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Bollache E, Guzzardi DG, Sattari S, Olsen KE, Di Martino ES, Malaisrie SC, van Ooij P, Collins J, Carr J, McCarthy PM, Markl M, Barker AJ, Fedak PWM. Aortic valve-mediated wall shear stress is heterogeneous and predicts regional aortic elastic fiber thinning in bicuspid aortic valve-associated aortopathy. J Thorac Cardiovasc Surg 2018; 156:2112-2120.e2. [PMID: 30060930 DOI: 10.1016/j.jtcvs.2018.05.095] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Revised: 05/03/2018] [Accepted: 05/26/2018] [Indexed: 12/16/2022]
Abstract
OBJECTIVES The objectives of this study were to investigate an association between the magnitude of flow-mediated aortic wall shear stress (WSS) and medial wall histopathology in patients with bicuspid aortic valve (BAV) with aortopathy. METHODS Patients with BAV (n = 27; 52 ± 15 years; 3 women; proximal thoracic aorta diameter = 4.4 ± 0.7 and 4.6 ± 0.5 cm) who underwent prophylactic aortic resection received preoperative 3-dimensional time-resolved phase-contrast magnetic resonance imaging with 3-dimensional velocity encoding to quantify WSS relative to a population of healthy age- and sex-matched tricuspid aortic valve control participants (n = 20). Quantitative histopathology was conducted on BAV aorta tissue samples resected at surgery (n = 93), and correlation was performed between elastic fiber thickness and in vivo aortic WSS as continuous variables. Validation of elastic fiber thickness was achieved by correlation relative to tissue stiffness determined using biaxial biomechanical testing (n = 22 samples). RESULTS Elastic fibers were thinner and WSS was higher along the greater curvature compared with other circumferential regions (vs anterior wall: P = .003 and P = .0001, respectively; lesser curvature: both P = .001). Increased regional WSS was associated with decreased elastic fiber thickness (r = -0.25; P = .02). Patient stratification with subanalysis showed an increase in the correlation between WSS and histopathology with aortic valve stenosis (r = -0.36; P = .002) and smaller aortic diameters (<4.5 cm: r = -0.39; P = .03). Elastic fiber thinning was associated with circumferential stiffness (r = -0.41; P = .06). CONCLUSIONS For patients with BAV, increased aortic valve-mediated WSS is significantly associated with elastic fiber thinning, particularly with aortic valve stenosis and in earlier stages of aortopathy. Elastic fiber thinning correlates with impaired tissue biomechanics. These novel findings further implicate valve-mediated hemodynamics in the progression of BAV aortopathy.
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Schäfer M, Truong U, Ivy DD, Fonseca B, Malone L, DiMaria M, Barker AJ, Vargas D, Hunter KS, Jone PN, Browne LP. Children with kawasaki disease present elevated stiffness of great arteries: Phase-contrast MRI study. J Magn Reson Imaging 2018; 48:1228-1236. [PMID: 29707843 DOI: 10.1002/jmri.26167] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 04/11/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Patients with diagnosed Kawasaki disease (KD) are known to develop extracardiac vascular lesions and are prone to accelerated stiffening of medium-size arteries. PURPOSE To noninvasively evaluate great vessel (central aorta and main pulmonary artery (MPA)) stiffness using phase-contrast MRI (PC-MRI). STUDY TYPE Retrospective review. SUBJECTS Thirty-three patients with previously diagnosed KD and 15 control subjects underwent PC-MRI evaluation. FIELD STRENGTH/SEQUENCE A free-breathing PC-MRI sequence was applied with Cartesian encoding and retrospective sorting using a 1.5 or 3.0T system. ASSESSMENT We evaluated regionally specific vessel stiffness using pulse-wave velocity (PWV) and relative area change (RAC) at the ascending aorta, descending aorta, and MPA. STATISTICAL TESTS Hemodynamics among patients with KD and controls were compared using Student's t-test, Wilcoxon Rank-sum, and χ2 . Additional group-specific comparisons were performed using Kruskal-Wallis or one-way analysis of variance (ANOVA). RESULTS Patients with KD showed elevated PWV in both ascending (5.0 ± 1.2 vs. 2.4 ± 0.5, P < 0.001) and descending aorta (4.4 ± 2.1 vs. 2.8 ± 0.8, P < 0.001). RAC was correspondingly reduced in both segments (both P < 0.01). PWV measured in MPA was increased in KD patients (2.2 ± 0.5 vs. 1.5 ± 0.6, P = 0.045) while the RAC was reduced (34 ± 6 vs. 47 ± 3, P = 0.045). There were no associations between considered vessel stiffness indices and respective ventricular size and function, functional indices, and no correlations were observed with KD severity markers. DATA CONCLUSION Patients with KD have elevated great vessel stiffness measured at the chronic stage of the disease. Accelerated stiffness process does not appear to affect biventricular function in youth Level of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1228-1236.
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Barker AJ, Markl M, Fedak PWM. Assessing wall stresses in bicuspid aortic valve-associated aortopathy: Forecasting the perfect storm? J Thorac Cardiovasc Surg 2018; 156:471-472. [PMID: 29666014 DOI: 10.1016/j.jtcvs.2018.03.092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 03/23/2018] [Indexed: 02/06/2023]
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Schäfer M, Ivy DD, Barker AJ, Kheyfets V, Shandas R, Abman SH, Hunter KS, Truong U. Characterization of CMR-derived haemodynamic data in children with pulmonary arterial hypertension. Eur Heart J Cardiovasc Imaging 2018; 18:424-431. [PMID: 27444679 DOI: 10.1093/ehjci/jew152] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 06/28/2016] [Indexed: 12/30/2022] Open
Abstract
Aims Paediatric pulmonary arterial hypertension (PAH) is manifested as increased arterial pressure and vascular resistive changes followed by progressive arterial stiffening. The aim of this study was to characterize regional flow haemodynamic patterns and markers of vascular stiffness in the proximal pulmonary arteries of paediatric PAH patients, and to explore the association with right ventricular (RV) function. Methods and results Forty paediatric PAH patients and 26 age- and size-matched controls underwent cardiac magnetic resonance studies in order to compute time-resolved wall shear stress metrics, oscillatory shear index (OSI), and vascular strain as measured by relative area change (RAC), and RV volumetric and functional parameters. Phase-contrast imaging planes were positioned perpendicular to the mid-main and right pulmonary arteries (MPA and RPA, respectively). Compared with controls, the PAH group had decreased systolic wall shear stress (dyne cm-2) and RAC (%) in both MPA (WSSsys: 6.5 vs. 4.3, P < 0.0001; RAC: 36 vs. 25, P < 0.0001) and RPA (WSSsys: 11.2 vs. 7.3, P < 0.0001; strain: 37 vs. 30, P < 0.05). The OSI was significantly higher in the MPA of PAH subjects (0.46 vs. 0.17, P < 0.05). WSS measured in the MPA correlated positively with RAC (r = 0.63, P < 0.0001) and RV ejection fraction (%) (r = 0.63, P < 0.0001). Conclusion Wall shear stress, the principal haemodynamic force driving endothelial functional changes, is severely decreased in paediatric PAH patients and correlates with increased stiffness in the proximal pulmonary vasculature and reduced RV function.
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Raghav V, Barker AJ, Mangiameli D, Mirabella L, Markl M, Yoganathan AP. Valve mediated hemodynamics and their association with distal ascending aortic diameter in bicuspid aortic valve subjects. J Magn Reson Imaging 2018; 47:246-254. [PMID: 28390180 PMCID: PMC5632568 DOI: 10.1002/jmri.25719] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 03/16/2017] [Indexed: 02/05/2023] Open
Abstract
PURPOSE Valve mediated hemodynamics have been postulated to contribute to pathology of the ascending aorta (AAo). The objective of this study is to assess the association of aortic valve morphology and hemodynamics with downstream AAo size in subjects with bicuspid aortic valve (BAV) disease. MATERIALS AND METHODS Four-dimensional flow MRI at 1.5 or 3 Tesla was used to evaluate the hemodynamics in the proximal AAo of 52 subjects: size-matched controls with tricuspid aortic valves (n = 24, mid ascending aorta [MAA] diameter = 38.0 ± 4.9 mm) and BAV patients with aortic dilatation (n = 14 right and left coronary leaflet fusion [RL]-BAV, MAA diameter = 38.1 ± 5.3 mm; n = 14 right and noncoronary leaflet fusion [RN]-BAV, MAA diameter = 36.5 ± 6.6 mm). A validated semi-automated technique was used to evaluate hemodynamic metrics (flow angle, flow displacement, and jet quadrant) and valve morphology (orifice circularity) for all subjects. Regression analysis of these metrics to AAo diameter was performed. RESULTS RN-BAV subjects displayed a stronger correlation between hemodynamic metrics in the proximal AAo with diameter in the distal AAo compared with size-matched tricuspid aortic valve (TAV) controls and RL-BAV subjects. The distal AAo diameter was found to be strongly correlated to the upstream flow displacement (R2adjusted = 0.75) and flow angle (R2adjusted = 0.66) measured at the sino-tubular junction (STJ). Orifice circularity was also strongly correlated (R2adjusted = 0.53) to the distal AAo diameter in RN-BAV subjects. For TAV controls and RL-BAV subjects, correlations were weaker (R2adjusted < 0.2). CONCLUSION Hemodynamics in the STJ were strongly correlated to the distal AAo diameter for the RN-BAV subjects. Hemodynamic metrics were more strongly correlated to the downstream aortic size when compared with valve morphology metrics. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:246-254.
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Schäfer M, Barker AJ, Kheyfets V, Stenmark KR, Crapo J, Yeager ME, Truong U, Buckner JK, Fenster BE, Hunter KS. Helicity and Vorticity of Pulmonary Arterial Flow in Patients With Pulmonary Hypertension: Quantitative Analysis of Flow Formations. J Am Heart Assoc 2017; 6:JAHA.117.007010. [PMID: 29263034 PMCID: PMC5779020 DOI: 10.1161/jaha.117.007010] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Background Qualitative and quantitative flow hemodynamic indexes have been shown to reflect right ventricular (RV) afterload and function in pulmonary hypertension (PH). We aimed to quantify flow hemodynamic formations in pulmonary arteries using 4‐dimensional flow cardiac magnetic resonance imaging and the spatial velocity derivatives helicity and vorticity in a heterogeneous PH population. Methods and Results Patients with PH (n=35) and controls (n=10) underwent 4‐dimensional flow magnetic resonance imaging study for computation of helicity and vorticity in the main pulmonary artery (MPA), the right pulmonary artery, and the RV outflow tract. Helicity and vorticity were correlated with standard RV volumetric and functional indexes along with MPA stiffness assessed by measuring relative area change. Patients with PH had a significantly decreased helicity in the MPA (8 versus 32 m/s2; P<0.001), the right pulmonary artery (24 versus 50 m/s2; P<0.001), and the RV outflow tract–MPA unit (15 versus 42 m/s2; P<0.001). Vorticity was significantly decreased in patients with PH only in the right pulmonary artery (26 versus 45 1/s; P<0.001). Total helicity computed correlated with the cardiac magnetic resonance imaging–derived ventricular‐vascular coupling (−0.927; P<0.000), the RV ejection fraction (0.865; P<0.0001), cardiac output (0.581; P<0.0001), mean pulmonary arterial pressure (−0.581; P=0.0008), and relative area change measured at the MPA (0.789; P<0.0001). Conclusions The flow hemodynamic character in patients with PH assessed via quantitative analysis is considerably different when compared with healthy and normotensive controls. A strong association between helicity in pulmonary arteries and ventricular‐vascular coupling suggests a relationship between the mechanical and flow hemodynamic domains.
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Geiger J, Rahsepar AA, Suwa K, Powell A, Ghasemiesfe A, Barker AJ, Collins JD, Carr JC, Markl M. 4D flow MRI, cardiac function, and T 1 -mapping: Association of valve-mediated changes in aortic hemodynamics with left ventricular remodeling. J Magn Reson Imaging 2017; 48:121-131. [PMID: 29206322 DOI: 10.1002/jmri.25916] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 11/20/2017] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Patients with bicuspid aortic valve (BAV) show altered hemodynamics in the ascending aorta that can be assessed by 4D flow MRI. PURPOSE Comprehensive cardiac MRI was applied to test the hypothesis that BAV-mediated changes in aortic hemodynamics (wall shear stress [WSS] and velocity) are associated with parameters of left ventricular (LV) remodeling. STUDY TYPE Retrospective data analysis. POPULATION Forty-nine BAV patients (mean age = 50.2 ± 13.5, 62% male). FIELD STRENGTH/SEQUENCE Balanced steady-state free precession (bSSFP)-CINE, pre- and postcontrast T1 mapping with modified Look-Locker inversion recovery (MOLLI), time-resolved 3D phase-contrast (PC) MRI with three-directional velocity encoding (4D flow MRI) at 1.5 and 3T. ASSESSMENT Quantification of LV volumetric data and myocardial mass, extracellular volume fraction (ECV), aortic valve stenosis (AS), and regurgitation (AR). 3D aortic segmentation, quantification of peak systolic velocities, and 3D WSS in the ascending aorta (AAo), arch, and descending aorta (DAo). STATISTICAL TESTS Two-sided nonpaired t-test to compare subgroups. Pearson correlation coefficient for correlations between aortic hemodynamics and LV parameters. RESULTS Of the 49 BAV patients, 35 had aortic valve dysfunction (AS [n = 7], AR [n = 16], both AS and AR [n = 12]). Mean systolic WSS in the AAo, peak systolic velocities in the AAo and arch, and LV mass were significantly higher (P < 0.001) in the AS/AR group compared to the patients without AS/AR. In the complete group, we observed significant relationships between increased LV mass and elevated peak systolic velocity (r = 0.57, r = 0.58; P < 0.001) and WSS in the AAo and arch, respectively (r = 0.54, r = 0.46; P < 0.001). We detected an association between ECV and WSS in the AAo (r = 0.38, P = 0.02). These relations did not hold true for patients without AV dysfunction. DATA CONCLUSION AS and AR in BAV patients have a major impact on elevated aortic peak velocities and WSS that were associated with parameters of LV remodeling. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017.
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Bollache E, Fedak PWM, van Ooij P, Rahman O, Malaisrie SC, McCarthy PM, Carr JC, Powell A, Collins JD, Markl M, Barker AJ. Perioperative evaluation of regional aortic wall shear stress patterns in patients undergoing aortic valve and/or proximal thoracic aortic replacement. J Thorac Cardiovasc Surg 2017; 155:2277-2286.e2. [PMID: 29248286 DOI: 10.1016/j.jtcvs.2017.11.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 10/11/2017] [Accepted: 11/06/2017] [Indexed: 10/18/2022]
Abstract
OBJECTIVES To assess in patients with aortopathy perioperative changes in thoracic aortic wall shear stress (WSS), which is known to affect arterial remodeling, and the effects of specific surgical interventions. METHODS Presurgical and postsurgical aortic 4D flow MRI were performed in 33 patients with aortopathy (54 ± 14 years; 5 women; sinus of Valsalva (d_SOV)/midascending aortic (d_MAA) diameters = 44 ± 5/45 ± 6 mm) scheduled for aortic valve (AVR) and/or root (ARR) replacement. Control patients with aortopathy who did not have surgery were matched for age, sex, body size, and d_MAA (n = 20: 52 ± 14 years; 3 women; d_SOV/d_MAA = 42 ± 4/42 ± 4 mm). Regional aortic 3D systolic peak WSS was calculated. An atlas of WSS normal values was used to quantify the percentage of at-risk tissue area with abnormally high WSS, excluding the area to be resected/graft. RESULTS Peak WSS and at-risk area showed low interobserver variability (≤0.09 [-0.3; 0.5] Pa and 1.1% [-7%; 9%], respectively). In control patients, WSS was stable over time (follow-up-baseline differences ≤0.02 Pa and 0.0%, respectively). Proximal aortic WSS decreased after AVR (n = 5; peak WSS difference ≤-0.41 Pa and at-risk area ≤-10%, P < .05 vs controls). WSS was increased after ARR in regions distal to the graft (peak WSS difference ≥0.16 Pa and at-risk area ≥4%, P < .05 vs AVR). Follow-up duration had no significant effects on these WSS changes, except when comparing ascending aortic peak WSS between ARR and AVR (P = .006). CONCLUSIONS Serial perioperative 4D flow MRI investigations showed distinct patterns of postsurgical changes in aortic WSS, which included both reductions and translocations. Larger longitudinal studies are warranted to validate these findings with clinical outcomes and prediction of risk of future aortic events.
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Schäfer M, Kheyfets VO, Barker AJ, Stenmark K, Hunter KS, McClatchey PM, Buckner JK, Reece TB, Jazaeri O, Fenster BE. Reduced shear stress and associated aortic deformation in the thoracic aorta of patients with chronic obstructive pulmonary disease. J Vasc Surg 2017; 68:246-253. [PMID: 28986100 DOI: 10.1016/j.jvs.2017.06.110] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 06/23/2017] [Indexed: 01/16/2023]
Abstract
OBJECTIVE Central aortic stiffness and chronic obstructive pulmonary disease (COPD) are associated with increased incidence of devastating aortopathies. However, the exact mechanism leading to elevated aortic stiffness in patients with COPD is unknown. The purpose of this study was to quantify flow and shear hemodynamic indices, known markers of vascular remodeling, in the thoracic aorta of patients with mild to moderate COPD (n = 16) and to compare these results with an age-matched control group (n = 10). METHODS Four-dimensional flow magnetic resonance imaging has been applied to measure hemodynamic wall shear stress (WSS) at four specific planes along the ascending aorta, aortic arch, and proximal descending aorta for all subjects. Peak systolic WSS and time-averaged WSS, which respectively reflect magnitude and temporal shear variability, were calculated at standardized planes. Aortic deformation was measured by means of relative area change (RAC) at the midlevel of the ascending and descending aorta. RESULTS Compared with controls, patients with COPD had significantly reduced RAC in the mid ascending aorta (9% vs 18%; P < .0001) and descending aorta (15% vs 19%; P = .0206). Peak systolic WSS in COPD patients was significantly reduced in all considered planes, with the most dramatic difference occurring in the descending aorta (0.46 vs 0.86 N/m2; P < .0001). Peak systolic WSS and time-averaged WSS were both significantly correlated with aortic RAC at each evaluated plane. CONCLUSIONS Reduced flow shear metrics assessed at specific aortic regions correlated with RAC, a marker of aortic stiffness. Reduced hemodynamic WSS may then contribute to central aortic stiffening and perpetuate the risk for development of severe aortopathy.
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Shen X, Schnell S, Barker AJ, Suwa K, Tashakkor L, Jarvis K, Carr JC, Collins JD, Prabhakaran S, Markl M. Voxel-by-voxel 4D flow MRI-based assessment of regional reverse flow in the aorta. J Magn Reson Imaging 2017; 47:1276-1286. [PMID: 28925047 DOI: 10.1002/jmri.25862] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 09/07/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Complex and reverse flow in the aorta has been implicated in aneurysm development and stroke via retrograde embolization. PURPOSE To evaluate global and regional differences between standard 2D plane-based and volumetric voxel-based quantification of regional forward/reverse flow, and reverse flow fraction (RFF) in the aorta. STUDY TYPE Retrospective. SUBJECTS In all, 35 subjects: 10 healthy controls (age: 57 ± 7 years, nine male), nine patients without aortic valve regurgitation (AR) (age: 63 ± 10 years, seven male), six patients with mild AR (age: 66 ± 6 years, five male), and 10 with moderate or severe AR (age: 60 ± 16 years, eight male). FIELD STRENGTH/SEQUENCE 4D flow MRI (3T and 1.5T) was employed to acquire 3D blood flow velocities with entire thoracic aorta in all subjects. ASSESSMENT Data analysis included standard 2D plane-based quantification of forward/reverse flow, and RFF-plane. In addition, a new semiautomatic workflow based on 3D segmentation and extraction of an aorta centerline was developed for voxel-by-voxel visualization (forward/reverse flow and RFF-voxel maps) and quantification of regional voxel-by-voxel forward/reverse flow in the entire thoracic aorta. STATISTICAL TESTS Kruskal-Wallis tests were performed to test for differences between groups. A two-sample t-test or Wilcoxon rank sum test was used to compare voxel-based and plane-based results. RESULTS Semiautomatic plane-based analysis showed excellent agreement with standard manual plane-based analysis for net flow and RFF-plane (RFF-plane: y = 0.99x-0.0, net flow: y = 1.00x-0.21, R > 0.99, P < 0.0001). Voxel-by-voxel maps demonstrated marked regional flow reversal in the ascending aorta in all patients and RFF-voxel was significantly increased (P < 0.001) compared to RFF-plane for all four groups, with the most pronounced differences for mild AR (18.0 ± 15.2% vs. 4.7 ± 5.4%). Voxel-based flow and RFF-voxel along the aorta showed areas with marked regional flow reversal (eg, vortex flow) compared to plane-based analysis. DATA CONCLUSION Voxel-based analysis demonstrated regional flow reversal that was not detected by plane-based analysis. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1276-1286.
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van Ooij P, Markl M, Collins JD, Carr JC, Rigsby C, Bonow RO, Malaisrie SC, McCarthy PM, Fedak PWM, Barker AJ. Aortic Valve Stenosis Alters Expression of Regional Aortic Wall Shear Stress: New Insights From a 4-Dimensional Flow Magnetic Resonance Imaging Study of 571 Subjects. J Am Heart Assoc 2017; 6:JAHA.117.005959. [PMID: 28903936 PMCID: PMC5634265 DOI: 10.1161/jaha.117.005959] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Background Wall shear stress (WSS) is a stimulus for vessel wall remodeling. Differences in ascending aorta (AAo) hemodynamics have been reported between bicuspid aortic valve (BAV) and tricuspid aortic valve patients with aortic dilatation, but the confounding impact of aortic valve stenosis (AS) is unknown. Methods and Results Five hundred seventy‐one subjects underwent 4‐dimensional flow magnetic resonance imaging in the thoracic aorta (210 right‐left BAV cusp fusions, 60 right‐noncoronary BAV cusp fusions, 245 tricuspid aortic valve patients with aortic dilatation, and 56 healthy controls). There were 166 of 515 (32%) patients with AS. WSS atlases were created to quantify group‐specific WSS patterns in the AAo as a function of AS severity. In BAV patients without AS, the different cusp fusion phenotypes resulted in distinct differences in eccentric WSS elevation: right‐left BAV patients exhibited increased WSS by 9% to 34% (P<0.001) at the aortic root and along the entire outer curvature of the AAo whereas right‐noncoronary BAV patients showed 30% WSS increase (P<0.001) at the distal portion of the AAo. WSS in tricuspid aortic valve patients with aortic dilatation patients with no AS was significantly reduced by 21% to 33% (P<0.01) in 4 of 6 AAo regions. In all patient groups, mild, moderate, and severe AS resulted in a marked increase in regional WSS (P<0.001). Moderate‐to‐severe AS further increased WSS magnitude and variability in the AAo. Differences between valve phenotypes were no longer apparent. Conclusions AS significantly alters aortic hemodynamics and WSS independent of aortic valve phenotype and over‐rides previously described flow patterns associated with BAV and tricuspid aortic valve with aortic dilatation. Severity of AS must be considered when investigating valve‐mediated aortopathy.
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Disha K, Dubslaff G, Rouman M, Fey B, Borger MA, Barker AJ, Kuntze T, Girdauskas E. Evidence of subannular and left ventricular morphological differences in patients with bicuspid versus tricuspid aortic valve stenosis: magnetic resonance imaging-based analysis. Interact Cardiovasc Thorac Surg 2017; 24:369-376. [PMID: 28040769 DOI: 10.1093/icvts/ivw363] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Accepted: 09/26/2016] [Indexed: 11/12/2022] Open
Abstract
Objectives Prospective analysis of left ventricular (LV) morphological/functional parameters in patients with bicuspid versus tricuspid aortic valve (TAV) stenosis undergoing aortic valve replacement (AVR) surgery. Methods A total of 190 consecutive patients with BAV ( n = 154) and TAV stenosis ( n = 36) (mean age 61 ± 8 years, 65% male) underwent AVR ± concomitant aortic surgery from January 2012 through May 2015. All patients underwent preoperative cardiac magnetic resonance imaging in order to evaluate: (i) left ventricular outflow tract (LVOT) dimensions, (ii) length of anterior mitral leaflet (AML), (iii) end-systolic and end-diastolic LV wall thickness, (iv) LV area, (v) LV end-systolic and end-diastolic diameters (LVESD, LVEDD), (vi) LV end-diastolic and end-systolic volumes (LVEDV, LVESV) and (vii) maximal diameter of aortic root. These parameters were compared between the two study groups. Results The LVOT diameter was significantly larger in BAV patients (21.7 ± 3 mm in BAV vs 18.9 ± 3 mm in TAV, P < 0.001). Moreover, BAV patients had significantly longer AML (24 ± 3 mm in BAV vs 22 ± 4 mm in TAV, P = 0.009). LVEDV and LVESV were significantly larger in BAV patients (LVEDV: 164.9 ± 68.4 ml in BAV groups vs 126.5 ± 53.1 ml in TAV group, P = 0.037; LVESV: 82.1 ± 57.9 ml in BAV group vs 52.9 ± 25.7 ml in TAV group, P = 0.008). A strong linear correlation was found between LVOT diameter and aortic annulus diameter in BAV patients ( r = 0.7, P < 0.001), whereas significantly weaker correlation was observed in TAV patients ( r = 0.5, P = 0.006, z = 1.65, P = 0.04). Presence of BAV morphology was independently associated with larger LVOT diameters (OR 9.0, 95% CI 1.0-81.3, P = 0.04). Conclusions We found relevant differences in LV morphological/functional parameters between BAV and TAV stenosis patients. Further investigations are warranted in order to determine the cause of these observed differences.
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Gurung A, Gates PE, Mazzaro L, Fulford J, Zhang F, Barker AJ, Hertzberg J, Aizawa K, Strain WD, Elyas S, Shore AC, Shandas R. Echo Particle Image Velocimetry for Estimation of Carotid Artery Wall Shear Stress: Repeatability, Reproducibility and Comparison with Phase-Contrast Magnetic Resonance Imaging. ULTRASOUND IN MEDICINE & BIOLOGY 2017; 43:1618-1627. [PMID: 28501327 DOI: 10.1016/j.ultrasmedbio.2017.03.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 02/17/2017] [Accepted: 03/27/2017] [Indexed: 06/07/2023]
Abstract
Measurement of hemodynamic wall shear stress (WSS) is important in investigating the role of WSS in the initiation and progression of atherosclerosis. Echo particle image velocimetry (echo PIV) is a novel ultrasound-based technique for measuring WSS in vivo that has previously been validated in vitro using the standard optical PIV technique. We evaluated the repeatability and reproducibility of echo PIV for measuring WSS in the human common carotid artery. We measured WSS in 28 healthy participants (18 males and 10 females, mean age: 56 ± 12 y). Echo PIV was highly repeatable, with an intra-observer variability of 1.0 ± 0.1 dyn/cm2 for peak systolic (maximum), 0.9 dyn/cm2 for mean and 0.5 dyn/cm2 for end-diastolic (minimum) WSS measurements. Likewise, echo PIV was reproducible, with a low inter-observer variability (max: 2.0 ± 0.2 dyn/cm2, mean: 1.3 ± 0.1 dyn/cm2, end-diastolic: 0.7 dyn/cm2) and more variable inter-scan (test-retest) variability (max: 7.1 ± 2.3 dyn/cm2, mean: 2.9 ± 0.4 dyn/cm2, min: 1.5 ± 0.1 dyn/cm2). We compared echo PIV with the reference method, phase-contrast magnetic resonance imaging (PC-MRI); echo PIV-based WSS measurements agreed qualitatively with PC-MRI measurements (r = 0.89, p < 0.05). Significant differences were observed in some WSS measurements (echo PIV vs. PC-MRI): WSS at peak systole: 21 ± 7.0 dyn/cm2 vs. 15 ± 5.0 dyn/cm2; time-averaged WSS: 8.9 ± 3.0 dyn/cm2 vs. 7.1 ± 3.0 dyn/cm2 (p < 0.05); WSS at end diastole: 3.8 ± 2.8 dyn/cm2 vs. 3.9 ± 2 dyn/cm2 (p > 0.05). For the first time, we report that echo PIV can measure WSS with good repeatability and reproducibility in adult humans with a broad age range. Echo PIV is feasible in humans and offers an easy-to-use, ultrasound-based, quantitative technique for measuring WSS in vivo in humans with good repeatability and reproducibility.
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Fatehi Hassanabad A, Barker AJ, Guzzardi D, Markl M, Malaisrie C, McCarthy PM, Fedak PWM. Evolution of Precision Medicine and Surgical Strategies for Bicuspid Aortic Valve-Associated Aortopathy. Front Physiol 2017; 8:475. [PMID: 28740468 PMCID: PMC5502281 DOI: 10.3389/fphys.2017.00475] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 06/21/2017] [Indexed: 12/15/2022] Open
Abstract
Bicuspid aortic valve (BAV) is a common congenital cardiac malformation affecting 1–2% of people. BAV results from fusion of two adjacent aortic valve cusps, and is associated with dilatation of the aorta, known as bicuspid valve associated aortopathy. Bicuspid valve aortopathy is progressive and associated with catastrophic clinical events, such as aortic dissection and rupture. Therefore, frequent monitoring and early intervention with prophylactic surgical resection of the proximal aorta is often recommended. However, the specific pattern of aortopathy is highly variable among patients, with different segments of the ascending aorta being affected. Individual patient risks are sometimes difficult to predict. Resection strategies are informed by current surgical guidelines which are primarily based on aortic size and growth criteria. These criteria may not optimally reflect the risk of important aortic events. To address these issues in the care of patients with bicuspid valve aortopathy, our translational research group has focused on validating use of novel imaging techniques to establish non-invasive hemodynamic biomarkers for risk-stratifying BAV patients. In this article, we review recent efforts, successes, and ongoing challenges in the development of more precise and individualized surgical approaches for patients with bicuspid aortic valves and associated aortic disease.
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Beretta D, Barker AJ, Maqueira-Albo I, Calloni A, Bussetti G, Dell'Erba G, Luzio A, Duò L, Petrozza A, Lanzani G, Caironi M. Thermoelectric Properties of Highly Conductive Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate Printed Thin Films. ACS APPLIED MATERIALS & INTERFACES 2017; 9:18151-18160. [PMID: 28466635 DOI: 10.1021/acsami.7b04533] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Organic conductors are being evaluated for potential use in waste heat recovery through lightweight and flexible thermoelectric generators manufactured using cost-effective printing processes. Assessment of the potentiality of organic materials in real devices still requires a deeper understanding of the physics behind their thermoelectric properties, which can pave the way toward further development of the field. This article reports a detailed thermoelectric study of a set of highly conducting inkjet-printed films of commercially available poly(3,4-ethylenedioxythiophene) polystyrene sulfonate formulations characterized by in-plane electrical conductivity, spanning the interval 10-500 S/cm. The power factor is maximized for the formulation showing an intermediate electrical conductivity. The Seebeck coefficient is studied in the framework of Mott's relation, assuming a (semi-)classical definition of the transport function. Ultraviolet photoelectron spectroscopy at the Fermi level clearly indicates that the shape of the density of states alone is not sufficient to explain the observed Seebeck coefficient, suggesting that carrier mobility is important in determining both the electrical conductivity and thermopower. Finally, the cross-plane thermal conductivity is reliably extracted thanks to a scaling approach that can be easily performed using typical pump-probe spectroscopy.
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Garcia J, van der Palen RLF, Bollache E, Jarvis K, Rose MJ, Barker AJ, Collins JD, Carr JC, Robinson J, Rigsby CK, Markl M. Distribution of blood flow velocity in the normal aorta: Effect of age and gender. J Magn Reson Imaging 2017; 47:487-498. [PMID: 28556277 DOI: 10.1002/jmri.25773] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 05/10/2017] [Indexed: 01/16/2023] Open
Abstract
PURPOSE To apply flow distribution analysis in the entire aorta across a wide age range from pediatric to adult subjects. MATERIAL AND METHODS In all, 98 healthy subjects (age 9-78 years, 41 women) underwent 4D flow MRI at 1.5T and 3T for the assessment of 3D blood flow in the thoracic aorta. Subjects were categorized into age groups: group 1 (n = 9, 5 women): 9-15 years; group 2 (n = 13, 8 women): 16-20 years; group 3 (n = 27, 14 women): 21-39 years; group 4 (n = 40, 11 women): 40-59 years; group 5 (n = 9, 3 women): >60 years. Data analysis included the 3D segmentation of the aorta, aortic valve peak velocity, mid-ascending aortic diameter, and calculation of flow velocity distribution descriptors (mean, median, standard deviation, incidence of velocities >1 m/s, skewness, and kurtosis of aortic velocity magnitude). Ascending aortic diameter was normalized by body surface area. RESULTS Age was significantly associated with normalized aortic diameter (R = 0.73, P < 0.001), skewness (R = 0.76, P < 0.001), and kurtosis (R = 0.74, P < 0.001), all adjusted by heart rate. Aortic peak velocity and velocity distribution descriptors, adjusted by heart rate, were significantly different between age groups (P < 0.001, analysis of covariance). Skewness and kurtosis significantly increased (P < 0.001) during adulthood (>40 years) as compared with childhood (<21 years). Men and women revealed significant differences (P ≤ 0.05) for peak velocity, incidence, mean, median, standard deviation, and skewness, all adjusted by heart rate. CONCLUSION Aortic hemodynamics significantly change with age and gender, indicating the importance of age- and gender-matched control cohorts for the assessment of the impact of cardiovascular disease on aortic blood flow. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018;47:487-498.
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Trinh B, Dubin I, Rahman O, Ferreira Botelho MP, Naro N, Carr JC, Collins JD, Barker AJ. Aortic Volumetry at Contrast-Enhanced Magnetic Resonance Angiography: Feasibility as a Sensitive Method for Monitoring Bicuspid Aortic Valve Aortopathy. Invest Radiol 2017; 52:216-222. [PMID: 27861233 PMCID: PMC5339069 DOI: 10.1097/rli.0000000000000332] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Bicuspid aortic valve patients can develop thoracic aortic aneurysms and therefore require serial imaging to monitor aortic growth. This study investigates the reliability of contrast-enhanced magnetic resonance angiography (CEMRA) volumetry compared with 2-dimensional diameter measurements to identify thoracic aortic aneurysm growth. MATERIALS AND METHODS A retrospective, institutional review board-approved, and Health Insurance Portability and Accountability Act-compliant study was conducted on 20 bicuspid aortic valve patients (45 ± 8.9 years, 20% women) who underwent serial CEMRA with a minimum imaging follow-up of 11 months. Magnetic resonance imaging was performed at 1.5 T with electrocardiogram-gated, time-resolved CEMRA. Independent observers measured the diameter at the sinuses of Valsalva (SOVs) and mid ascending aorta (MAA) as well as ascending aorta volume between the aortic valve annulus and innominate branch. Intraobserver/interobserver coefficient of variation (COV) and intraclass correlation coefficient (ICC) were computed to assess reliability. Growth rates were calculated and assessed by Student t test (P < 0.05, significant). The diameter of maximal growth (DMG), defined as the diameter at SOV or MAA with the faster growth rate, was recorded. RESULTS The mean time of follow-up was 2.6 ± 0.82 years. The intraobserver COV was 0.01 for SOV, 0.02 for MAA, and 0.02 for volume (interobserver COV: 0.02, 0.03, 0.04, respectively). The ICC was 0.83 for SOV, 0.86 for MAA, 0.90 for DMG, and 0.95 for volume. Average aortic measurements at baseline and (follow-up) were 42 ± 3 mm (42 ± 3 mm, P = 0.11) at SOV, 46 ± 4 mm (47 ± 4 mm, P < 0.05) at MAA, and 130 ± 23 mL (144 ± 24 mL, P < 0.05). Average size changes were 0.2 ± 0.6 mm/y (1% ± 2%) at SOV, 0.5 ± 0.8 mm/y (1% ± 2%) at MAA, 0.7 ± 0.7 mm/y (2% ± 2%) at DMG, and 6 ± 3 mL/y (4% ± 3%) with volumetry. CONCLUSIONS Three-dimensional CEMRA volumetry exhibited a larger effect when examining percentage growth, a better ICC, and a marginally lower COV. Volumetry may be more sensitive to growth and possibly less affected by error than diameter measurements.
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Geiger J, Hirtler D, Gottfried K, Rahman O, Bollache E, Barker AJ, Markl M, Stiller B. Longitudinal Evaluation of Aortic Hemodynamics in Marfan Syndrome: New Insights from a 4D Flow Cardiovascular Magnetic Resonance Multi-Year Follow-Up Study. J Cardiovasc Magn Reson 2017; 19:33. [PMID: 28327193 PMCID: PMC5361800 DOI: 10.1186/s12968-017-0347-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 02/21/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The aim of this 4D flow cardiovascular magnetic resonance (CMR) follow-up study was to investigate longitudinal changes in aortic hemodynamics in adolescent patients with Marfan syndrome (MFS). METHODS 4D flow CMR for the assessment of in-vivo 3D blood flow with full coverage of the thoracic aorta was performed twice (baseline scan t1/follow-up scan t2) in 19 adolescent MFS patients (age at t1: 12.7 ± 3.6 years, t2: 16.2 ± 4.3 years) with a mean follow-up duration of 3.5 ± 1.2 years. Ten healthy volunteers (24 ± 3.8 years) served as a control group. Data analysis included aortic blood flow visualization by color-coded 3D pathlines, and grading of flow patterns (helices/vortices) on a 3-point scale (none, moderate, severe; blinded reading, 2 observers). Regional aortic peak systolic velocities and systolic 3D wall shear stress (WSS) along the entire aortic wall were quantified. Z-Scores of the aortic root and proximal descending aorta (DAo) were assessed. RESULTS Regional systolic WSS was stable over the follow-up duration, except for a significant decrease in the proximal inner DAo segment (p = 0.02) between t1 and t2. MFS patients revealed significant lower mean systolic WSS in the proximal inner DAo compared with volunteers (0.78 ± 0.15 N/m2) at baseline t1 (0.60 ± 0.18 N/m2; p = 0.01) and follow-up t2 (0.55 ± 0.16 N/m2; p = 0.001). There were significant relationships (p < 0.01) between the segmental WSS in the proximal inner DAo, DAo Z-scores (r = -0.64) and helix/vortex pattern grading (r = -0.55) at both t1 and t2. The interobserver agreement for secondary flow patterns assessment was excellent (Cohen's k = 0.71). CONCLUSIONS MFS patients have lower segmental WSS in the inner proximal DAo segment which correlates with increased localized aberrant vortex/helix flow patterns and an enlarged diameter at one of the most critical sites for aortic dissection. General aortic hemodynamics are stable but these subtle localized DAo changes are already present at young age and tend to be more pronounced in the course of time.
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van der Palen RLF, Barker AJ, Bollache E, Garcia J, Rose MJ, van Ooij P, Young LT, Roest AAW, Markl M, Robinson JD, Rigsby CK. Altered aortic 3D hemodynamics and geometry in pediatric Marfan syndrome patients. J Cardiovasc Magn Reson 2017; 19:30. [PMID: 28302143 PMCID: PMC5356404 DOI: 10.1186/s12968-017-0345-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 02/16/2017] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Blood flow dynamics make it possible to better understand the development of aortopathy and cardiovascular events in patients with Marfan syndrome (MFS). Aortic 3D blood flow characteristics were investigated in relation to aortic geometry in children and adolescents with MFS. METHODS Twenty-five MFS patients (age 15.6 ± 4.0 years; 11 females) and 21 healthy controls (age 16.0 ± 2.6 years; 12 females) underwent magnetic resonance angiography and 4D flow CMR for assessment of thoracic aortic size and 3D blood flow velocities. Data analysis included calculation of aortic diameter and BSA-indexed aortic dimensions (Z-score) along the thoracic aorta, 3D mean systolic wall shear stress (WSSmean) in ten aortic segments and assessment of aortic blood flow patterns. RESULTS Aortic root (root), ascending (AAo) and descending (DAo) aortic size was significantly larger in MFS patients than healthy controls (Root Z-score: 3.56 ± 1.45 vs 0.49 ± 0.78, p < 0.001; AAo Z-score 0.21 ± 0.95 vs -0.54 ± 0.64, p = 0.004; proximal DAo Z-score 2.02 ± 1.60 vs 0.56 ± 0.66, p < 0.001). A regional variation in prevalence and severity of flow patterns (vortex and helix flow patterns) was observed, with the aortic root and the proximal DAo (pDAo) being more frequently affected in MFS. MFS patients had significantly reduced WSSmean in the proximal AAo (pAAo) outer segment (0.65 ± 0.12 vs. 0.73 ± 0.14 Pa, p = 0.029) and pDAo inner segment (0.74 ± 0.17 vs. 0.87 ± 0.21 Pa, p = 0.021), as well as higher WSSmean in the inner segment of the distal AAo (0.94 ± 0.14 vs. 0.84 ± 0.15 Pa, p = 0.036) compared to healthy subjects. An inverse relationship existed between pDAo WSSmean and both pDAo diameter (R = -0.53, p < 0.001) and % diameter change along the pDAo segment (R = -0.64, p < 0.001). CONCLUSIONS MFS children and young adults have altered aortic flow patterns and differences in aortic WSS that were most pronounced in the pAAo and pDAo, segments where aortic dissection or rupture often originate. The presence of vortex flow patterns and abnormal WSS correlated with regional size of the pDAo and are potentially valuable additional markers of disease severity.
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Bollache E, Barker AJ, Dolan RS, Carr JC, van Ooij P, Ahmadian R, Powell A, Collins JD, Geiger J, Markl M. k-t accelerated aortic 4D flow MRI in under two minutes: Feasibility and impact of resolution, k-space sampling patterns, and respiratory navigator gating on hemodynamic measurements. Magn Reson Med 2017; 79:195-207. [PMID: 28266062 DOI: 10.1002/mrm.26661] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 02/08/2017] [Accepted: 02/08/2017] [Indexed: 01/29/2023]
Abstract
PURPOSE To assess the performance of highly accelerated free-breathing aortic four-dimensional (4D) flow MRI acquired in under 2 minutes compared to conventional respiratory gated 4D flow. METHODS Eight k-t accelerated nongated 4D flow MRI (parallel MRI with extended and averaged generalized autocalibrating partially parallel acquisition kernels [PEAK GRAPPA], R = 5, TRes = 67.2 ms) using four ky -kz Cartesian sampling patterns (linear, center-out, out-center-out, random) and two spatial resolutions (SRes1 = 3.5 × 2.3 × 2.6 mm3 , SRes2 = 4.5 × 2.3 × 2.6 mm3 ) were compared in vitro (aortic coarctation flow phantom) and in 10 healthy volunteers, to conventional 4D flow (16 mm-navigator acceptance window; R = 2; TRes = 39.2 ms; SRes = 3.2 × 2.3 × 2.4 mm3 ). The best k-t accelerated approach was further assessed in 10 patients with aortic disease. RESULTS The k-t accelerated in vitro aortic peak flow (Qmax), net flow (Qnet), and peak velocity (Vmax) were lower than conventional 4D flow indices by ≤4.7%, ≤ 11%, and ≤22%, respectively. In vivo k-t accelerated acquisitions were significantly shorter but showed a trend to lower image quality compared to conventional 4D flow. Hemodynamic indices for linear and out-center-out k-space samplings were in agreement with conventional 4D flow (Qmax ≤ 13%, Qnet ≤ 13%, Vmax ≤ 17%, P > 0.05). CONCLUSION Aortic 4D flow MRI in under 2 minutes is feasible with moderate underestimation of flow indices. Differences in k-space sampling patterns suggest an opportunity to mitigate image artifacts by an optimal trade-off between scan time, acceleration, and k-space sampling. Magn Reson Med 79:195-207, 2018. © 2018 International Society for Magnetic Resonance in Medicine.
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Schäfer M, Ivy DD, Abman SH, Barker AJ, Browne LP, Fonseca B, Kheyfets V, Hunter KS, Truong U. Apparent Aortic Stiffness in Children With Pulmonary Arterial Hypertension: Existence of Vascular Interdependency? Circ Cardiovasc Imaging 2017; 10:e005817. [PMID: 28193613 PMCID: PMC5314208 DOI: 10.1161/circimaging.116.005817] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 12/15/2016] [Indexed: 01/08/2023]
Abstract
BACKGROUND Left ventricular dysfunction, mediated by ventricular interdependence, has been associated with negative outcomes in children with pulmonary arterial hypertension (PAH). Considering the dilation of the pulmonary arteries as a paramount sign of PAH, we hypothesized that the ascending aorta will present signs of apparent stiffness in children with PAH and that this effect may be because of mechanical interaction with the dilated main pulmonary artery (MPA). METHODS AND RESULTS Forty-two children with PAH and 26 age- and size-matched controls underwent comprehensive cardiac magnetic resonance evaluation. Assessment of aortic stiffness was evaluated by measuring pulse wave velocity, aortic strain, and distensibility. Children with PAH had significantly increased pulse wave velocity in the ascending aorta (3.4 versus 2.3 m/s for PAH and controls, respectively; P=0.001) and reduced aortic strain (23% versus 29%; P<0.0001) and distensibility (0.47 versus 0.64%/mm Hg; P=0.02). Indexed MPA diameter correlated with pulse wave velocity (P=0.04) and with aortic strain (P=0.02). The ratio of MPA to aortic size correlated with pulse wave velocity (P=0.0098), strain (P=0.0099), and distensibility (P=0.015). Furthermore, aortic relative area change was associated with left ventricular ejection fraction (P=0.045) and ventricular-vascular coupling ratio (P=0.042). CONCLUSIONS Pediatric PAH patients have increased apparent ascending aortic stiffness, which was strongly associated with the degree of MPA distension. We speculate that distension of the MPA may play a major role in limiting full aortic expansion during systole, which modulates left ventricular performance and impacts systemic hemodynamics in pediatric PAH.
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McGee K, Bollache E, Barker AJ, Carr JC, Markl M, Kansal P. Impact of Beta-blocker, ACE Inhibitor, and ARB therapy on thoracic aorta wall shear stress in bicuspid aortic valve patients. J Cardiovasc Magn Reson 2016. [PMCID: PMC5032525 DOI: 10.1186/1532-429x-18-s1-p345] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Rose MJ, Jarvis KB, Barker AJ, Schnell S, Allen BD, Robinson JD, Markl M, Rigsby CK. Evaluating the disease progression of pediatric bicuspid aortic valve patients using 4D flow MRI data. J Cardiovasc Magn Reson 2016. [PMCID: PMC5032329 DOI: 10.1186/1532-429x-18-s1-p170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Bollache E, Ooij PV, Powell AL, Carr JC, Markl M, Barker AJ. 4D Flow and 2D PC MRI: impact of volumetric coverage and three-directional velocity encoding on quantification of aortic hemodynamics. J Cardiovasc Magn Reson 2016. [PMCID: PMC5032784 DOI: 10.1186/1532-429x-18-s1-p357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Jarvis KB, Wu C, Giri S, Schnell S, Barker AJ, Collins JD, Carr JC, Markl M. Improved assessment of aortic 3D blood flow with combined k-t accelerated 3D CINE bSSFP & 4D flow MRI. J Cardiovasc Magn Reson 2016. [PMCID: PMC5032281 DOI: 10.1186/1532-429x-18-s1-p232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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