Titus Kuehne

Charité Universitätsmedizin Berlin, Berlín, Berlin, Germany

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Publications (102)388.43 Total impact

  • American Heart Association, Chicago , IL 2014; 11/2014
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    ABSTRACT: Current models for real time study of the effects of myocardial ischemia/reperfusion have major limitations and confounders. Confounders include the surgical stresses of a thoracotomy and abnormal physiology of an open chest. The need to reposition the animal interferes with the study of the early changes associated with ischemia. Direct comparison of pre-ischemia and post-ischemia images is then difficult. We developed a novel “closed chest” model of ischemia/reperfusion to overcome these issues. Following thoracotomy, we sutured a balloon occluder to the left coronary artery of male Sprague–Dawley rats. We used both visual inspection and ECG to assess for successful occlusion and reperfusion of the coronary artery at the time of operation by brief inflation and deflation of the balloon. The tubing was then placed under the skin and the incision closed. Following a recovery period (5–10 days), the animals underwent MRI. We performed baseline assessment of left ventricle function, and repeated LV measurement during a 15-min coronary occlusion and again during a 60-min reperfusion period following reopening of the coronary artery. The occluder was successfully placed in 40 of 44 animals. Four developed intraoperative complications; two large myocardial infarction, two terminal bleeding. Six died in the week following surgery, [four sudden deaths (presumed arrhythmic), one anterior infarction, one sepsis]. Cine-MRI demonstrated localised hypokinesia in 31 of the remaining 34 animals. LV ejection fraction (EF) was reduced from 63 ± 7 % at baseline, to 49 ± 9 % during coronary occlusion. LV EF recovered to 61 ± 2 %. The area at risk on staining of the heart was 41.9 ± 15.8 %. This method allows the effects of ischemia/reperfusion to be studied before, during, and after coronary occlusion. Ischemia can be caused while the animal is in the MRI. This new and clinically relevant small animal model is a valuable tool to study the effects of single or repeated coronary occlusion/reperfusion in real-time.
    The International Journal of Cardiovascular Imaging 10/2014; · 2.65 Impact Factor
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    ABSTRACT: Pressure drop associated with coarctation of the aorta (CoA) can be successfully treated surgically or by stent placement. However, a decreased life expectancy associated with altered aortic hemodynamics was found in long-term studies. Image-based computational fluid dynamics (CFD) is intended to support particular diagnoses, to help in choosing between treatment options, and to improve performance of treatment procedures. This study aimed to prove the ability of CFD to improve aortic hemodynamics in CoA patients. In 13 patients (6 males, 7 females; mean age 25 ± 14 years), we compared pre- and post-treatment peak systole hemodynamics [pressure drops and wall shear stress (WSS)] vs. virtual treatment as proposed by biomedical engineers. Anatomy and flow data for CFD were based on MRI and angiography. Segmentation, geometry reconstruction and virtual treatment geometry were performed using the software ZIBAmira, whereas peak systole flow conditions were simulated with the software ANSYS(®) Fluent(®). Virtual treatment significantly reduced pressure drop compared to post-treatment values by a mean of 2.8 ± 3.15 mmHg, which significantly reduced mean WSS by 3.8 Pa. Thus, CFD has the potential to improve post-treatment hemodynamics associated with poor long-term prognosis of patients with coarctation of the aorta. MRI-based CFD has a huge potential to allow the slight reduction of post-treatment pressure drop, which causes significant improvement (reduction) of the WSS at the stenosis segment.
    Annals of biomedical engineering. 09/2014;
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    ABSTRACT: This study compared pressure fields by 4-dimensional (4D), velocity-encoded cine (VEC) cardiac magnetic resonance imaging (CMR) with pressures measured by the clinical gold standard catheterization. Thirteen patients (n = 7 male, n = 6 female) with coarctation were studied. The 4D-VEC-CMR pressure fields were computed by solving the Pressure-Poisson equation. The agreement between catheterization and CMR-based methods was determined at 5 different measurement sites along the aorta. For all sites, the correlation coefficients between measures varied between 0.86 and 0.97 (p < 0.001). The Bland-Altman test showed good agreement between peak systolic pressure gradients across the coarctation. The nonsignificant (p > 0.2) bias was +2.3 mm Hg (± 6.4 mm Hg, 2 SDs) for calibration with dynamic pressures and +1.5 mm Hg (± 4.6 mm Hg, 2 SDs) for calibration with static pressure. In a clinical setting of coarctation, pressure fields can be accurately computed from 4D-VEC-CMR–derived flows. In patients with coarctation, this noninvasive technique might evolve to an alternative to invasive catheterization.
    JACC: Cardiovascular Imaging. 09/2014; 7(9):920–926.
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    European heart journal cardiovascular Imaging. 05/2014; 15(suppl 1):i1-i7.
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    ABSTRACT: PurposeTo reduce the need for diagnostic catheterization and optimize treatment in a variety of congenital heart diseases, magnetic resonance imaging (MRI)-based computational fluid dynamics (CFD) is proposed. However, data about the accuracy of CFD in a clinical context are still sparse. To fill this gap, this study compares MRI-based CFD to catheterization in the coarctation of aorta (CoA) setting.Materials and Methods Thirteen patients with CoA were investigated by routine MRI prior to catheterization. 3D whole-heart MRI was used to reconstruct geometries and 4D flow-sensitive phase-contrast MRI was used to acquire flows. Peak systolic flows were simulated using the program FLUENT.ResultsPeak systolic pressure drops in CoA measured by catheterization and CFD correlated significantly for both pre- and posttreatment measurements (pre: r = 0.98, p = 0.00; post: r = 0.87, p = 0.00). The pretreatment bias was −0.5 ± 3.33 mmHg (95% confidence interval −2.55 to 1.47 mmHg). CFD predicted a reduction of the peak systolic pressure drop after treatment that ranged from 17.6 ± 5.56 mmHg to 6.7 ± 5.58 mmHg. The posttreatment bias was 3.0 ± 2.91 mmHg (95% CI −1.74 to 5.43 mmHg).Conclusion Peak systolic pressure drops can be reliably calculated using MRI-based CFD in a clinical setting. Therefore, CFD might be an attractive noninvasive alternative to diagnostic catheterization.J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 04/2014; · 2.57 Impact Factor
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    ABSTRACT: Strongly evolving imaging technologies such as magnetic resonance imaging (MRI) nowadays provide a multitude of new complementary techniques for the analysis of cardiovascular tissue properties, function, and hemodynamics. The purpose of the presented work is to provide a research tool, which enables a quick validation of newly developed imaging techniques and supports the co-development of clinically usable analysis tools, which allow an integration with existing complementary examination methods. The concepts combined to this end consist of an integration with the open source research PACS OsiriX, an advanced heuristic DICOM classification and preprocessing as well as an integrative data model, which accumulates patient-specific image data, results and the data relations. Specific processing and analysis plugins can easily be integrated in such a way that they use the data integration and visualization infrastructure as well as results from other existing plugins. The presented example applications, such as the evaluation of slice orientations for cardiac function quantification or the integrated analysis of different types of image data for diagnosis of myocarditis show that the provided tool can be successfully used for a multitude of research applications in cardiovascular imaging.
    02/2014;
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    ABSTRACT: A unique feature of cardiac magnetic resonance is its ability to characterize myocardium. Proton relaxation times, T1, T2, and T2* are a reflection of the composition of individual tissues, and change in the presence of disease. Research into T1 mapping has largely been focused in the study of cardiomyopathies, but T1 mapping also shows huge potential in the study of ischaemic heart disease. In fact, the first cardiac T1 maps were used to characterize myocardial infarction. Robust high-resolution myocardial T1 mapping is now available for use as a clinical tool. This quantitative technique is simple to perform and analyse, minimally subjective, and highly reproducible. This review aims to summarize the present state of research on the topic, and to show the clinical potential of this method to aid the diagnosis and treatment of patients with ischaemic heart disease.
    European heart journal cardiovascular Imaging. 02/2014;
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    ABSTRACT: Double aortic arch is a rare congenital anomaly. It is usually diagnosed and surgically corrected at an early age due to symptoms as dyspnea and dysphagia caused by an obstruction of trachea and/or esophagus in the vascular ring. We present the case of an asymptomatic 14-year-old patient with complete double aortic arch as demonstrated by CMR. Blood flow in the right and left aortic arch was visualized and quantified by 4D-flow MRI.
    Cardiovascular diagnosis and therapy. 02/2014; 4(1):44-6.
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    ABSTRACT: We aimed to investigate the histological and clinical presentations of EAM induced by different immunization schemes. Male young Lewis rats were divided into 5 groups immunized by porcine myocardial myosin: subcutaneously (SC) 1 2 mg (in two 1 mg doses on day 0 and 7); 0 mg (sham group) subcutaneously into rear footpads (RF), 0.25 mg RF, 0.5 mg RF or 1 mg RF (all RF once on day 0). On day 21 left ventricular (LV) function was assessed by cardiac magnetic resonance imaging and cardiac catheterization. The type and degree of myocardial inflammatory infiltrates were determined by conventional histology and immunohistochemistry. In the SC immunized rats and in the RF sham group we observed 0% mortality, while in the actively RF immunized rats mortality was 20%, 20% and 44% for the 0.25 mg, 0.5 mg and 1 mg myosin doses respectively. Morbidity as defined by inflammatory infiltrates on HE staining was 22% in the SC immunized rats, 0% in the RF sham group and 100% in all actively RF immunized groups. We observed augmented relative ventricle weight and spleen weight, increased LV end-diastolic pressure, reduced LV developed pressure and reduced LV ejection fraction in all with myosin immunized RF groups without any systematic dose effect. Subcutaneous immunization to the neck and flanks did not induce a reproducible EAM, while RF myosin administration reliably led to EAM. Lower myosin doses seem to induce the complete histological and clinical picture of EAM while being associated with lower mortality, non-specific symptoms and animal distress. This article is protected by copyright. All rights reserved.
    Acta Physiologica 01/2014; · 4.38 Impact Factor
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    ABSTRACT: -In repaired congenital heart disease, there is increasing evidence of gender differences in cardiac remodelling, but there is a lack of comparable data for specific congenital heart defects, such as in repaired tetralogy of Fallot (r-ToF). -In a prospective multicentre study, a cohort of 272 contemporary patients (158 male, mean age 14.3± 3.3, range 8-20 years) with r-ToF underwent cardiac magnetic resonance for ventricular function and metabolic exercise testing. All data were transformed to standard deviation scores (SDS) according to the Lambda-Mu-Sigma method by relating individual values to their respective 50(th) percentile (SDS=0) in sex-specific healthy controls. No gender differences were observed in age at repair, the type of repair conducted or in overall hemodynamic results. Relative to sex-specific controls, female r-ToF patients had larger right ventricular (RV) end-systolic volumes (SDS females +4.35, males +3.25, p=0.001), lower RV ejection fraction (females -2.83, males -2.12, p=0.011), lower RV muscle mass (females +1.58, males +2.45, p=0.001), poorer peak oxygen uptake (females -1.65, males -1.14, p<0.001), higher VE/VCO2-slopes (females +0.88, males +0.58, p=0.012) and reduced peak heart rate (females -2.16, males -1.74, p=0.017). Left ventricular parameters did not differ between genders. -Relative to their respective sex-specific healthy controls, derived standard deviation scores in r-ToF suggest that females perform poorer than males in terms of right ventricular systolic function as tested by CMR and exercise capacity. This effect cannot be explained by selection bias. Further outcome data are required from longitudinal cohort studies. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT00266188.
    Circulation Cardiovascular Imaging 10/2013; · 5.80 Impact Factor
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    ABSTRACT: Aortic coarctation (CoA) accounting for 3-11% of congenital heart disease can be successfully treated. Long-term results, however, have revealed decreased life expectancy associated with abnormal hemodynamics. Accordingly, an assessment of hemodynamics is the key factor in treatment decisions and successful long-term results. In this study, 3D angiography whole heart (3DWH) and 4D phase-contrast magnetic resonance imaging (MRI) data were acquired. Geometries of the thoracic aorta with CoAs were reconstructed using ZIB-Amira software. X-ray angiograms were used to evaluate the post-treatment geometry. Computational fluid dynamics models in three patients were created to simulate pre- and post-treatment situations using the FLUENT program. The aim of the study was to investigate the impact of the inlet velocity profile (plug vs. MRI-based) with a focus on the peak systole pressure gradient and wall shear stress (WSS). Results show that helical flow at the aorta inlet can significantly affect the assessment of pressure drop and WSS. Simplified plug inlet velocity profiles significantly (p < 0.05) overestimate the pressure drop in pre- and post-treatment geometries and significantly (p < 0.05) underestimate surface-averaged WSS. We conclude that the use of the physiologically correct but time-expensive 4D MRI-based in vivo velocity profile in CFD studies may be an important step towards a patient-specific analysis of CoA hemodynamics.
    Annals of Biomedical Engineering 08/2013; · 3.23 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the left ventricular (LV) myocardial contractility index-Emax using transesophageal real time three-dimensional echocardiography (RT3DE) combined with catheterization. Transesophageal RT3DE (single beat, X7-2 × matrix, iE33, Philips) was used to obtain real time LV volumes in pigs. Volumes were integrated with LV pressures from conductance catheterization (CC) to create RT3DE pressure-volume relations. At the same time, CC was used for measuring conventional pressure-volume relations that served as reference. The slope Emax was determined from RT3DE and CC end-systolic pressure-volume relations. All measurements were made at rest and during dobutamine infusion. In six pigs, the mean ± SD (mmHg/mL) values were Emax-CC 1.86 ± 1.1 and Emax-RT3DE 1.78 ± 1.2 (P = 0.502) at baseline. On dobutamine, mean Emax-CC was 3.43 ± 1.5 and Emax-RT3DE 3.60 ± 1.23 (P = 0.171). Bland-Altman analysis showed good agreements between the RT3DE- and CC-derived Emax for measurements performed at baseline and on dobutamine. Emax can be determined from RT3DE integrated with catheterization-derived pressures. RT3DE is a promising method for enhancing clinical applicability of pressure-volume relations for assessment of myocardial contractility.
    Echocardiography 07/2013; · 1.26 Impact Factor
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    ABSTRACT: To analyze the impact of surgery and pericardial integrity on right atrial function and total heart volume variation in the setting of pulmonary valve insufficiency. Right atrial function and total heart volume variation were analyzed in 2 subgroups of patients with pulmonary valve insufficiency compared with healthy controls: group 1 with surgically repaired tetralogy of Fallot (n = 20 patients) and group 2 after balloon angioplasty of pulmonary valve stenosis in patients with isolated valve disease without surgery (n = 7 patients). Volumetric analysis of magnetic resonance imaging data revealed parameters of atrial function (reservoir, conduit, and pump functions and cyclic volume change) and of total heart volume (end-diastolic and end-systolic total heart volume and the variation). Statistical analysis included uncorrected and corrected pairwise comparisons and the calculation of groupwise Pearson correlation coefficients. In group 1 with a pulmonary regurgitation fraction of 31.0% ± 14.9%, right atrial function was clearly impaired, with reduced reservoir and elevated conduit function, and total heart volume variation was elevated to 13.9% ± 3.4%. In group 2 with a pulmonary regurgitation fraction of 22.8% ± 6.9%, the values were close to normal, with unaffected atrial function and a total heart volume variation of 9.9% ± 3.3%. The hydrodynamic effect of pulmonary valve insufficiency alone is likely not the only reason for impaired right atrial function and elevated total heart volume variation in patients with tetralogy of Fallot; it is rather the scar in the right atrium, the injured pericardium, and the disease itself that are responsible for the energetically unfavorable alterations.
    The Journal of thoracic and cardiovascular surgery 07/2013; · 3.41 Impact Factor
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    ABSTRACT: Aortic coarctation (CoA) accounts for approximately 10% of congenital heart diseases1. CoA causing high pressure gradient can be successfully treated surgical or catheter-based. Long-term results, however, revealed decreased life expectancy associated with abnormal hemodynamics1. To develop a next-generation personalized diagnostic-prognostic tools allowing treatment optimization and thus to improve life expectance, the innovative combination of imaging science, biofluid mechanics, and computer modeling is necessary. Patient-specific computational fluid dynamics (CFD) models of the CoA based on MRI data were created to analyze pre- and post-treatment hemodynamics with a focus on pressure gradient.
    ASME 2013 Summer Bioengineering Conference; 06/2013
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    ABSTRACT: Background: The admittance and Wei's equation is a new technique for ventricular volumetry to determine pressure-volume relations that addresses traditional conductance related issues of parallel conductance and field correction factor. These issues with conductance have prevented researchers from obtaining real-time absolute ventricular volumes. Moreover, the time consuming steps involved in processing conductance catheter data has warranted the need for a better catheter-based technique for ventricular volumetry. We aimed to compare the accuracy of left ventricular (LV) volumetry between the new admittance catheterization technique and transesophageal real time three-dimensional echocardiography (RT3DE) in a large animal model. Methods: Eight pigs were used in the study. A 7F admittance catheter was positioned in the LV via right carotid artery. The catheter was connected to an admittance control unit (ADVantage, Transonic Scisense Inc.) and data was recorded on a 4-channel acquisition system (FA404, iWorx Systems). Admittance catheterization data and transesophageal RT3DE (X7-2, Philips) data were simultaneously obtained with the animal ventilated, paralyzed and monitored at 2 conditions: baseline, and during dobutamine infusion. LV volumes measured from admittance catheterization (Labscribe, iWorx Systems) and RT3DE (QLab, Philips) were compared. In a subset of 4 animals, admittance volumes were compared with those obtained from traditional conductance catheterization (MPVS Ultra, Millar Instruments). Results: Of 37 sets of measurements compared, admittance and RT3DE derived LV volumes and ejection fractions at baseline and on dobutamine exhibited general agreement, with mean percentage inter-method differences of 10% for end-diastolic volumes, 14% for end systolic volumes and 9% for ejection fraction; the respective inter-method differences between admittance and conductance in 8 datasets compared were 11%, 11% and 12%. Admittance volumes were generally higher than those by RT3DE, especially among the larger ventricles. Conclusion: It is feasible to derive pressure-volume relations using admittance catheterization in large animals. This study demonstrated agreements between admittance and RT3DE to within 10-14% mean inter-method difference in the estimation of LV volumes. Further investigation will be required to examine accuracy of volumes in largest ventricles where inter-method divergence is greatest.
    Experimental physiology 02/2013; · 3.17 Impact Factor
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    ABSTRACT: Background and objectives Flow profiles are important determinants of fluid-vessel wall interactions. The aim of this study was to assess blood flow profiles in the aorta and pulmonary trunk in patients with transposition and different ventriculoarterial connection, and hence different mechanics of the coherent pump. METHODS: In all, 29 patients with operated transposition - concordant atrioventricular and discordant ventriculoarterial connection, and no other cardiac malformation - and eight healthy volunteers were assessed with cardiac magnetic resonance imaging: n = 17 patients after atrial redirection, with a morphologic right ventricle acting as systemic pump and a morphologic left ventricle connected to the pulmonary trunk, and n = 12 patients after the arterial switch procedure, with physiologic ventriculoarterial connections. Flow-sensitive four-dimensional velocity-encoded magnetic resonance imaging was used to analyse systolic flow patterns in the aorta and pulmonary trunk, relating to helical flow and vortex formation. RESULTS: In the aorta, overall helicity was present in healthy volunteers, but it was absent in all patients independent on the operation technique. Partial helices were observed in the ascending aorta of 58% of patients after arterial switch. In the pulmonary trunk, mostly parallel flow was seen in healthy volunteers and in patients after arterial switch, whereas vortex formation was present in 88% of patients after atrial redirection. Conclusion Blood flow patterns differ substantially between the groups. In addition to varying mechanics of the coherent pumping ventricles, the absent overall helicity in all patients might be explained by the missing looping of the aorta in transposition.
    Cardiology in the Young 01/2013; · 0.95 Impact Factor
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    ABSTRACT: Purpose:To validate the use of particle traces derived from four-dimensional (4D) flow magnetic resonance (MR) imaging to quantify in vivo the caval flow contribution to the pulmonary arteries (PAs) in patients who had been treated with the Fontan procedure.Materials and Methods:The institutional review boards approved this study, and informed consent was obtained. Twelve healthy volunteers and 10 patients with Fontan circulation were evaluated. The particle trace method consists of creating a region of interest (ROI) on a blood vessel, which is used to emit particles with a temporal resolution of approximately 40 msec. The flow distribution, as a percentage, is then estimated by counting the particles arriving to different ROIs. To validate this method, two independent observers used particle traces to calculate the flow contribution of the PA to its branches in volunteers and compared it with the contribution estimated by measuring net forward flow volume (reference method). After the method was validated, caval flow contributions were quantified in patients. Statistical analysis was performed with nonparametric tests and Bland-Altman plots. P < .05 was considered to indicate a significant difference.Results:Estimation of flow contributions by using particle traces was equivalent to estimation by using the reference method. Mean flow contribution of the PA to the right PA in volunteers was 54% ± 3 (standard deviation) with the reference method versus 54% ± 3 with the particle trace method for observer 1 (P = .4) and 54% ± 4 versus 54% ± 4 for observer 2 (P = .6). In patients with Fontan circulation, 87% ± 13 of the superior vena cava blood flowed to the right PA (range, 63%-100%), whereas 55% ± 19 of the inferior vena cava blood flowed to the left PA (range, 22%-82%).Conclusion:Particle traces derived from 4D flow MR imaging enable in vivo quantification of the caval flow distribution to the PAs in patients with Fontan circulation. This method might allow the identification of patients at risk of developing complications secondary to uneven flow distribution.© RSNA, 2013Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120778/-/DC1.
    Radiology 01/2013; · 6.34 Impact Factor
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    ABSTRACT: AIMS: We investigated the left ventricular (LV) myocardial contractility index-Emax using transoesophageal real-time three-dimensional echocardiography (RT3DE) combined with catheterization. METHODS AND RESULTS: Transoesophageal RT3DE (single beat, X7-2 X matrix, iE33, Philips) was used to obtain real-time LV volumes in pigs. Volumes were integrated with LV pressures from conductance catheterization (CC) with micromanometer to create RT3DE pressure-volume relations. At the same time, CC was used for measuring conventional pressure-volume relations that served as reference. The slope Emax was determined from RT3DE and CC end systolic pressure-volume relations. All measurements were made at rest and during dobutamine infusion. Six pigs were studied. At baseline, the mean ± SD (mmHg/mL) values were Emax-CC 1.86 ± 1.1 and Emax-RT3DE 1.78 ± 1.2 (P = 0.502). On dobutamine, mean Emax-CC was 3.43 ± 1.5 and Emax-RT3DE 3.60 ± 1.23 (P = 0.171). Bland-Altman analysis showed good agreements between the RT3DE and CC-derived Emax for measurements performed at baseline and on dobutamine. CONCLUSION: Emax can be determined from RT3DE integrated with catheterization-derived pressures. RT3DE is a promising method for enhancing clinical applicability of pressure-volume relations for assessment of myocardial contractility.
    European heart journal cardiovascular Imaging. 01/2013;
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    Journal of Cardiovascular Magnetic Resonance 01/2013; 15(1). · 4.44 Impact Factor

Publication Stats

806 Citations
388.43 Total Impact Points

Institutions

  • 2013–2014
    • Charité Universitätsmedizin Berlin
      Berlín, Berlin, Germany
    • University of Nebraska at Omaha
      • Division of Cardiology
      Omaha, NE, United States
    • University of Nebraska Medical Center
      Omaha, Nebraska, United States
  • 2005–2014
    • Deutsches Herzzentrum Berlin
      • Department of Congenital Heart Disease / Pediatric Cardiology
      Berlín, Berlin, Germany
  • 2012
    • Deutsche Gesellschaft für Pädiatrische Kardiologie e.V.
      Düsseldorf, North Rhine-Westphalia, Germany
    • Asklepios Klinik Altona
      Hamburg, Hamburg, Germany
  • 2010–2012
    • King's College London
      • Division of Imaging Sciences and Biomedical Engineering
      Londinium, England, United Kingdom
    • Universitätsmedizin Göttingen
      Göttingen, Lower Saxony, Germany
  • 2011
    • Competence Network for Congenital Heart Defects
      Berlín, Berlin, Germany
  • 2009–2011
    • Deutsches Herzzentrum München
      • Department of Cardiovascular Surgery
      München, Bavaria, Germany
    • Hannover Medical School
      • Department of Cardiothoracic, Transplantation and Vascular Surgery (HTTG)
      Hanover, Lower Saxony, Germany
    • Berlin Heart
      Berlín, Berlin, Germany
    • Guy's and St Thomas' NHS Foundation Trust
      Londinium, England, United Kingdom
  • 2008
    • Universität Heidelberg
      • Department of Cardiac Surgery
      Heidelberg, Baden-Wuerttemberg, Germany
  • 2006
    • German Cancer Research Center
      • Division of Medical and Biological Informatics
      Heidelberg, Baden-Wuerttemberg, Germany
  • 2001–2005
    • University of California, San Francisco
      San Francisco, California, United States
  • 2003
    • Stanford University
      • Department of Radiology
      Stanford, CA, United States