Flow Cardiovascular Magnetic Resonance Research Articles

Oscillatory shear stress is elevated in patients with bicuspid aortic valve and aortic regurgitation: a 4D flow cardiovascular magnetic resonance cross-sectional study.

Patients with bicuspid aortic valve (BAV) and aortic regurgitation have higher rate of aortic complications compared with patients with BAV and stenosis, as well as BAV without valvular disease. Aortic regurgitation alters blood haemodynamics not only in systole but also during diastole. We therefore sought to investigate wall shear stress (WSS) during the whole cardiac cycle in BAV with aortic regurgitation. Fifty-seven subjects that underwent 4D flow cardiovascular magnetic resonance imaging were included: 13 patients with BAVs without valve disease, 14 BAVs with aortic regurgitation, 15 BAVs with aortic stenosis, and 22 normal controls with tricuspid aortic valve. Peak and time averaged WSS in systole and diastole and the oscillatory shear index (OSI) in the ascending aorta were computed. Student's t-tests were used to compare values between the four groups where the data were normally distributed, and the non-parametric Wilcoxon rank sum tests were used otherwise. BAVs with regurgitation had similar peak and time averaged WSS compared with the patients with BAV without valve disease and with stenosis, and no regions of elevated WSS were found. BAV with aortic regurgitation had twice as high OSI as the other groups (P ≤ 0.001), and mainly in the outer mid-to-distal ascending aorta. OSI uniquely characterizes altered WSS patterns in BAVs with aortic regurgitation, and thus could be a haemodynamic marker specific for this specific group that is at higher risk of aortic complications. Future longitudinal studies are needed to verify this hypothesis.

Quantifying 4D flow cardiovascular magnetic resonance vortices in patients with pulmonary hypertension: A pilot study.

In this 4D flow cardiovascular magnetic resonance (CMR) study, vortical blood flow in the main pulmonary artery (MPA) is quantified using circulation (ᴦ), a metric used in fluid dynamics to quantify the rotational components of flow. Circulation (ᴦ) is a 4D flow CMR metric that quantifies the vortical blood flow pattern in the MPA of patients with pulmonary hypertension (PH), distinguishes them from healthy controls, and shows high correlation with invasive markers of PH severity.

Intraventricular 4D flow cardiovascular magnetic resonance for assessing patients with heart failure with preserved ejection fraction: a pilot study.

Diagnosing heart failure with preserved ejection fraction (HFpEF) remains challenging. Intraventricular four-dimensional flow (4D flow) phase-contrast cardiovascular magnetic resonance (CMR) can assess different components of left ventricular (LV) flow including direct flow, delayed ejection, retained inflow and residual volume. This could be utilised to identify HFpEF. This study investigated if intraventricular 4D flow CMR could differentiate HFpEF patients from non-HFpEF and asymptomatic controls. Suspected HFpEF patients and asymptomatic controls were recruited prospectively. HFpEF patients were confirmed using European Society of Cardiology (ESC) 2021 expert recommendations. Non-HFpEF patients were diagnosed if suspected HFpEF patients did not fulfil ESC 2021 criteria. LV direct flow, delayed ejection, retained inflow and residual volume were obtained from 4D flow CMR images. Receiver operating characteristic (ROC) curves were plotted. 63 subjects (25 HFpEF patients, 22 non-HFpEF patients and 16 asymptomatic controls) were included in this study. 46% were male, mean age 69.8 ± 9.1years. CMR 4D flow derived LV direct flow and residual volume could differentiate HFpEF vs combined group of non-HFpEF and asymptomatic controls (p < 0.001 for both) as well as HFpEF vs non-HFpEF patients (p = 0.021 and p = 0.005, respectively). Among the 4 parameters, direct flow had the largest area under curve (AUC) of 0.781 when comparing HFpEF vs combined group of non-HFpEF and asymptomatic controls, while residual volume had the largest AUC of 0.740 when comparing HFpEF and non-HFpEF patients. CMR 4D flow derived LV direct flow and residual volume show promise in differentiating HFpEF patients from non-HFpEF patients.

4D flow cardiovascular magnetic resonance for the assessment of aortic valve repair with ozaki technique

Abstract Funding Acknowledgements Type of funding sources: None. Background Aortic valve neocuspidalization (Av-Neo) aims to replace the three aortic cusps with autologous pericardium pre-treated with glutaraldehyde and is becoming a valid alternative to traditional aortic valve replacement (AVR). 4D-flow cardiac magnetic resonance (4D-CMR) imaging of patients allows the derivation of shear stress on the aortic wall (WSS). Different studies support the presence of a link between increased WSS at 4D-CMR and the presence of histological alterations of the aortic wall. Purpose To compare the WSS of the ascending aorta in patients who underwent Av-Neo vs AVR with biological prostheses. Methods We performed 4D-flow CMR on 20 patients who underwent AV-Neo (Group A) or AVR (Group B), 10 patients for each group. Results The WSS in the Ozaki group was significantly lower in the proximal and distal aortic outer curvature compared to AVR patients (p 0.0179 and 0.0412, respectively, Figure 1 and 2). WSS levels remained significantly lower at the proximal aorta’s outer curvature segment in the Av-Neo population, also after adjusting the WSS for the ejection fraction and the LVOT-Aorta angle (p 0.02). Conclusions Av-neo hemodynamical features showed to be non-inferior to the ones provided by the commercially available bioprosthetic valves. Av-Neo procedures may be considered in patients affected by collagenopathy and other predisposing risk factors for the development of ascending aortic aneurism and aortic dissection other than classical AVR.

Fluid dynamics by 4D flow CMR in Marfan and Loeys-Dietz patients before and after valve sparing aortic root replacement

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III (Spain), Sociedad Española de Cardiología Introduction Patients with Marfan or Loeys-Dietz syndrome present abnormal aortic flow patterns in the arch and the proximal descending aorta that may contribute to aortic dilation (1,2). Valve sparing aortic root replacement, which is effective in reducing the risk of aortic dissection in case of severe dilation, may also normalize flow patterns beyond the replaced aorta and potentially slow its progressive aortic dilation. Purpose To assess aortic flow dynamics in these patients with Marfan or Loeys-Dietz by 4D flow cardiovascular magnetic resonance (CMR) before and after valve sparing aortic root replacement (David surgery), and to compare the results with those of healthy volunteers (HV). Methods Patients with Marfan or Loeys-Dietz syndrome underwent two non-contrast enhanced 4D flow CMR, one before and another after undergoing David surgery. Healthy volunteers matched for age, sex and BSA were also included for comparison. Maximum velocity, in-plane rotational flow (IRF), systolic flow reversal ratio (SFRR) and wall shear stress (WSS) magnitude and its axial and circumferential components were obtained at 24 planes covering the thoracic aorta from the sinotubular junction to the descending aorta at the diaphragmatic level (3–5). Results Sixteen patients and 21 healthy volunteers were included. Demographic and clinical data is presented in Table. The mean time between the CMR prior and posterior to surgery was 15 months. Compared to HV, patients with CTD before intervention presented lower maximum velocity at the proximal ascending aorta (Figure 1A), lower IRF and circumferential WSS at the arch and the proximal descending aorta (Figure 1B and F), lower magnitude and axial WSS at the proximal ascending and descending aorta (Figure 1E and D), and increased SFRR at the proximal descending aorta (Figure 1C). The intervention completely restored maximum velocity and partially-restored physiological helical flow and circumferential WSS, but barely improved axial WSS and SFRR. Conclusion Valve sparing aortic root replacement in patients with Marfan or Loeys-Dietz syndrome partially restore to physiological level both in-plane rotational flow and circumferential wall shear stress in the descending aorta.

4D Flow Cardiovascular Magnetic Resonance-Derived Flow Biomarkers for Early Detection of Flow Abnormalities: A Multicohort New Zealand Based Study

Four-dimensional (4D) flow cardiovascular magnetic resonance (4D flow CMR) imaging has evolved as a versatile imaging technique for the assessment of cardiovascular three-dimensional time resolved haemodynamics. This study aimed to examine the utility and metrics derived from 4D flow CMR in different patient cohorts. Controls (n=26), adult tetralogy of Fallot (rToF; n=14), and left ventricular hypertrophy (LVH; n=10) patients were scanned at the Centre of Advanced MRI, University of Auckland. Quantification of flow and examination of between-group differences were performed. Intraclass correlation coefficients (ICC) were used to correlate 4D and 2D CMR. Forward flow rates averaged in the pulmonary veins were significantly greater in LVH than controls (79.11±54.24 mL/sec vs 32.58±35.98 mL/sec, respectively, p<0.05), as was the pulmonary venous atrial reversal peak velocity (–0.44±0.23 m/sec vs –0.13±0.27 m/sec, respectively, p<0.05). Mitral indices of net flow and peak velocity expressed no significant between-group differences. In the rToF group, quantification of pulmonary artery and branches demonstrated a good correlation with 2D CMR. Greatest correlation was between pulmonary artery backward flow (difference of s–2.50±6.91 mL/cycle, ICC 0.96). In relation to pulmonary valve regurgitation categorisation, 1 of 14 cases were differently categorised using 4D flow (ICC 0.91). Quantification of flow with 4D flow CMR was feasible, with a single acquisition introducing an array of flow metrics that may be valuable for the evaluation of various conditions. Larger scale investigations of 4D flow CMR are required, with wider-scale application in routine clinical workflows.

'Conventional' haemodynamics even in the quadricuspid aortic valve: clinical recognition using multimodality imaging.

A 76-year-old male with congestive heart failure, accompanied by dyspnoea and irregular rhythm, was transferred to our hospital for treatment of congestive heart failure (NYHAIII/IV). Atrial fibrillation was confirmed by electrocardiography, and transoesophageal echocardiography (TEE) for electrical cardioversion was performed due to poor response to medical therapy. Two- and three-dimensional TEE revealed a quadricuspid aortic valve (QAV) with central leaflet malcoaptation and restriction of valve leaflet opening (Panels A and B; Supplementary data online, Videos S1 and S2). After electrical cardioversion, transthoracic echocardiography showed severe aortic stenosis with a 4.9 m/s peak aortic valve flow velocity, mean pressure gradient of 56 mm Hg (Panel C), and severe aortic regurgitation; the regurgitant volume was 61 mL/beat, and vena contracta width was 6.1 mm (Panel D; Supplementary data online, Video S3). Multi-detector row computed tomography confirmed the QAV and showed no dilatation of the ascending aorta (diameter, 34 mm) (Panels E and F). Four-dimensional flow cardiovascular magnetic resonance was confirmed that blood flow in the ascending aorta had a normal flow pattern; peak systolic wall shear stress values were not high, and symmetrical helical flow was observed (Panels G and H; Supplementary data online, Videos S4 and S5). Based on these results, TAVI was also considered, but we determined that simultaneous intervention for atrial fibrillation was necessary. Therefore, surgical aortic valve replacement (bioprosthetic valve), pulmonary vein isolation, and left atrial appendage closure were performed (Panels I and J). This case underlines the importance of multimodality approach to the diagnosis and treatment strategy of QAV.

Population-based reference values for 4D flow MRI derived aortic blood flow parameters

Objective. This study assesses age-related differences of thoracic aorta blood flow profiles and provides age- and sex-specific reference values using 4D flow cardiovascular magnetic resonance (CMR) data. Approach. 126 volunteers (age 20–80 years, female 51%) underwent 4D flow CMR and 12 perpendicular analysis planes in the thoracic aorta were specified. For these planes the following parameters were evaluated: body surface area-adjusted aortic area (A′), normalized flow displacement (NFD), the degree of wall parallelism (WPD), the minimal relative cross-sectional area through which 80% of the volume flow passes (A80) and the angle between flow direction and centerline (α). Main results. Age-related differences in blood flow parameters were seen in the ascending aorta with higher values for NFD and angle and lower values for WPD and A80 in older subjects. All parameters describing blood flow patterns correlated with the cross-sectional area in the ascending aorta. No relevant sex-differences regarding blood flow profiles were found. Significance. These age- and sex-specific reference values for quantitative parameters describing blood flow within the aorta might help to study the clinical relevance of flow profiles in the future.

Evaluation of left ventricular blood flow kinetic energy in patients with hypertension by four-dimensional flow cardiovascular magnetic resonance imaging: a preliminary study.

To evaluate the intra-cavity left ventricular (LV) blood flow kinetic energy (KE) parameters using four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) in patients with hypertension (HTN). Forty-two HTN patients and twenty age-/gender-matched healthy controls who underwent CMR including cines, pre-/post-T1 mapping, and whole-heart 4D flow imaging were retrospectively evaluated. HTN patients were further divided into two subgroups: with preserved ejection fraction (HTN-pEF) and with reduced ejection fraction (HTN-rEF). KE parameters were indexed to LV end-diastolic volume (EDV) to obtain averaged LV, minimal, systolic, diastolic, peak E-wave, peak A-wave, E-wave, and A-wave KEiEDV, as well as the proportion of in-plane LV KE (%), the time difference (TD). These parameters were compared between the HTN group and healthy controls, also between two subgroups. The correlation of LV blood flow KE parameters with LV function and extracellular volume fraction (ECV) were analyzed in the HTN group using multivariate regression analysis. Peak E-wave KEiEDV in the HTN group was significantly lower (p = 0.01), while in-plane KE and TD were significantly higher (all p < 0.01) than those in healthy controls. Compared to the HTN-pEF subgroup, the proportion of in-plane KE and TD was significantly increased in the HTN-rEF subgroup (all p < 0.01). Only the proportion of in-plane KE demonstrated an independent correlation with ECV (β* = 0.59, p < 0.01). The decreased peak E-wave KEiEDV and the increased proportion of in-plane KE, TD reflected the alterations of LV blood flow in HTN patients, and the proportion of in-plane KE was independently associated with ECV. • 4D flow CMR demonstrated that the peak E-wave KEiEDV was decreased, while the in-plane KE and time difference (TD) were increased in hypertensive (HTN) patients. • The proportion of in-plane KE and TD was further increased in HTN patients with reduced ejection fraction than in HTN patients with preserved ejection fraction, and the proportion of in-plane KE was independently associated with extracellular volume fraction in HTN patients. • 4D flow CMR intra-cavity blood flow KE parameters might reveal the LV hemodynamic status in preclinical HTN patients.

Changes of aortic hemodynamics after aortic valve replacement-A four dimensional flow cardiovascular magnetic resonance follow up study.

Non-invasive assessment of aortic hemodynamics using four dimensional (4D) flow magnetic resonance imaging (MRI) provides new information on blood flow patterns and wall shear stress (WSS). Aortic valve stenosis (AS) and/or bicuspid aortic valves (BAV) are associated with altered aortic flow patterns and elevated WSS. Aim of this study was to investigate changes in aortic hemodynamics over time in patients with AS and/or BAV with or without aortic valve replacement. We rescheduled 20 patients for a second 4D flow MRI examination, whose first examination was at least 3 years prior. A total of 7 patients received an aortic valve replacement between baseline and follow up examination (=operated group = OP group). Aortic flow patterns (helicity/vorticity) were assessed using a semi-quantitative grading approach from 0 to 3, flow volumes were evaluated in 9 planes, WSS in 18 and peak velocity in 3 areas. While most patients had vortical and/or helical flow formations within the aorta, there was no significant change over time. Ascending aortic forward flow volumes were significantly lower in the OP group than in the NOP group at baseline (NOP 69.3 mL ± 14.2 mL vs. OP 55.3 mL ± 1.9 mL p = 0.029). WSS in the outer ascending aorta was significantly higher in the OP group than in the NOP group at baseline (NOP 0.6 ± 0.2 N/m2 vs. OP 0.8 ± 0.2 N/m2, p = 0.008). Peak velocity decreased from baseline to follow up in the aortic arch only in the OP group (1.6 ± 0.6 m/s vs. 1.2 ± 0.3 m/s, p = 0.018). Aortic valve replacement influences aortic hemodynamics. The parameters improve after surgery.

Age- and sex-specific reference values of biventricular flow components and kinetic energy by 4D flow cardiovascular magnetic resonance in healthy subjects

BackgroundAdvances in four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) have allowed quantification of left ventricular (LV) and right ventricular (RV) blood flow. We aimed to (1) investigate age and sex differences of 4D flow CMR-derived LV and RV relative flow components and kinetic energy (KE) parameters indexed to end-diastolic volume (KEiEDV) in healthy subjects; and (2) assess the effects of age and sex on these parameters. MethodsWe performed 4D flow analysis in 163 healthy participants (42% female; mean age 43 ± 13 years) of a prospective registry study (NCT03217240) who were free of cardiovascular diseases. Relative flow components (direct flow, retained inflow, delayed ejection flow, residual volume) and multiple phasic KEiEDV (global, peak systolic, average systolic, average diastolic, peak E-wave, peak A-wave) for both LV and RV were analysed. ResultsCompared with men, women had lower median LV and RV residual volume, and LV peak and average systolic KEiEDV, and higher median values of RV direct flow, RV global KEiEDV, RV average diastolic KEiEDV, and RV peak E-wave KEiEDV. ANOVA analysis found there were no differences in flow components, peak and average systolic, average diastolic and global KEiEDV for both LV and RV across age groups. Peak A-wave KEiEDV increased significantly (r = 0.458 for LV and 0.341 for RV), whereas peak E-wave KEiEDV (r = − 0.355 for LV and − 0.318 for RV), and KEiEDV E/A ratio (r = − 0.475 for LV and − 0.504 for RV) decreased significantly, with age. ConclusionThese data using state-of-the-art 4D flow CMR show that biventricular flow components and kinetic energy parameters vary significantly by age and sex. Age and sex trends should be considered in the interpretation of quantitative measures of biventricular flow.Clinical trial registration https://www.clinicaltrials.gov. Unique identifier: NCT03217240.

Validation of 4D flow cardiovascular magnetic resonance in TIPS stent grafts using a 3D-printed flow phantom

BackgroundFour-dimensional (4D) flow cardiovascular magnetic resonance (CMR) is feasible for portal blood flow evaluation after placement of transjugular intrahepatic portosystemic shunts (TIPS) in patients with liver cirrhosis. However, clinical acceptance of 4D flow CMR in TIPS patients is limited due to the lack of validation studies. The purpose of this study was to validate 4D flow CMR-derived measurements in TIPS stent grafts using a three-dimensional (3D)-printed flow phantom. MethodsA translucent flow phantom of the portal vasculature was 3D-printed. The phantom consisted of the superior mesenteric vein and the splenic vein draining into the portal vein, the TIPS-tract, and the hepatic vein. A TIPS stent graft (Gore® Viatorr®) was positioned within the TIPS-tract. Superior mesenteric vein and splenic vein served as inlets for blood-mimicking fluid. 4D flow CMR acquisitions were performed at 3T at preset flow rates of 0.8 to 2.8 l/min using velocity encoding of both 1.0 and 2.0 m/s. Flow rates and velocities were measured at predefined levels in the portal vasculature and within the stent graft. Accuracy of 4D flow CMR was assessed through linear regression with reference measurements obtained by flow sensors and two-dimensional (2D) phase contrast (PC) CMR. Intra- and interobserver agreement were assessed through Bland–Altman analyses. ResultsAt a velocity encoding of 2.0 m/s, 4D flow CMR-derived flow rates and velocities showed an excellent correlation with preset flow rates and 2D PC CMR-derived flow velocities at all vascular levels and within the stent graft (all r ≥ 0.958, p ≤ 0.003). At a velocity encoding of 1.0 m/s, aliasing artifacts were present within the stent graft at flow rates ≥ 2.0 l/min. 4D flow CMR-derived measurements revealed high intra- and interobserver agreement. ConclusionsThe in vitro accuracy and precision of 4D flow CMR is unaffected by the presence of TIPS stent grafts, suggesting that 4D flow CMR may be used to monitor TIPS patency in patients with liver cirrhosis.

Differences in blood flow dynamics between balloon- and self-expandable valves in patients with aortic stenosis undergoing transcatheter aortic valve replacement

BackgroundThe differences in pre- and early post-procedural blood flow dynamics between the two major types of bioprosthetic valves, the balloon-expandable valve (BEV) and self-expandable valve (SEV), in patients with aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR), have not been investigated. We aimed to investigate the differences in blood flow dynamics between the BEV and SEV using four-dimensional flow cardiovascular magnetic resonance (4D flow CMR). MethodsWe prospectively examined 98 consecutive patients with severe AS who underwent TAVR between May 2018 and November 2021 (58 BEV and 40 SEV) after excluding those without CMR because of a contraindication, inadequate imaging from the analyses, or patients' refusal. CMR was performed in all participants before (median interval, 22 [interquartile range (IQR) 4–39] days) and after (median interval, 6 [IQR 3–6] days) TAVR. We compared the changes in blood flow patterns, wall shear stress (WSS), and energy loss (EL) in the ascending aorta (AAo) between the BEV and SEV using 4D flow CMR. ResultsThe absolute reductions in helical flow and flow eccentricity were significantly higher in the SEV group compared in the BEV group after TAVR (BEV: − 0.22 ± 0.86 vs. SEV: − 0.85 ± 0.80, P < 0.001 and BEV: − 0.11 ± 0.79 vs. SEV: − 0.50 ± 0.88, P = 0.037, respectively); there were no significant differences in vortical flow between the groups. The absolute reduction of average WSS was significantly higher in the SEV group compared to the BEV group after TAVR (BEV: − 0.6 [− 2.1 to 0.5] Pa vs. SEV: − 1.8 [− 3.5 to − 0.8] Pa, P = 0.006). The systolic EL in the AAo significantly decreased after TAVR in both the groups, while the absolute reduction was comparable between the groups. ConclusionsHelical flow, flow eccentricity, and average WSS in the AAo were significantly decreased after SEV implantation compared to BEV implantation, providing functional insights for valve selection in patients with AS undergoing TAVR. Our findings offer valuable insights into blood flow dynamics, aiding in the selection of valves for patients with AS undergoing TAVR. Further larger-scale studies are warranted to confirm the prognostic significance of hemodynamic changes in these patients.

Repeatability and reproducibility of various 4D Flow MRI postprocessing software programs in a multi-software and multi-vendor cross-over comparison study

BackgroundDifferent software programs are available for the evaluation of 4D Flow cardiovascular magnetic resonance (CMR). A good agreement of the results between programs is a prerequisite for the acceptance of the method. Therefore, the goal was to compare quantitative results from a cross-over comparison in individuals examined on two scanners of different vendors analyzed with four postprocessing software packages. MethodsEight healthy subjects (27 ± 3 years, 3 women) were each examined on two 3T CMR systems (Ingenia, Philips Healthcare; MAGNETOM Skyra, Siemens Healthineers) with a standardized 4D Flow CMR sequence. Six manually placed aortic contours were evaluated with Caas (Pie Medical Imaging, SW-A), cvi42 (Circle Cardiovascular Imaging, SW-B), GTFlow (GyroTools, SW-C), and MevisFlow (Fraunhofer Institute MEVIS, SW-D) to analyze seven clinically used parameters including stroke volume, peak flow, peak velocity, and area as well as typically scientifically used wall shear stress values. Statistical analysis of inter- and intrareader variability, inter-software and inter-scanner comparison included calculation of absolute and relative error (ER), intraclass correlation coefficient (ICC), Bland–Altman analysis, and equivalence testing based on the assumption that inter-software differences needed to be within 80% of the range of intrareader differences. ResultsSW-A and SW-C were the only software programs showing agreement for stroke volume (ICC = 0.96; ER = 3 ± 8%), peak flow (ICC: 0.97; ER = −1 ± 7%), and area (ICC = 0.81; ER = 2 ± 22%). Results from SW-A/D and SW-C/D were equivalent only for area and peak flow. Other software pairs did not yield equivalent results for routinely used clinical parameters. Especially peak maximum velocity yielded poor agreement (ICC ≤ 0.4) between all software packages except SW-A/D that showed good agreement (ICC = 0.80). Inter- and intrareader consistency for clinically used parameters was best for SW-A and SW-D (ICC = 0.56–97) and worst for SW-B (ICC = -0.01–0.71). Of note, inter-scanner differences per individual tended to be smaller than inter-software differences. ConclusionsOf all tested software programs, only SW-A and SW-C can be used equivalently for determination of stroke volume, peak flow, and vessel area. Irrespective of the applied software and scanner, high intra- and interreader variability for all parameters have to be taken into account before introducing 4D Flow CMR in clinical routine. Especially in multicenter clinical trials a single image evaluation software should be applied.

Systolic reverse flow derived from 4D flow cardiovascular magnetic resonance in bicuspid aortic valve is associated with aortic dilation and aortic valve stenosis: a cross sectional study in 655 subjects

BackgroundBicuspid aortic valve (BAV) disease is associated with increased risk of aortopathy. In addition to current intervention guidelines, BAV mediated changes in aortic 3D hemodynamics have been considered as risk stratification measures. We aimed to evaluate the association of 4D flow cardiovascular magnetic resonance (CMR) derived voxel-wise aortic reverse flow with aortic dilation and to investigate the role of aortic valve regurgitation (AR) and stenosis (AS) on reverse flow in systole and diastole. Methods510 patients with BAV (52 ± 14 years) and 120 patients with trileaflet aortic valve (TAV) (61 ± 11 years) and mid-ascending aorta diameter (MAAD) > 35 mm who underwent CMR including 4D flow CMR were retrospectively included. An age and sex-matched healthy control cohort (n = 25, 49 ± 12 years) was selected. Voxel-wise reverse flow was calculated in the aorta and quantified by the mean reverse flow in the ascending aorta (AAo) during systole and diastole. ResultsBAV patients without AS and AR demonstrated significantly increased systolic and diastolic reverse flow (222% and 13% increases respectively, p < 0.01) compared to healthy controls and also had significantly increased systolic reverse flow compared to TAV patients with aortic dilation (79% increase, p < 0.01). In patients with isolated AR, systolic and diastolic AAo reverse flow increased significantly with AR severity (c = − 83.2 and c = − 205.6, p < 0.001). In patients with isolated AS, AS severity was associated with an increase in both systolic (c = − 253.1, p < 0.001) and diastolic (c = − 87.0, p = 0.02) AAo reverse flow. Right and left/right and non-coronary fusion phenotype showed elevated systolic reverse flow (> 17% increase, p < 0.01). Right and non-coronary fusion phenotype showed decreased diastolic reverse flow (> 27% decrease, p < 0.01). MAAD was an independent predictor of systolic (p < 0.001), but not diastolic, reverse flow (p > 0.1). Conclusion4D flow CMR derived reverse flow associated with BAV was successfully captured even in the absence of AR or AS and in comparison to TAV patients with aortic dilation. Diastolic AAo reverse flow increased with AR severity while AS severity strongly correlated with increased systolic reverse flow in the AAo. Additionally, increasing MAAD was independently associated with increasing systolic AAo reverse flow. Thus, systolic AAo reverse flow may be a valuable metric for evaluating disease severity in future longitudinal outcome studies.

Non-invasive cardiovascular magnetic resonance assessment of pressure recovery distance after aortic valve stenosis

BackgroundDecisions in the management of aortic stenosis are based on the peak pressure drop, captured by Doppler echocardiography, whereas gold standard catheterization measurements assess the net pressure drop but are limited by associated risks. The relationship between these two measurements, peak and net pressure drop, is dictated by the pressure recovery along the ascending aorta which is mainly caused by turbulence energy dissipation. Currently, pressure recovery is considered to occur within the first 40–50 mm distally from the aortic valve, albeit there is inconsistency across interventionist centers on where/how to position the catheter to capture the net pressure drop. MethodsWe developed a non-invasive method to assess the pressure recovery distance based on blood flow momentum via 4D Flow cardiovascular magnetic resonance (CMR). Multi-center acquisitions included physical flow phantoms with different stenotic valve configurations to validate this method, first against reference measurements and then against turbulent energy dissipation (respectively n = 8 and n = 28 acquisitions) and to investigate the relationship between peak and net pressure drops. Finally, we explored the potential errors of cardiac catheterisation pressure recordings as a result of neglecting the pressure recovery distance in a clinical bicuspid aortic valve (BAV) cohort of n = 32 patients. ResultsIn-vitro assessment of pressure recovery distance based on flow momentum achieved an average error of 1.8 ± 8.4 mm when compared to reference pressure sensors in the first phantom workbench. The momentum pressure recovery distance and the turbulent energy dissipation distance showed no statistical difference (mean difference of 2.8 ± 5.4 mm, R2 = 0.93) in the second phantom workbench. A linear correlation was observed between peak and net pressure drops, however, with strong dependences on the valvular morphology. Finally, in the BAV cohort the pressure recovery distance was 78.8 ± 34.3 mm from vena contracta, which is significantly longer than currently accepted in clinical practise (40–50 mm), and 37.5% of patients displayed a pressure recovery distance beyond the end of the ascending aorta. ConclusionThe non-invasive assessment of the distance to pressure recovery is possible by tracking momentum via 4D Flow CMR. Recovery is not always complete at the ascending aorta, and catheterised recordings will overestimate the net pressure drop in those situations. There is a need to re-evaluate the methods that characterise the haemodynamic burden caused by aortic stenosis as currently clinically accepted pressure recovery distance is an underestimation.

Abstract 11710: Sex Differences in Right Ventricular Flow Dynamics and Kinetic Energy in Healthy Volunteers

Introduction: Accurate right ventricular (RV) flow and function is crucial for optimal cardiovascular health. However, research on RV flow and function has lagged behind that for the left ventricle. Whole-heart 4D flow cardiovascular magnetic resonance (CMR) uniquely quantifies simultaneous multi-directional phasic blood flow and kinetic energy (KE). Gender differences in these parameters have not been well studied and may contribute to the predilection for developing certain cardiovascular diseases among females. This study aims to compare RV flow and KE parameters in healthy female and male subjects. Methods: Healthy subjects from 2 centers (n=163) were prospectively recruited to undergo 4D flow CMR. RV flow components —direct flow, retained inflow, delayed ejection flow and residual volume —and KE (KE=1/2·ρ blood · V voxel · v 2 where ρ blood is blood density 1.06 g/cm 3 ; V voxel , voxel volume; and v , velocity) were calculated. All KE parameters were indexed to RV end-diastolic volume (KEi EDV ) and expressed in μJ/ml. KEi EDV parameters at physiologically relevant epochs (global [entire cycle], systole, diastole) and cardiac cycle time points (peak systole, peak E-wave, peak A-wave) were extracted from a time-resolved KEi EDV curve. Results: Compared to males (n=95, mean age 44 years old), females (n=68, mean age 42 years old) had higher RV ejection fraction but smaller RV volumes; higher RV direct flow (38 vs 34%, P=0.007) and delayed ejection flow (17 vs 15%, P=0.043) and lower RV residual volume (27 vs 33%, P=0.001). Females had higher global KEi EDV (8.9 vs 7.5μJ/ml, P=0.005), diastolic KEi EDV (6.7 vs 5.6μJ/ml, P&lt;0.001), peak E-wave KEi EDV (14.4 vs 11.9μJ/ml, P&lt;0.001) and E-wave/A-wave ratio (1.68 vs 1.30, P=0.028) than males. No differences were observed for RV retained inflow, RV peak systolic, average systolic and peak A-wave KEi EDV between gender. Conclusion: Females have higher RV direct flow and lower RV residual volume, higher preload-adjusted RV global, average diastolic, peak E-wave and E-wave/A-wave ratio KEi EDV , compared to males by 4D flow cardiovascular magnetic resonance imaging. These parameters that related to right heart efficiency may lead to further understanding of the sex-based predispositions to right heart disease.

Aortic flow patterns by 4D flow CMR in Marfan and Loeys-Dietz patients before and after valve sparing aortic root replacement: a comparison with healthy volunteers

Abstract Introduction Abnormal aortic flow patterns in patients with a connective tissue disorder (CTD), such as Marfan or Loeys-Dietz syndrome, may contribute to aortic root dilation [1,2]. Valve sparing aortic root replacement, which is effective in reducing the risk of aortic dissection in case of severe dilation, may also normalize flow patterns beyond the replaced aorta and potentially slow its progressive aortic dilation. Purpose To assess aortic flow dynamics in patients with a CTD by 4D flow cardiovascular magnetic resonance (CMR) before and after valve sparing aortic root replacement, and to compare the results with those of healthy volunteers (HV). Methods Patients with Marfan or Loeys-Dietz syndrome underwent two non-contrast enhanced 4D flow CMR, one before and another after undergoing valve sparing aortic root replacement. Healthy volunteers matched for age, sex and BSA were also included for comparison. Maximum velocity, in-plane rotational flow (IRF), systolic flow reversal ratio (SFRR) and wall shear stress (WSS) magnitude and its axial and circumferential components were obtained at 24 planes covering the thoracic aorta from the sinotubular junction to the descending aorta at the diaphragmatic level [3–5]. Results Sixteen patients and 21 healthy volunteers were included. Demographic and clinical data is presented in Table. The mean time between the CMR prior and posterior to surgery was 15 months. Compared to HV, patients with CTD before intervention presented lower maximum velocity at the proximal ascending aorta (Fig. 1A), lower IRF and circumferential WSS at the arch and the proximal descending aorta (Fig. 1B and F), lower magnitude and axial WSS at the proximal ascending and descending aorta (Fig. 1E and D), and increased SFRR at the proximal descending aorta (Fig. 1C). The intervention completely restored maximum velocity and partially-restored physiological helical flow and circumferential WSS, but barely improved axial WSS and SFRR. Conclusion Valve sparing aortic root replacement in patients with Marfan or Loeys-Dietz syndrome partially restore to physiological level both in-plane rotational flow and circumferential wall shear stress in the descending aorta. This flow normalization may contribute to prevent progressive dilation after the surgery. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III (Spain) (PI17/00381)Spanish Society of Cardiology (SEC/FEC-INV-CLI 20/015)

Evaluation of Left Ventricular Function Using Four-Dimensional Flow Cardiovascular Magnetic Resonance: A Systematic Review.

There is increasing recognition of the value of four-dimensional flow cardiovascular magnetic resonance (4D-flow MRI) as a potential means to detect and measure abnormal flow behaviour that occurs during early left ventricular (LV) dysfunction. We performed a systematic review of current literature on the role of 4D-flow MRI-derived flow parameters in quantification of LV function with a focus on potential clinical applicability. A comprehensive literature search was performed in March 2022 on available databases. A total of 1186 articles were identified, and 30 articles were included in the final analysis. All the included studies were ranked as “highly clinically applicable”. There was considerable variability in the reporting of methodologies and analyses. All the studies were small-scale feasibility or pilot studies investigating a diverse range of flow parameters. The most common primary topics of investigation were energy-related flow parameters, flow components and vortex analysis which demonstrated potentials for quantifying early diastolic dysfunction, whilst other parameters including haemodynamic forces, residence time distribution and turbulent kinetic energy remain in need of further evaluation. Systematic quantitative comparison of study findings was not possible due to this heterogeneity, therefore limiting the collective power of the studies in evaluating clinical applicability of the flow parameters. To achieve broader clinical application of 4D-flow MRI, larger scale investigations are required, together with standardisation of methodologies and analytical approach.

Validation of time-resolved, automated peak trans-mitral velocity tracking: Two center four-dimensional flow cardiovascular magnetic resonance study

ObjectiveWe aim to validate four-dimensional flow cardiovascular magnetic resonance (4D flow CMR) peak velocity tracking methods for measuring the peak velocity of mitral inflow against Doppler echocardiography. MethodFifty patients were recruited who had 4D flow CMR and Doppler Echocardiography. After transvalvular flow segmentation using established valve tracking methods, peak velocity was automatically derived using three-dimensional streamlines of transvalvular flow. In addition, a static-planar method was used at the tip of mitral valve to mimic Doppler technique. ResultsPeak E-wave mitral inflow velocity was comparable between TTE and the novel 4D flow automated dynamic method (0.9 ± 0.5 vs 0.94 ± 0.6 m/s; p = 0.29) however there was a statistically significant difference when compared with the static planar method (0.85 ± 0.5 m/s; p = 0.01). Median A-wave peak velocity was also comparable across TTE and the automated dynamic streamline (0.77 ± 0.4 vs 0.76 ± 0.4 m/s; p = 0.77). A significant difference was seen with the static planar method (0.68 ± 0.5 m/s; p = 0.04). E/A ratio was comparable between TTE and both the automated dynamic and static planar method (1.1 ± 0.7 vs 1.15 ± 0.5 m/s; p = 0.74 and 1.15 ± 0.5 m/s; p = 0.5 respectively). Both novel 4D flow methods showed good correlation with TTE for E-wave (dynamic method; r = 0.70; P < 0.001 and static-planar method; r = 0.67; P < 0.001) and A-wave velocity measurements (dynamic method; r = 0.83; P < 0.001 and static method; r = 0.71; P < 0.001). The automated dynamic method demonstrated excellent intra/inter-observer reproducibility for all parameters. ConclusionAutomated dynamic peak velocity tracing method using 4D flow CMR is comparable to Doppler echocardiography for mitral inflow assessment and has excellent reproducibility for clinical use.