4D Flow Magnetic Resonance Imaging Research Articles

Eleven Years After Scimitar Syndrome Repair With the Lugones Technique: Usefulness of Four-Dimensional Flow Magnetic Resonance Imaging.

Anatomic and physiologic assessment of surgical repair of scimitar syndrome can be challenging. We evaluated the first patient who underwent the Lugones procedure in 2012 using 4D flow magnetic resonance imaging. With this technology, we demonstrate that the reconstructed right pulmonary venous return drains into the left atrium with laminar flow, just as normal pulmonary veins do.

Repaired coarctation of the aorta does not affect four-dimensional flow metrics in bicuspid aortic valve disease.

The objective of this study was primarily to compare 4D flow magnetic resonance imaging (MRI) metrics in the ascending aorta (AA) of patients with right-left fusion type bicuspid aortic valve (RL-BAV) and repaired CoA to RL-BAV without CoA. Metrics of patients with RL-BAV were also compared to the matched group of patients with common tricuspid aortic valve (TAV). 11 patients with RL-BAV and CoA, 11 patients with RL-BAV without CoA, and 22 controls with TAV, were investigated. Peak velocity (cm/s), peak flow (ml/s), and flow displacement (FD, %) were analyzed at five pre-defined AA levels. In addition, regional wall shear stress (WSS, mN/m2), circumferential WSS (WSSc), and axial WSS (WSSa) at all levels were quantified in six sectors of the aortic circle. Averaged WSS values on each level (WSSavg, WSSc, avg and WSSa, avg) were calculated as well. Peak velocity at the proximal tubular AA was significantly lower in BAV and CoA group (p = 0.047) compared to BAV without CoA. In addition, the WSSa, avg was found to be higher for the BAV and CoA group at proximal AA respectively (p = 0.040). No other significant differences were found between these groups.BAV group's peak velocity was higher at every level (p < 0.001-0.004) compared to TAV group. FD was significantly higher for the BAV group at every level (p < 0.001) besides at the most distal level. All averaged WSS values were significantly higher in BAV patients in distal AA (p < 0.001-0.018). Repaired CoA does not relevantly alter 4D flow metrics in the AA of patients with RL-BAV. However, RL-BAV majorly alters flow dynamics in the AA when compared to patients with TAV. https://www.clinicaltrials.gov/study/NCT05065996, Unique Protocol ID 5063566.

4D flow MRI: value and clinical perspectives in patients with pathology of the heart and great vessels. A review

The study of blood flow is becoming a new trend in cardiology and cardiovascular surgery. Based on the literature and our own data, a review is presented on the use of 4D flow in diseases of the heart and blood vessels. The main state of the question about the features of the application of the technique in various pathologies of the cardiovascular system is described in detail, the priorities, limitations and promising directions of the technique application are considered taking into account the goals of practical medicine. The review consists of two parts. The first is devoted to general issues, limitations of the technique, and issues of 4D flow mapping in patients with lesions of the great vessels. In the second part, the emphasis is on the use of 4D flow magnetic resonance imaging in the study of intraventricular blood flow and the application of the technique in congenital heart and vascular diseases.

Quantitative evaluation of pulmonary hypertension using 4D flow MRI: a retrospective study

BackgroundPulmonary hypertension (PH) is a severe vascular disorder that may affect 50% of patients with heart failure. Currently, right-sided heart catheterization is required to definitively diagnose PH. However, this method is invasive and thus may not be appropriate for repeated, long-term monitoring of PH patients. This retrospective study’s aim was to evaluate whether 4D flow magnetic resonance imaging (MRI) can be used to quantitively measure flow parameters to identify patients with PH. MethodsThe study cohort included 97 patients recruited from a single institution and divided into three groups based on echocardiographic estimate of pulmonary artery systolic pressure (PASP): normal group with PASP<36mmHg, borderline PH group with PASP of 37–50mmHg, and PH group with PASP>50mmHg. 4D flow MRI was used to quantitively assess blood flow and velocity, regurgitation, wall shear stress (WSS) and kinetic energy in the pulmonary artery trunk, right main pulmonary artery, and left pulmonary artery. Two experienced radiologists independently analyzed the MR images, blinded to clinical details. ResultsWe found a significant difference in WSS in the pulmonary artery trunk, right main pulmonary artery and left main pulmonary artery among the three patient groups. We also found significant differences in the kinetic energy and average through velocity in the pulmonary artery trunk and right main pulmonary artery, and significant differences in the flow rate in the right main pulmonary artery. ConclusionThese data suggest that 4D flow MRI can quantitate pulmonary artery flow parameters and distinguish between patients with and without PH.

Assessment of aortic hemodynamics in patients with thoracoabdominal aortic aneurysm using four-dimensional magnetic resonance imaging: a cross-sectional study.

Thoracoabdominal aortic aneurysms (TAAAs) are rare but complicated aortic pathologies that can result in high morbidity and mortality. The whole-aorta hemodynamic characteristics of TAAA survivors remains unknown. This study sought to obtain a comprehensive view of flow hemodynamics of the whole aorta in patients with TAAA using four-dimensional flow (4D flow) magnetic resonance imaging (MRI). This study included patients who had experienced TAAA or abdominal aortic aneurysm (AAA) and age- and sex-matched volunteers who had attended China Hospital from December 2021 to December 2022 in West. Patients with unstable ruptured aneurysm or other cardiovascular diseases were excluded. 4D-flow MRI that covered the whole aorta was acquired. Both planar parameters [(regurgitation fraction (RF), peak systolic velocity (Vmax), overall wall shear stress (WSS)] and segmental parameters [pulse wave velocity (PWV) and viscous energy loss (VEL)] were generated during postprocessing. The Student's t-test or Mann-Whitney test was used to compare flow dynamics among the three groups. A total of 11 patients with TAAA (mean age 53.2±11.9 years; 10 males), 19 patients with AAA (mean age 58.0±11.7 years; 16 males), and 21 controls (mean age 55.4±15.0 years; 19 males) were analyzed. The patients with TAAA demonstrated a significantly higher RF and lower Vmax in the aortic arch compared to healthy controls. The whole length of the aorta in patients with TAAA was characterized by lower WSS, predominantly in the planes of pulmonary artery bifurcation and the middle infrarenal planes (all P values <0.001). As for segmental hemodynamics, compared to controls, patients with TAAA had a significantly higher PWV in the thoracic aorta (TAAA: median 11.41 m/s, IQR 9.56-14.32 m/s; control: median 7.21 m/s, IQR 5.57-7.79 m/s; P<0.001) as did those with AAA (AAA: median 8.75 m/s, IQR 7.35-10.75 m/s; control: median 7.21 m/s, IQR 5.57-7.79 m/s; P=0.024). Moreover, a greater VEL was observed in the whole aorta and abdominal aorta in patients with TAAA. Patients with TAAA exhibited a stiffer aortic wall with a lower WSS and a greater VEL for the whole aorta, which was accompanied by a higher RF and lower peak velocity in the dilated portion of the aorta.

311 Rupture-Risk Stratifying Patients With Cerebral Arteriovenous Malformations Using Quantitative Hemodynamic Flow Measurements

INTRODUCTION: Up to 60% of cerebral arteriovenous malformations (AVMs) present with an intracranial hemorrhage, however, noninvasive neuroimaging has increasingly diagnosed incidental AVMs. AVM management depends on weighing the lifetime rupture risk against the risks of intervention. Although AVM rupture risk relies primarily on angioarchitectural features, measuring hemodynamic flow is gaining traction. An accurate understanding of AVM hemodynamic flow parameters will help stratify patients by rupture risk and select treatment plans. METHODS: The literature was reviewed for articles that quantified AVM flow. RESULTS: Quantitative digital subtraction angiography (QDSA), 4D spin-labeled magnetic resonance angiography (4D-SL-MRA), and 4D-Flow magnetic resonance imaging (4D-Flow-MRI) studies measure relative flow; 3D phase-contrast MRI (PC-MRI) studies measure relative and true flow; and quantitative MRA (QMRA) studies measure true flow. QDSA studies have correlated increased rupture risk with prolonged venous outflow, however there are mixed findings with respect to arterial inflow. Similarly, a higher AVM inflow-to-outflow ratio has been associated with greater rupture risk in studies using PC-MRI. 4D-SL-MRA studies, on the other hand, have demonstrated a lower time-to-peak draining-vein-to-feeder-artery ratio in patients with AVM rupture. Finally, 4D-Flow-MRI studies have shown inconsistent findings whereas QMRA studies have found no significant associations between AVM hemodynamic flow parameters and rupture risk. CONCLUSIONS: Quantitative hemodynamic studies on the relationship between AVM flow and rupture risk have not reached a clear consensus; however, the preponderance of data suggests that higher arterial inflow and lower venous outflow in the AVM nidus contribute to increased hemorrhagic risk. Future studies should consider using larger sample sizes and standardized definitions of hemodynamic parameters to reach a consensus. In the meantime, classic angioarchitectural features may be more strongly correlated with AVM rupture than the amount of blood flow.

Enhanced echocardiographic assessment of intracardiac flow in congenital heart disease.

4D flow magnetic resonance imaging (4D flow MRI) can assess and measure the complex flow patterns of the right ventricle (RV) in congenital heart diseases, but its limited availability makes the broad application of intracardiac flow assessment challenging. Color Doppler imaging velocity reconstruction from conventional echocardiography is an emerging alternative, but its validity against 4D flow MRI needs to be established. To compare intracardiac flow parameters measured by color Doppler velocity reconstruction (DoVeR) against parameters measured from 4D flow MRI. We analyzed 20 subjects, including 7 normal RVs and 13 abnormal RVs (10 with repaired Tetralogy of Fallot, and 3 with atrial-level shunts). Intracardiac flow parameters such as relative pressure difference, vortex strength, total kinetic energy, and viscous energy loss were quantified using DoVeR and 4D flow MRI. The agreement between the two methods was determined by comparing the spatial fields and quantifying the cross-correlation and normalized difference between time-series measurements. The hemodynamic parameters obtained from DoVeR and 4D flow MRI showed similar flow characteristics and spatial distributions. The time evolutions of the parameters were also in good agreement between the two methods. The median correlation coefficient between the time-series of any parameter was between 0.87 and 0.92, and the median L2-norm deviation was between 10% to 14%. Our study shows that DoVeR is a reliable alternative to 4D flow MRI for quantifying intracardiac hemodynamic parameters in the RV.

Four-dimensional flow magnetic resonance imaging for noninvasive diagnosis of clinically significant portal hypertension and high-risk gastroesophageal varices in patients with cirrhosis

IntroductionNoninvasive diagnoses of clinically significant portal hypertension (CSPH) and high-risk gastroesophageal varices are clinically relevant but challenging. Four-dimensional (4D) flow magnetic resonance imaging (MRI) provides comprehensive flow information and is a promising alternative. This study evaluated the efficacy of 4D flow MRI as a noninvasive method for diagnosing CSPH and high-risk varices in patients with liver cirrhosis. MethodsThis prospective study enrolled consecutive patients diagnosed with liver cirrhosis at a tertiary referral center between October 2020 and March 2021. Each participant underwent abdominal 4D flow MRI. Hemodynamic parameters within the portal vein, including the average and peak flow velocities, normalized flow volume (Qnormal), and regurgitant fraction (R%), were extracted and compared between healthy individuals and patients with CSPH and between participants with high- and low-risk varices. Subsequently, these parameters were incorporated into a logistic regression (LR) model refined using L1 regularization and validated using five-fold cross-validation. The diagnostic efficacy was evaluated using receiver operating characteristic (ROC) curves. ResultsEighty-two participants were enrolled (71 patients diagnosed with liver cirrhosis and 11 healthy individuals serving as controls). Among hemodynamic parameters, patients with CSPH exhibited a notable increase in Qnormal of 0.66 ​± ​0.19 ​ml∗m2/[cycle∗kg] (P ​= ​0.001) and an R% of 1.98 (2.05) (P ​= ​0.002). Similarly, patients with high-risk varices showed a higher Qnormal of 0.61 ​± ​0.15 ​ml∗m2/[cycle∗kg] (P ​< ​0.001) and R% of 1.88 (2.81) (P ​= ​0.006). ROC analysis revealed an area under the curve (AUC) for Qnormal of 0.93 and 0.91 for R% for diagnosing CSPH, while the LR model showcased a superior AUC of 0.95. For high-risk varices, Qnormal and R% showed AUC values of 0.75 and 0.70, respectively, whereas the LR model showed a higher AUC of 0.84. ConclusionAs a noninvasive imaging modality, 4D flow MRI exhibits considerable potential for the diagnosis of CSPH and high-risk gastroesophageal varices; thus, it may minimize the reliance on invasive procedures in patients with cirrhosis.

Hemodynamic assessments of unilateral pulsatile tinnitus with jugular bulb wall dehiscence using 4D flow magnetic resonance imaging.

Pulsatile tinnitus (PT) is a type of tinnitus characterized by a rhythmic sound that is synchronous with the heartbeat. One of the possible causes of PT is the jugular bulb wall dehiscence (JBWD). However, the hemodynamics of this condition are not well understood. To elucidate this issue, the present study aimed to compare the blood flow of PT patients with JBWD, PT patients with sigmoid sinus wall dehiscence (SSWD), and volunteers. A retrospective case-control study was conducted, which enrolled patients with unilateral PT who had undergone both computed tomography angiography (CTA) and four-dimensional (4D) flow magnetic resonance imaging (MRI) examinations at the Department of Otolaryngology-Head and Neck Surgery of Beijing Friendship Hospital affiliated to Capital Medical University between January 2019 and July 2023. After excluding the possible causes of PT, the patients were divided into the JBWD group and SSWD group according to the presence or absence of JBWD and/or SSWD. Finally, 11 female unilateral PT patients with JBWD (JBWD group, 11sides), 22 age- and side-matched female patients with SSWD (SSWD group, 22 sides), and 22 age-matched female volunteers (volunteer group, 36 sides) were enrolled. The area, maximum voxel velocity (Vv-max), maximum velocity (Vmax), average velocity (Vavg), and average blood flow rate (Q) were measured in the transverse sinuses (TSs), sigmoid sinuses (SSs), and jugular bulb (JB). The vortex flow pattern was also assessed. Fisher's exact test and Bonferroni correction were used for count data, with P<0.017 was considered statistically significant. Shapiro-Wilk test, one-way analysis of variance (ANOVA), Kruskal-Wallis H test, paired-samples t-test, and Wilcoxon matched-pairs signed-rank test were used for continuous variables depending on the distribution and variance of the data. The P<0.05 and corrected P<0.05 was considered statistically significant. The area and Q of TSs and JB on the symptomatic side were higher than those on the contralateral side in the JBWD group (TSs: Parea=0.004, Pflow=0.002; JB: Parea=0.034, Pflow=0.018). The area was larger and velocities were lower in the JBWD group at the TSs than the SSWD group (Parea=0.004, PVv-max=0.009, PVmax=0.021, PVavg=0.026), and velocities were higher at the distal TSs and SSs than the volunteer group (TSs: PVv-max=0.042, PVmax=0.046, PVavg=0.040; SSs: PVv-max=0.007, PVmax=0.001, PVavg=0.001). At the JB, the JBWD group also had higher Vv-max than the volunteer group (P=0.012). The occurrence rate of vortex at JB in the JBWD group was higher than both the JBWD and the volunteer groups (P=0.002<0.017 and P=0.009<0.017, respectively). The blood flow of the intracranial venous sinus was different between the JBWD group and the SSWD group. The indicators that can differentiate include Vv-max, Vmax, Vavg, vortex, and TSs cross-sectional area.

Verification Study of in Silico Computed Intracardiac Blood Flow With 4D Flow MRI.

Major challenges for clinical applications of in silico medicine are limitations in time and computational resources. Computational approaches should therefore be tailored to specific applications with relatively low complexity and must be verified and validated against clinical gold standards. This study performed computational fluid dynamics simulations of left ventricular hemodynamics of different complexity based on shape reconstruction from steady state gradient echo magnetic resonance imaging (MRI) data. Computed flow results of a rigid wall model (RWM) and a prescribed motion fluid-structure interaction (PM-FSI) model were compared against phase-contrast MRI measurements for three healthy subjects. Extracted boundary conditions from the steady state MRI sequences as well as computed metrics, such as flow rate, valve velocities, and kinetic energy show good agreement with in vivo flow measurements. Regional flow analysis reveals larger differences. Basic flow structures are well captured with RWM and PM-FSI. For the computation of further biomarkers like washout or flow efficiency, usage of PM-FSI is required. Regarding boundary-near flow, more accurate anatomical models are inevitable. These results delineate areas of application of both methods and lay a foundation for larger validation studies and sensitivity analysis for healthy and diseased cases, being an essential step upon clinical translations.

Kiosk 1R-FC-01 - 4D Flow Magnetic Resonance Imaging Evaluation After Transcatheter Closure of Sinus Venosus Defects

Kiosk 1R-FC-01 - 4D Flow Magnetic Resonance Imaging Evaluation After Transcatheter Closure of Sinus Venosus Defects

Effect of flow reduction surgery in a patient with high flow arteriovenous fistula with aortic dissection using 4D flow magnetic resonance imaging: A case report.

This study aimed to investigate cardiovascular function in a patient with high-flow arteriovenous fistula (AVF) who underwent aortic dissection (AD) using four-dimensional (4D) flow magnetic resonance imaging (MRI) as well as analyze the effect of flow reduction surgery on AD. On March 12, 2017, a 60-year-old woman underwent emergency surgery for AD. After that, she experienced acute kidney injury, and hemodialysis was initiated. On April 24, 2017, a left brachiocephalic arteriovenous fistula (AVF) was created to facilitate her dialysis. However, after 5 years, the patient presented with a high-flow AVF, and a flow reduction surgery was performed on March 11, 2022. To evaluate the procedure's effectiveness, we measured the changes in left ventricular (LV) function and blood flow in the aorta and vascular access before and after surgery using 4D flow MRI. Notable changes were observed in LV function, blood flow in the aorta before and after the surgery, and maximum velocity and flow volume after surgery. During the 6-month follow-up after the surgery, the maximum velocity and flow volume in the aorta and vascular access were reduced; also, indicators such as LV volume, cardiac output, cardiac index, and LV mass were improved. In patients with high-flow AVF, flow reduction surgery should be considered as it may improve LV function and reduce the risk of AD recurrence by lowering the flow volume of the aorta.

Hemodynamic effects of entry and exit tear size in aortic dissection evaluated with in vitro magnetic resonance imaging and fluid–structure interaction simulation

Understanding the complex interplay between morphologic and hemodynamic features in aortic dissection is critical for risk stratification and for the development of individualized therapy. This work evaluates the effects of entry and exit tear size on the hemodynamics in type B aortic dissection by comparing fluid–structure interaction (FSI) simulations with in vitro 4D-flow magnetic resonance imaging (MRI). A baseline patient-specific 3D-printed model and two variants with modified tear size (smaller entry tear, smaller exit tear) were embedded into a flow- and pressure-controlled setup to perform MRI as well as 12-point catheter-based pressure measurements. The same models defined the wall and fluid domains for FSI simulations, for which boundary conditions were matched with measured data. Results showed exceptionally well matched complex flow patterns between 4D-flow MRI and FSI simulations. Compared to the baseline model, false lumen flow volume decreased with either a smaller entry tear (− 17.8 and − 18.5%, for FSI simulation and 4D-flow MRI, respectively) or smaller exit tear (− 16.0 and − 17.3%). True to false lumen pressure difference (initially 11.0 and 7.9 mmHg, for FSI simulation and catheter-based pressure measurements, respectively) increased with a smaller entry tear (28.9 and 14.6 mmHg), and became negative with a smaller exit tear (− 20.6 and − 13.2 mmHg). This work establishes quantitative and qualitative effects of entry or exit tear size on hemodynamics in aortic dissection, with particularly notable impact observed on FL pressurization. FSI simulations demonstrate acceptable qualitative and quantitative agreement with flow imaging, supporting its deployment in clinical studies.

Biological sex and vessel specific relationships between cerebral pulsatility and white matter hyperintensities: a 4D flow MRI study

AbstractBackgroundBrain vascular dysfunction is a contributing factor to the increased risk of Alzheimer’s disease with advancing age. Cerebral pulsatility represents a marker of vascular function that quantifies fluctuations in blood flow within each cardiac cycle in the cerebral arteries. Increases in cerebral pulsatility may contribute to structural damage in the brain such as white matter hyperintensities (WMH). Additionally, biological sex differences are apparent in brain vascular function and Alzheimer’s disease risk. As such, this research aimed to determine associations between cerebral pulsatility and WMH and evaluate the influence of sex. This research tested the hypothesis that elevated cerebral pulsatility is associated with higher WMH, and that the associations are sex‐specific.Method407 cognitively healthy middle‐aged and older adults (45‐87 years of age; 271 females) completed magnetic resonance imaging (MRI) performed on a 3T MRI scanner. WMH volumes were evaluated from T2 fluid‐attenuated inversion retention (FLAIR) images, while cerebral pulsatility index (PI) was evaluated in multiple intracranial arteries from 4D flow MRI. WMH fraction was calculated as the cubic root of WMH volume relative to intracranial volume.ResultPI in the vertebral arteries (VA) and basilar artery was positively associated with WMH fraction in females only (all female P≤0.01, all male P≥0.20). In contrast, PI in the internal carotid arteries (ICA) and middle cerebral arteries (MCA) was positively associated with WMH fraction in both sexes (all P≤0.01). However, the relationship between WMH fraction and PI in the MCA differed by sex such that the slope of the relationship was stronger in males than females (all P≤0.03). For example, higher right MCA PI was associated with greater WMH fraction in males (β = 0.39±0.09 a.u., R2 = 0.13) compared with females (β = 0.18±0.05 a.u., R2 = 0.05).ConclusionThese data suggest that, among cognitively healthy middle‐aged and older adults, elevated cerebral pulsatility is linked to greater WMH. However, the associations are sex‐ and vessel‐specific which may contribute to sex‐specific trajectories in Alzheimer’s disease with advancing age. The present results support the idea that elevated cerebral pulsatility contributes to structural alterations in the brain and thus reducing cerebral pulsatility may represent a promising target for mitigating cognitive decline.

Biological sex and vessel specific relationships between cerebral pulsatility and white matter hyperintensities: a 4D flow MRI study

AbstractBackgroundBrain vascular dysfunction is a contributing factor to the increased risk of Alzheimer’s disease with advancing age. Cerebral pulsatility represents a marker of vascular function that quantifies fluctuations in blood flow within each cardiac cycle in the cerebral arteries. Increases in cerebral pulsatility may contribute to structural damage in the brain such as white matter hyperintensities (WMH). Additionally, biological sex differences are apparent in brain vascular function and Alzheimer’s disease risk. As such, this research aimed to determine associations between cerebral pulsatility and WMH and evaluate the influence of sex. This research tested the hypothesis that elevated cerebral pulsatility is associated with higher WMH, and that the associations are sex‐specific.Method407 cognitively healthy middle‐aged and older adults (45‐87 years of age; 271 females) completed magnetic resonance imaging (MRI) performed on a 3T MRI scanner. WMH volumes were evaluated from T2 fluid‐attenuated inversion retention (FLAIR) images, while cerebral pulsatility index (PI) was evaluated in multiple intracranial arteries from 4D flow MRI. WMH fraction was calculated as the cubic root of WMH volume relative to intracranial volume.ResultPI in the vertebral arteries (VA) and basilar artery was positively associated with WMH fraction in females only (all female P = 0.01, all male P = 0.20). In contrast, PI in the internal carotid arteries (ICA) and middle cerebral arteries (MCA) was positively associated with WMH fraction in both sexes (all P = 0.01). However, the relationship between WMH fraction and PI in the MCA differed by sex such that the slope of the relationship was stronger in males than females (all P = 0.03). For example, higher right MCA PI was associated with greater WMH fraction in males (ß = 0.39±0.09 a.u., R2 = 0.13) compared with females (ß = 0.18±0.05 a.u., R2 = 0.05).ConclusionThese data suggest that, among cognitively healthy middle‐aged and older adults, elevated cerebral pulsatility is linked to greater WMH. However, the associations are sex‐ and vessel‐specific which may contribute to sex‐specific trajectories in Alzheimer’s disease with advancing age. The present results support the idea that elevated cerebral pulsatility contributes to structural alterations in the brain and thus reducing cerebral pulsatility may represent a promising target for mitigating cognitive decline.

Variations of arterial compliance and vascular resistance due to plaque or infarct in a single vascular territory of the middle cerebral artery.

Arterial compliance (AC) and vascular resistance (VR) are crucial for the regulation capacity of the vascular system. However, alterations of these features and hemodynamics due to atherosclerosis in a single intracranial artery territory have not been extensively investigated. Thus this study aimed to examine the AC, VR, and hemodynamic variations due to plaque and infarction in the middle cerebral artery (MCA). Patients with symptomatic MCA atherosclerosis were recruited. Both sides of the MCA were assessed and then classified according to the following scheme: group 0, without plaque; group 1, with plaque but without infarct; group 2, with plaque and infarct in the supplying territories. Data on AC, VR, blood flow, and pulsatility index (PI) were obtained based on 4D flow magnetic resonance imaging (MRI) and the Windkessel model. A total of 63 patients were recruited. After 17 MCAs were excluded (occlusion, n=6; poor image quality, n=11), datasets on 109 MCAs were finally collected and classified into group 0 (n=39), group 1 (n=40), and group 2 (n=30). From groups 0 to 2, there was a decrease in AC (0.0060±0.0031 vs. 0.0052±0.0029 vs. 0.0026±0.0020 mL/mmHg) and an increase in VR [28.65±16.11 vs. 42.59±27.53 vs. 63.21±40.37 mmHg/(mL/s)]. Compared to group 1, group 2 had significantly decreased AC (0.0052±0.0029 vs. 0.0026±0.0020 mL/mmHg; P=0.003) and increased VR [42.59±27.53 vs. 63.21±40.37 mmHg/(mL/s); P=0.021]. From group 0 to group 2, there was a decrease in blood flow (179.29±73.57 vs. 125.11±59.04 vs. 92.05±48.79 mL/min; P<0.001). The PI varied significantly among the 3 groups (0.86±0.20 vs. 1.12±0.50 vs. 0.79±0.16; P<0.001), with group 1 having the highest PI. With the occurrence of plaque and infarct, AC and blood flow progressively decrease while VR increases. The PI was the highest in the group with plaque and without infarct. Assessments of vascular function and hemodynamics in a single artery territory can clarify comprehensive alterations in the cerebral vascular system (CVS).

An oral glucose tolerance test does not affect cerebral blood flow: role of NOS.

Animal data indicate that insulin triggers a robust nitric oxide synthase (NOS)-mediated dilation in cerebral arteries similar to the peripheral tissue vasodilation observed in healthy adults. Insulin's role in regulating cerebral blood flow (CBF) in humans remains unclear but may be important for understanding the links between insulin resistance, diminished CBF, and poor brain health outcomes. We tested the hypothesis that an oral glucose challenge (oral glucose tolerance test, OGTT), which increases systemic insulin and glucose, would acutely increase CBF in healthy adults due to NOS-mediated vasodilation, and that changes in CBF would be greater in anterior regions where NOS expression or activity may be greater. In a randomized, single-blind approach, 18 young healthy adults (24 ± 5 yr) underwent magnetic resonance imaging (MRI) with a placebo before and after an OGTT (75 g glucose), and 11 of these adults also completed an NG-monomethyl-l-arginine (l-NMMA) visit. Four-dimensional (4-D) flow MRI quantified macrovascular CBF and arterial spin labeling (ASL) quantified microvascular perfusion. Subjects completed baseline imaging with a placebo (or l-NMMA), then consumed an OGTT followed by MRI scans and blood sampling every 10-15 min for 90 min. Contrary to our hypothesis, total CBF (P = 0.17) and global perfusion (P > 0.05) did not change at any time point up to 60 min after the OGTT, and no regional changes were detected. l-NMMA did not mediate any effect of OGTT on CBF. These data suggest that insulin-glucose challenge does not acutely alter CBF in healthy adults.

Valvular and ascending aortic hemodynamics of the On-X aortic valved conduit by same-day echocardiography and 4D flow MRI.

This study aims to assess whether the On-X aortic valved conduit better restores normal valvular and ascending aortic hemodynamics than other commonly used bileaflet mechanical valved conduit prostheses from St. Jude Medical and Carbomedics by using same-day transthoracic echocardiography (TTE) and 4D flow magnetic resonance imaging (MRI) examinations. TTE and 4D flow MRI were performed back-to-back in 10 patients with On-X, six patients with St. Jude (two) and Carbomedics (four) prostheses, and 36 healthy volunteers. TTE evaluated valvular hemodynamic parameters: transvalvular peak velocity (TPV), mean and peak transvalvular pressure gradient (TPG), and effective orifice area (EOA). 4D flow MRI evaluated the peak systolic 3D viscous energy loss rate (VELR) density and mean vorticity magnitude in the ascending aorta (AAo). While higher TPV and mean and peak TPG were recorded in all patients compared to healthy subjects, the values in On-X patients were closer to those in healthy subjects (TPV 1.9 ± 0.3 vs. 2.2 ± 0.3 vs. 1.2 ± 0.2 m/s, mean TPG 7.4 ± 1.9 vs. 9.2 ± 2.3 vs. 3.1 ± 0.9 mmHg, peak TPG 15.3 ± 5.2 vs. 18.9 ± 5.2 vs. 6.1 ± 1.8 mmHg, p < 0.001). Likewise, while higher VELR density and mean vorticity magnitude were recorded in all patients than in healthy subjects, the values in On-X patients were closer to those in healthy subjects (VELR: 50.6 ± 20.1 vs. 89.8 ± 35.2 vs. 21.4 ± 9.2 W/m3, p < 0.001) and vorticity (147.6 ± 30.0 vs. 191.2 ± 26.0 vs. 84.6 ± 20.5 s-1, p < 0.001). This study demonstrates that the On-X aortic valved conduit may produce less aberrant hemodynamics in the AAo while maintaining similar valvular hemodynamics to St. Jude Medical and Carbomedics alternatives.

Hemodynamic forces from 4D flow magnetic resonance imaging for optimised prediction of cardiac resynchronisation therapy outcome

Abstract Background Patients with heart failure and left bundle branch block (LBBB) may receive cardiac resynchronisation therapy (CRT), but many patients have limited treatment response (1). The use of imaging to optimise patient selection has been repeatedly attempted with some success (2), and scar detected on late gadolinium enhancement (LGE) imaging has been associated with reduced response rates (3). Intraventricular hemodynamic force (HDF) analysis has been suggested as a novel marker for assessment of patients eligible for CRT (4). The aim of this study was therefore to investigate if septal scar from LGE or left ventricular HDF computed from cardiac magnetic resonance (CMR) imaging can improve prediction of CRT outcome. Methods Patients with heart failure, EF&amp;lt;35% and LBBB (n=22) underwent CMR with 4D flow at 1.5T or 3T (Achieva, Philips Healthcare) prior to CRT (Figure 1). Scar was assessed by LGE. Left ventricular HDF were computed based on the Navier-Stokes equations, using a validated module in the software Segment v3.3 R10057 (Medviso, Lund, Sweden) (5). Forces (N) were analysed in three orthogonal directions as root mean square (RMS) and peak values, reported in median [interquartile range]. Transversal/longitudinal HDF ratio was calculated for systole and diastole. Echocardiography was performed before and six months after CRT, and patients with end-systolic volume reduction ≥15% at follow-up were defined as responders. The Mann-Whitney U test was used for group comparisons, Fisher’s exact test for binary categorical data, Wilcoxon test for paired comparisons, and receiver operating characteristic analysis for prediction of CRT response. Results There was no difference between responders and non-responders in LGE (Table 1). Non-responders had smaller HDF than responders in the inferior-anterior direction in systole (RMS: 0.055 [0.027] vs 0.070 [0.032], p=0.04; peak: 0.11 [0.069] vs 0.15 [0.083], p=0.03), and in the apex-base direction in diastole (RMS: 0.087 [0.018] vs 0.11 [0.046], p=0.047). Non-responders had larger diastolic HDF ratio than responders (RMS: 0.89 [0.45] vs 0.67 [0.20], p=0.004; peak: 1.1 [0.51] vs 0.57 [0.40], p=0.01) (Figure 1). Receiver operating characteristic analysis of diastolic HDF ratio found an area under the curve of 0.88 (p=0.005). Identification of non-responders using diastolic HDF ratio with a specificity of 100%, resulted in a ratio of &amp;gt;0.87 for non-responders, with a sensitivity of 57%. Intragroup comparison found higher HDF ratio in systole than diastole for responders but not for non-responders (Figure 1). Conclusions Prediction of left ventricular remodelling following CRT may be optimized by hemodynamic force analysis from 4D flow CMR, while septal scar from LGE was not found indicative of CRT outcome in this pilot study. Larger-scale studies are required before clinical implementation of HDF analysis.Table 1Figure 1

The effect of resveratrol on aortic growth and function in patients with marfan syndrome

Abstract Background Patients with Marfan syndrome (MFS) have an increased risk of life-threatening aortic complications, mostly preceded by aortic dilatation. Resveratrol, a dietary supplement that intervenes in cellular metabolism has been shown to reduce aortic dilatation rate in a rodent study (1). Purpose To investigate if treatment with Resveratrol reduces aortic dilatation rate in patients with MFS. Methods In this investigator-initiated, prospective, pre-post observational, multicenter trial, we analysed Resveratrol treatment in adults with MFS. Primary endpoint was the change in aortic dilatation rate at five predetermined locations along the thoracic aorta following the daily intake of 500 mg Resveratrol for one year. Aortic dilatation rate was calculated using diastolic Magnetic Resonance Imaging (MRI) aorta diameters acquired at three time points: the most recent MRI examination available prior to inclusion and two Dixon 3D examinations on a 3 Tesla MRI system acquired at baseline and after one year Resveratrol administration. Additionally, we quantified and investigated regional changes in aortic hemodynamics (wall shear stress (WSS), flow velocity and pulse wave velocity (PWV)) determined by 4D-flow MRI. Results A total of 57 participants, mean age of 37 ± 9 years, of which 28 males (49%) were included in the study. Twenty-six (46%) had undergone aortic root replacement prior to the study. All aortic dimensions remained stable after 1.2 ± 0.3 years follow-up. A significant decrease in growth rate (mm/year) in the ascending aorta was observed during the trial compared to pre-trial, from 0.54 (IQR: 0.09–1.39) to 0.00 (IQR: -0.99–0.67), p=0.004. Global PWV and regional mean WSS and velocity did not change after one year of Resveratrol use. PWV (m/s) was significantly higher for patients with a history of aortic root surgery (9.83 ± 1.8 versus 8.42 ± 1.91, p=0.034). Additionally, using Spearman’s ρ correlation coefficient, a positive correlation between PWV and age was found; r=0.452, p=0.003. Conclusion In adult patients with MFS, Resveratrol treatment shows promising results towards stabilizing aortic growth rate after 1.2 year follow up, without major changes in aorta hemodynamics. These findings may warrant a subsequent larger study with a longer follow-up period.RESVcue study summary figure