4D Flow Cardiovascular Magnetic Resonance Research Articles

False lumen hemodynamics and partial thrombosis in chronic aortic dissection of the descending aorta.

Partial thrombosis of the false lumen (FL) in patients with chronic aortic dissection (AD) of the descending aorta has been associated with poor outcomes. Meanwhile, the fluid dynamic and biomechanical characteristics associated with partial thrombosis remain to be elucidated. This retrospective, single-center study tested the association between FL fluid dynamics and biomechanics and the presence and extent of FL thrombus. Patients with chronic non-thrombosed or partially thrombosed FLs in the descending aorta after an aortic dissection underwent computed tomography angiography, cardiovascular magnetic resonance (CMR) angiography, and a 4D flow CMR study. A comprehensive quantitative analysis was performed to test the association between FL thrombus presence and extent (percentage of FL with thrombus) and FL anatomy (diameter, entry tear location and size), fluid dynamics (inflow, rotational flow, wall shear stress, kinetic energy, and flow acceleration and stasis), and biomechanics (pulse wave velocity). Sixty-eight patients were included. In multivariate logistic regression FL kinetic energy (p = 0.038) discriminated the 33 patients with partial FL thrombosis from the 35 patients with no thrombosis. Similarly, in separated multivariate linear correlations kinetic energy (p = 0.006) and FL inflow (p = 0.002) were independently related to the extent of the thrombus. FL vortexes, flow acceleration and stasis, wall shear stress, and pulse wave velocity showed limited associations with thrombus presence and extent. In patients with chronic descending aorta dissection, false lumen kinetic energy is related to the presence and extent of false lumen thrombus. In patients with chronic aortic dissection of the descending aorta, false lumen hemodynamic parameters are closely linked with the presence and extent of false lumen thrombosis, and these non-invasive measures might be important in patient management. • Partial false lumen thrombosis has been associated with aortic growth in patients with chronic descending aortic dissection; therefore, the identification of prothrombotic flow conditions is desirable. • The presence of partial false lumen thrombosis as well as its extent was related with false lumen kinetic energy. • The assessment of false lumen hemodynamics may be important in the management of patients with chronic aortic dissection of the descending aorta.

Kiosk 3R-TB-01 - Improved Quantitative Flow Analysis of Main and Branch Pulmonary Arteries Distal to the Vortex in Repaired Tetralogy of Fallot- a Single Center 4D Flow Cardiovascular Magnetic Resonance Study

Kiosk 3R-TB-01 - Improved Quantitative Flow Analysis of Main and Branch Pulmonary Arteries Distal to the Vortex in Repaired Tetralogy of Fallot- a Single Center 4D Flow Cardiovascular Magnetic Resonance Study

Hemodynamics and plasma biomarkers in individuals with mild-to-moderate ascending aortic dilatation and tricuspid aortic valves

Abstract Background Ascending aortic (AA) dilatation is a silent disease that requires frequent follow-up measurements of the AA diameter. Unfortunately, the AA diameter is an insufficient predictor of future growth and complications. Hemodynamic and circulating biomarkers represent promising ways of improving the risk stratification in AA dilatation. Most patients with AA dilatation have tricuspid aortic valves (TAV). However, previous studies have mainly focused on AA dilation in individuals with bicuspid aortic valves (BAV) using either hemodynamic or circulating biomarkers separately. Purpose To assess the relationship between hemodynamics in the AA and circulating biomarkers in individuals with mild-to-moderate AA dilatation and age-and-sex matched controls with TAV. Methods The study cohort of individuals with mild-to-moderate AA dilatation were identified based on AA diameter on coronary CT angiography in the population-based Swedish CardioPulmonary BioImage Study (SCAPIS) in Linköping. 54 cases with AA diameter >= 40 mm and 50 controls with AA diameter <40 mm (mean age 59, 19% female) underwent 4D Flow cardiovascular magnetic resonance imaging (CMR). The 4D Flow CMR images were processed to compute mean and maximum velocities, wall shear stress (WSS), flow displacement (FD) at peak systole, and oscillatory shear index (OSI) in the AA. Markers of collagen synthesis and degradation; type I collagen α1 chain (COL1α1), matrix metalloproteinase (MMP)-1,-2,-3,-9,-12) and their inhibitors (TIMP-1,-2,-3,-4), were quantified in plasma (n=104). High sensitivity C-reactive protein and interleukin(IL)-6 were used to assess systemic inflammation. Results FD at the location of maximum dilatation, mean FD and mean OSI were higher in cases compared to controls. Mean velocity, mean WSS and maximum WSS were lower in cases compared to controls. None of the circulating biomarkers differed significantly between cases and controls. Interestingly, several circulating biomarkers correlated with hemodynamics markers in the whole cohort. COL1α1, MMP-2 and TIMP-2 correlated inversely with max OSI (r=-0.342, p=0.001; r=-0.277, p=0.006; r=-0.238, p=0.018, respectively) while MMP-3 correlated positively with mean velocity (r=0.274, p=0.006), mean WSS (r=0.270, p=0.007), max WSS (r=0.220, p=0.029), and inversely with FD at the location of maximum dilatation (r=-0.218, p=0.031). TIMP-4 correlated with mean OSI (r=-0.284, p=0.005). Conclusions Several hemodynamic markers obtained with 4D Flow CMR were altered in mild-to-moderate AA dilatation with TAV, while circulating biomarkers did not differ from controls. However, significant correlations were identified between several biomarkers and hemodynamic markers. We therefore speculate that the levels of circulating biomarkers may be altered as the disease progresses. Future studies should examine the implications of these novel findings along the trajectory of AA dilation and its association with complication risk.Methods figureHemodynamics markers table

Abstract 14833: Association of RV Hemodynamics From 4D Flow CMR With RV Restrictive Physiology From Pediatric to Adult Repaired Tetralogy of Fallot

Introduction: Right ventricular restrictive physiology (RVRP) is common after repair of Tetralogy of Fallot (rTOF), especially with residual pulmonary regurgitation. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) quantitates biventricular blood flow components and kinetic energy (KE) parameters, but their association with RVRP is unclear. We aimed to study 4D flow CMR parameters in adult and pediatric rTOF patients vs healthy controls and associations of 4D flow parameters with RVRP in rTOF. Methods: 103 rTOF patients (40 pediatric, 63 adult; age 24±17 years; 53M:50F) and 171 healthy controls (14 pediatric, 157 adult; age 40±15 years; 97M:74F) were prospectively recruited from centers in Singapore (2) and China (1) to undergo 4D flow CMR on multi-vendor scanners. LV and RV flow components—direct flow, retained inflow, delayed ejection flow and residual volume—and KE parameters (normalized to end-diastolic volume, KEi EDV )—global, peak systolic, average systolic, average diastolic, peak E-wave and peak A-wave—were analyzed. KE discordance was calculated as the ratio of RV and LV average systolic KEi EDV . Results: See Table. RVRP was identified in 70 patients (68%). rTOF with RVRP exhibited higher median RV stroke volume index, RV ejection fraction, RV direct flow, RV peak E-wave and E-wave/A-wave, and lower RV residual volume compared to rTOF without RVRP (all P<0.05). Using binary multivariable logistic regression analysis—and after adjustment for age, pulmonary regurtitation, LV and RV ejection fraction, RV direct flow was found to be independently associated with RVRP in rTOF (P<0.001). Conclusion: Patients with RVRP had higher RV direct flow, RVEF and RV peak E-wave energy, indicating the potential compensatory adaptations in patients with RVRP.

Abstract 16562: Subclinical Flow Inefficiencies in Non-Obstructive Hypertrophic Cardiomyopathy Subgroups Revealed by 4D Flow Cardiovascular Magnetic Resonance

Background Patients with non-obstructive hypertrophic cardiomyopathy (nHCM) may exhibit flow inefficiencies despite normal flow profiles on transthoracic echocardiogram. We investigated whether left ventricular (LV) kinetic energy (KE) and hemodynamic forces (HDF) on 4D flow CMR are abnormal in nHCM, and examined the impact of genotype and hypertrophy phenotype on flow profiles. Methods 90 participants (70 HCM without echocardiographic outflow tract obstruction and 20 healthy controls) underwent 4D flow CMR. Patients were categorized as phenotype positive (P+) if they had LV hypertrophy (≥15mm or ≥13mm with an HCM family history), or phenotype negative (P-) referring to pre-hypertrophic pathogenic sarcomeric variant carriers. LV KE, HDF and transversal/longitudinal HDF ratio were computed from 4D flow CMR. Results P+ patients and controls were of similar age, but P- were younger. P+, P- and controls had comparable LV ejection fraction on CMR, and LV outflow tract pressure gradients and diastolic velocities on echocardiography (Table 1). Systolic KE was higher in P+ compared to controls (Table 1, Figure 1). Early diastolic KE was higher in P- than P+, reflecting younger P-, but did not differ between P+ and controls. Late diastolic KE was higher in P+ versus P- and controls. Systolic HDF ratio was higher in P+ than controls (Table 1, Figure 1). Diastolic HDF and HDF ratio were similar between P+ and controls. Conclusion Despite comparable flow velocities on echocardiography, nHCM exhibited higher systolic KE and HDF ratio, and late diastolic KE on 4D flow CMR relative to controls. Both the extent and pattern of hypertrophy are important determinants of abnormalities in KE and HDF.

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.

4D-Flow Cardiovascular Magnetic Resonance Versus 3D Transesophageal Echocardiography in Multifenestrated Atrial Septal Defect.

4D-Flow Cardiovascular Magnetic Resonance Versus 3D Transesophageal Echocardiography in Multifenestrated Atrial Septal Defect.

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.

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.

Validating aortic stiffness parameters by cardiac magnetic resonance against mechanical testing of ex-vivo aortic aneurysms specimens

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III, Sociedad Española de Cardiología Background Aortic stiffness is a predictor of incident cardiovascular events and mortality in the general population (1). Cardiovascular magnetic resonance (CMR) imaging allow to compute a number of parameters, such as pulse wave velocity (PWV), distensibility (AD) and aortic longitudinal strain, theoretically related to aortic wall stiffness, but no formal validation has ever been reported. Purpose To test the correlation between aortic PWV, AD and longitudinal strain and aortic wall stiffness as assessed via ex-vivo mechanical testing of aortic specimens. Methods Patients undergoing ascending aorta (AAo) aneurysms resection underwent a CMR study which included bSSFP images and a 4D flow CMR of the thoracic aorta. At surgery 2 AAo specimens (each 15x5 mm, one oriented in the longitudinal and the other in circumferential aortic direction) were extracted, maintaining a record of their in-vivo position and orientation, and frozen. Specimens were tested under control for extension force (I5558, INSTRON) and elongation was quantifies by laser video extensometer (2663–281, INSTRON). The Young's modulus (E), i.e. tangent of the stress-strain curve, was quantified at the patient’s diastolic pressure during CMR (2). AAo PWV was extracted from 4D flow CMR study and the product of Eh (h being wall thickness) was computed via the Moens-Korteweg equation using the mean AAo diameter(3,4). AD was quantified from cine CMR at the pulmonary artery level using ARTFUN software (INSERM U678, France) while AAo longitudinal strain was assessed as mean deformation of the AAo by tracking the aortic root during the cardiac cycle (5). Results Twenty patients were included: age 52.5 [37.3 – 71.0] years, 13 (65%) male, BSA 1.94 [1.74 – 1.94] m2. Most of patients had AAo aneurysms of degenerative origin and a tricuspid aortic valve, while 2 patients had a bicuspid aortic valve, and 9 patients had connective tissue disorders. Due to missing data, one AD a two PWV could not have been computed while the specimen in circumferential direction of a patient could not be tested. AAo PWV, Eh and AD were strongly associated with circumferential elastic modulus at diastolic blood pressure (R = 0.652, R = 0.602 and R = -0.502, respectively) (Figure 1). Strong association was also obtained between AAo longitudinal strain and longitudinal elastic modulus at diastolic blood pressure (R = -0.513). Conclusion Pulse wave velocity and the derived Eh product, aortic distensibility and aortic longitudinal strain as non-invasively assessed by CMR are reliable representation of aortic wall stiffness.

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.

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.

Mitral regurgitation quantification by cardiac magnetic resonance imaging (MRI) remains reproducible between software solutions.

Background: The reproducibility of mitral regurgitation (MR) quantification by cardiovascular magnetic resonance (CMR) imaging using different software solutions remains unclear. This research aimed to investigate the reproducibility of MR quantification between two software solutions: MASS (version 2019 EXP, LUMC, Netherlands) and CAAS (version 5.2, Pie Medical Imaging). Methods: CMR data of 35 patients with MR (12 primary MR, 13 mitral valve repair/replacement, and ten secondary MR) was used. Four methods of MR volume quantification were studied, including two 4D-flow CMR methods (MR MVAV and MR Jet) and two non-4D-flow techniques (MR Standard and MR LVRV). We conducted within-software and inter-software correlation and agreement analyses. Results: All methods demonstrated significant correlation between the two software solutions: MR Standard (r=0.92, p<0.001), MR LVRV (r=0.95, p<0.001), MR Jet (r=0.86, p<0.001), and MR MVAV (r=0.91, p<0.001). Between CAAS and MASS, MR Jet and MR MVAV, compared to each of the four methods, were the only methods not to be associated with significant bias. Conclusions: We conclude that 4D-flow CMR methods demonstrate equivalent reproducibility to non-4D-flow methods but greater levels of agreement between software solutions.

4D-Flow Cardiovascular Magnetic Resonance Sequence for Aortic Assessment: Multi-Vendor and Multi-Magnetic Field Reproducibility in Healthy Volunteers.

Four-dimensional (4D) flow cardiac magnetic resonance (CMR) represents an emerging technique for non-invasive evaluation of the aortic flow. The aim of this study was to investigate a 4D-flow CMR sequence for the assessment of thoracic aorta comparing different vendors and different magnetic fields of MR scanner in fifteen healthy volunteers. CMR was performed on three different MRI scanners: one at 1.5 T and two at 3 T. Flow parameters and planar wall shear stress (WSS) were extracted from six transversal planes along the full thoracic aorta by three operators. Inter-vendor comparability as well as scan-rescan, intra- and interobserver reproducibility were examined. A high heterogeneity was found in the comparisons for each operator and for each scanner in the six transversal planes analysis (Friedman rank-sum test; p-value ≤ 0.05). Among all, the most reproducible measures were extracted for the sinotubular junction plane and for the flow parameters. Our results suggest that standardized procedures have to be defined to make more comparable and reproducible 4D-flow parameters and mainly, clinical impactfulness. Further studies on sequences development are needed to validate 4D-flow MRI assessment across vendors and magnetic fields also compared to a missing gold standard.

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.

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.

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.

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.