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Objectives:
Current risk assessment strategies in type B aortic dissection are focused on anatomic parameters, although haemodynamic abnormalities that result in false lumen (FL) pressurization are thought to play a significant role in aortic growth. The objective of this study was to evaluate blood flow of the FL using 4D flow magnetic resonance...
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Context 1
... = 0.001), and the entry tear distance from the LSC (b = 0.07, SE 0.02, 95% CI 0.02-0.12; P = 0.016), with the overall model adjusted R 2 = 0.87 (Table 3). The significance of predictors in the regression model did not change when patients with connective tissue disease (Supplementary Material, Table S1) or repaired type-A dissection and connective tissue disease (Supplementary Material, Table S2) were excluded. ...Similar publications
Aberrant right subclavian artery is the most frequent anomaly of the aortic arch, and in 60% of cases is associated with Kommerell diverticulum. It is usually asymptomatic but may present with dysphagia or asthma due to esophageal and tracheal compression. Indications for surgical repair have not been established; however, when Kommerell diverticul...
The aortic major branches after thoracic endovascular aortic repair (TEVAR) could be preserved by in situ fenestration (ISF). This study aims to explore the hemodynamic consequences of ISF-TEVAR with double fenestrations. Two patients with aortic dissection and aneurysm, respectively, were treated by ISF-TEVAR and both the left carotid artery (LCA)...
Aberrant right subclavian artery is the most frequent anomaly of the aortic arch, and in 60% of cases is associated with Kommerell diverticulum. It is usually asymptomatic but may present with dysphagia or asthma due to esophageal and tracheal compression. Indications for surgical repair have not been established; however, when Kommerell diverticul...
An aberrant right subclavian artery (ARSA) is a rare developmental anomaly (0.4-1.8%)of the aorta in which the right subclavian artery arises from the aortic arch distal to the origin of the left subclavian artery often coursing behind the esophagus to reach the right arm. It courses behind the esophagus in about 80% of cases, between the esophagus...
A 39-year old obese male with a history of previously repaired Type-A aortic dissection presented to ED with complaints of sudden onset, retrosternal chest pain radiating to back for 4 hours, without any associated dyspnoea or diaphoresis. Primary survey was unremarkable and included a blood pressure of 122/76 mmHg, heart rate of 88 beats per minut...
Citations
... Adding to morphological measures, recent studies increasingly investigated hemodynamics to further advance prediction models. For example, decreased outflow through FL branch vessels 11 , increased FL ejection fraction [15][16][17] , and FL pressurization [18][19][20] were determined to promote late adverse events. Further, these hemodynamic features have been associated with patient-specific morphology. ...
Understanding the complex interplay between morphologic and hemodynamic features in aortic dissection is critical for risk stratification and for the development of individualized therapy. This work evaluates the effects of entry and exit tear size on the hemodynamics in type B aortic dissection by comparing fluid-structure interaction (FSI) simulations with in vitro 4D-flow magnetic resonance imaging (MRI). A baseline patient-specific 3D-printed model and two variants with modified tear size (smaller entry tear, smaller exit tear) were embedded into a flow- and pressure-controlled setup to perform MRI as well as 12-point catheter-based pressure measurements. The same models defined the wall and fluid domains for FSI simulations, for which boundary conditions were matched with measured data. Results showed exceptionally well matched complex flow patterns between 4D-flow MRI and FSI simulations. Compared to the baseline model, false lumen flow volume decreased with either a smaller entry tear (-17.8 and -18.5 %, for FSI simulation and 4D-flow MRI, respectively) or smaller exit tear (-16.0 and -17.3 %). True to false lumen pressure difference (initially 11.0 and 7.9 mmHg, for FSI simulation and catheter-based pressure measurements, respectively) increased with a smaller entry tear (28.9 and 14.6 mmHg), and became negative with a smaller exit tear (-20.6 and -13.2 mmHg). This work establishes quantitative and qualitative effects of entry or exit tear size on hemodynamics in aortic dissection, with particularly notable impact observed on FL pressurization. FSI simulations demonstrate acceptable qualitative and quantitative agreement with flow imaging, supporting its deployment in clinical studies.
... Compared with contrast-enhanced CT, 4D flow MRI does not require radiation or contrast media, making it a non-invasive method. A previous study revealed the feasibility of utilizing flow in TL and FL [23] as predictors of aortic growth rate in patients with uncomplicated type B aortic dissection [24]. In an extensive study of 4D flow MRI for type B dissection, it was reported that the flow pattern and the rate are related to FL enlargement and adverse aortic events [25]. ...
Objective
We evaluated the blood flow within the downstream aortic false lumen after frozen elephant trunk repair for acute aortic dissection and identified hemodynamic predictors of false lumen expansion and negative false lumen remodeling using four-dimensional flow magnetic resonance imaging.
Methods
Thirty-one patients (Stanford type A, n = 28; Stanford type B, n = 3) with patent false lumen who underwent frozen elephant trunk procedures for acute aortic dissection were included in this observational study. Each patient underwent computed tomography during the follow-up period and four-dimensional flow magnetic resonance imaging within 3 postoperative months. The false lumen volumetric expansion rate was calculated using computed tomography data. The direction and the rate of flow in the lower descending aortic false lumen were analyzed. Negative false lumen remodeling was defined as a volumetric increase of > 10% from the baseline volume.
Results
Negative false lumen remodeling had developed in 6 of the 31 patients during the observation period. Most of the false lumen flows were biphasic during systole. The range between peak and nadir flow rates was associated with the false lumen volumetric expansion rate ( β coefficient = 6.77; p < 0.01, R ² = 0.43).
Conclusions
The range between peak and nadir flow rates may serve as a hemodynamic predictor of negative false lumen remodeling, enabling further treatment for patients at risk of expansion in the downstream aorta.
... In vivo blood-flow characterization with 4D flow MRI has potential utility in identifying TBAD patients with enlarging aortas by the quantitative flow pattern assessment at the entry tear and in the FL [1,6,[9][10][11][12][13][14][15][16][17][18][19]. Despite its benefits, long scan times associated with the multidimensional imaging and single velocity encoding (venc) level potentially limit the clinical adoption of the traditional 4D flow MRI. ...
The aim of this study is to investigate the applicability of the dual-venc (DV) 4D flow magnetic resonance imaging (MRI) to quantify the complex flow patterns in type B aortic dissection (TBAD). One GRAPPA-accelerated single-venc (SV) and one compressed-sensing (CS) accelerated DV 4D flow MRI sequences are used to scan all subjects, including twelve chronic TBAD patients and two volunteers. The scans are performed twice for the reproducibility assessment of the scan protocols. Voxelwise quantitative flow parameters including kinetic energy (KE), peak velocity (PV), forward and reverse flows (FF, RF) and stasis are calculated. High-venc (HV) data from the DV acquisition are separately analyzed. The scan time reduction by the CS-accelerated DV 4D flow MRI acquisition is 46.4% compared with the SV acquisition. The DV velocity-to-noise ratio (VNR) is higher compared with HV (p = 0.000). No true lumen (TL) parameter shows a significant difference among the acquisition types (p > 0.05). The false lumen (FL) RF is higher in SV compared with the DV acquisition (p = 0.009). The KE is higher (p = 0.038) and stasis is lower (p = 0.01) in HV compared with SV acquisition. All FL parameters except stasis are higher and stasis is lower in HV compared with DV acquisition (p < 0.05). Positive Pearson correlations among the acquisition types in TL and high agreements between the two scans for all acquisition types are observed except HV RF in the FL, which demonstrates a moderate agreement. The CS-accelerated DV 4D flow MRI may have utility in the clinical daily routine with shortened scan times and improved velocity measurements while providing high VNR in TBAD. The observed hemodynamic flow trends are similar between GRAPPA-accelerated SV and CS-accelerated DV 4D flow MRI acquisitions; however, parameters are more impacted by CS-accelerated HV protocol in FL, which may be secondary to the CS regularization effects.
... where t is the start time of the final cycle and T is the cycle period. FL ejection fraction (FLEF), a predictor of aortic growth rate, 8 was also assessed by evaluating R=F across the PET. ...
... Higher levels of reversed FL flow, FL ejection fraction (FLEF) and TMP mean are associated with rapid aortic growth due to their associations with elevated FL pressure. 8,42 Despite substantial aneurysmal growth in this patient, a low-to-moderate degree of reverse flow and negligible FLEF (<2%) were observed in both simulations and 4DMR. Furthermore, TMP mean did not exceed 1.7 mmHg anywhere, well below the 5 mmHg observed in other aneurysmal patients. ...
Type-B aortic dissection (TBAD) is a disease in which a tear develops in the intimal layer of the descending aorta forming a true lumen and false lumen (FL). Because disease outcomes are thought to be influenced by haemodynamic quantities such as pressure and wall shear stress (WSS), their analysis via numerical simulations may provide valuable clinical insights. Major aortic branches are routinely included in simulations but minor branches are virtually always neglected, despite being implicated in TBAD progression and the development of complications. As minor branches are estimated to carry about 7–21% of cardiac output, neglecting them may affect simulation accuracy. We present the first simulation of TBAD with all pairs of intercostal, subcostal and lumbar arteries, using 4D-flow MRI (4DMR) to inform patient-specific boundary conditions. Compared to an equivalent case without minor branches, their inclusion improved agreement with 4DMR velocities, reduced time-averaged WSS (TAWSS) and transmural pressure and elevated oscillatory shear in regions where FL dilatation and calcification were observed in vivo . Minor branch inclusion resulted in differences of 60-75% in these metrics of potential clinical relevance, indicating a need to account for minor branch flow loss if simulation accuracy is sought.
... Similar findings of higher FL velocity and more helical flow in the FL relating to faster aortic growth were reported in another study involving 12 medically treated TBAD patients. 72 Burris et al. 73 compared anatomical and haemodynamic parameters between the patients with stable (n¼8) and unstable aortic growth (n¼10). The maximum diameter was found to be significantly different between the two groups (mean: stable, 40.1 mm versus enlarging, 50.7 mm). ...
Patients with either a repaired or medically managed aortic dissection have varying degrees of risk of developing late complications. High-risk patients would benefit from earlier intervention to improve their long-term survival. Currently serial imaging is used for risk stratification, which is not always reliable. On the other hand, understanding aortic haemodynamics within a dissection is essential to fully evaluate the disease and predict how it may progress. In recent decades, computational fluid dynamics (CFD) has been extensively applied to simulate complex haemodynamics within aortic diseases, and more recently, four-dimensional (4D)-flow magnetic resonance imaging (MRI) techniques have been developed for in vivo haemodynamic measurement. This paper presents a comprehensive review on the application of image-based CFD simulations and 4D-flow MRI analysis for risk prediction in aortic dissection. The key steps involved in patient-specific CFD analyses are demonstrated. Finally, we propose a workflow incorporating computational modelling for personalised assessment to aid in risk stratification and treatment decision-making.
... Although a patent false lumen in the descending aorta has been associated with aortic enlargement [13], need of aortic intervention/repair or late mortality [14], studies quantifying flow in the false lumen and its relationship with aortic growth rate are still limited. Studies based on 4-dimensional (4D) phase-contrast cardiovascular magnetic resonance (4D flow CMR) analysing flow dynamics in the true and false lumen have been published [15][16][17][18][19]. However, these studies reported qualitative or semi-quantitative analysis of flow data [16,17], included a limited number of patients (≤ 20), and mixed individuals with and without genetic connective tissue disorders [15][16][17][18][19]. Additionally, the potential role of wall shear stress (WSS) and the biomechanical properties of the aortic wall (aortic stiffness) in patients with a chronic, patent false lumen in the descending aorta after an AD still remain unexplored. ...
... Studies based on 4-dimensional (4D) phase-contrast cardiovascular magnetic resonance (4D flow CMR) analysing flow dynamics in the true and false lumen have been published [15][16][17][18][19]. However, these studies reported qualitative or semi-quantitative analysis of flow data [16,17], included a limited number of patients (≤ 20), and mixed individuals with and without genetic connective tissue disorders [15][16][17][18][19]. Additionally, the potential role of wall shear stress (WSS) and the biomechanical properties of the aortic wall (aortic stiffness) in patients with a chronic, patent false lumen in the descending aorta after an AD still remain unexplored. ...
... Retrograde systolic and diastolic flow were calculated as the time-integral of backward through-plane flow rate curve over systolic or diastolic phases, respectively. False lumen retrograde flow fraction was calculated as the ratio of retrograde diastolic flow rate over the anterograde systolic flow rate, as proposed [18]. IRF, a parameter used to quantify flow rotation within a plane, was calculated as the integral of vorticity with respect to cross-sectional area at the systolic peak [24,25] (Fig. 2D). ...
Background
Patency of the false lumen in chronic aortic dissection (AD) is associated with aortic dilation and long-term aortic events. However, predictors of adverse outcomes in this population are limited. The aim of this study was to evaluate the relationship between aortic growth rate and false lumen flow dynamics and biomechanics in patients with chronic, patent AD.
Methods
Patients with a chronic AD with patent false lumen in the descending aorta and no genetic connective tissue disorder underwent an imaging follow-up including a contrast-enhanced 4D flow cardiovascular magnetic resonance (CMR) protocol and two consecutive computed tomography angiograms (CTA) acquired at least 1 year apart. A comprehensive analysis of anatomical features (including thrombus quantification), and false lumen flow dynamics and biomechanics (pulse wave velocity) was performed.
Results
Fifty-four consecutive patients with a chronic, patent false lumen in the descending aorta were included (35 surgically-treated type A AD with residual tear and 19 medically-treated type B AD). Median follow-up was 40 months. The in-plane rotational flow, pulse wave velocity and the percentage of thrombus in the false lumen were positively related to aortic growth rate (p = 0.006, 0.017, and 0.037, respectively), whereas wall shear stress showed a trend for a positive association (p = 0.060). These results were found irrespectively of the type of AD.
Conclusions
In patients with chronic AD and patent false lumen of the descending aorta, rotational flow, pulse wave velocity and wall shear stress are positively related to aortic growth rate, and should be implemented in the follow-up algorithm of these patients. Further prospective studies are needed to confirm if the assessment of these parameters helps to identify patients at higher risk of adverse clinical events.
... These parameters should be evaluated as metrics predicting the risk of rupture from aneurysmal dilatation of abdominal aortic dissections, in long-term follow-up studies. Burris et al. reported early studies in the thoracic aorta of patients with type B aortic dissection [102]. These investigators found that the false lumen ejection fraction, as defined as the proportion between retrograde and antegrade flow measured at the dominant entry tear, was an independent predictor of growth rate. ...
4D flow MRI is a quantitative MRI technique that allows the comprehensive assessment of time-resolved hemodynamics and vascular anatomy over a 3-dimensional imaging volume. It effectively combines several advantages of invasive and non-invasive imaging modalities like ultrasound, angiography, and computed tomography in a single MRI acquisition and provides an unprecedented characterization of velocity fields acquired non-invasively in vivo. Functional and morphological imaging of the abdominal vasculature is especially challenging due to its complex and variable anatomy with a wide range of vessel calibers and flow velocities and the need for large volumetric coverage. Despite these challenges, 4D flow MRI is a promising diagnostic and prognostic tool as many pathologies in the abdomen are associated with changes of either hemodynamics or morphology of arteries, veins, or the portal venous system. In this review article, we will discuss technical aspects of the implementation of abdominal 4D flow MRI ranging from patient preparation and acquisition protocol over post-processing and quality control to final data analysis. In recent years, the range of applications for 4D flow in the abdomen has increased profoundly. Therefore, we will review potential clinical applications and address their clinical importance, relevant quantitative and qualitative parameters, and unmet challenges.
Graphical abstract
... However, recent studies using 4D flow MRI have suggested that in vivo hemodynamic assessment of blood flow at entry tears and in the false lumen may help identify TBAD patients with Abbreviations: TBAD, type B aortic dissection; TAAD, type A aortic dissection; rTAAD, repaired TAAD with residual TBAD; TEVAR, thoracic endovascular aortic repair; CTA, computed tomography angiography; MRA, magnetic resonance angiography; PC-MRA, 3D phase-contrast angiogram; AARO, adverse aortarelated outcomes; FOV, field of view; TR, repetition time; TE, echo time; VENC, velocity encoding; TL, true lumen; FL, false lumen; KE, kinetic energy; PV, peak velocity; FF, forward flow; RF, reverse flow. growing aortas (17)(18)(19)(20). In the current study, we seek to further expand on these findings by using 4D flow MRI to perform voxel-wise hemodynamic quantification of the TL and FL. ...
... Again, retrograde flow in the FL (specifically at the dissection tear) was analyzed as FL ejection fraction (EF: diastolic retrograde flow divided by systolic antegrade flow through an entry tear) in 18 patients by Burris et al. and in 12 patients by Marlevi et al. Both studies reported a strong positive correlation between FL EF and aortic growth rate, contrary to the negative correlation that we found (17,18). This discrepancy may due to the fact that our analysis of reverse flow involves data collected from an entire luminal volume, and further studies focusing on a specific location of interest may reveal regional hemodynamic differences in this parameter. ...
PurposeThe purpose of our study was to assess the value of true lumen and false lumen hemodynamics compared to aortic morphological measurements for predicting adverse-aorta related outcomes (AARO) and aortic growth in patients with type B aortic dissection (TBAD).Materials and Methods
Using an IRB approved protocol, we retrospectively identified patients with descending aorta (DAo) dissection at a large tertiary center. Inclusion criteria includes known TBAD with ≥ 6 months of clinical follow-up after initial presentation for TBAD or after ascending aorta intervention for patients with repaired type A dissection with residual type B aortic dissection (rTAAD). Patients with prior descending aorta intervention were excluded. The FL and TL of each patient were manually segmented from 4D flow MRI data, and 3D parametric maps of aortic hemodynamics were generated. Groups were divided based on (1) presence vs. absence of AARO and (2) growth rate ≥ vs. < 3 mm/year. True and false lumen kinetic energy (KE), stasis, peak velocity (PV), reverse/forward flow (RF/FF), FL to TL KE ratio, as well as index aortic diameter were compared between groups using the Mann–Whitney U or independent t-test.ResultsA total of n = 51 patients (age: 58.4 ± 15.0 years, M/F: 31/20) were included for analysis of AARO. This group contained n = 26 patients with TBAD and n = 25 patients with rTAAD. In the overall cohort, AARO patients had larger baseline diameters, lower FL-RF, FL stasis, TL-KE, TL-FF and TL-PV. Among patients with de novo TBAD, those with AAROs had larger baseline diameter, lower FL stasis and TL-PV. In both the overall cohort and in the subgroup of de novo TBAD, subjects with aortic growth ≥ 3mm/year, patients had a higher KE ratio.Conclusion
Our study suggests that 4D flow MRI is a promising tool for TBAD evaluation that can provide information beyond traditional MRA or CTA. 4D flow has the potential to become an integral aspect of TBAD work-up, as hemodynamic assessment may allow earlier identification of at-risk patients who could benefit from earlier intervention.
... A comprehensive methodology can help to identify those parameters related to aortic dilation in patients with BAV. Previously, we have developed a seamless computational framework to obtain several 3D quantitative parameters, which have been validated in phantoms and different cohorts of patients including aortic dissection (24,25) and transposition of the great arteries (26,27). This study aimed to compare quantitative 3D hemodynamic parameters between healthy volunteers (HVs) and patients with BAV and their relationships with aortic dilation in clinically relevant subgroups of patients with BAV. ...
Background and Purpose: Prognostic models based on cardiovascular hemodynamic parameters may bring new information for an early assessment of bicuspid aortic valve (BAV) patients, playing a key role in reducing the long-term risk of cardiovascular events. This work quantifies several three-dimensional hemodynamics parameters in different BAV patients and ranks their relationships with aortic diameter.
Materials and Methods: Using 4D-flow CMR data of 74 BAV patients (49 right-left and 25 right-noncoronary) and 48 healthy volunteers, aortic 3D-maps of seventeen different hemodynamics parameters were quantified along the thoracic aorta. BAV patients were divided in two morphotypes categories, BAV-NonAAoD (where we include 18 non-dilated patients and 7 root-dilated patients), and BAV-AAoD (where we include the 49 patient with dilatation of the ascending aorta). Differences between volunteers and patients were evaluated using MANOVA with Pillai's Trace statistic, Mann-Whitney U-test, ROC-curves and minimum redundancy maximum relevance algorithm. Spearman correlation was used to correlate the dilation with each hemodynamics parameter.
Results: The flow eccentricity, backward velocity, velocity angle, regurgitation fraction, circumferential wall shear stress, axial vorticity and axial circulation allowed to discriminate between volunteers and BAV patients, even in the absence of dilation. In BAV patients, the diameter presented an strong correlation (> |+/-0.7|) with forward velocity and velocity angle, and a good correlation (> |+/-0.5|) with regurgitation fraction, wall shear stress, wall shear stress axial and vorticity, also for morphotypes and phenotypes, some of them are correlated with the diameter. The velocity angle proved to be an excellent biomarker in the differentiation between volunteers and BAV patients, BAV morphotypes and BAV phenotypes, with an area under the curve bigger than 0.90, and higher predictor important scores.
Conclusions: Through the application of a novel 3D quantification method, hemodynamic parameters related to flow direction, such as flow eccentricity, velocity angle, and regurgitation fraction, presented the best relationships with local diameter and effectively differentiated BAV patients from healthy volunteers.
... [38][39][40] Burris et al. has proposed an interesting concept of "ejection fraction of the false lumen," which describes the proportion of exiting flow from the false lumen at diastole measured at the primary entry tear. 41 They reported that the index revealed a moderate-to-strong correlation with aortic growth rate. As the outflow from the false lumen overcomes the pressure of the true lumen, the index may reflect the elevated pressure of the false lumen. ...
Blood vessels can be regarded as autonomous organs. The endothelial cells on the vessel surface serve as mechanosensors or mechanoreceptors for the flow velocity and turbulence of the blood flow in terms of wall shear stress (WSS), thereby monitoring changes in the flow velocity. Accordingly, the endothelial cells regulate the flow velocity by releasing numerous mediators. Such regulatory systems also trigger atherosclerosis, where the WSS decreases or fluctuates to maintain the flow velocity or local WSS. As occurrences of abdominal aortic aneurysms and aortic dissection are closely related to atherosclerosis, understanding the hemodynamics of the abdominal aorta is necessary to obtain useful information concerning the pathogenesis, diagnosis, and interventions. 4D flow MRI is beneficial for measuring the hemodynamics through comprehensive retrospective flowmetry of the entire spatio-temporal distributions of the flow vectors. This section focuses on abdominal aortic aneurysms and aortic dissection as representative examples of abdominal aortic diseases. Their hemodynamic characteristics and how hemodynamics is involved in their progression are described, and how 4D flow MRI can contribute to their assessment is also explained.
