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Fernandes JF, Gill H, Nio A, Faraci A, Galli V, Marlevi D, Bissell M, Ha H, Rajani R, Mortier P, Myerson SG, Dyverfeldt P, Ebbers T, Nordsletten DA, Lamata P. Non-invasive cardiovascular magnetic resonance assessment of pressure recovery distance after aortic valve stenosis. J Cardiovasc Magn Reson 2023; 25:5. [PMID: 36717885 PMCID: PMC9885657 DOI: 10.1186/s12968-023-00914-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 01/05/2023] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND Decisions in the management of aortic stenosis are based on the peak pressure drop, captured by Doppler echocardiography, whereas gold standard catheterization measurements assess the net pressure drop but are limited by associated risks. The relationship between these two measurements, peak and net pressure drop, is dictated by the pressure recovery along the ascending aorta which is mainly caused by turbulence energy dissipation. Currently, pressure recovery is considered to occur within the first 40-50 mm distally from the aortic valve, albeit there is inconsistency across interventionist centers on where/how to position the catheter to capture the net pressure drop. METHODS We developed a non-invasive method to assess the pressure recovery distance based on blood flow momentum via 4D Flow cardiovascular magnetic resonance (CMR). Multi-center acquisitions included physical flow phantoms with different stenotic valve configurations to validate this method, first against reference measurements and then against turbulent energy dissipation (respectively n = 8 and n = 28 acquisitions) and to investigate the relationship between peak and net pressure drops. Finally, we explored the potential errors of cardiac catheterisation pressure recordings as a result of neglecting the pressure recovery distance in a clinical bicuspid aortic valve (BAV) cohort of n = 32 patients. RESULTS In-vitro assessment of pressure recovery distance based on flow momentum achieved an average error of 1.8 ± 8.4 mm when compared to reference pressure sensors in the first phantom workbench. The momentum pressure recovery distance and the turbulent energy dissipation distance showed no statistical difference (mean difference of 2.8 ± 5.4 mm, R2 = 0.93) in the second phantom workbench. A linear correlation was observed between peak and net pressure drops, however, with strong dependences on the valvular morphology. Finally, in the BAV cohort the pressure recovery distance was 78.8 ± 34.3 mm from vena contracta, which is significantly longer than currently accepted in clinical practise (40-50 mm), and 37.5% of patients displayed a pressure recovery distance beyond the end of the ascending aorta. CONCLUSION The non-invasive assessment of the distance to pressure recovery is possible by tracking momentum via 4D Flow CMR. Recovery is not always complete at the ascending aorta, and catheterised recordings will overestimate the net pressure drop in those situations. There is a need to re-evaluate the methods that characterise the haemodynamic burden caused by aortic stenosis as currently clinically accepted pressure recovery distance is an underestimation.
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Affiliation(s)
- Joao Filipe Fernandes
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.
| | - Harminder Gill
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | - Amanda Nio
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | - Alessandro Faraci
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | | | - David Marlevi
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Solna, Sweden
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Malenka Bissell
- Department of Biomedical Imaging Science, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK
| | - Hojin Ha
- Department of Mechanical and Biomedical Engineering, Kangwon National University, Chuncheon, Korea
| | - Ronak Rajani
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
- Cardiovascular Directorate, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | | | - Saul G Myerson
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, UK
| | - Petter Dyverfeldt
- Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Tino Ebbers
- Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - David A Nordsletten
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
- Department of Biomedical Engineering and Cardiac Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Pablo Lamata
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
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Gill H, Fernandes J, Chehab O, Prendergast B, Redwood S, Chiribiri A, Nordsletten D, Rajani R, Lamata P. Evaluation of aortic stenosis: From Bernoulli and Doppler to Navier-Stokes. Trends Cardiovasc Med 2023; 33:32-43. [PMID: 34920129 DOI: 10.1016/j.tcm.2021.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 12/07/2021] [Accepted: 12/07/2021] [Indexed: 02/01/2023]
Abstract
Uni-dimensional Doppler echocardiography data provide the mainstay of quantative assessment of aortic stenosis, with the transvalvular pressure drop a key indicator of haemodynamic burden. Sophisticated methods of obtaining velocity data, combined with improved computational analysis, are facilitating increasingly robust and reproducible measurement. Imaging modalities which permit acquisition of three-dimensional blood velocity vector fields enable angle-independent valve interrogation and calculation of enhanced measures of the transvalvular pressure drop. This manuscript clarifies the fundamental principles of physics that underpin the evaluation of aortic stenosis and explores modern techniques that may provide more accurate means to grade aortic stenosis and inform appropriate management.
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Affiliation(s)
- Harminder Gill
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.
| | - Joao Fernandes
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | - Omar Chehab
- Cardiology Department, Guy's and St. Thomas's Hospital NHS Foundation Trust, London, UK
| | - Bernard Prendergast
- Cardiology Department, Guy's and St. Thomas's Hospital NHS Foundation Trust, London, UK
| | - Simon Redwood
- Cardiology Department, Guy's and St. Thomas's Hospital NHS Foundation Trust, London, UK
| | - Amedeo Chiribiri
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
| | - David Nordsletten
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK; Department of Surgery and Biomedical Engineering, University of Michigan, 2800 Plymouth Rd, 48109, Ann Arbor, MI, USA
| | - Ronak Rajani
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK; Cardiology Department, Guy's and St. Thomas's Hospital NHS Foundation Trust, London, UK
| | - Pablo Lamata
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK
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Shen M, Tastet L, Capoulade R, Arsenault M, Bédard É, Clavel MA, Pibarot P. Effect of bicuspid aortic valve phenotype on progression of aortic stenosis. Eur Heart J Cardiovasc Imaging 2021; 21:727-734. [PMID: 32386199 DOI: 10.1093/ehjci/jeaa068] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 02/12/2020] [Accepted: 03/25/2020] [Indexed: 11/14/2022] Open
Abstract
AIMS To compare the progression of aortic stenosis (AS) in patients with bicuspid aortic valve (BAV) or tricuspid aortic valve (TAV). METHODS AND RESULTS One hundred and forty-one patients with mild-to-moderate AS, recruited prospectively in the PROGRESSA study, were included in this sub-analysis. Baseline clinical, Doppler echocardiography and multidetector computed tomography characteristics were compared between BAV (n = 32) and TAV (n = 109) patients. The 2-year haemodynamic [i.e. peak aortic jet velocity (Vpeak) and mean transvalvular gradient (MG)] and anatomic [i.e. aortic valve calcification density (AVCd) and aortic valve calcification density ratio (AVCd ratio)] progression of AS were compared between the two valve phenotypes. The 2-year progression rate of Vpeak was: 16 (-0 to 40) vs. 17 (3-35) cm/s, P = 0.95; of MG was: 1.8 (-0.7 to 5.8) vs. 2.6 (0.4-4.8) mmHg, P = 0.56; of AVCd was 32 (2-109) vs. 52 (25-85) AU/cm2, P = 0.15; and of AVCd ratio was: 0.08 (0.01-0.23) vs. 0.12 (0.06-0.18), P = 0.16 in patients with BAV vs. TAV. In univariable analyses, BAV was not associated with AS progression (all, P ≥ 0.26). However, with further adjustment for age, AS baseline severity, and several risk factors (i.e. sex, history of hypertension, creatinine level, diabetes, metabolic syndrome), BAV was independently associated with faster haemodynamic (Vpeak: β = 0.31, P = 0.02) and anatomic (AVCd: β = 0.26, P = 0.03 and AVCd ratio: β = 0.26, P = 0.03) progression of AS. CONCLUSION In patients with mild-to-moderate AS, patients with BAV have faster haemodynamic and anatomic progression of AS when compared to TAV patients with similar age and risk profile. This study highlights the importance and necessity to closely monitor patients with BAV and to adequately control and treat their risk factors. CLINICAL TRIAL REGISTRATION https://clinicaltrials.gov Unique identifier: NCT01679431.
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Affiliation(s)
- Mylène Shen
- Department of Medicine, Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval/Quebec Heart & Lung Institute-Laval University, 2725 Chemin Sainte-Foy, Quebec City, Quebec G1V 4G5, Canada
| | - Lionel Tastet
- Department of Medicine, Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval/Quebec Heart & Lung Institute-Laval University, 2725 Chemin Sainte-Foy, Quebec City, Quebec G1V 4G5, Canada
| | - Romain Capoulade
- Inserm UMR 1087/CNRS UMR 6291, IRS-UN, L'institut du thorax, CHU Nantes, UNIV Nantes, 8 quai Moncousu, BP 70721, 44007 Nantes Cedex 1, France
| | - Marie Arsenault
- Department of Medicine, Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval/Quebec Heart & Lung Institute-Laval University, 2725 Chemin Sainte-Foy, Quebec City, Quebec G1V 4G5, Canada
| | - Élisabeth Bédard
- Department of Medicine, Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval/Quebec Heart & Lung Institute-Laval University, 2725 Chemin Sainte-Foy, Quebec City, Quebec G1V 4G5, Canada
| | - Marie-Annick Clavel
- Department of Medicine, Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval/Quebec Heart & Lung Institute-Laval University, 2725 Chemin Sainte-Foy, Quebec City, Quebec G1V 4G5, Canada
| | - Philippe Pibarot
- Department of Medicine, Institut universitaire de cardiologie et de pneumologie de Québec-Université Laval/Quebec Heart & Lung Institute-Laval University, 2725 Chemin Sainte-Foy, Quebec City, Quebec G1V 4G5, Canada
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Gavazzoni M, Zuber M, Taramasso M, Maisano F, Jenni R. A Double-Envelope Mitral Inflow Spectral Doppler Profile After MitraClip. J Cardiothorac Vasc Anesth 2021; 35:3440-3444. [PMID: 34172367 DOI: 10.1053/j.jvca.2021.05.039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 05/17/2021] [Indexed: 11/11/2022]
Affiliation(s)
- Mara Gavazzoni
- Heart Center, Zürich University Hospital, University of Zürich, Zürich, Switzerland.
| | - Michel Zuber
- Ambulatory Heart Clinic, Othmarsingen, Switzerland
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Abbas AE, Mando R, Hanzel G, Goldstein J, Shannon F, Pibarot P. Hemodynamic principles of prosthetic aortic valve evaluation in the transcatheter aortic valve replacement era. Echocardiography 2020; 37:738-757. [DOI: 10.1111/echo.14663] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/28/2020] [Accepted: 03/29/2020] [Indexed: 12/01/2022] Open
Affiliation(s)
- Amr E. Abbas
- Beaumont Health Royal Oak Michigan
- Oakland University William Beaumont School of Medicine Auburn Hills Michigan
| | | | - George Hanzel
- Beaumont Health Royal Oak Michigan
- Oakland University William Beaumont School of Medicine Auburn Hills Michigan
| | - James Goldstein
- Beaumont Health Royal Oak Michigan
- Oakland University William Beaumont School of Medicine Auburn Hills Michigan
| | - Francis Shannon
- Beaumont Health Royal Oak Michigan
- Oakland University William Beaumont School of Medicine Auburn Hills Michigan
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6
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Cobey FC, Khoche S. Double Envelope With Continuous Wave Doppler: Not an Artifact. J Cardiothorac Vasc Anesth 2019; 33:3223-3227. [DOI: 10.1053/j.jvca.2019.05.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 05/31/2019] [Indexed: 11/11/2022]
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7
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Mittal TK, Reichmuth L, Bhattacharyya S, Jain M, Baltabaeva A, Rahman Haley S, Mirsadraee S, Panoulas V, Kabir T, Nicol ED, Dalby M, Long Q. Inconsistency in aortic stenosis severity between CT and echocardiography: prevalence and insights into mechanistic differences using computational fluid dynamics. Open Heart 2019; 6:e001044. [PMID: 31413845 PMCID: PMC6667934 DOI: 10.1136/openhrt-2019-001044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 06/02/2019] [Accepted: 07/04/2019] [Indexed: 02/05/2023] Open
Abstract
Objectives The aims of this study were to evaluate the inconsistency of aortic stenosis (AS) severity between CT aortic valve area (CT-AVA) and echocardiographic Doppler parameters, and to investigate potential underlying mechanisms using computational fluid dynamics (CFD). Methods A total of 450 consecutive eligible patients undergoing transcatheter AV implantation assessment underwent CT cardiac angiography (CTCA) following echocardiography. CT-AVA derived by direct planimetry and echocardiographic parameters were used to assess severity. CFD simulation was performed in 46 CTCA cases to evaluate velocity profiles. Results A CT-AVA>1 cm2 was present in 23% of patients with echocardiographic peak velocity≥4 m/s (r=−0.33) and in 15% patients with mean Doppler gradient≥40 mm Hg (r=−0.39). Patients with inconsistent severity grading between CT and echocardiography had higher stroke volume index (43 vs 38 mL/m2, p<0.003) and left ventricular outflow tract (LVOT) flow rate (235 vs 192 cm3/s, p<0.001). CFD simulation revealed high flow, either in isolation (p=0.01), or when associated with a skewed velocity profile (p=0.007), as the main cause for inconsistency between CT and echocardiography. Conclusion Severe AS by Doppler criteria may be associated with a CT-AVA>1 cm2 in up to a quarter of patients. CFD demonstrates that haemodynamic severity may be exaggerated on Doppler analysis due to high LVOT flow rates, with or without skewed velocity profiles, across the valve orifice. These factors should be considered before making a firm diagnosis of severe AS and evaluation with CT can be helpful.
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Affiliation(s)
- Tarun Kumar Mittal
- Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK.,Faculty of Medicine, NHLI, Imperial College London, London, United Kingdom
| | - Luise Reichmuth
- Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK
| | - Sanjeev Bhattacharyya
- Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK
| | - Manish Jain
- Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK
| | - Aigul Baltabaeva
- Cardiology, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom
| | - Shelley Rahman Haley
- Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK
| | - Saeed Mirsadraee
- Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK.,Faculty of Medicine, NHLI, Imperial College London, London, United Kingdom
| | - Vasileios Panoulas
- Faculty of Medicine, NHLI, Imperial College London, London, United Kingdom.,Cardiology, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom
| | - Tito Kabir
- Cardiology, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom
| | - Edward David Nicol
- Heart Assessment, Royal Brompton and Harefield NHS Foundation Trust, London, Middlesex, UK.,Faculty of Medicine, NHLI, Imperial College London, London, United Kingdom
| | - Miles Dalby
- Faculty of Medicine, NHLI, Imperial College London, London, United Kingdom.,Cardiology, Royal Brompton and Harefield NHS Foundation Trust, London, United Kingdom
| | - Quan Long
- Institute of Bioengineering, Brunel University, Uxbridge, Middlesex, UK
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8
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Abbas AE, Pibarot P. Hemodynamic characterization of aortic stenosis states. Catheter Cardiovasc Interv 2019; 93:1002-1023. [PMID: 30790429 DOI: 10.1002/ccd.28146] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 01/29/2019] [Indexed: 11/12/2022]
Abstract
Aortic stenosis (AS) has become an increasingly prevalent clinical condition, as a result of the "greying of the population", the widespread application of sophisticated diagnostic tools including non-invasive imaging and invasive techniques, and the advent of minimally invasive surgical and percutaneous valve therapies. The diagnosis of severe AS traditionally has relied on the assessment of the mean transvalvular gradient (ΔPmean ) and aortic valve area (AVA) by either echocardiography or catheterization. However, other hemodynamic variables as flow, pressure recovery, and jet eccentricity also play a major role in determining the final hemodynamic state of AS. Moreover, mismatch between ΔPmean and AVA as in low flow low gradient AS and discordance between catheterization and echocardiographic studies in grading severity of AS have increased the complexity of AS diagnosis. The present case-based treatise emphasizes a multi-modality approach to delineation of the hemodynamic pathophysiology of different AS states. KEY POINTS: Reduction in the aortic valve area, flow across the aortic valve, and direction of the aortic stenosis jet determine the pressure gradient generated across the aortic valve in patients with aortic stenosis. Discordance between echo and catheterization maximum gradients is related to the inherent temporal differences between the times of their acquisition. Discordance between echo and catheterization mean gradients is related to pressure recovery and assumptions in the application of Bernoulli equation to estimate the aortic valve gradient. Pressure recovery relates to the ratio of the aortic valve area and ascending aortic diameter as well as the jet direction. Mismatch between area and gradient criteria for aortic stenosis severity may occur with or without concordance between echocardiographic and catheterization data. Errors of measurement should be excluded prior to assuming any mismatch or discordance between the data. Area gradient mismatch occurs when the aortic valve area is in the severe range, while the gradient is in the non-severe range as in low flow low gradient aortic stenosis. Reverse area gradient mismatch occurs when the gradient is in the severe range, while the aortic valve area is in the non-severe range as in congenital aortic stenosis with an eccentric jet.
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Affiliation(s)
- Amr E Abbas
- Department of Cardiovascular Medicine, Beaumont Health, Royal Oak, Michigan.,Department of Internal Medicine, Oakland University William Beaumont School of Medicine, Auburn Hills, Michigan
| | - Philippe Pibarot
- Department of Medicine, Laval University, Quebec City, QC, Canada
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Fernando RJ, Garner C, Slaughter TF. A Review of the 2017 American Society of Echocardiography Guidelines for Evaluation of Aortic Stenosis: Considerations for Perioperative Echocardiography. J Cardiothorac Vasc Anesth 2018; 32:1800-1814. [PMID: 29735221 DOI: 10.1053/j.jvca.2018.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Rohesh J Fernando
- Cardiothoracic Section, Department of Anesthesiology, Wake Forest School of Medicine, Winston Salem, NC.
| | - Chandrika Garner
- Cardiothoracic Section, Department of Anesthesiology, Wake Forest School of Medicine, Winston Salem, NC
| | - Thomas F Slaughter
- Cardiothoracic Section, Department of Anesthesiology, Wake Forest School of Medicine, Winston Salem, NC
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10
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Shen M, Tastet L, Capoulade R, Larose É, Bédard É, Arsenault M, Chetaille P, Dumesnil JG, Mathieu P, Clavel MA, Pibarot P. Effect of age and aortic valve anatomy on calcification and haemodynamic severity of aortic stenosis. Heart 2016; 103:32-39. [DOI: 10.1136/heartjnl-2016-309665] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/21/2016] [Accepted: 07/13/2016] [Indexed: 11/03/2022] Open
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Turbulent Kinetic Energy Measurement Using Phase Contrast MRI for Estimating the Post-Stenotic Pressure Drop: In Vitro Validation and Clinical Application. PLoS One 2016; 11:e0151540. [PMID: 26978529 PMCID: PMC4792455 DOI: 10.1371/journal.pone.0151540] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 02/29/2016] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Although the measurement of turbulence kinetic energy (TKE) by using magnetic resonance imaging (MRI) has been introduced as an alternative index for quantifying energy loss through the cardiac valve, experimental verification and clinical application of this parameter are still required. OBJECTIVES The goal of this study is to verify MRI measurements of TKE by using a phantom stenosis with particle image velocimetry (PIV) as the reference standard. In addition, the feasibility of measuring TKE with MRI is explored. METHODS MRI measurements of TKE through a phantom stenosis was performed by using clinical 3T MRI scanner. The MRI measurements were verified experimentally by using PIV as the reference standard. In vivo application of MRI-driven TKE was explored in seven patients with aortic valve disease and one healthy volunteer. Transvalvular gradients measured by MRI and echocardiography were compared. RESULTS MRI and PIV measurements of TKE are consistent for turbulent flow (0.666 < R2 < 0.738) with a mean difference of -11.13 J/m3 (SD = 4.34 J/m3). Results of MRI and PIV measurements differ by 2.76 ± 0.82 cm/s (velocity) and -11.13 ± 4.34 J/m3 (TKE) for turbulent flow (Re > 400). The turbulence pressure drop correlates strongly with total TKE (R2 = 0.986). However, in vivo measurements of TKE are not consistent with the transvalvular pressure gradient estimated by echocardiography. CONCLUSIONS These results suggest that TKE measurement via MRI may provide a potential benefit as an energy-loss index to characterize blood flow through the aortic valve. However, further clinical studies are necessary to reach definitive conclusions regarding this technique.
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