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Three-dimensional (3D) time-resolved phase-contrast cardiac magnetic resonance (4D flow CMR) allows for unparalleled quantification of blood velocity. Despite established potential in aortic diseases, the analysis is time-consuming and requires expert knowledge, hindering clinical application. The present research aimed to develop and test a fully automatic machine learning-based pipeline for aortic 4D flow CMR analysis.Four hundred and four subjects were prospectively included. Ground-truth to train the algorithms was generated by experts. The cohort was divided into training (323 patients) and testing (81) sets and used to train and test a 3D nnU-Net for segmentation and a Deep Q-Network algorithm for landmark detection. In-plane (IRF) and through-plane (SFRR) rotational flow descriptors and axial and circumferential wall shear stress (WSS) were computed at ten planes covering the ascending aorta and arch.Automatic aortic segmentation resulted in a median Dice score (DS) of 0.949 and average symmetric surface distance of 0.839 (0.632-1.071) mm, comparable with the state of the art. Aortic landmarks were located with a precision comparable with experts in the sinotubular junction and first and third supra-aortic vessels (p = 0.513, 0.592 and 0.905, respectively) but with lower precision in the pulmonary bifurcation (p = 0.028), resulting in precise localisation of analysis planes. Automatic flow assessment showed excellent (ICC0.9) agreement with manual quantification of SFRR and good-to-excellent agreement (ICC0.75) in the measurement of IRF and axial and circumferential WSS.Fully automatic analysis of complex aortic flow dynamics from 4D flow CMR is feasible. Its implementation could foster the clinical use of 4D flow CMR.• 4D flow CMR allows for unparalleled aortic blood flow analysis but requires aortic segmentation and anatomical landmark identification, which are time-consuming, limiting 4D flow CMR widespread use. • A fully automatic machine learning pipeline for aortic 4D flow CMR analysis was trained with data of 323 patients and tested in 81 patients, ensuring a balanced distribution of aneurysm aetiologies. • Automatic assessment of complex flow characteristics such as rotational flow and wall shear stress showed good-to-excellent agreement with manual quantification.

Aims To assess the progression of the disease and evolution of the main echocardiographic variables for quantifying AS in patients with severe low-flow low-gradient (LFLG) AS compared to other severe AS subtypes. Methods and results Longitudinal, observational, multicenter study including consecutive asymptomatic patients with severe AS (aortic valve area, AVA < 1.0 cm²) and normal left ventricle ejection fraction (LVEF ≥ 50%). Patients were classified according to baseline echocardiography into: HG (high gradient; mean gradient ≥ 40 mmHg), NFLG (normal-flow low-gradient; mean gradient < 40 mmHg, indexed systolic volume (SVi) > 35mL/m2), or LFLG (mean gradient < 40 mmHg, SVi ≤ 35 mL/m²). AS progression was analyzed by comparing patients’ baseline measurements and their last follow-up measurements or those taken prior to aortic valve replacement (AVR). Of the 903 included patients, 401 (44.4%) were HG, 405 (44.9%) NFLG, and 97 (10.7%) LFLG. Progression of the mean gradient in a linear mixed regression model was greater in low-gradient groups: LFLG vs. HG (regression coefficient 0.124, P = 0.005) and NFLG vs. HG (regression coefficient 0.068, P = 0.018). No differences were observed between the LFLG and NFLG groups (regression coefficient 0.056, P = 0.195). However, AVA reduction was slower in the LFLG group compared to the NFLG (P < 0.001). During follow-up, in conservatively-managed patients, 19.1% (n = 9) of LFLG patients evolved to having NFLG AS and 44.7% (n = 21) to having HG AS. In patients undergoing AVR, 58.0% (n = 29) of LFLG baseline patients received AVR with a HG AS. Conclusion LFLG AS shows an intermediate AVA and gradient progression compared to NFLG and HG AS. The majority of patients initially classified as having LFLG AS changed over time to having other severe forms of AS, and most of them received AVR with a HG AS.

This study sought to assess the predictive value of wall shear stress (WSS) for colocalized ascending aorta (AAo) growth rate (GR) in patients with bicuspid aortic valve (BAV).BAV is associated with AAo dilation, but there is limited knowledge about possible predictors of aortic dilation in patients with BAV. An increased WSS has been related to aortic wall damage in patients with BAV, but no previous prospective study tested its predictive value for dilation rate. Recently, a registration-based technique for the semiautomatic mapping of aortic GR has been presented and validated.Forty-seven patients with BAV free from valvular dysfunction prospectively underwent 4-dimensional flow cardiac magnetic resonance to compute WSS and subsequent follow-up with 2 electrocardiogram-gated high-resolution contrast-enhanced computed tomography angiograms for GR assessment.During a median follow-up duration of 43 months, mid AAo GR was 0.24 mm/year. WSS and its circumferential component showed statistically significant association with mid AAo GR in bivariate (P = 0.049 and P = 0.014, respectively) and in multivariate analysis corrected for stroke volume and either baseline AAo diameter (P = 0.046 and P = 0.014, respectively) or z-score (P = 0.036 and P = 0.012, respectively). GR mapping further detailed that GR was heterogeneous in the AAo and that circumferential WSS, but not WSS magnitude, showed statistically significant positive associations with GR in the regions with the fastest growth.4D flow cardiac magnetic resonance-derived WSS and, in particular, its circumferential component predict progressive dilation of the ascending aorta in patients with BAV. Thus, the assessment of WSS may be considered in the follow-up of these patients.

Objective Thoracic endovascular aortic repair (TEVAR) is widely used for the treatment of patients with blunt traumatic thoracic aortic injury (BTAI). However, aortic haemodynamic and biomechanical implications of this intervention are poorly investigated. This study aimed to assess whether patients treated by TEVAR following BTAI have thoracic aortic abnormalities in geometry, stiffness, and haemodynamics. Methods Patients with BTAI treated by TEVAR at Vall d’Hebron Hospital between 1999 and 2019 were compared with propensity score matched healthy volunteers (HVs). All subjects underwent cardiovascular magnetic resonance (CMR) comprising a 4D flow CMR sequence. Spatially resolved aortic diameter, length, volume, and curvature were assessed. Pulse wave velocity, distensibility, and longitudinal strain (all measurements of aortic stiffness) were determined regionally. Moreover, advanced haemodynamic descriptors were quantified: systolic flow reversal ratio (SFRR), quantifying backward flow during systole, and in plane rotational flow (IRF), measuring in plane strength of helical flow. Results Twenty-six BTAI patients treated by TEVAR were included and matched with 26 HVs. They did not differ in terms of age, sex, and body surface area. Patients with TEVAR had a larger and longer ascending aorta (AAo) and marked abnormalities in local curvature. Aortic stiffness was greater in the aortic segments proximal and distal to TEVAR compared with controls. Moreover, TEVAR patients presented strongly altered flow dynamics compared with controls: a reduced IRF from the distal AAo to the proximal descending aorta and an increased SFRR in the whole thoracic aorta. These differences persisted adjusting for cardiovascular risk factors and were independent of time elapsed since TEVAR implantation. Conclusion At long term follow up, previously healthy patients who underwent TEVAR implantation following BTAI had increased diameter, length and volume of the ascending aorta, and increased aortic stiffness and abnormal flow patterns in the whole thoracic aorta compared with matched controls. Further studies should address whether these alterations have clinical implications.

Background Partial thrombosis of the false lumen (FL) in patients with chronic aortic dissection (AD) of the descending aorta has been associated with faster aortic dilation. Four-dimensional phase-contrast cardiovascular magnetic resonance (4D flow CMR) studies analyzing flow dynamics and biomechanics in the FL and their relationship with partial thrombosis are lacking. This study aimed to compare FL flow dynamics and biomechanics between patients with a patent and partially thrombosed FL. Materials and methods Patients with a chronic, patent (no thrombus) or partially thrombosed FL in the descending aorta after an AD underwent an imaging follow-up including a magnetic resonance angiography (MRA) and a 4D flow CMR study. FL thrombosis was quantified as the ratio of thrombus volume and FL volume on MRA. FL flow dynamics was assessed in terms of forward flow, wall shear stress (WSS), maximum kinetic energy (KE) and acceleration, and flow stasis on 4D flow CMR. Aortic stiffness in the FL was quantified using pulse wave velocity (PWV). Results and conclusions Sixty-five patients with a complete imaging protocol were included in the study (patency in 34 patients, partial thrombosis in 31). Partial thrombosis of the FL was associated with a reduction in the amount and energy of flow in the FL (reduced forward systolic flow, KE and acceleration), and a more stagnated flow in the FL (increased flow stasis). Axial WSS showed a tendency to be lower in the partial thrombosis group compared to the patency group, while PWV were similar in both of them. Funding IJC2018-037349-I.

Background Despite the high prevalence of ascending aorta (AAo) dilation in bicuspid aortic valve (BAV) patients there is limited evidence of dilation aetiology. Several cross-sectional studies pointed to a role for wall shear stress (WSS), but this hypothesis has not been tested. Recently, a technique for 3D-maps of aortic growth from two contrast-enhanced computed tomography angiograms (CTA) was presented and validated. We aim to test if local WSS predicts local dilation rates in BAV patients. Materials and methods Forty BAV patients free from aortic valve disease and previous relevant interventions underwent a baseline 4D flow CMR followed by two CTA. WSS, and its axial and circumferential components, and growth rate (GR) were computed at 64 standardized regions in the ascending aortic (AAo). A two-tailed p-value < 0.05 was considered statistically significant. Results and conclusions Patients were relatively young (51 ± 13 yeas) and follow-up duration was 44.8 ± 2.6 months. Growth rate was heterogeneous in the AAo, with fastest progression located in the outer mid AAo region and in the inner region of the proximal-mid AAo. WSS magnitude and WSS axial component were maximum in the right region of the mid AAo while circumferential WSS was highest in the outer region of the mid AAo, the region experiencing fastest growth. Significant associations between GR and circumferential WSS were located in the regions with fastest progressive dilation, while WSS magnitude and its axial component resulted in limited predictive capacity. In conclusion, circumferential WSS is related to fast progressive dilation in BAV patients. Funding PI17/00381,SEC/FEC-INV-CLI20/015,LCF/BQ/PR22/11920008,RTC2019-007280-1.

Bicuspid aortic valve (BAV), the most common congenital valve defect, is associated with increased risk of aortic dilation and related complications; however, current risk assessment is not effective. Most of BAV have three leaflets with a fusion between two of them of variable length. This study aimed to ascertain whether the extent of leaflet fusion (often called raphe) is related to aortic dilation and flow abnormalities in BAV with no significant valvular dysfunction. One hundred and twenty BAV patients with no significant valvular dysfunction or history of surgical repair or aortic valve replacement were consecutively and prospectively enrolled (September 2014–October 2018). Cardiac magnetic resonance protocol included a 4D flow sequence for haemodynamic assessment. Moreover, a stack of double-oblique cine images of the aortic valve were used to quantify fusion length (in systole) and leaflet length (diastole). Inter- and intra-observer reproducibility was tested in 30 randomly selected patients. Aortic valve leaflet fusion was measurable in 112 of 120 (93%) cases with good reproducibility (ICC = 0.826). Fusion length varied greatly (range: 2.3–15.4 mm; mean: 7.8 ± 3.2 mm). After correction for demographic and clinical conditions, fusion length was independently associated with diameter and z-score at the sinus of Valsalva (p = 0.002 and p = 0.002, respectively) and ascending aorta (p = 0.028 and p = 0.046). Fusion length was positively related to flow asymmetry, vortices and circumferential wall shear stress, thereby possibly providing a pathophysiological link with aortic dilation. Aortic valve fusion length is related to aortic dilation and flow abnormalities in BAV patients. • The length of the fusion between leaflets in non-dysfunctional bicuspid aortic valves varies substantially and can be reliably measured by cine CMR. • Aortic valve leaflet fusion length is independently related to aortic sinus and ascending aorta diameter. • Increased flow asymmetry, circumferential wall shear stress and presence of vortices are positively related to aortic valve leaflet fusion length.

ObjectivesTo describe the aortic-related risks associated with pregnancy in women with bicuspid aortic valve (BAV) and to evaluate changes in aortic diameter in pregnancy.MethodsProspective observational study of patients with BAV from a single-site registry of pregnant women with structural heart disease between 2013 and 2020. Cardiac, obstetric and neonatal outcomes were studied. An assessment of aortic dimensions was performed during pregnancy by two-dimensional echocardiography. Aortic diameters were measured at the annulus, root, sinotubular junction and maximum ascending aorta diameter, and the largest diameter was used. Measurements of the aorta were made using the end-diastolic leading edge-to-leading edge convention.ResultsForty-three women (32.9 years, IQR 29.6–35.3) with BAV were included: 9 (20.9%) had repaired aortic coarctation; 23 (53.5%) had moderate or severe aortic valve disease; 5 (11.6%) had a bioprosthetic aortic valve; and 2 (4.7%) had a mechanical prosthetic aortic valve. Twenty (47.0%) were nulliparous. The mean aortic diameter in the first trimester was 38.5 (SD 4.9) mm, and that in the third trimester was 38.4 (SD 4.8) mm. Forty (93.0%) women had an aortic diameter of 50 mm. Three women (6.9%) with BAV presented cardiovascular complications during pregnancy or the postpartum period (two prosthetic thrombosis and one heart failure). No aortic complications were reported. There was a small but significant increase in aortic diameter during pregnancy (third trimester vs first trimester, 0.52 (SD 1.08) mm; p=0.03). Obstetric complications appeared in seven (16.3%) of pregnancies, and there were no maternal deaths. Vaginal non-instrumental delivery was performed in 21 (51.2%) out of 41 cases. There were no neonatal deaths, and the mean newborn weight was 3130 g (95% CI 2652 to 3380).ConclusionsPregnancy in BAV women had a low rate of cardiac complications with no aortic complications observed in a small study group. Neither aortic dissection nor need for aortic surgery was reported. A low but significant aortic growth was observed during pregnancy. Although requiring follow-up, the risk of aortic complications in pregnant women with BAV and aortic diameters of

Background Bicuspid aortic valve (BAV), a congenital heart defect, is associated with ascending aorta (AAo) dilation. Whether the high prevalence of dilation in BAV patients is related to alteration of aortic blood flow and thus in wall shear stress (WSS) [1,2], which have been associated with aortic wall degeneration [3], or intrinsic abnormalities of the aortic wall, such as altered aortic stiffness [4], has not been established. Recently, a technique for the semi-automatic quantification of progressive aortic dilation maps via image registration has been introduced [5]. Purpose To test whether ascending aorta WSS predicts co-localized progressive dilation in BAV patients. Methods Forty BAV patients free from moderate and severe aortic valve regurgitation (regurgitant fraction Results Demographic and clinical characteristics of the patients are shown in Table 1. WSS and growth rate maps are shown in Figure 1. Follow-up duration was 44.8±2.6 months. Growth rate (Figure 1A) was heterogeneously distributed, being highest (up to 0.26 mm/year) in the outer region of the mid AAo and in the inner region of the proximal-mid AAo. Circumferential WSS showed highest values in the outer region of the mid AAo (Figure 1C) while WSS (magnitude) and its axial component (Figure 1B and D) presented maximum values in the right region of the mid AAo. Maps of statistically significant association between GR and WSS values showed circumferential WSS to be correlated with GR in regions where progressive dilation was fastest, while WSS magnitude and its axial component resulted in limited associations with GR maps. Conclusions Circumferential wall shear stress predicts location-matched progressive dilation in bicuspid aortic valve patients. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This study has received funding from the Instituto de Salud Carlos III (PI17/00381). Guala A. has received funding from Spanish Ministry of Science, Innovation and Universities (IJC2018-037349-I). Table 1. DemographicsFigure 1. GR and WSS maps and correlations

Introduction Accurate assessment of aortic diameters and growth rates is key for clinical management of patients with aortic aneurysms [1]. Manual assessment on multiplanar reformatted views of computed tomography angiograms (CTA) is recommended [1], although its reproducibility in the assessment of growth rates has not been reported [2]. Image registration has been proposed to provide 3D maps of aortic diameters and growth [3], but its accuracy and reproducibility have not been established. Purpose To quantify accuracy and inter-observer reproducibility of aortic root and thoracic aorta diameters and growth rate by registration of serial CTAs compared to current standard. Methods Forty non-operated patients with ≥2 contrast-enhanced ECG-gated CTA acquired at least 6 months apart were included. Aortic diameters and growth rates were measured in the aortic root and thoracic aorta by two independent observers, both with the current standard and with the registration-based technique. To perform registration-based assessment, each observer semi-automatically segmented the aorta at baseline and located typical anatomical landmarks (Fig. 1A). Then, deformable image registration was used to map baseline and follow-up CT scans and deformation was applied to the baseline aortic surface points to obtain their location at follow-up (Fig. 1B). Finally, aortic root diameters and growth rate and 3D maps of thoracic aortic diameters and growth rate were automatically obtained (Fig. 1C). Agreement between techniques and their inter-observer reproducibility were calculated. Results Follow-up duration was 3.3±1.5 years (range 0.52–6.2). Compared with manual assessment, registration-based aortic diameters presented low bias and excellent agreement in the aortic root (0.42 mm, ICC=0.99) and the thoracic aorta (0.55 mm, ICC=0.99), and similar inter-observer reproducibility (ICC=0.99 for both). Compared with manual assessment, registration-based growth rates presented low bias and good agreement in the aortic root (0.12 mm/y, ICC=0.84) and the thoracic aorta (0.03 mm/y, ICC=0.77) (Fig. 2A), and much higher inter-observer reproducibility (ICC=0.96 vs 0.68 in the aortic root, ICC=0.96 vs 0.80 in the thoracic aorta) (Fig. 2B and C). Registration-based aortic growth rates reproducibility at 6 months follow-up was comparable to that obtained by manual assessment at 2.7 years (LoA = [−0.01, 0.33] and LoA = [−0.13, 0.21], respectively). Aortic diameters and growth rate 3D maps were highly reproducible (ICC>0.9) in the whole thoracic aorta. Conclusions Progressive aortic dilation assessment via registration of CTAs is accurate and more reproducible than the current standard even over follow-ups as short as 6 months, and further provides robust 3D mapping of aortic diameters and growth rates. Its application may provide new insights in aneurysms pathophysiology and improve the clinical management of these patients. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This study has received funding from the Instituto de Salud Carlos III (PI17/00381). Guala A. has received funding from Spanish Ministry of Science, Innovation and Universities (IJC2018-037349-I). Figure 1. Methodology.Figure 2. Growth rate comparison.

Supplemental Digital Content is available in the text., Objective: To assess the relationship between regional wall shear stress (WSS) and oscillatory shear index (OSI) and aortic dilation in patients with bicuspid aortic valve (BAV). Approach and Results: Forty-six consecutive patients with BAV (63% with right-left-coronary-cusp fusion, aortic diameter ≤ 45 mm and no severe valvular disease) and 44 healthy volunteers were studied by time-resolved 3-dimensional phase-contrast magnetic resonance imaging. WSS and OSI were quantified at different levels of the ascending aorta and the aortic arch, and regional WSS and OSI maps were obtained. Seventy percent of BAV had ascending aorta dilation. Compared with healthy volunteers, patients with BAV had increased WSS and decreased OSI in most of the ascending aorta and the aortic arch. In both BAV and healthy volunteers, regions of high WSS matched regions of low OSI and vice versa. No regions of both low WSS and high OSI were identified in BAV compared with healthy volunteers. Patients with BAV with dilated compared with nondilated aorta presented low and oscillatory WSS in the aortic arch, but not in the ascending aorta where dilation is more prevalent. Furthermore, no regions of concomitant low WSS and high OSI were identified when BAV were compared according to leaflet fusion pattern, despite the well-known differences in regional dilation prevalence. Conclusions: Regions with low WSS and high OSI do not match those with the highest prevalence of dilation in patients with BAV, thus providing no evidence to support the low and oscillatory shear stress theory in the pathogenesis of proximal aorta dilation in the presence of BAV.

INTRODUCTION: Arterial tortuosity has emerged as a predictor of adverse outcomes in congenital aortopathies using 3D reconstructed images. We validated a new method to estimate aortic arch tortuosity on 2D CT. We hypothesize that arch tortuosity may identify bicuspid aortic valve (BAV) patients at high risk to develop thoracic aortic aneurysms or aortic dissections (TAD). METHODS: BAV subjects with chest CT scans were retrospectively identified in our clinical records and matched to tricuspid aortic valve (TAV) controls by age, gender, and presentation with TAD. Subjects with prior ascending aortic intervention were excluded. Measurements included aortic arch tortuosity, length, angle, width and height. Total aortic tortuosity was estimated in subjects with available abdominal images. RESULTS: 120 BAV and 234 TAV subjects were included. Our 2D measurements were highly correlated with 3D midline arch measurements and had high inter- and intra-observer reliability. Compared to TAV, BAV subjects had increased arch tortuosity (median 1.76 [Q1-Q3: 1.62-1.95] vs. 1.63 [1.53-1.78], P < 0.01), length (149 [136-160] vs. 135 [122-152] mm, P < 0.01),height (46 [41-53]vs. 39[34-7]mm, P < 0.01),and vertex acuity (70[61-77]vs.75 [68-81] degree, P < 0.01). In a multivariable analysis, arch tortuosity remained independently associated with BAV after adjusting for aortic diameter and other clinical characteristics. CONCLUSIONS: We found that aortic arch tortuosity is significantly increased in BAV and may identify BAV patients who are at increased risk for TAD. Further studies to evaluate the association between tortuosity and clinical outcomes are in progress.

Objectives This study sought to ascertain whether patients with a bicuspid aortic valve (BAV) have an intrinsic alteration in regional aortic stiffness compared with patients with tricuspid aortic valve (TAV) and Marfan syndrome (MFS) patients with similar aortic sizes, as well as to assess the influence of ascending aorta (AAo) dilation on regional stiffness parameters in BAV patients. Background Imaging biomarkers as predictors of BAV, MFS, and degenerative AAo aneurysms in TAV patients (DA-TAV) are lacking. Biomechanical characterization has been proposed as a possible tool for further aneurysm stratification. Methods A total 234 subjects (136 BAV, 44 MFS, and 18 DA-TAV patients and 36 healthy control subjects) were included. The cardiac magnetic resonance protocol comprised 4-dimensional flow to assess AAo and descending aorta (DAo) pulse wave velocities (PWVs) and double-oblique, 2-dimensional, steady-state free-precession cine cardiac magnetic resonance to compute aortic distensibility (AD). Results On adjusted analysis, nondilated BAV patients had similar PWV and AD as healthy control subjects in both AAo and DAo, whereas dilated BAV did not differ from DA-TAV. In contrast, AAo and DAo stiffness in MFS patients was markedly greater than in BAV patients, increasing slightly with dilation severity. AAo PWV showed a biphasic pattern in BAV patients: it first decreased and then increased throughout AAo dilation, with a clear turning point at 50 mm, whereas distensibility did not discern mildly dilated aorta. In multivariate analysis adjusted for clinical and demographic characteristics, only PWV was related to AAo dilation in BAV patients. Conclusions The mechanical properties of AAo aneurysms are similar in BAV and TAV patients, whereas MFS patients have a stiffer aorta. Aortic stiffness strongly depends on dilation severity. AAo PWV resulted in a potentially clinically useful biphasic trend with respect to aneurysm diameter, whereas distensibility did not discern mildly dilated aorta. Beyond clinical risk factors, PWV but not AD was independently related to AAo dilation in BAV patients.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Guala A. received funding from the Spanish Ministry of Science, Innovation and Universities Introduction The heterogeneous characteristic of the thoracic aorta implies that all biomarkers with potential for risk stratification need to be references to a specific location. This is the case, for example, of diameter [1], stiffness [2] and wall shear stress [3]. This is normally achieved by the manual identification of a limited number of key anatomic landmarks [4], which is a time-demanding task and may impact biomarkers accuracy and reproducibility. Automatic identification of these anatomic landmarks may speed-up the analysis and allow for the creation of fully automatic image analysis pipelines. Machine learning (ML) algorithms might be suitable for this task. Purpose The aim of this study was to test the performance of a ML algorithm in localizing key thoracic anatomical landmarks on phase-contrast enhanced magnetic resonance angiograms (PC-MRA). Methods PC-MRA of 323 patients with native aorta and aortic valve and a variety of aortic conditions (141 bicuspid aortic valve patients, 60 patients with degenerative aortic aneurysms, 82 patients with genetic aortopathy and 40 healthy volunteers) were included in this study. Four anatomical landmarks were manually identified on PC-MRA by an experienced researcher: sinotubular junction, the pulmonary artery bifurcation and the first and third supra-aortic vessel braches. A reinforcement learning algorithm (DQN), combining Q-learning with deep neural networks, was trained. The algorithm was tested in a separate set of 30 PC-MRA with similar distribution of aortic conditions in which human intra-observer reproducibility was quantified. The distance between points was used as quality metric and human annotation was considered as ground-truth. Repeated-measures ANOVA was used for statistical testing. Results ML algorithm resulted in performance similar to the intra-observer variability obtained by the experienced human reader in the identification of the sinotubular junction (11.1 ± 8.6 vs 11.0 ± 8.1 mm, p = 0.949) and first (6.8 ± 5.6 vs 6.6 ± 3.9 mm, p = 0.886) and third (8.4 ± 7.4 vs 6.8 ± 4.0 mm, p = 0.161) supra-aortic vessels branches. However, the algorithm did not reach human-level performance in the localization of the pulmonary artery bifurcation (15.2 ± 13.1 vs 10.2 ± 7.0 mm, p = 0.008). The time needed to the ML algorithm to locate all points ranged between 0.8 and 1.6 seconds on a standard computer while manual annotation required around two minutes to be performed. Conclusions The rapid identification of key aortic anatomical landmarks by a reinforced learning algorithm is feasible with human-level performance. This approach may thus be used for the design of fully-automatic pipeline for 4D flow CMR analysis.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Guala A. received funding from the Spanish Ministry of Science, Innovation and Universities Background Phase-contrast (PC) enhanced magnetic resonance (MR) angiography (MRA) is a class of angiogram exploiting velocity data to increase the signal-to-noise ratio, thus avoiding the administration of external contrast agent, normally used to segment 4D flow MR data. To train deep-learning algorithms to segment PC-MRA a large amount of manually annotated data is needed: however, the relatively novelty of the sequence, its rapid evolution and the extensive time needed to manually segment data limit its availability. Purpose The aim of this study was to test a deep learning algorithm in the segmentation of multi-center and multi-vendor PC-MRA and to test if transfer learning (TL) improves performance. Methods A large dataset (LD) of 262 and a small one (SD) of 22 PC-MRA, acquired without contrast agent at 1.5 T in a General Electric and a Siemens scanner, respectively, were manually annotated and divided into training (232 and 15 cases) and testing (30 and 7) sets. They both included PC-MRA of healthy subjects and patients with aortic diseases (excluding dissections) and native aorta. A convolutional neural networks (CNN) based on nnU-Net framework [1] was trained in the LD and another in the SD. The left ventricle was removed semi-automatically from the DL segmentations of the LD as it was not relevant for this application. Networks were then tested on the test sets of the dataset there were trained and the other dataset to assess generalizability. Finally, a fine-tuning transfer learning approach was applied to LD network and the performance on both test sets were tested. Dice score, Hausdorff distance, Jaccard score and Average Symmetrical Surface Distance were used as segmentation quality metrics. Results LD network achieved good performance in LD test set, with a DS of 0.904, ASSD of 1.47, J of 0.827 and HD of 6.35, which further improve after removing the left ventricle in the post-processing to a DS of 0.942, ASSD of 0.93, J of 0.892 and HD of 3.32. SD network results in an average DS of 0.895, ASSD of 0.59, J of 0.812 and HD of 2.05. Once tested on the testing set of the other dataset, LD network resulted in a DS of 0.612 while SD network in DS of 0.375, thus showing limited generalizability. However, the application of transfer learning to LD network resulted in the improvement of the evaluation metrics on the SD from a DS of 0.612 to 0.858, while slightly worsening in the first one without post-processing to 0.882. Conclusions nnU-net framework is effective for fast automatic segmentation of the aorta from multi-center and multi-vendor PC-MRA, showing performance comparable with the state of the art. The application of transfer learning allows for increased generalization to data from center not included in the original training. These results unlock the possibility for fully-automatic analysis of multi-vendor multi-center 4D flow MR.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Guala A. received funding from the Spanish Ministry of Science, Innovation and Universities. Background Bicuspid aortic valve (BAV), a congenital heart defect, is associated with ascending aorta dilation, possibly via alteration of aortic blood flow [1]. In BAV abnormal flow condition have been associated with aortic extracellular matrix dysregulation and elastic fiber degeneration [2]. Current morphological classification of BAV patients with aortic valve with a single fusion between two adjacent leaflets does not allow for risk stratification. Purpose This research work tested whether the extent of fusion between leaflets is related to AAo diameter and flow alterations. Methods Ninety BAV patients free from moderate and severe aortic valve disease and with no previous aortic or aortic valve surgery or replacement were prospectively enrolled. A comprehensive magnetic resonance protocol comprised a stack of double-oblique 2D balanced steady-state free-precession (bSSFP) cine CMR of the aortic valve, which was used to measure the length of the fusion between leaflets, a cine CMR at the level of the pulmonary bifurcation to assess aortic diameter and 4D flow MRI sequence to assess flow characteristics and regional stiffness [3]. Jet angle and flow radial displacement, quantifying the extent of flow eccentricity, and systolic flow reversal ratio (SFRR), assessing the relative amount of backward flow during systole, were computed at 8 equidistant planes in the ascending aorta and 4 equidistant planes in the aortic arch [4]. A two-tailed p-value < 0.05 was considered statistically significant. Results The length of leaflet fusion varied widely (median 7.7 mm, inter-quartile range [5.5; 10.2]), Table 1). In bivariate analysis, fusion length was also associated to ascending aortic diameter (R = 0.391, p Conclusions Bicuspid aortic valve fusion extent varies greatly and it is associated with aortic diameter, possibly through flow alterations. Prospective longitudinal studies are needed to establish whether fusion length may allow for risk stratification in bicuspid aortic valve patients.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): La Marató de TV3, Instituto de Salud Carlos III through the project and Spanish Ministry of Science, Innovation and Universities. BACKGROUND Loeys-Dietz (LDS) and Marfan (MFS) syndromes are rare genetic connective tissue disorders associated with progressive aortic dilation, however, aortic dissections have been observed at lower aortic root diameters in LDS than in MFS. Recent CMR studies in MFS patients reported increased aortic stiffness (1–3) and altered rotational flow (4), but research on aortic flow dynamics and biomechanics in LDS is lacking. PURPOSE The aim of this study was to assess rotational aortic flow and aortic stiffness in LDS compared to healthy volunteers (HV) and MFS patients, using 4Dflow CMR. METHODS Twenty-one LDS and 44 MFS patients, without previous aortic dissection or surgery, and 43 HV underwent a non-contrast-enhanced 4D flow CMR. Aortic stiffness was quantified at the AAo and DAo using pulse wave velocity (PWV). In-plane rotational flow (IRF), systolic flow reversal ratio (SFRR) (5) and local aortic diameters were obtained at 20 equidistant planes from the ascending (AAo) to the proximal descending aorta (DAo). RESULTS LDS patients had lower IRF at the distal AAo and proximal DAo compared to HV (p = 0.053 and 0.004, respectively), once adjusted for age, stroke volume and local aortic diameter; but no differences were found with respect to MFS (Figure). Although SFRR at the proximal DAo was increased in LDS patients compared to both HV (p = 0.037) and MFS populations (p = 0.015), once adjusted for age and aortic diameter, the difference in magnitude was small (Figure). On the other hand, AAo and DAo PWV revealed stiffer aortas in LDS patients compared to HV but no differences versus MFS patients (Table). CONCLUSIONS Patients with Loeys-Dietz syndrome showed decreased in-plane rotational flow and abnormally-high regional aortic stiffness compared to healthy controls, and similar hemodynamics and aortic stiffness with respect to patients with Marfan syndrome.

Manual assessment of aortic diameters on double-oblique reformatted computed tomography angiograms (CTA) is considered the current standard, although the reproducibility for growth rates has not been reported. Deformable registration of CTA has been proposed to provide 3D aortic diameters and growth maps, but validation is lacking. This study aimed to quantify accuracy and inter-observer reproducibility of registration-based and manual assessment of aortic diameters and growth rates. Forty patients with ≥ 2 CTA acquired at least 6 months apart were included. Aortic diameters and growth rate were obtained in the aortic root and the entire thoracic aorta using deformable image registration by two independent observers, and compared with the current standard at typical anatomical landmarks. Compared with manual assessment, the registration-based technique presented low bias (0.46 mm), excellent agreement (ICC = 0.99), and similar inter-observer reproducibility (ICC = 0.99 for both) for aortic diameters; and low bias (0.10 mm/year), good agreement (ICC = 0.82), and much higher inter-observer reproducibility for growth rates (root: ICC = 0.96 vs 0.68; thoracic aorta: ICC = 0.96 vs 0.80). Registration-based growth rate reproducibility over a 6-month-long follow-up was similar to that obtained by manual assessment after 2.7 years (LoA = [− 0.01, 0.33] vs [− 0.13, 0.21] mm/year, respectively). Mapping of diameter and growth rate was highly reproducible (ICC > 0.9) in the whole thoracic aorta. Registration-based assessment of aortic dilation on CTA is accurate and substantially more reproducible than the current standard, even at follow-up as short as 6 months, and provides robust 3D mapping of aortic diameters and growth rates beyond the pre-established anatomic landmarks. • Registration-based semi-automatic assessment of progressive aortic dilation on CTA is accurate and substantially more reproducible than the current standard. • The registration-based technique allows robust growth rate assessment at follow-up as short as 6 months, with a similar reproducibility to that obtained by manual assessment at around 3 years. • The use of image registration provides robust 3D mapping of aortic diameters and growth rates beyond the pre-established anatomic landmarks.

Imatge de perfusió miocàrdica per TC; Isquèmia miocàrdica; Relació de perfusió transmural CT myocardial perfusion imaging; Myocardial ischaemia; Transmural perfusion ratio Imágenes de perfusión miocárdica por TC; Isquemia miocárdica; Relación de perfusión transmural Purpose To compare performance of visual and quantitative analyses for detecting myocardial ischaemia from single- and dual-energy computed tomography (CT) in patients with suspected coronary artery disease (CAD). Methods Eighty-four patients with suspected CAD were scheduled for dual-energy cardiac CT at rest (CTA) and pharmacological stress (CTP). Myocardial CT perfusion was analysed visually and using three parameters: mean attenuation density (MA), transmural perfusion ratio (TPR) and myocardial perfusion reserve index (MPRI), on both single-energy CT and CT-based iodine images. Significant CAD was defined in AHA-segments by concomitant myocardial hypoperfusion identified visually or quantitatively (parameter < threshold) and coronary stenosis detected by CTA. Single-photon emission CT and invasive coronary angiography were used as reference. Perfusion-parameter cut-off values were calculated in a randomly-selected subgroup of 30 patients. Results The best-performing thresholds for TPR, MPRI and MA were 0.96, 23 and 0.5 for single-energy CT and 0.97, 47 and 0.3 for iodine imaging. For both CT-imaging modalities, TPR yielded the highest area under receiver operating characteristic curve (AUC) (0.99 and 0.97 for single-energy CT and iodine imaging, respectively, in vessel-based analysis) compared to visual analysis, MA and MPRI. Visual interpretation on iodine imaging resulted in higher AUC compared to that on single-energy CT in per-vessel (AUC: 0.93 vs 0.86, respectively) and per-patient (0.94 vs 0.93) analyses. Conclusion Transmural perfusion ratio on both CT-imaging modalities is the best-performing parameter for detecting myocardial ischaemia compared to visual method and other perfusion parameters. Visual analysis on CT-based iodine imaging outperforms that on single-energy CT.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Spanish Ministry of Science, Innovation and Universities; La Marató de TV3 Introduction Automatic analysis of medical imaging data may improve their clinical impact by reducing analysis time and improving reproducibility. Many medical imaging data, like 4D-flow magnetic resonance imaging (MRI), are often quantified regionally, implying the need for anatomical landmark identification to locate correspondences in the extracted data and compare among patients. Machine learning (ML) techniques hold potential for automatic analysis of medical imaging. Phase-contrast enhanced magnetic resonance angiography (PC-MRA) is a class of angiograms not requiring the administration of contrast agents. Purpose We aimed to test whether a machine learning algorithm can be trained to identify key anatomical cardiovascular landmarks on PC-MRA images and compare its performance with humans. Methods Three-hundred twenty-three aortic PC-MRA were manually annotated with the location of 4 landmarks: sinotubular junction, pulmonary artery bifurcation and first and third supra-aortic vessels (Figure 1), often used to separate the aorta in sub-regions. Patients included in the training dataset comprised healthy volunteers (40), bicuspid aortic valve patients (141), patients with degenerative aortic disease (60) and patients with genetically-triggered aortic disease (82), all without previous aortic surgery and with native aortic valve. PC-MRA images and manual annotations were used to train a DQN, a reinforcement learning algorithm that combines Q-learning with deep neural networks. The agents can navigate the images and optimally find the landmarks by following the policies learned during training. Data from thirty patients, distributed in terms of aortic condition as the training set, unseen by the algorithm in the training phase, were used to quantify intra-observer reproducibility and to assess ML algorithm performance. Distance between points was used as metric for comparisons, original human annotation was used as ground-truth and repeated-measures ANOVA was used for statistical testing. Results Human and machine learning performed similarly in the identification of the sinotubular junction (distance between points of 11.0 ± 8.1 vs. 11.1 ± 8.6 mm, respectively, p = 0.949) and first (6.6 ± 3.9 vs. 6.8 ± 5.6 mm, p = 0.886) and third (6.8 ± 4.0 vs. 8.4 ± 7.4 mm, p = 0.161) supra-aortic vessels branches but human annotation outperformed ML landmark detection in the identification of the pulmonary artery bifurcation (10.2 ± 7.0 vs. 15.2 ± 13.1 mm, p = 0.008). Computation time for landmark detection by ML was between 0.8 and 1.6 seconds on a standard computer while human annotation took approximatively two minutes. Conclusions ML-based aortic landmarks detection from phase-contrast enhanced magnetic resonance angiography is feasible and fast and performs similarly to human. Reinforced learning anatomical landmark identification unlock automatic extraction of a variety of regional aortic data, including complex 4D flow parameters. Abstract Figure

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Spanish Ministry of Science, Innovation and Universities ; Instituto de Salud Carlos III Introduction The aorta is a 3D hollow, curvilinear elastic structure whose diseases have life-threatening consequences. Despite much effort has been paid to study aortic diameter, diameter is a poor predictor of events. Conversely, much less is known about aortic curvature, its distribution in the thoracic aorta and the potential impact of risk factors in aneurysms associated with different conditions. Currently, 4D flow magnetic resonance imaging (4D flow CMR) allows to obtain 3D geometry, 4D flow data and regional aortic stiffness. Purpose We aim to study regional aortic curvature in thoracic aorta aneurysms of different aetiologies and define its relationship with established risk factors. Methods One-hundred twenty patients (40 for each group, selected out of prospective cohorts of 156 bicuspid aortic valve – BAV-, 77 Marfan –MFS- and 67 patients with a degenerative aneurysm – TAVdeg-) were matched for age, sex and BSA via propensity score with 40 healthy volunteers (HV). The thoracic aorta was semi-automatically segmented from angiograms and the centreline was computed. Local curvature was assessed at 20 planes covering the thoracic aorta from the sinotubular junction to the proximal descending aorta (DAo) at the level of the pulmonary artery bifurcation. Local curvature was normalized by subject mean thoracic aorta curvature. Length was measured as centreline length. Aortic stiffness was measured in the DAo by pulse wave velocity (PWV). Aneurysm was defined by z-score ≥ 2 using diameters measured by double-oblique cine CMR. Results Matching was successful in all groups with the exception of a residual age difference between HV and TAVdeg. Curvature in HV showed a fairly smooth transition between the straighter ascending aorta (AAo) and DAo to a more curved aortic arch, with a peak in the mid aortic arch (Figure 1A). Conversely, all patients’ groups presented a peak in curvature in the proximal DAo and a decreased local curvature in the aortic arch and mid DAo close to the level of the pulmonary artery. BAV and TAVdeg patients showed also increased curvature in the mid AAo, were dilation is prevalent. Conversely, in the same area MFS showed a reduced curvature and limited prevalence of aneurysm. In the overall population, age, AAo and root diameters, mean blood pressure, DAo PWV and aortic length, all established risk factors for aortic events, were inversely related to curvature in the distal AAo and aortic arch (Figure 1B). Conclusions Aneurysms related to different aetiologies show similar abnormalities in aortic curvature, with limited curvature in the aortic arch and a peak soon after the third supra-aortic vessel. Age, aortic diameter, length, stiffness and blood pressure, all known risk factors, are all related to reduced curvature in the distal ascending aorta and aortic arch. Abstract Figure.

The lack of standardized pipelines for image processing has prevented the application of deep learning (DL) techniques for the segmentation of the aorta in phase-contrast enhanced magnetic resonance angiography (PC-MRA). Furthermore, large, well-curated and annotated datasets, which are needed to create DL-based models able to generalize, are rare. We present the adaptation of the popular nnU-net DL framework to automatically segment the aorta in 4D flow MRI-derived angiograms. The resulting segmentations in a large database (\(> 300\) cases) with normal cases and examples of different pathologies of the aorta provided from a single centre were excellent after post-processing (Dice score of 0.944). Subsequently, we explored the generalisation of the trained network in a small dataset of images (around 20 cases) acquired in a different hospital with another scanner. Without domain adaptation, only with a model trained with the large dataset, the obtained results were substantially worst than with adding a few cases of the small dataset (Dice scores of 0.61 vs 0.86, respectively). The obtained results created good quality segmentations of the aorta in 4D flow MRI, which can later be post-processed to assess blood flow patterns, similarly than with manual annotations. However, advanced domain adaptation schemes are very important in 4D flow MRI due to the large differences in image characteristics between different vendor scanners available in multiple centers.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Spanish Ministry of Science, Innovation and Universities; Instituto de Salud Carlos III Introduction In Marfan syndrome (MFS) patients reduced longitudinal strain of the ascending aorta (AAo) as measured by applying feature-tracking on cine cardiac magnetic resonance (CMR) images predicts aortic root dilation and aortic events during the follow-up. Speckle-tracking is well established for cardiac deformation assessment but proximal aorta applications are challenging due to limited wall thickness and substantial cardiac motion. Moreover, echocardiography is widely used in the clinical assessment aortic diseases. Purpose We aimed to test a speckle-tracking tool for root longitudinal strain analysis in terms of comparison with CMR-derived AAo longitudinal strain and reproducibility and as predictor of dilation in MFS patients. Methods Thirty-five MFS patients diagnosed by original GHENT criteria, with maximum aortic root diameter of 45 mm and free from previous aortic dissection or cardiac/aortic surgery and non-severe aortic regurgitation were consecutive enrolled and followed-up. CMR and echocardiography were performed less than 2 months apart. Baseline and final aortic root diameter were measured on CMR images. To quantify aortic root cyclic elongation by echocardiography, two regions of interests were manually created covering both walls in a parasternal long-axis view and tracked along the cardiac cycle (Figure 1). Longitudinal strain was computed as the average of maximum increase in relative distance of several sub-regions covering both walls. CMR-derived AAo longitudinal strain was available in 29 patients. Intra-observer reproducibility was tested in 15 patients via intraclass correlation coefficient (ICC) for single-rater absolute agreement. Results Aortic root longitudinal strain by echocardiography was mildly related to CMR-derived AAo longitudinal strain (R = 0.27) and was larger compared to CMR-derived values (16.2 ± 6.0 vs 11.3 ± 4.3). Reproducibility was high, with ICC of 0.811, R = 0.802, p Conclusions The measurement of aortic root longitudinal strain by speckle-tracking echocardiography is feasible. Aortic root longitudinal strain is an independent predictor of progressive dilation in MFS patients. This may permit the improvement of risk-stratification in aortic diseases in large scale studies. Abstract Figure 1

Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Spanish Ministry of Science, Innovation and Universities Instituto de Salud Carlos III Background. Dilation of the aortic root is a key feature of Marfan syndrome and it is related to the occurrence of aortic events and death. On top of maximum diameter, rapid annual growth rate is suggested by guidelines for indication of aortic root replacement. Current gold-standard for aortic root diameter assessment is manual quantification on multiplanar reformatted 3D computed tomography (CT) or magnetic resonance angiogram. However, inter- and intra-observer reproducibility are limited and different measurement methods, i.e. cusp-to-cusp and cusp-to-commissure, may be used in different clinical centres, leading to difficulties in the clinical assessment of progressive dilation. Purpose. We aimed to test whether aortic root growth rate during follow-up can be reliably quantified by semi-automatic co-registration of two CT angiograms. Methods. Seven Marfan syndrome patients, free from previous aortic surgery, with a total of 11 pairs of CT were identified. Manual assessment of six aortic root diameters (right-non coronary -RN- , right-left -RL- and left-non coronary -LN- cusp-to-cusp and R, L and N cusp-to-commissure) was obtained from all CTs by an experienced researcher blind to semi-automatic results. The thoracic aorta and the outflow tract were semi-automatically segmented in the baseline CT and commissure and cusps were manually located. A 10 mm-thick region of interest containing the aortic wall was automatically generated from segmentation boundary. Co-registration was obtained with three, fully-automatic steps. Firstly, baseline and follow-up CT scans were aligned by means of a rigid registration. Then, scans were co-registered with multi-resolution affine followed by b-spline non-rigid registrations based on mutual information metric. The transformation pertaining to the location of baseline commissure and cusps points was used to locate the same points in the follow-up scan (Fig. 1 top). Results. Follow-up duration was 35 ± 22 (range 12-70.3) months. Automatic quantification of diameter growth during the follow-up was obtained in 62 out of 66 (94%) diameter comparisons. High Pearson correlation coefficients (R) and ICC were found between manual and semi-automatic assessment of growth rate, both for cusp-to-cusp and cusp-to-commissure diameters: R = 0.727 and ICC = 0.678 for RN; R = 0.822 and ICC = 0.602 for RL; R = 0.648 and ICC = 0.668 for LN; R = 0.726 and ICC = 0.711 for R; R = 0.911 and ICC = 0.895 for L and R = 0.553 and ICC = 0.482 for N. Scatter and Bland-Altman plots for all growth rates (Fig. 1) confirmed very good correlation (R = 0.810) but a slight tendency (R=-0.270) for underestimation at high growth rate. No correlation was found between follow-up duration and difference between techniques (R = 0.06). Conclusions. Semi-automatic quantification of aortic root growth rate by co-registration of pairs of CT angiograms is feasible for follow-up as short as one year. Larger studies are needed to confirm these preliminary data. Abstract Figure. CT measurements. Automatic vs manual.

Background: Thoracic endovascular aortic repair (TEVAR) is becoming the preferred treatment option to repair the proximal descending aorta after rupture following blunt traumatic injury. However, hemodynamic and mechanic implications of this intervention are poorly understood. Exploiting the possibilities of 4D flow magnetic resonance imaging, hemodynamics, stiffness and local dilation in the ascending aorta in patients following aortic repair by TEVAR are studied. Methods: Fifteen apparently healthy individuals who underwent TEVAR implantation after traumatic descending aortic injury and 44 healthy volunteers (HV) underwent 4D flow-MRI. Ascending aorta pulse wave velocity was computed [1]. Moreover, at eight planes equally distributed in the ascending aorta systolic flow reversal ratio, i.e. relative amount of backward flow during systole, and in-plane rotational flow, measuring the strength of helical flow, were computed [2,3]. Results: TEVAR patients and HV did not differ in terms of age, sex, BSA and blood pressure (Table). However, compared to HV, TEVAR patients showed reduced in-plane rotational flow in the distal ascending aorta in patients with TEVAR and increased backward systolic flow in the whole ascending aorta (Figure). Patients with TEVAR had a stiffer ascending aorta, with pulse wave velocity higher compared control (7.8 ± 4.2 vs 5.3 ± 1.9, p = 0.004). Finally, aortic root and ascending aorta diameters were larger in TEVAR patients compared to HV (Table). Healthy volunteers TEVAR patients p N 44 15 Age [years] 40 ± 12 43 ± 10 0.392 Sex [% male] 66 80 0.075 Years from intervention [years] N/A 10.3 ± 6.4 N/A Body surface area [m2] 1.87 ± 0.15 1.96 ± 0.23 0.088 Systolic blood pressure [mmHg] 127 ± 19 131 ± 15 0.389 Diastolic blood pressure [mmHg] 70 ± 11 74 ± 9 0.198 Aortic root diameter [mm] 31 ± 4 34 ± 4 0.026 Ascending aorta diameter [mm] 28 ± 4 32 ± 3 0.003 Ascending aorta PWV [m/s] 5.3 ± 1.9 7.8 ± 4.2 0.004 FigureIn-plane rotational flow (IRF, left) and systolic flow reversal ratio (SFRR, right) in healthy volunteers (black) and TEVAR patients (yellow) in the proximal (planes 1 to 4) and distal (planes 5 to 8) ascending aorta. Stars show statistically-significant differences (p < 0.05). Conclusions: The implantation of TEVAR in apparently healthy individuals after traumatic rupture of the proximal descending aorta is associated with altered hemodynamics, higher stiffness and larger aortic diameter in the region proximal to the TEVAR.

Background Connective tissue disorders, such as Loeys-Dietz (LDS) and Marfan (MFS) syndromes, are rare genetic diseases associated with progressive aortic dilation. Aortic dissections have been observed at lower aortic root diameters in LDS than in MFS, and research on aortic flow dynamics and biomechanics in LDS is lacking. Purpose To evaluate rotational aortic flow and aortic stiffness in LDS compared to healthy volunteers (HV) and MFS patients, using 4Dflow CMR. Methods Twenty-one LDS and 44 MFS patients, without previous aortic dissection or surgery, and 44 HV underwent a non-contrast-enhanced 4D flow CMR. In-plane rotational flow (IRF), systolic flow reversal ratio (SFRR) and local aortic diameters were obtained at 20 equidistant planes from the ascending (AAo) to the proximal descending aorta (DAo). Aortic stiffness was quantified at the AAo and DAo using pulse wave velocity (PWV). Results LDS patients had lower IRF at the distal AAo and proximal DAo compared to HV (p=0.053 and 0.004, respectively), once adjusted for age, stroke volume and local aortic diameter; but no differences were found with respect to MFS (Figure). Although SFRR at the proximal DAo was increased in LDS patients compared to both HV (p=0.037) and MFS populations (p=0.015), once adjusted for age and aortic diameter, the difference in magnitude was small (Figure). On the other hand, AAo and DAo PWV revealed stiffer aortas in LDS patients compared to HV but no differences versus MFS patients (Table). Conclusions LDS patients showed decreased in-plane rotational flow and abnormally-high regional aortic stiffness compared to healthy controls, and similar hemodynamics and aortic stiffness with respect to MFS patients Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): Instituto de Salud Carlos III, La Maratό TV3

Aims To assess aortic flow and stiffness in patients with Loeys–Dietz syndrome (LDS) by 4D flow and cine cardiovascular magnetic resonance (CMR) and compare the results with those of healthy volunteers (HV) and Marfan syndrome (MFS) patients. Methods and results Twenty-one LDS and 44 MFS patients with no previous aortic dissection or surgery and 35 HV underwent non-contrast-enhanced 4D flow CMR. In-plane rotational flow (IRF), systolic flow reversal ratio (SFRR), and aortic diameters were obtained at 20 planes from the ascending (AAo) to the proximal descending aorta (DAo). IRF and SFRR were also quantified for aortic regions (proximal and distal AAo, arch and proximal DAo). Peak-systolic wall shear stress (WSS) maps were also estimated. Aortic stiffness was quantified using pulse wave velocity (PWV) and proximal AAo longitudinal strain. Compared to HV, LDS patients had lower rotational flow at the distal AAo (P = 0.002), arch (P = 0.002), and proximal DAo (P Conclusion Greater aortic stiffness as well as impaired IRF and WSS were present in LDS patients compared to HV. Conversely, similar aortic stiffness and overlapping aortic flow features were found in Loeys–Dietz and Marfan patients.

Background: Impaired ascending aorta (AAo) longitudinal strain, a marker of AAo deformation due to aorto-ventricular mechanical interaction, is related to progressive dilation and aortic events in Marfan syndrome [1]. Whether the high prevalence of dilation in bicuspid aortic valve (BAV) is due to intrinsically-altered aortic wall properties [2] or hemodynamic [3] is widely-discussed [4]. Whether AAo longitudinal strain is altered in BAV patients has never been assessed. Methods: One-hundred five BAV patients, 47 patients with AAo dilation and tricuspid aortic valve (TAV) and 31 healthy volunteers, free from previous cardiac/aortic surgery, dissection and moderate/severe valvular disease had cine MR images to compute AAo longitudinal strain [1]. Results: Compared to healthy volunteers, the 25 non-dilated (z-score < 2) BAV patients were older (p < 0.001), had higher systolic blood pressure (SBP, p = 0.001), clinically-meaningless (BAV z-score = 0.74 ± 1.1) larger AAo diameter (p < 0.001) and similar diastolic blood pressure (DBP), BSA, stroke volume and heart rate. AAo longitudinal strain was lower in non-dilated BAV compared to healthy volunteers (13.7 vs 10.3%, p = 0.008) but this difference was not significant after correction for age. Compared to dilated TAV, dilated BAV patients were younger (p < 0.001), had lower BSA (p = 0.010) and AAo diameter (p = 0.003), higher DBP (p = 0.032) and similar SBP, stroke volume and heart rate. AAo longitudinal strain was higher in dilated BAV compared to dilated TAV (10 vs 7.2%, p < 0.001) but this difference was not significant after correction for age, BSA and DBP. Conclusion: AAo longitudinal strain is similar in BAV and TAV matched for aortic dilation.