Robert Manka

University of Zurich, Zürich, Zurich, Switzerland

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Publications (59)323.68 Total impact

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    ABSTRACT: The aim of this study was to quantify the response of the myocardial transverse relaxation times (ΔT2*) to hyperoxic respiratory challenge (HRC) at different field strengths in an intra-individual comparison of healthy volunteers and in a patient with coronary artery disease. Blood oxygenation level-dependent (BOLD) cardiovascular MR (CMR) data were acquired in 10 healthy volunteers (five women, five men; mean age, 29 ± 3 years; range, 22–35 years) at 1.5 and 3.0 T. Medical air (21% O2), pure oxygen and carbogen (95% O2, 5% CO2) were administered in a block-design temporal pattern to induce normoxia, hyperoxia and hyperoxic hypercapnia, respectively. Average T2* times were derived from measurements by two independent and blind readers in 16 standard myocardial segments on three short-axis slices per patient. Inter- and intra-reader correlations of T2* measurements were good [intra-class correlation coefficient (ICC) = 0.75 and ICC = 0.79, both p < 0.001]. During normoxia, the mean T2* times were 29.9 ± 6.1 ms at 1.5 T and 27.1 ± 6.6 ms at 3.0 T. Both hyperoxic gases induced significant (all p < 0.01) T2* increases (∆T2* hyperoxia: 1.5 T, 12.7%; 3.0 T, 11.2%; hyperoxic hypercapnia: 1.5 T, 13.1%; 3.0 T, 17.7%). Analysis of variance (ANOVA) results indicated a significant (both p < 0.001) effect of the inhaled gases on the T2* times at both 1.5 T (F = 17.74) and 3.0 T (F = 39.99). With regard to the patient imaged at 1.5 T, HRC induced significant T2* increases during hyperoxia and hyperoxic hypercapnia in normal myocardial segments, whereas the T2* response was not significant in ischemic segments (p > 0.23). The myocardial ∆T2* response to HRC can reliably be imaged and quantified with BOLD CMR at both 1.5 and 3.0 T. During HRC, hyperoxia and hyperoxic hypercapnia induce a significant increase in T2*, with ∆T2* being largest at 3.0 T and during hyperoxic hypercapnia in normal myocardial segments. Copyright © 2014 John Wiley & Sons, Ltd.
    NMR in Biomedicine 04/2014; · 3.45 Impact Factor
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    ABSTRACT: -The value of standard two-dimensional transthoracic echocardiographic (TTE) parameters for risk stratification in patients with arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is controversial. -We investigated the impact of right ventricular fractional area change (FAC) and tricuspid annulus plane systolic excursion (TAPSE) for prediction of major adverse cardiovascular events (MACE) defined as the occurrence of cardiac death, heart transplantation, survived sudden cardiac death, ventricular fibrillation, sustained ventricular tachycardia or arrhythmogenic syncope. Among 70 patients who fulfilled the 2010 ARVC/D Task Force Criteria and underwent baseline TTE, 37 (53%) patients experienced a MACE during a median follow-up period of 5.3 (IQR 1.8-9.8) years. Average values for FAC, TAPSE, and TAPSE indexed to body surface area (BSA) decreased over time (p=0.03 for FAC, p=0.03 for TAPSE and p=0.01 for TAPSE/BSA, each vs. baseline). In contrast, median right ventricular end-diastolic area (RVEDA) increased (p=0.001 vs. baseline). Based on the results of Kaplan-Meier estimates, the time between baseline TTE and experiencing MACE was significantly shorter for patients with FAC <23% (p<0.001), TAPSE <17mm (p=0.02) or right atrial (RA) short axis/BSA ≥25mm/m(2) (p=0.04) at baseline. A reduced FAC constituted the strongest predictor of MACE (hazard ratio 1.08 per 1% decrease; 95% confidence interval 1.04-1.12; p<0.001) on bivariable analysis. -This long-term observational study indicates that TAPSE and dilation of right-sided cardiac chambers are associated with an increased risk for MACE in ARVC/D patients with advanced disease and a high risk for adverse events. However, FAC is the strongest echocardiographic predictor of adverse outcome in these patients. Our data advocate a role for TTE in risk stratification in patients with ARVC/D, although our results may not be generalizable to lower risk ARVC/D cohorts.
    Circulation Cardiovascular Imaging 02/2014; · 5.80 Impact Factor
  • European Heart Journal 02/2014; · 14.10 Impact Factor
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    ABSTRACT: To evaluate the inter-study, inter-reader and intra-reader reproducibility of cardiac cine and scar imaging in rats using a clinical 3.0 Tesla magnetic resonance (MR) system. Thirty-three adult rats (Sprague-Dawley) were imaged 24 hours after surgical occlusion of the left anterior descending coronary artery using a 3.0 Tesla clinical MR scanner (Philips Healthcare, Best, The Netherlands) equipped with a dedicated 71 mm solenoid receive-only coil. Left-ventricular (LV) volumes, mass, ejection fraction and amount of myocardial scar tissue were measured. Intra-and inter-observer reproducibility was assessed in all animals. In addition, repeat MR exams were performed in 6 randomly chosen rats within 24 hours to assess inter-study reproducibility. The MR imaging protocol was successfully completed in 32 (97%) animals. Bland-Altman analysis demonstrated high intra-reader reproducibility (mean bias%: LV end-diastolic volume (LVEDV), -1.7%; LV end-systolic volume (LVESV), -2.2%; LV ejection fraction (LVEF), 1.0%; LV mass, -2.7%; and scar mass, -1.2%) and high inter-reader reproducibility (mean bias%: LVEDV, 3.3%; LVESV, 6.2%; LVEF, -4.8%; LV mass, -1.9%; and scar mass, -1.8%). In addition, a high inter-study reproducibility was found (mean bias%: LVEDV, 0.1%; LVESV, -1.8%; LVEF, 1.0%; LV mass, -4.6%; and scar mass, -6.2%). Cardiac MR imaging of rats yielded highly reproducible measurements of cardiac volumes/function and myocardial infarct size on a clinical 3.0 Tesla MR scanner system. Consequently, more widely available high field clinical MR scanners can be employed for small animal imaging of the heart e.g. when aiming at serial assessments during therapeutic intervention studies.
    BMC Medical Imaging 12/2013; 13(1):44. · 1.09 Impact Factor
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    ABSTRACT: The purpose of our study was (1) to assess retrospectively, in healthy subjects and in patients with moderate and severe functional mitral regurgitation (FMR), the normal mitral annular dimensions, (2) to determine differences in mitral annular geometry between healthy subjects and patients with FMR, and (3) to evaluate potential errors in 2-dimensional (2D) measurements given the 3D nature of the mitral annulus. 15 patients with no cardiac abnormalities (referred to as normals), 13 with moderate and 15 with severe FMR as determined by echocardiography underwent contrast-enhanced cardiac 64-slice Computed tomography (CT) with prospective electrocardiography-gating for excluding coronary artery disease. With an advanced visualization, segmentation, and image analysis software, the area, intercommissural distance (CC), septolateral distance (SLD), and the anterior and posterior circumference of the MA were measured in diastole. We found significant (P < .001) differences between normals and patients with severe FMR for area, SLD and posterior circumference in 3D (P < .001) and 2D (P < .001). Similarly, the SLD and the posterior circumference in both 3D (P = .002) and 2D (P = .001) were significantly smaller in patients with moderate FMR as compared to those with severe FMR. In contrast, there were no significant differences between groups regarding the CC and the anterior circumference both in 3D and 2D (all, P > .05). Measurements in 3D differed significantly from those with 2D for all circumference measurements and groups (P < .01), with a systematic underestimation of the posterior circumference of 2.1 ± 1.5 mm in normals, 1.8 ± 1.3 mm in patients with moderate FMR, and 1.9 ± 1.9 mm in patients with severe FMR for 2D. Our study provides in vivo human CT data on MA dimensions in normals and patients with FMR, indicating differences in patients for the area, posterior circumference and SLD but not for the anterior circumference and CC. Systematic differences exist between 2D and 3D measurements for all circumferential measurements.
    The international journal of cardiovascular imaging 12/2013; · 2.15 Impact Factor
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    ABSTRACT: In this study, an iterative k-t principal component analysis (PCA) algorithm with nonrigid frame-to-frame motion correction is proposed for dynamic contrast-enhanced three-dimensional perfusion imaging. An iterative k-t PCA algorithm was implemented with regularization using training data corrected for frame-to-frame motion in the x-pc domain. Motion information was extracted using shape-constrained nonrigid image registration of the composite of training and k-t undersampled data. The approach was tested for 10-fold k-t undersampling using computer simulations and in vivo data sets corrupted by respiratory motion artifacts owing to free-breathing or interrupted breath-holds. Results were compared to breath-held reference data. Motion-corrected k-t PCA image reconstruction resolved residual aliasing. Signal intensity curves extracted from the myocardium were close to those obtained from the breath-held reference. Upslopes were found to be more homogeneous in space when using the k-t PCA approach with motion correction. Iterative k-t PCA with nonrigid motion correction permits correction of respiratory motion artifacts in three-dimensional first-pass myocardial perfusion imaging. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 07/2013; · 3.27 Impact Factor
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    ABSTRACT: BACKGROUND: Intracoronary administration of autologous bone marrow derived mononuclear cells (BM-MNC) may improve remodeling of the left ventricle (LV) after acute myocardial infarction (AMI). The optimal time point of administration of BM-MNC is still uncertain and has rarely been addressed prospectively in randomized clinical trials. METHODS AND RESULTS: In a multi-centre study, we randomized 200 patients with large, successfully reperfused ST segment elevation myocardial infarction (STEMI) in a 1:1:1 pattern into an open-labeled control and two BM-MNC treatment groups. In the BM-MNC groups cells were either administered "early", i.e. 5-7 days, or "late", i.e. 3-4 weeks after AMI. Cardiac magnetic resonance imaging was performed at baseline and after 4 months. The primary endpoint was the change from baseline to 4 months in global LV ejection fraction (LVEF) between the two treatment groups and the control group. The absolute change in LVEF from baseline to 4 months was -0.4±8.8% (mean±SD; p= 0.74 vs. baseline) in the control group, 1.8±8.4% (p = 0.12 vs. baseline) in the early group and 0.8±7.6% (p = 0.45 vs. baseline) in the late group. The treatment effect of BM-MNC as estimated by ANCOVA was 1.25 (95% CI -1.83 to 4.32; p = 0.42) for the early and 0.55 (95% CI -2.61 to 3.71; p = 0.73) for the late therapy group. CONCLUSIONS: Among patients with STEMI and LV dysfunction following successful reperfusion, intracoronary infusion of BM-MNC either at 5-7 days or 3-4 weeks after AMI, did not improve LV-function at 4 months follow-up. CLINICAL TRIAL REGISTRATION INFORMATION: http://www.clinicaltrials.gov; Identifier: NCT00355186.
    Circulation 04/2013; · 15.20 Impact Factor
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    ABSTRACT: In this work, an iterative k-t PCA algorithm is proposed where an additional spatial transformation is used to further sparsify the data. Training data based regularization is performed in a motion corrected x-pc domain where each time frame is warped to a reference respiratory position. Spatial transformations are derived from frame-by-frame composite images using atlas-based image registration. Using 3D perfusion data acquired in vivo it is demonstrated that this approach successfully corrects for incomplete unfolding due to respiratory bulk motion.
    ISMRM; 04/2013
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    ABSTRACT: Cardiac magnetic resonance imaging enables noninvasive assessment of myocardial perfusion. However, standard 2D multi-slice CMR perfusion techniques only provide limited coverage and hence prohibit computation of myocardial ischemic burden. Recently, 3D CMR perfusion has proven highly diagnostic in two single-center studies. In this preliminary assessment of our multi-center study 3D CMR perfusion imaging proved highly diagnostic for the detection of functionally significant CAD as defined by FFR.
    ISMRM; 04/2013 · 4.44 Impact Factor
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    ABSTRACT: BACKGROUND: The heart is subject to structural and functional changes with advancing age. However, the magnitude of cardiac age-dependent transformation has not been conclusively elucidated. METHODS: This retrospective cardiac magnetic resonance (CMR) study included 183 subjects with normal structural and functional ventricular values. End systolic volume (ESV), end diastolic volume (EDV), and ejection fraction (EF) were obtained from the left and the right ventricle in breath-hold cine CMR. Patients were classified into four age groups (20--29, 30--49, 50--69, and >=70 years) and cardiac measurements were compared using Pearson's rank correlation over the four different groups. RESULTS: With advanced age a slight but significant decrease in ESV (r=-0.41 for both ventricles, P<0.001) and EDV (r=-0.39 for left ventricle, r=-0.35 for right ventricle, P<0.001) were observed associated with a significant increase in left (r=0.28, P<0.001) and right (r=0.27, P<0.01) ventricular EF reaching a maximal increase in EF of +8.4% (P<0.001) for the left and +6.1% (P<0.01) for the right ventricle in the oldest compared to the youngest patient group. Left ventricular myocardial mass significantly decreased over the four different age groups (P<0.05). CONCLUSIONS: The aging process is associated with significant changes in left and right ventricular EF, ESV and EDV in subjects with no cardiac functional and structural abnormalities. These findings underline the importance of using age adapted values as standard of reference when evaluating CMR studies.
    BMC Medical Imaging 02/2013; 13(1):6. · 1.09 Impact Factor
  • European Heart Journal 02/2013; · 14.10 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 01/2013; 15(1). · 4.44 Impact Factor
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    Journal of Cardiovascular Magnetic Resonance 01/2013; 15(1). · 4.44 Impact Factor
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    ABSTRACT: CMR allows investigating cardiac contraction, rotation and torsion non-invasively by the use of tagging sequences. Three-dimensional tagging has been proposed to cover the whole-heart but data acquisition requires three consecutive breath holds and hence demands considerable patient cooperation. In this study we have implemented and studied k-t undersampled cine 3D tagging in conjunction with k-t PCA reconstruction to potentially permit for single breath-hold acquisitions. The performance of undersampled cine 3D tagging was investigated using computer simulations and in-vivo measurements in 8 healthy subjects and 5 patients with myocardial infarction. Fully sampled data was obtained and compared to retrospectively and prospectively undersampled acquisitions. Fully sampled data was acquired in three consecutive breath holds. Prospectively undersampled data was obtained within a single breath hold. Based on harmonic phase (HARP) analysis, circumferential shortening, rotation and torsion were compared between fully sampled and undersampled data using Bland-Altman and linear regression analysis. In computer simulations, the error for circumferential shortening was 2.8 ± 2.3% and 2.7 ± 2.1% for undersampling rates of R = 3 and 4 respectively. Errors in ventricular rotation were 2.5 ± 1.9% and 3.0 ± 2.2% for R = 3 and 4. Comparison of results from fully sampled in-vivo data acquired with prospectively undersampled acquisitions showed a mean difference in circumferential shortening of -0.14 ± 5.18% and 0.71 ± 6.16% for R = 3 and 4. The mean differences in rotation were 0.44 ± 1.8° and 0.73 ± 1.67° for R = 3 and 4, respectively. In patients peak, circumferential shortening was significantly reduced (p < 0.002 for all patients) in regions with late gadolinium enhancement. Undersampled cine 3D tagging enables significant reduction in scan time of whole-heart tagging and facilitates quantification of shortening, rotation and torsion of the left ventricle without adding significant errors compared to previous 3D tagging approaches.
    Journal of Cardiovascular Magnetic Resonance 08/2012; 14:60. · 4.44 Impact Factor
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    ABSTRACT: In acute myocardial infarction (AMI), both tissue necrosis and edema are present and both might be implicated in the development of intraventricular dyssynchrony. However, their relative contribution to transient dyssynchrony is not known. Cardiovascular magnetic resonance (CMR) can detect necrosis and edema with high spatial resolution and it can quantify dyssynchrony by tagging techniques. Patients with a first AMI underwent percutaneous coronary interventions (PCI) of the infarct-related artery within 24 h of onset of chest pain. Within 5-7 days after the event and at 4 months, CMR was performed. The CMR protocol included the evaluation of intraventricular dyssynchrony by applying a novel 3D-tagging sequence to the left ventricle (LV) yielding the CURE index (circumferential uniformity ratio estimate; 1 = complete synchrony). On T2-weighted images, edema was measured as high-signal (>2 SD above remote tissue) along the LV mid-myocardial circumference on 3 short-axis images (% of circumference corresponding to the area-at-risk). In analogy, on late-gadolinium enhancement (LGE) images, necrosis was quantified manually as percentage of LV mid-myocardial circumference on 3 short-axis images. Necrosis was also quantified on LGE images covering the entire LV (expressed as %LV mass). Finally, salvaged myocardium was calculated as the area-at-risk minus necrosis (expressed as % of LV circumference). After successful PCI (n = 22, 2 female, mean age: 57 ± 12y), peak troponin T was 20 ± 36ug/l and the LV ejection fraction on CMR was 41 ± 8%. Necrosis mass was 30 ± 10% and CURE was 0.91 ± 0.05. Edema was measured as 58 ± 14% of the LV circumference. In the acute phase, the extent of edema correlated with dyssynchrony (r2 = -0.63, p < 0.01), while extent of necrosis showed borderline correlation (r2 = -0.19, p = 0.05). PCI resulted in salvaged myocardium of 27 ± 14%. LV dyssynchrony (=CURE) decreased at 4 months from 0.91 ± 0.05 to 0.94 ± 0.03 (p < 0.004, paired t-test). At 4 months, edema was absent and scar %LV slightly shrunk to 23.7 ± 10.0% (p < 0.002 vs baseline). Regression of LV dyssynchrony during the 4 months follow-up period was predicted by both, the extent of edema and its necrosis component in the acute phase. In the acute phase of infarction, LV dyssynchrony is closely related to the extent of edema, while necrosis is a poor predictor of acute LV dyssynchrony. Conversely, regression of intraventricular LV dyssynchrony during infarct healing is predicted by the extent of necrosis in the acute phase.
    Journal of Cardiovascular Magnetic Resonance 07/2012; 14:47. · 4.44 Impact Factor
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    ABSTRACT: An approach to efficiently measure three-dimensional velocity vector fields and turbulent kinetic energy of blood flow is presented. Multipoint phase-contrast imaging is used in combination with Bayesian analysis to map both mean and fluctuating velocities over a large dynamic range and for practically relevant signal-to-noise ratios. It is demonstrated that the approach permits significant spatiotemporal undersampling to allow for clinically acceptable scan times. Using numerical simulations and in vitro measurements in aortic valve phantoms, it is shown that for given scan time, Bayesian multipoint velocity encoding provides consistently lower errors of velocity and turbulent kinetic energy over a larger dynamic range relative to previous methods. In vitro, significant differences in both peak velocity and turbulent kinetic energy between the aortic CoreValve (150 cm/s, 293 J/m(3) ) and the St. Jude Medical mechanical valve (120 cm/s, 149 J/m(3) ) were found. Comparison of peak turbulent kinetic energy measured in a patient with aortic stenosis (950 J/m(3) ) and in a patient with an implanted aortic CoreValve (540 J/m(3) ) revealed considerable differences relative to the values detected in healthy subjects (149 ± 12 J/m(3) ) indicating the potential of the method to provide a comprehensive hemodynamic assessment of valve performance in vivo. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 06/2012; · 3.27 Impact Factor
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    ABSTRACT: Dynamic three-dimensional-cardiac magnetic resonance (3D-CMR) perfusion proved highly diagnostic for the detection of angiographically defined coronary artery disease (CAD) and has been used to assess the efficacy of coronary stenting procedures. The present study aimed to relate significant coronary lesions as assessed by fractional flow reserve (FFR) to the volume of myocardial hypoenhancement on 3D-CMR adenosine stress perfusion imaging and to define the inter-study reproducibility of stress inducible 3D-CMR hypoperfusion. A total of 120 patients with known or suspected CAD were examined in two CMR centres using 1.5 T systems. The protocol included cine imaging, 3D-CMR perfusion during adenosine infusion, and at rest followed by delayed enhancement (DE) imaging. Fractional flow reserve was recorded in epicardial coronary arteries and side branches with ≥2 mm luminal diameter and >40% severity stenosis (pathologic FFR < 0.75). Twenty-five patients underwent an identical repeat CMR examination for the determination of inter-study reproducibility of 3D-CMR perfusion deficits induced by adenosine. Three-dimensional CMR perfusion scans were visually classified as pathologic if one or more segments showed an inducible perfusion deficit in the absence of DE. Myocardial ischaemic burden (MIB) was measured by segmentation of the area of inducible hypoenhancement and normalized to left ventricular myocardial volume (MIB, %). Three-dimensional CMR perfusion resulted in a sensitivity, specificity, and diagnostic accuracy of 90, 82, and 87%, respectively. Substantial concordance was found for inter-study reproducibility [Lin's correlation coefficient: 0.98 (95% confidence interval: 0.96-0.99)]. Three-dimensional CMR stress perfusion provided high diagnostic accuracy for the detection of functionally significant CAD. Myocardial ischaemic burden measurements were highly reproducible and allowed the assessment of CAD severity.
    European Heart Journal 06/2012; 33(16):2016-24. · 14.10 Impact Factor
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    ABSTRACT: The tracer dose in dynamic contrast-enhanced magnetic resonance imaging is crucial for myocardial perfusion quantification. Higher dose is beneficial for myocardial signal-to-noise ratio, but increases the risk of left-ventricular signal saturation in the image due to shorter T1. This study introduces a new acquisition method for the arterial input function using a pencil-beam probe. It is demonstrated that signal saturation in the probe can be avoided by reducing the delay after the saturation pulse. Perfusion quantification from 3D perfusion imaging with the pencil beam probe versus image based assessment of the arterial input function at half and full dose is shown.
    ISMRM; 05/2012
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    ABSTRACT: Scan acceleration methods have proven invaluable for dynamic contrast-enhanced perfusion imaging. One practical issue, however, relates to the requirement of breathholding or shallow breathing which cannot always be ensured in clinical routine exams. An extended k-t PCA algorithm is proposed which corrects for non-rigid frame-to-frame motion based on motion operators derived from two pencil-beam navigators for feet-head and anterior-posterior motion detection and the fully sampled k-t training data. It is demonstrated that this approach successfully corrects for respiratory motion artifacts and hence enables free-breathing 3D cardiac perfusion MRI.
    ISMRM; 05/2012
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    Journal of Cardiovascular Magnetic Resonance 02/2012; 14 Suppl 1:W9. · 4.44 Impact Factor

Publication Stats

526 Citations
323.68 Total Impact Points

Institutions

  • 2011–2013
    • University of Zurich
      • Center for Integrative Human Physiology
      Zürich, Zurich, Switzerland
  • 2010–2013
    • ETH Zurich
      • Institute for Biomedical Engineering
      Zürich, ZH, Switzerland
  • 2012
    • University Hospital of Lausanne
      Lausanne, Vaud, Switzerland
  • 2010–2011
    • University Hospital RWTH Aachen
      • Department of Neurology
      Aachen, North Rhine-Westphalia, Germany
  • 2008–2011
    • Berlin Heart
      Berlín, Berlin, Germany
    • Deutsches Herzzentrum Berlin
      Berlín, Berlin, Germany