratio of ≥2.0 was a 100% sensitive and 91% specific predictor of PVE. CONCLUSIONS: Both visual and quantitative assessments of FDG PET/CT have a high diagnostic accuracy in patients in whom PVE is suspected. FDG PET/CT should be implemented early in the diagnostic workup to prevent the negative confounding effects of low inflammatory activity (eg, attributable to prolonged antibiotic therapy). Recent valve implantation was not a significant predictor of false-positive interpretations, but surgical adhesives used during implantation were.

18F-fluorodeoxyglucose positron emission/computed tomography and computed tomography angiography in prosthetic heart valve endocarditis: from guidelines to clinical practice.

The timely diagnosis of prosthetic heart valve endocarditis remains challenging yet of utmost importance. 18F-fluorodeoxyglucose (18 F-FDG) positron emission/computed tomography (PET/CT) and cardiac computed tomography angiography (CTA) were recently introduced as additional diagnostic tools in the most recent ESC guidelines on infective endocarditis. However, how to interpret PET/CT findings with regard to what is to be considered abnormal, what the potential confounders may be, as well as which patients benefit most from these additional imaging techniques and how to best perform them in these often-complex patients, remains unclear. This review focusses on factors regarding patient selection and image acquisition that need to be taken into account when employing 18F-FDG PET/CT and CTA in daily clinical practice, and the importance of a multidisciplinary Endocarditis Team herein. Furthermore, it emphasizes the need for standardized acquisition protocols and image interpretation, especially now that these techniques are starting to be widely embraced by the cardiovascular society.

Advanced CT acquisition protocol with a third-generation dual-source CT scanner and iterative reconstruction technique for comprehensive prosthetic heart valve assessment.

OBJECTIVES: Multidetector CT (MDCT) is a valuable tool for functional prosthetic heart valve (PHV) assessment. However, radiation exposure remains a concern. We assessed a novel CT-acquisition protocol for comprehensive PHV evaluation at limited dose. METHODS: Patients with a PHV were scanned using a third-generation dual-source CT scanner (DSCT) and iterative reconstruction technique (IR). Three acquisitions were obtained: a non-enhanced scan; a contrast-enhanced, ECG-triggered, arterial CT angiography (CTA) scan with reconstructions at each 5 % of the R-R interval; and a delayed high-pitch CTA of the entire chest. Image quality was scored on a five-point scale. Radiation dose was obtained from the reported CT dose index (CTDI) and dose length product (DLP). RESULTS: We analysed 43 CT examinations. Mean image quality score was 4.1±1.4, 4.7±0.5 and 4.2±0.6 for the non-contrast-enhanced, arterial and delayed acquisitions, respectively, with a total mean image quality of 4.3±0.7. Mean image quality for leaflet motion was 3.9±1.4. Mean DLP was 28.2±17.1, 457.3±168.6 and 68.5±47.2 mGy.cm for the non-contrast-enhanced (n=40), arterial (n=43) and delayed acquisition (n=43), respectively. The mean total DLP was 569±208 mGy.cm and mean total radiation dose was 8.3±3.0 mSv (n=43). CONCLUSION: Comprehensive assessment of PHVs is possible using DSCT and IR at moderate radiation dose. KEY POINTS: • Prosthetic heart valve dysfunction is a potentially life-threatening condition. • Dual-source CT can adequately assess valve leaflet motion and anatomy. • We assessed a comprehensive protocol with three acquisitions for PHV evaluation. • This protocol is associated with good image quality and limited dose.

Standardized uptake values in FDG PET/CT for prosthetic heart valve endocarditis: a call for standardization.

BACKGROUND: The significance of and threshold values for the standardized uptake value (SUV) in FDG PET/CT to diagnose prosthetic heart valve (PHV) endocarditis (PVE) are unclear at present. METHODS: A literature search was performed in the PubMed and EMBASE medical databases, comprising the following terms: (FDG OR *fluorode* OR *fluoro-de*) AND (endocarditis OR prosthetic heart valve OR valve replacement). Studies reporting SUVs correlated to the diagnosis of PVE were selected for analysis. RESULTS: 8 studies were included, with a total of 330 PHVs assessed. SUVs for PVE varied substantially across studies due to differences in acquisition, reconstruction, and measurement protocols, with median SUVmax values for rejected PVE ranging from 0.5 to 4.9 and for definite PVE ranging from 4.2 to 7.4. CONCLUSION: Reported SUV values for PVE are not interchangeable between sites, and further standardization of quantification is desirable. To this end, optimal protocols for patient preparation, image acquisition, and reconstruction and measurement methods need to be standardized across centers.

18F-FDG-Uptake in Mediastinal Lymph Nodes in Suspected Prosthetic Valve Endocarditis: Predictor or Confounder?

Introduction: Prosthetic valve endocarditis (PVE) is a serious disease affecting ~0.4% of prosthetic valve recipients per year. 18F-FDG-PET/CT has high sensitivity and specificity for PVE and is included as major criterion for the diagnosis in recent guidelines of the European Society of Cardiology. We addressed the question whether increased FDG-uptake in mediastinal lymph nodes could help to support the visual diagnostic assessment of PVE. Methods: In this sub-analysis of a previously published retrospective multicentre study, 160 unique patients were identified who underwent 18F-FDG-PET/CT for evaluation of suspected PVE. 18F-FDG-PET/CT was performed in adherence to the European Association of Nuclear Medicine guidelines of 2015 and scans were assessed for signs of mediastinal lymph node activity by 2 experienced nuclear medicine physicians who were blinded to clinical context. Clinical diagnosis of PVE had been established based on surgical findings or multidisciplinary consensus after a 1-year follow-up in 80 of 160 patients (50%). Results: In total, 52 patients showed increased mediastinal lymph node activity. Mediastinal lymph node activity on 18F-FDG-PET/CT did not increase diagnostic accuracy when added to the visual analysis of scans for signs of PVE: X 2: 0.118, p = 0.731). After excluding patients with known confounders for 18F-FDG-PET/CT, namely use of Bioglue® during prosthetic valve implantation and C-reactive protein levels below 40 mg/L, mediastinal lymph node activity was still not of additional diagnostic value compared to visual analysis alone (X2:0.129, p = 0.723). Discussion: Assessment of mediastinal lymph node activity did not improve 18F-FDG-PET/CT diagnostic accuracy for suspected PVE compared to visual assessment of the valve alone, as it seems to be a rather a specific finding, that might be caused by sternal wound or mediastinal infections or even by subclinical respiratory infections. Future studies might elucidate whether increased FDG active lymph nodes indicate a high-risk patient group and whether more detailed assessment of mediastinal lymph nodes could improve their additional diagnostic benefit.

CT angiography for depiction of complications after the Bentall procedure.

Following a Bentall procedure, which comprises a composite replacement of both the aortic valve and the ascending aorta, the imaging modality of choice to depict known or suspected complications is CT angiography. An update and extension of the literature regarding complications after the Bentall procedure is provided. The wider availability of ECG-gating has allowed for a clearer depiction of the aortic valve and ascending aorta. This resulted not only in the identification of previously undetectable complications, but also in a more precise assessment of the pathophysiology and morphology of known ones, reducing the need for additional imaging modalities. Moreover, the possibility to combine positron emission tomography images with CT angiography offers new insights in case of suspected infection. Due to the complexity of the operation itself and concomitant or subsequent additional procedures, as well as the wide spectrum of underlying pathology, new scenarios with multiple complications can be expected.

Peri-aortic fluid after surgery on the ascending aorta: Worrisome indicator of complications or innocent postoperative finding?

OBJECTIVE: The Bentall procedure is associated with several complications often accompanied by accumulation of fluid around the aortic graft. CT is the imaging modality of choice to detect these complications. Since these early complications are, however, not easily distinguished from physiological postoperative changes, our aim was to compare the appearance and amount of peri-aortic fluid on early CT scans following Bentall procedures with either an uncomplicated or a complicated course and follow-up. METHODS: Ninety-four scans performed within 3 months of a Bentall procedure were retrospectively included. Patients were divided into either the uncomplicated or the complicated group based on occurrence of Bentall-related complications or death up until 1-year after surgery. Diffuse fluid ("stranding") was distinguished from organized, more clearly delineated fluid collections such as haematomas, and was graded both subjectively and quantitatively. RESULTS: Forty-seven patients were assigned to each group. Stranding was found on most of the scans, both in the uncomplicated (7.7±3.9mm, range 0-17mm) and complicated (6.9±5.5mm, range 0-19mm) groups (p=0.32). There were, however, significantly more fluid collections (6 vs. 28; p <0.001), particularly haematomas (1 vs. 17; p<0.001), in the complicated group. When looking at isolated stranding, there was still no significant difference between the two groups (7.8±3.6mm vs. 9.2±3.7mm; p=0.22). CONCLUSION: Isolated stranding of up to 17mm is a common finding on postoperative CT within three months of a Bentall procedure, regardless of the occurrence of complications during the procedure or within a 1-year follow-up. Fluid collections are more worrisome indicators of complications that may require closer monitoring.

Cloud-processed 4D CMR flow imaging for pulmonary flow quantification.

OBJECTIVES: In this study, we evaluated a cloud-based platform for cardiac magnetic resonance (CMR) four-dimensional (4D) flow imaging, with fully integrated correction for eddy currents, Maxwell phase effects, and gradient field non-linearity, to quantify forward flow, regurgitation, and peak systolic velocity over the pulmonary artery. METHODS: We prospectively recruited 52 adult patients during one-year period from July 2014. The 4D flow and planar (2D) phase-contrast (PC) were acquired during same scanning session, but 4D flow was scanned after injection of a gadolinium-based contrast agent. Eddy-currents were semi-automatically corrected using the web-based software. Flow over pulmonary valve was measured and the 4D flow values were compared against the 2D PC ones. RESULTS: The mean forward flow was 92 (±30) ml/cycle measured with 4D flow and 86 (±29) ml/cycle measured with 2D PC, with a correlation of 0.82 and a mean difference of -6ml/cycle (-41-29). For the regurgitant fraction the correlation was 0.85 with a mean difference of -0.95% (-17-15). Mean peak systolic velocity measured with 4D flow was 92 (±49) cm/s and 108 (±56) cm/s with 2D PC, having a correlation of 0.93 and a mean difference of 16cm/s (-24-55). CONCLUSION: 4D flow imaging post-processed with an integrated cloud-based application accurately quantifies pulmonary flow. However, it may underestimate the peak systolic velocity.

Qualitative grading of aortic regurgitation: a pilot study comparing CMR 4D flow and echocardiography.

Over the past 10 years there has been intense research in the development of volumetric visualization of intracardiac flow by cardiac magnetic resonance (CMR).This volumetric time resolved technique called CMR 4D flow imaging has several advantages over standard CMR. It offers anatomical, functional and flow information in a single free-breathing, ten-minute acquisition. However, the data obtained is large and its processing requires dedicated software. We evaluated a cloud-based application package that combines volumetric data correction and visualization of CMR 4D flow data, and assessed its accuracy for the detection and grading of aortic valve regurgitation using transthoracic echocardiography as reference. Between June 2014 and January 2015, patients planned for clinical CMR were consecutively approached to undergo the supplementary CMR 4D flow acquisition. Fifty four patients(median age 39 years, 32 males) were included. Detection and grading of the aortic valve regurgitation using CMR4D flow imaging were evaluated against transthoracic echocardiography. The agreement between 4D flow CMR and transthoracic echocardiography for grading of aortic valve regurgitation was good (j = 0.73). To identify relevant,more than mild aortic valve regurgitation, CMR 4D flow imaging had a sensitivity of 100 % and specificity of 98 %. Aortic regurgitation can be well visualized, in a similar manner as transthoracic echocardiography, when using CMR 4D flow imaging.