Showing papers by "Jens-Uwe Voigt published in 2020"

Measurement of the Permanent Electric Dipole Moment of the Neutron.

Abstract: We present the result of an experiment to measure the electric dipole moment EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ultracold neutrons (UCN). Our measurement stands in the long history of EDM experiments probing physics violating time reversal invariance. The salient features of this experiment were the use of a Hg-199 co-magnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic field changes. The statistical analysis was performed on blinded datasets by two separate groups while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is $d_{\rm n} = (0.0\pm1.1_{\rm stat}\pm0.2_{\rmsys})\times10^{-26}e\,{\rm cm}$.

Proposed Requirements for Cardiovascular Imaging-Related Machine Learning Evaluation (PRIME): A Checklist: Reviewed by the American College of Cardiology Healthcare Innovation Council.

Abstract: Machine learning (ML) has been increasingly used within cardiology, particularly in the domain of cardiovascular imaging. Due to the inherent complexity and flexibility of ML algorithms, inconsistencies in the model performance and interpretation may occur. Several review articles have been recently published that introduce the fundamental principles and clinical application of ML for cardiologists. This paper builds on these introductory principles and outlines a more comprehensive list of crucial responsibilities that need to be completed when developing ML models. This paper aims to serve as a scientific foundation to aid investigators, data scientists, authors, editors, and reviewers involved in machine learning research with the intent of uniform reporting of ML investigations. An independent multidisciplinary panel of ML experts, clinicians, and statisticians worked together to review the theoretical rationale underlying 7 sets of requirements that may reduce algorithmic errors and biases. Finally, the paper summarizes a list of reporting items as an itemized checklist that highlights steps for ensuring correct application of ML models and the consistent reporting of model specifications and results. It is expected that the rapid pace of research and development and the increased availability of real-world evidence may require periodic updates to the checklist.

How to do LA strain

Abstract: Modern speckle tracking allows the assessment of atrial strain in the clinic. The approach is new, lacks standardization and the user might encounter several problems in its routine use. This article provides guidance on how avoid pitfalls and how to perform reliable and reproducible atrial strain measurements according to current recommendations.

Imaging predictors of response to cardiac resynchronization therapy: left ventricular work asymmetry by echocardiography and septal viability by cardiac magnetic resonance

Abstract: The study was supported by Center for Cardiological Innovation. J.M.A. was supported by a grant from the Norwegian Health Association. C.K.L. was recipient of a clinical research fellowship from the South-Eastern Norway Regional Health Authority. The study and J.D. were supported by a research grant of the University Leuven (OT12/084). J.-U.V. holds a research mandate of the Research Foundation Flanders (FKM1832917N).

Acute redistribution of regional left ventricular work by cardiac resynchronization therapy determines long-term remodelling.

Abstract: AIMS Investigating the acute impact of cardiac resynchronization therapy (CRT) on regional myocardial work distribution in the left ventricle (LV) and to which extent it is related to long-term reverse remodelling. METHODS AND RESULTS One hundred and thirty heart failure patients, referred for CRT implantation, were recruited in our prospective multicentre study. Regional myocardial work was calculated from non-invasive segmental stress-strain loop area before and immediately after CRT. The magnitude of volumetric reverse remodelling was determined from the change in LV end-systolic volume, 11 ± 2 months after implantation. CRT caused acute redistribution of myocardial work across the LV, with an increase in septal work, and decrease in LV lateral wall work (all P < 0.05). Amongst all LV walls, the acute change in work in the septum and lateral wall of the four-chamber view correlated best and significantly with volumetric reverse remodelling (r = 0.62, P < 0.0001), with largest change seen in patients with most volumetric reverse remodelling. In multivariate linear regression analysis, including conventional parameters, such as pre-implant QRS morphology and duration, LV ejection fraction, ischaemic origin of cardiomyopathy, and the redistribution of work across the septal and lateral walls, the latter appeared as the strongest determinant of volumetric reverse remodelling after CRT (model R2 = 0.414, P < 0.0001). CONCLUSION The acute redistribution of regional myocardial work between the septal and lateral wall of the LV is an important determinant of reverse remodelling after CRT implantation. Our data suggest that the treatment of the loading imbalance should, therefore, be the main aim of CRT.

Manual zur Indikation und Durchführung der Echokardiographie – Update 2020 der Deutschen Gesellschaft für Kardiologie

Abstract: Das neue Manual zur Indikation und Durchfuhrung der Echokardiographie bezieht sich primar auf die transthorakale Echokardiographie. Die Durchfuhrung der standardisierten Dokumentation in der transthorakalen Echokardiographie erfordert mehrere Bildsequenzen und Messungen, die in Abbildungen einschlieslich eines Befundschemas illustriert werden. Die erweiterten Dokumentationen der transthorakalen Echokardiographie werden im Hinblick auf pathologische kardiale Veranderungen im Speziellen vorgestellt. Dazu gehoren Veranderungen der linksventrikularen Wanddicke, die globale sowie regionale Reduktion der linksventrikularen Funktion, die diastolische Dysfunktion bei normaler linksventrikularer systolischer Funktion, die Druck- und Volumenbelastung des rechten Ventrikels sowie die Reduktion der rechtsventrikularen Funktion und pathologische Veranderungen an den Herzklappen. In speziellen Abschnitten wird die Echokardiographie bei Aortenklappenstenose und -insuffizienz, bei Mitralklappenstenose und -insuffizienz, bei Trikuspidalklappeninsuffizienz sowie bei weiteren seltenen Vitien und bei der Endokarditis vorgestellt. Das Manual endet mit Abschnitten zu echokardiographischen Zusatzuntersuchungen, der Befundung und dem Einsatz der Echokardiographie im Notfall.

Speckle tracking deformation imaging to detect regional fibrosis in hypertrophic cardiomyopathy: a comparison between 2D and 3D echo modalities.

Abstract: AIMS We aimed at directly comparing three-dimensional (3D) and two-dimensional (2D) deformation parameters in hypertrophic hearts and depict which may best reflect underlying fibrosis in hypertrophic cardiomyopathy (HCM), defined by late gadolinium enhancement (LGE) in cardiac magnetic resonance (CMR). METHODS AND RESULTS We included 40 HCM [54.1 ± 14.3 years, 82.5% male, maximum wall thickness (MWT) 19.3 ± 4.8 mm] and 15 hypertensive (HTN) patients showing myocardial hypertrophy (58.1 ± 15.6 years, 80% male, MWT 12.8 ± 1.4 mm) who have consecutively undergone 2D-, 3D-speckle tracking echocardiography and LGE CMR. Deformation parameters (2D and 3D) presented overall poor to moderate correlations, with 3D_longitudinal strain (LS) and 3D_circumferential strain (CS) values being constantly higher compared to 2D derivatives. By regression analysis, hypertrophy substrate (HCM vs. hypertension) and hypertrophy magnitude were the parameters to influence 2D-3D LS and CS strain correlations (R2 = 0.66, P < 0.001 and R2 = 0.5, P = 0.001 accordingly). Among segmental deformation indices, 2D_LS showed the best area under the curve [AUC = 0.78, 95% confidence intervals (CI) (0.75-0.81), P < 0.0005] to detect fibrosis, with 3D deformation parameters showing similar AUC (0.65) and 3D_LS presenting the highest specificity [93.1%, 95% CI (90.6-95.1)]. CONCLUSIONS In hypertrophic hearts, 2D and 3D deformation parameters are not interchangeable, showing modest correlations. Thickness, substrate, and tracking algorithm calculating assumptions seem to induce this variability. Nevertheless, among HCM patients 2D_peak segmental longitudinal strain remains the best strain parameter for tissue characterization and fibrosis detection.

Subclinical left atrial dysfunction profiles for prediction of cardiac outcome in the general population.

Abstract: OBJECTIVE Echocardiographic definitions of subclinical left atrial dysfunction based on epidemiological data remain scarce. In this population study, we derived outcome-driven thresholds for echocardiographic left atrial function parameters discriminating between normal and abnormal values. METHODS In 1306 individuals (mean age, 50.7 years; 51.6% women), we echocardiographically assessed left atrial function and LV global longitudinal strain. We derived cut-off values for left atrial emptying fraction (LAEF), left atrial function index (LAFI) and left atrial reservoir strain (LARS) to define left atrial dysfunction using receiver-operating curve threshold analysis. Main outcome was the incidence of cardiac events and atrial fibrillation (AFib) on average 8.5 years later. RESULTS For prediction of new-onset AFib, left atrial cut-offs yielding the best balance between sensitivity and specificity (highest Youden index) were: LAEF less than 55%, LAFI less than 40.5 and LARS less than 23%. Applying these cut-offs, abnormal LAEF, LAFI and LARS were, respectively, present in 27, 37.1 and 18.1% of the cohort. Abnormal LARS (<23%) was independently associated with higher risk for cardiac events and new-onset AFib (P ≤ 0.012). Participants with both abnormal LAEF and LARS presented a significantly higher risk to develop cardiac events (hazard ratio: 2.10; P = 0.014) and AFib (hazard ratio: 6.45; P = 0.0036) than normal counterparts. The concomitant presence of an impaired LARS and LV global longitudinal strain improved prognostic accuracy beyond a clinical risk model for cardiac events and the CHARGE-AF Risk Score for AFib. CONCLUSION Left atrial dysfunction based on outcome-driven thresholds predicted cardiac events and AFib independent of conventional risk factors. Screening for subclinical left atrial and LV systolic dysfunction may enhance cardiac disease prediction in the community.

A Novel 2-D Speckle Tracking Method for High-Frame-Rate Echocardiography

Abstract: Speckle tracking echocardiography (STE) is a clinical tool to noninvasively assess regional myocardial function through the quantification of regional motion and deformation. Even if the time resolution of STE can be improved by high-frame-rate (HFR) imaging, dedicated HFR STE algorithms have to be developed to detect very small interframe motions. Therefore, in this article, we propose a novel 2-D STE method, purposely developed for HFR echocardiography. The 2-D motion estimator consists of a two-step algorithm based on the 1-D cross correlations to separately estimate the axial and lateral displacements. The method was first optimized and validated on simulated data giving an accuracy of ~3.3% and ~10.5% for the axial and lateral estimates, respectively. Then, it was preliminarily tested in vivo on ten healthy volunteers showing its clinical applicability and feasibility. Moreover, the extracted clinical markers were in the same range as those reported in the literature. Also, the estimated peak global longitudinal strain was compared with that measured with a clinical scanner showing good correlation and negligible differences (−20.94% versus −20.31%, ${p}$ -value = 0.44). In conclusion, a novel algorithm for STE was developed: the radio frequency (RF) signals were preferred for the axial motion estimation, while envelope data were preferred for the lateral motion. Furthermore, using 2-D kernels, even for 1-D cross correlation, makes the method less sensitive to noise.

Interplay of cardiac remodelling and myocardial stiffness in hypertensive heart disease: a shear wave imaging study using high-frame rate echocardiography.

Abstract: AIMS To determine myocardial stiffness by means of measuring the velocity of naturally occurring myocardial shear waves (SWs) at mitral valve closure (MVC) and investigate their changes with myocardial remodelling in patients with hypertensive heart disease. METHODS AND RESULTS Thirty-three treated arterial hypertension (HT) patients with hypertrophic left ventricular (LV) remodelling (59 ± 14 years, 55% male) and 26 aged matched healthy controls (55±15 years, 77% male) were included. HT patients were further divided into a concentric remodelling (HT1) group (13 patients) and a concentric hypertrophy (HT2) group (20 patients). LV parasternal long-axis views were acquired with an experimental ultrasound scanner at 1266 ± 317 frames per seconds. The SW velocity induced by MVC was measured from myocardial acceleration maps. SW velocities differed significantly between HT patients and controls (5.83 ± 1.20 m/s vs. 4.04 ± 0.96 m/s; P < 0.001). In addition, the HT2 group had the highest SW velocities (P < 0.001), whereas values between controls and the HT1 group were comparable (P = 0.075). Significant positive correlations were found between SW velocity and LV remodelling (interventricular septum thickness: r = 0.786, P < 0.001; LV mass index: r = 0.761, P < 0.001). SW velocity normalized for wall stress indicated that myocardial stiffness in the HT2 group was twice as high as in controls (P < 0.001), whereas values of the HT1 group overlapped with the controls (P = 1.00). CONCLUSIONS SW velocity as measure of myocardial stiffness is higher in HT patients compared with healthy controls, particularly in advanced hypertensive heart disease. Patients with concentric remodelling have still normal myocardial properties whereas patients with concentric hypertrophy show significant stiffening.

Shear Wave Elastography Using High-Frame-Rate Imaging in the Follow-Up of Heart Transplantation Recipients

Abstract: Objectives The purpose of this study was to investigate whether propagation velocities of naturally occurring shear waves (SWs) at mitral valve closure (MVC) increase with the degree of diffuse myocardial injury (DMI) and with invasively determined LV filling pressures as a reflection of an increase in myocardial stiffness in heart transplantation (HTx) recipients. Background After orthotopic HTx, allografts undergo DMI that contributes to functional impairment, especially to increased passive myocardial stiffness, which is an important pathophysiological determinant of left ventricular (LV) diastolic dysfunction. Echocardiographic SW elastography is an emerging approach for measuring myocardial stiffness in vivo. Natural SWs occur after mechanical excitation of the myocardium, for example, after MVC, and their propagation velocity is directly related to myocardial stiffness, thus providing an opportunity to assess myocardial stiffness at end-diastole. Methods A total of 52 HTx recipients who underwent right heart catheterization (all) and cardiac magnetic resonance (CMR) (n = 23) during their annual check-up were prospectively enrolled. Echocardiographic SW elastography was performed in parasternal long axis views of the LV using an experimental scanner at 1,135 ± 270 frames per second. The degree of DMI was quantified with T1 mapping. Results SW velocity at MVC correlated best with native myocardial T1 values (r = 0.75; p Conclusions End-diastolic SW propagation velocities, as measure of myocardial stiffness, showed a good correlation with CMR-defined diffuse myocardial injury and with invasively determined LV filling pressures in patients with HTx. Thus, these findings suggest that SW elastography has the potential to become a valuable noninvasive method for the assessment of diastolic myocardial properties in HTx recipients.

Mechanical Effects on Right Ventricular Function From Left Bundle Branch Block and Cardiac Resynchronization Therapy

Abstract: Objectives The purpose of this study was to investigate how LBBB and CRT modify RV free wall function by direct ventricular interaction. Background Right ventricular (RV) function influences prognosis in patients with left bundle branch block (LBBB) and cardiac resynchronization therapy (CRT). There is, however, limited insight into how LBBB and CRT affect RV function. Methods In 24 patients with LBBB with nonischemic cardiomyopathy, RV and left ventricular (LV) strain by speckle-tracking echocardiography was measured before and after CRT. Underlying mechanisms were studied in 16 anesthetized dogs with ultrasonic dimension crystals and micromanometers. Results Patients with LBBB demonstrated distinct early systolic shortening in the RV free wall, which coincided with the typical abnormal early systolic septal shortening. In animals, this RV free wall contraction pattern resulted in reduced myocardial work as a large portion of the shortening occurred against low pressure during early systole, coinciding with abnormal leftward septal motion. RV systolic function was maintained by vigorous contraction in the late-activated LV lateral wall, which pushed the septum toward the RV. CRT reduced abnormal septal motion and increased RV free wall work because there was less inefficient shortening against low pressure. Conclusions LBBB reduces workload on the RV free wall because of abnormal septal motion and delayed activation of the LV lateral wall. Restoring septal and LV function by CRT increases workload in RV free wall and may explain why patients with RV failure respond poorly to CRT. (Contractile Reserve in Dyssynchrony: A Novel Principle to Identify Candidates for Cardiac Resynchronization Therapy [CRID-CRT]; NCT02525185)

Application of strain echocardiography in valvular heart diseases.

Abstract: Echocardiographic strain imaging allows new insight into a complex cardiac mechanics and enables more precise evaluation of cardiac function. Hence, it has been shown to have clinical utility in a variety of valvular heart diseases. In particular, global longitudinal strain has been shown to be more sensitive to detect systolic dysfunction than left ventricular ejection fraction. In patients with valvular heart diseases, it provides both diagnostic and prognostic information in addition to standard echocardiographic and clinical parameters. In this review, we summarize current clinical application of strain echocardiography in patients with valvular heart diseases and discuss pathophysiological mechanisms that lead to respective findings in specific diseases.

Source Mass Characterization in the ARIADNE Axion Experiment

Abstract: The Axion Resonant InterAction Detection Experiment (ARIADNE) is a collaborative effort to search for the QCD axion using nuclear magnetic resonance (NMR), where the axion acts as a mediator of spin-dependent forces between an unpolarized tungsten source mass and a sample of polarized helium-3 gas. Since the experiment involves precision measurement of a small magnetization, it relies on limiting ordinary magnetic noise with superconducting magnetic shielding. In addition to the shielding, proper characterization of the noise level from other sources is crucial. We investigate one such noise source in detail: the magnetic noise due to impurities and Johnson noise in the tungsten source mass.

Echocardiographic assessment of myocardial function during His bundle and right ventricular pacing

Abstract: Die His-Bundel-Stimulation (HBS) verspricht im Vergleich zur konventionellen rechtsventrikularen Stimulation (RVS) eine synchronere Aktivierung des linksventrikularen (LV) Myokards bei Schrittmachertherapie. Es wurde untersucht, inwieweit dieser Effekt mittels zeitgemaser echokardiographischer Funktionsbildgebung objektivierbar ist. Jeweils 15 Patienten mit RVS (6 weiblich, mittleres Alter: 76,6 ± 4,1 Jahre) und HBS (6 weiblich, mittleres Alter: 74,6 ± 3,7 Jahre) wurden mit und ohne Schrittmacherstimulation echokardiographisch untersucht. Neben der Messung von LV enddiastolischem Volumen (EDV), Ejektionsfraktion (EF) und globalem Strain (GLS) wurden auch die globale und regionale Arbeit des Myokards und die LV-Effizienz mittels nichtinvasiv erzeugter Druck-Strain-Schleifen ausgewertet. Bei allen HBS-Patienten konnten bei der Schrittmacheroptimierung unmittelbar funktionelle Veranderungen festgestellt werden. Unter Schrittmacherstimulation kam es bei gleichbleibendem EDV in der RVS-Gruppe zu einem hoheren Abfall der Ejektionsfraktion als bei der HBS-Gruppe (−7 vs. −3 %). Der Index fur die geleistete globale Arbeit und die Effizienz der LV-Funktion fielen in der RVS-Gruppe signifikant ab (−621 mm Hg% und −10,3 %), was in der HBS-Gruppe nicht in dem Mase der Fall war (−45 mm Hg% und −2,9 %). Anderungen der regionalen und globalen Myokardfunktion konnen echokardiographisch gut erfasst werden. Die HBS zeigt im Vergleich zur RVS funktionelle Vorteile.

The association of mechanical dyssynchrony and resynchronization therapy with survival in heart failure with a wide QRS complex: a two-world study

Abstract: Setting up a randomized trial to assess the association of mechanical dyssynchrony (MD) and the success of cardiac resynchronization therapy (CRT) in heart failure with a wide QRS complex is ethically challenging. We therefore investigated this association in a retrospective cohort study observing different treatment strategies which were chosen based on the availability of health care resources. The survival of 500 patients from six Western European centers treated with CRT was compared to their 137 Eastern European counterparts not treated with CRT, with regard to the presence of MD. MD was visually assessed and was defined as the presence of apical rocking and/or septal flash. Patients were followed for a mean of 26 ± 8 months for the occurrence of death of any cause. As compared with medical therapy alone, CRT was associated with a more favorable survival (hazard ratio (HR), 0.53; 95% confidence interval (CI) 0.35–0.79; P = 0.002). Patients with MD treated by CRT had better survival than patients belonging to all other groups—they showed 72%, 66% and 56% reduction in all-cause mortality, respectively, compared to patients with MD not treated by CRT (HR 0.28; 95% CI 0.17–0.44), patients without MD treated by CRT (HR 0.34; 95% CI 0.22–0.52) and patients without MD not treated by CRT (HR 0.44; 95% CI 0.25–0.76). Patients with wide QRS complex who are treated with CRT have a significantly better survival when MD is present.

The Effect of Different Coherence-Based Beamforming Techniques on the Accuracy of High Frame Rate Speckle Tracking Echocardiography

Abstract: Although high frame rate (HFR) imaging could be a promising technique for a better assessment of myocardial function, the higher temporal resolution comes with decreased image quality, which affects the accuracy of speckle tracking echocardiography (STE). Since several adaptive beamforming algorithms have already been proposed to improve image quality, the aim of this study was to assess to what extent this impacts the accuracy of HFR STE. Simulated datasets were used to compare 7 coherence-based beamforming schemes. The STE results were similar for different beamformers with root mean square errors between 0.36 and 0.50%. Next, in vivo apical 4-chamber views were recorded from 3 healthy volunteers using the same beamforming schemes. The related strain curves were similar for the different beamforming methods and the end-systolic values showed no significant difference among beamformers and volunteers. In conclusion, our findings suggest that the choice of beamforming method does not significantly affect HFR STE in a clinical setting.

High frame rate color Doppler to measure intraventricular pressure gradients

Abstract: In echocardiography, Color Doppler imaging (CDI) is mainly used for a qualitative analysis of abnormal blood flows. Indeed, any quantitative assessment is hampered by the compromise between frame rate, field of view, and measurement quality. Recently, we showed that high frame rate (HFR) imaging techniques, applied to CDI, soften those limitations at the expense of reduced image quality and penetration depth. Therefore, the aim of this study was to assess whether HFR-CDI could provide non-invasive, quantitative estimates of the intraventricular pressure gradient (IVPG), which may be an important marker for the diagnosis of diastolic function. Acquisitions, conducted on 29 healthy volunteers, showed that both diverging wave and multiline transmission allow achieving a high enough frame rate for a quantitative use of CDI. Indeed, diastolic IVPG peak values obtained with HFR-CDI where not statistically different from those obtained with standard color M-Mode, i.e. the gold standard reference.