Laurens E. Swart

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.

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

BackgroundThe 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.MethodsA 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.Results8 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.ConclusionReported 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-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

ObjectivesMultidetector 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.MethodsPatients 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).ResultsWe 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).ConclusionComprehensive 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.

Improving the diagnostic performance of 18F-FDG PET/CT 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.Laurens E. Swart, MD; Anna Gomes, MD, PhD; Asbjørn M. Scholtens, MD; Bhanu Sinha, MD, PhD; Wilco Tanis, MD, PhD; Marnix G.E.H. Lam, MD, PhD; Maureen J. van der Vlugt, MD, PhD; Sebastian A.F. Streukens, MD; Erik H.J.G. Aarntzen, PhD; Jan Bucerius, MD, PhD; Sander van Assen, MD, PhD; Chantal P. Bleeker-Rovers, MD, PhD; Peter Paul van Geel, MD, PhD; Gabriel P. Krestin, MD, PhD; Joost P. van Melle, MD, PhD, Jolien W. Roos-Hesselink, MD, PhD; Riemer H.J.A. Slart, MD, PhD; Andor W.J.M. Glaudemans, MD, PhD; Ricardo P.J. Budde MD PhD

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.

Remote CMR 4D Flow Quantification of Pulmonary Flow

Background 4D MR flow has shown to have advantages over standard cardiac magnetic resonance (CMR), offering both anatomical and functional information in just a single acquisition. Pulmonary stenosis and pulmonary regurgitation are common problems in follow-up of patients with congenital heart disease. In this study we tested flow quantification at the level of the pulmonary valve (forward and backward flow, regurgitation fraction and peak systolic velocity) using a cloudbased software platform fully integrated with correction for eddy currents, Maxwell phase effects and gradient field non-linearity, visualization of the flow and anatomy, and flow quantification. Standard planar phase contrast CMR was used as a reference.