Hemodynamic Assessment in Bicuspid Aortic Valve Disease and Aortic Dilation: New Insights From Voxel-By-Voxel Analysis of Reverse Flow, Stasis, and Energetics

Objectives: Clinical management decisions surrounding ascending aorta (AAo) dilation in bicuspid aortic valve (BAV) disease benefit from personalized predictive tools. 4D-flow MRI may provide patient-specific markers reflective of BAV-associated aortopathy. This study aims to explore novel 4D-flow MRI parametric voxel-by-voxel forward flow, reverse flow, kinetic energy and stasis in BAV disease. We hypothesize that novel parametric voxel-by-voxel markers will be associated with aortic dilation and referral for surgery and can enhance our understanding of BAV hemodynamics beyond standard metrics.Methods: A total of 96 subjects (73 BAV patients, 23 healthy controls) underwent MRI scan. Healthy controls had no known cardiovascular disease. Patients were clinically referred for AAo dilation assessment. Indexed diameters were obtained by dividing the aortic diameter by the patient’s body surface area. Patients were followed for the occurrence of aortic surgery. 4D-flow analysis was performed by a single observer in five regions: left ventricular outflow tract (LVOT), AAo, arch, proximal descending aorta (PDAo), and distal descending aorta (DDAo). In each region peak velocity, kinetic energy (KE), forward flow (FF), reverse flow (RF), and stasis were measured on a voxel-by-voxel basis. T-tests (or non-parametric equivalent) compared flow parameters between cohorts. Univariate and multivariate analyses explored associations between diameter and parametric voxel-by-voxel parameters.Results: Compared to controls, BAV patients showed reduced stasis (p < 0.01) and increased RF and FF (p < 0.01) throughout the aorta, and KE remained similar. In the AAo, indexed diameter correlated with age (R = 0.326, p = 0.01), FF (R = −0.648, p < 0.001), RF (R = −0.441, p < 0.001), and stasis (R = −0.288, p < 0.05). In multivariate analysis, FF showed a significant inverse association with AAo indexed diameter, independent of age. During a median 179 ± 180 days of follow-up, 23 patients (32%) required aortic surgery. Compared to patients not requiring surgery, they showed increased KE and peak velocity in the proximal aorta (p < 0.01), accompanied by increased RF and reduced stasis throughout the entire aorta (p < 0.01).Conclusion: Novel voxel-by-voxel reverse flow and stasis were altered in BAV patients and are associated with aortic dilation and surgical treatment.

Download Full-text

Abstract 14914: Advanced 4D-flow Measurements of Aortic Forward Flow, Reverse Flow, and Stasis in Bicuspid Aortic Valve Patients Without Aortic Stenosis or Regurgitation

Circulation ◽

10.1161/circ.142.suppl_3.14914 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Patrick Geeraert ◽

Fatemehsadat jamalidinan ◽

Ali Fatehi Hassanabad ◽

James White ◽

Julio Garcia Flores

Keyword(s):

Aortic Valve ◽

Aortic Stenosis ◽

Bicuspid Aortic Valve ◽

Cardiac Cycle ◽

Reverse Flow ◽

Left Ventricular ◽

Healthy Controls ◽

4D Flow ◽

Descending Aorta ◽

Forward Flow

Introduction: Precise analysis of aortic hemodynamics is crucial in the study of bicuspid aortic valve (BAV) disease. This study provides a comprehensive evaluation of aortic forward flow (FF), reverse flow (RF) and stasis in BAV patients using novel 3D-based techniques previously shown to be more accurate than traditional 2D analysis methods. Hypothesis: BAV patients without valve dysfunction show abnormal aortic FF, RF, and stasis compared to healthy controls. Methods: We recruited 44 BAV patients (48±15 yrs, 27% female) and 23 healthy controls (37±14 yrs, 35% female). Cardiac MRI at 3T was performed inclusive of 4D-flow imaging. Patients with any aortic stenosis (AS) or ≥mild regurgitation (AR) were excluded. Flow analysis was performed by segmented volumetric regions: left ventricular outflow tract (LVOT), ascending aorta (AAo), arch, proximal descending aorta (PDAo), and distal descending aorta (DDAo). In each region, forward flow (FF), reverse flow (RF) and stasis were averaged over the cardiac cycle on a voxel-by-voxel basis. Left ventricular (LV) end-diastolic volume, end-systolic volume and ejection fraction were also measured. T-tests (or non-parametric equivalent) compared differences in parameters between cohorts. Results: BAV patients were significantly older than controls (48±15 vs. 37±14 yrs; p=0.01) but exhibited no significant differences in LV measures. Patients showed reduced FF in the AAo (0.09±0.03 vs. 0.11±0.04 mL/cycle; p<0.01), but greater FF in all downstream regions (eg. PDA: 0.02±0.03 vs. 0.01±0.02 mL/cycle; p=0.01). RF was significantly elevated in patients in the AAo (0.06±0.02 vs. 0.02±0.02 mL/cycle; p<0.01). BAV patients exhibited significantly less stasis in every region except the DDAo (eg. AAo: 23±11 vs. 50±10 % of cardiac cycle). Conclusions: 3D-derived measurements of FF, RF, and stasis are significantly altered in the thoracic aorta of BAV patients in the absence of AS or AR.

Download Full-text

Abstract 14367: Abnormal Pulmonary Flow is Associated With Impaired Right Ventricular Coupling in Patients With COPD

Circulation ◽

10.1161/circ.142.suppl_3.14367 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Ani Oganesyan ◽

Alex J Barker ◽

Benjamin S Frank ◽

Dunbar D IVY ◽

Lorna Browne ◽

...

Keyword(s):

Strong Association ◽

Pulmonary Arteries ◽

Healthy Controls ◽

4D Flow Mri ◽

4D Flow ◽

Pulmonary Flow ◽

Copd Patients ◽

Flow Mri ◽

Pulmonary Arterial ◽

Rv Function

Introduction: Cor Pulmonale or right ventricular (RV) dysfunction due to pulmonary disease is an expected complication of COPD resulting from increased afterload mediated by hypoxic pulmonary vasoconstriction as well as the destruction of the pulmonary vascular bed. Early detection of elevated RV afterload has been previously demonstrated by visualization of abnormal flow patterns in the proximal pulmonary arteries. Prior quantitative analysis of helicity in the pulmonary arteries of pulmonary hypertension patients has demonstrated a strong association between helicity and increased RV afterload. Hypothesis: Patients with COPD will have abnormal pulmonary flow as evaluated by 4D-Flow MRI and associated with RV function and pulmonary arterial stiffness. Methods: Patients with COPD (n=15) (65yrs ± 6) and controls (n=10) (58yrs ± 9) underwent 4D-Flow MRI to calculate helicity (Figure 1A). The helicity was calculated in 2 segments: 1) the main pulmonary artery (MPA) and 2) along the RV outflow tract (RVOT) - MPA axis. Main pulmonary arterial stiffness was measured using the relative area change (RAC). Results: COPD patients had decreased helicity relative to healthy controls in the MPA (19.4±7.8 vs 32.8±15.9 s -2 , P=0.007) (Figure 1B). Additionally, COPD patients had reduced helicity along the RVOT-MPA axis (33.2±9.0 vs 43.5±8.3 s -2 , P=0.010). The helicity measured in the MPA was associated with RV end-systolic volume (R=0.59, P = 0.002), RVEF (R=0.631, P<0.001), RAC (R=-0.61, P=0.001). e combined helicity along the MPA-RVOT axis was associated with RVEF (R=0.74, P<0.001), RVESV (R=-0.57, P=0.004), and RAC (R=0.42, P=0.005). Conclusion: Patients with COPD show quantitatively abnormal flow hemodynamics, when compared with healthy controls, as assessed by 4D-Flow MRI. A strong association between helicity along the MPA-RV outflow tract axis and RV function suggests that 4D-Flow MRI might be a sensitive tool in evaluating RV - pulmonary arterial coupling in COPD.

Download Full-text

Abstract 14534: In vitro Assessment of Transvalvular Peak Velocity Measurement for Various Orifice Shapes: Comparison Between 4D Flow MRI vs. Doppler Echocardiography

Circulation ◽

10.1161/circ.142.suppl_3.14534 ◽

2020 ◽

Vol 142 (Suppl_3) ◽

Author(s):

Jeesoo Lee ◽

Nadia El hangouche ◽

Liliana Ma ◽

Michael Scott ◽

Michael Markl ◽

...

Keyword(s):

Temporal Resolution ◽

Continuous Wave ◽

Peak Velocity ◽

Left Ventricular ◽

Patient Specific ◽

Maximal Velocity ◽

4D Flow Mri ◽

4D Flow ◽

Flow Phantom ◽

Flow Mri

Introduction: 4D flow MRI can assess transvalvular velocity, but validation against continuous wave (CW) Doppler echo is limited in high-velocity regurgitation and stenosis situations. We sought to compare 4D flow MRI and echo peak velocity using a pulsatile echo-MRI flow phantom. Materials and Methods: An MRI-compatible flow phantom with restrictive orifice situated was driven by a left ventricular assist device at 50 bpm (figure 1A). Three orifice shapes were tested: circular, elliptical and 3D-printed patient-specific mitral regurgitant orifice model of prolapse with areas of 0.5, 0.41 and 0.35 cm 2 , respectively. CW Doppler was acquired with peak velocity extracted from the profile. Retrospectively-gated 4D flow MRI was performed (spatial resolution = 2 mm isotropic, temporal resolution = 36 ms, encoding velocity = 400 cm/s). Maximal velocity magnitude was extracted volumetrically (figure 1B). An echo-mimicking profile was also obtained with a “virtual” ultrasound beam in the 4D flow data to simulate CW Doppler (figure 1C). Bland-Altman analysis was used to assess the agreement of temporal peak velocities. Results: 4D flow MRI demonstrated a centrally directed jet for the circular and elliptical orifices and an oblique jet for the prolapse orifice (figure 1B). Peak velocities were in excellent agreement between 4D flow MRI vs. echo for the circular (peak: 5.13 vs. 5.08 m/s, bias = 0.06 ± 0.66 m/s, figure 1D) and the elliptical orifice (peak: 4.95 vs. 4.79 m/s, bias = 0.07 ± 0.87 m/s, figure 1E). The prolapse orifice velocity was underestimated somewhat by MRI by ~10% (peak: 4.41 vs. 4.90 m/s, bias=0.26±1.18, figure 1F). Conclusion: 4D flow MRI can quantify high velocities like echo for simple geometries while underestimating for more complex geometry, likely due to partial volume effects. Further investigation is warranted to systematically investigate the effects of 4D flow MRI spatial and temporal resolution as well as the jet angle on velocity quantification accuracy.

Download Full-text

Voxel-by-voxel 4D flow MRI-based assessment of regional reverse flow in the aorta

Journal of Magnetic Resonance Imaging ◽

10.1002/jmri.25862 ◽

2017 ◽

Vol 47 (5) ◽

pp. 1276-1286 ◽

Cited By ~ 7

Author(s):

Xin Shen ◽

Susanne Schnell ◽

Alex J. Barker ◽

Kenichiro Suwa ◽

Lingzi Tashakkor ◽

...

Keyword(s):

Reverse Flow ◽

4D Flow Mri ◽

4D Flow ◽

Flow Mri

Download Full-text

Blood Flow Patterns In The Ascending Aorta after TAVI And Surgical Aortic Valve Replacement: A Study Using 4D Flow MRI

10.14293/p2199-8442.1.sop-med.p0low9.v1 ◽

2014 ◽

Author(s):

Ralf Felix Trauzeddel ◽

Ulrike Löbe ◽

Alex Barker ◽

Carmen Gelsinger ◽

Christian Butter ◽

...

Keyword(s):

Blood Flow ◽

Aortic Valve ◽

Flow Patterns ◽

Ascending Aorta ◽

Shear Stresses ◽

Healthy Controls ◽

4D Flow Mri ◽

4D Flow ◽

Flow Mri ◽

Blood Flow Patterns

Background Transcatheter aortic valve implantation (TAVI) is a new method for treating patients with severe aortic stenosis with high risk for or rejected from conventional heart surgery. Its impact on blood flow patterns and parameters in the ascending aorta are unknown. Using 4-dimensional phase contrast MRI (4D Flow MRI) we examined the hemodynamics in the ascending aorta after TAVI and compared them to stented bioprostheses and healthy controls. Methods We used 4D Flow MRI (spatial resolution 1.8x1.8x2.5mm3; temporal resolution 13-22 phases/heart cycle) of the ascending aorta in 14 patients with TAVI (mean age 76 years, 8 males, all Edwards Sapien), 12 patients with different stented bioprostheses (mean age 77 years, 8 males) and 9 healthy controls (mean age 55 years, 8 males) controls using a 1.5T MR system. We examined the distribution of the maximum systolic wall shear stresses as well as the maximum blood flow velocities in the mid-ascending aorta. Results Patients with TAVI and stented bioprosthesis revealed an asymetric distribution of the wall shear stresses with significantly elevated values at the anterior and right-anterior curvature and significantly lower values at the posterior curvature compared to the healthy controls. Concerning the maximum velocities both TAVI and stented bioprostheses revealed an asymetric distribution along the right-anterior curvature where TAVI showed a more anterior distribution compared to the healty controls which showed a central distribution. Conclusion The blood flow patterns in patients with TAVI and stented bioprostheses differs significantly from the ones in healthy controls. However, TAVI and stented bioprosthesis showed small but significant regional differences.

Download Full-text

Abnormal aortic hemodynamics at predilection sites for dissection in patients with Marfan Syndrome: a 4D flow study

European Heart Journal - Cardiovascular Imaging ◽

10.1093/ehjci/jeab090.067 ◽

2021 ◽

Vol 22 (Supplement_2) ◽

Author(s):

MM Van Andel ◽

P Van Ooij ◽

L Gottwald ◽

V De Waard ◽

AH Zwinderman ◽

...

Keyword(s):

Blood Pressure ◽

Aortic Dissection ◽

Phase Contrast ◽

Ascending Aorta ◽

4D Flow Mri ◽

4D Flow ◽

Descending Aorta ◽

Flow Mri ◽

Directed Velocity ◽

Pressure Characteristics

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): AMC Foundation Horstingstuit Foundation Introduction Patients with Marfan syndrome (MFS) may develop aneurysmatic dilatation and dissection of the aorta with a consequence of sudden death at relatively young age. We performed an aortic 4D flow MRI analysis, providing a comprehensive quantification and visualization of abnormal aortic velocity and wall shear stress (WSS) magnitude and direction with recently developed techniques (1,2). We hypothesize that abnormal hemodynamics are found at predilection sites for aortic dissection in MFS patients. Methods This prospective study included 56 MFS patients and 25 healthy subjects as controls. Aortic 4D flow MRI was performed on a 3T Philips Ingenia system (Best, Netherlands). The aorta was manually segmented on time-averaged phase contrast MR angiogram images (phase contrast images multiplied by absolute velocity) by thresholding, watershed, and manual voxel in-/exclusion. The segmentations were used to mask the velocities, calculate WSS, and co-registration for quantification of abnormal hemodynamics (3). Abnormally elevated velocity and WSS were defined as higher than the three-dimensional 95% confidence interval as determined in the control group. Abnormally directed velocity and WSS were defined as vector angle differences higher than 120°. The aorta was subdivided in six regions of interest (ROIs) for total multiple linear regression with age, aortic diameter, and blood pressure characteristics. Independent predictors were defined as characteristics that were significant in the total model. Significance was defined as p < 0.05 with Bonferonni correction. The 3D-maps with abnormal hemodynamics were co-registered and added to create 3D-maps that show the incidence of abnormal hemodynamics. Results Figure 1 shows examples of maps with abnormal velocity and WSS magnitude and direction respectively. Ascending elevated velocity was associated with age, aortic diameter and blood pressure characteristics, whereas elevated WSS was associated with blood pressure characteristics only. No independent predictors were found for abnormally directed hemodynamics. Figure 2 shows the incidence maps for abnormally elevated velocity and abnormally directed WSS in two patients. The maximum incidence for elevated velocity and WSS were 32% and 20%, respectively, and found in the ascending aorta. The maxima for abnormally directed velocity and WSS were 18% and 39%, respectively, and found in the inner proximal descending aorta. Conclusion Altered aortic geometry and wall properties in MFS patients cause detectable hemodynamic effects in 30% of our cohort at known predilection sites for aortic dissection in MFS patients: the ascending aorta and proximal descending aorta. Independent measures of altered hemodynamics could possibly indicate individual patients at risk for aortic dissection.

Download Full-text