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.

Left atrial vortex flow and its relationship with left atrial functions in patients with congenital heart disease

BackgroundFour-dimensional flow magnetic resonance imaging (MRI) enables blood flow visualization. The absence of left atrial vortex flow (LAVF) has been implicated in the development of thrombus formation and arrhythmias. However, the clinical relevance of this phenomenon in patients with congenital heart disease (CHD) remains unclear. This study aimed to unravel the relationship of LAVF with left atrial functions in patients with CHD.ResultsTwenty-five participants who underwent cardiac MRI examinations were included (8 postoperative patients with CHD aged 17–41 years and 17 volunteers aged 21–31 years). All participants were in sinus rhythm. Four-dimensional flow MRI (velocity encoding 100 cm/s) assessed the presence of LAVF, and its relationship with left atrial function determined by transthoracic echocardiography was explored. LAVF was detected in 16 patients. Upon classification of the participants based on the presence or absence of LAVF, 94% of participants in the LAVF group were volunteers, while 78% of those in the without LAVF group were postoperative patients. Participants without LAVF had a significantly lower left atrial ejection fraction (61% vs. 70%, p = 0.019), reservoir (32% vs. 47%, p = 0.006), and conduit (22% vs. 36%, p = 0.002) function than those with LAVF.ConclusionsLAVF occurred during the late phase of ventricular systole, and left atrial reservoir function may have contributed to its occurrence. Many postoperative patients with CHD experienced a loss of LAVF. LAVF may indicate early left atrial dysfunction resulting from left atrial remodeling.

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.

Blood flow assessment technology in aortic surgery: a narrative review.

Blood flow assessment is an emerging technique that allows for assessment of hemodynamics in the heart and blood vessels. Recent advances in cardiovascular imaging technologies have made it possible for this technique to be more accessible to clinicians and researchers. Blood flow assessment typically refers to two techniques: measurement-based flow visualization using echocardiography or four-dimensional flow magnetic resonance imaging (4D flow MRI), and computer-based flow simulation based on computational fluid dynamics modeling. Using these methods, blood flow patterns can be visualized and quantitative measurements of mechanical stress on the walls of the ventricles and blood vessels, most notably the aorta, can be made. Thus, blood flow assessment has been enhancing the understanding of cardiac and aortic diseases; however, its introduction to clinical practice has been negligible yet. In this article, we aim to discuss the clinical applications and future directions of blood flow assessment in aortic surgery. We then provide our unique perspective on the technique's translational impact on the surgical management of aortic disease. Articles from the PubMed database and Google Scholar regarding blood flow assessment in aortic surgery were reviewed. For the initial search, articles published between 2013 and 2023 were prioritized, including original articles, clinical trials, case reports, and reviews. Following the initial search, additional articles were considered based on manual searches of the references from the retrieved literature. In aortic root pathology and ascending aortic aneurysms, blood flow assessment can elucidate postoperative hemodynamic changes after surgical reconfiguration of the aortic valve complex or ascending aorta. In cases of aortic dissection, analysis of blood flow can predict future aortic dilatation. For complicated congenital aortic anomalies, surgeons may use preoperative imaging to perform "virtual surgery", in which blood flow assessment can predict postoperative hemodynamics for different surgical reconstructions and assist in procedural planning even before entering the operating room. Blood flow assessment and computational modeling can evaluate hemodynamics and flow patterns by visualizing blood flow and calculating biomechanical forces in patients with aortic disease. We anticipate that blood flow assessment will become an essential tool in the treatment planning and understanding of the progression of aortic disease.

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.

Four-dimensional flow magnetic resonance imaging demonstrates near normalization of aortic flow after the Ross procedure

Four-dimensional flow magnetic resonance imaging demonstrates near normalization of aortic flow after the Ross procedure

Investigating the importance of left atrial compliance on fluid dynamics in a novel mock circulatory loop.

The left atrium (LA) hemodynamic indices hold prognostic value in various cardiac diseases and disorders. To understand the mechanisms of these conditions and to assess the performance of cardiac devices and interventions, in vitro models can be used to replicate the complex physiological interplay between the pulmonary veins, LA, and left ventricle. In this study, a comprehensive and adaptable in vitro model was created. The model includes a flexible LA made from silicone and allows distinct control over the systolic and diastolic functions of both the LA and left ventricle. The LA was mechanically matched with porcine LAs through expansion tests. Fluid dynamic measures were validated against the literature and pulmonary venous flows recorded on five healthy individuals using magnetic resonance flow imaging. Furthermore, the fluid dynamic measures were also used to construct LA pressure-volume loops. The in vitro pressure and flow recordings expressed a high resemblance to physiological waveforms. By decreasing the compliance of the LA, the model behaved realistically, elevating the a- and v-wave peaks of the LA pressure from 12 to 19mmHg and 22 to 26mmHg, respectively, while reducing the S/D ratio of the pulmonary venous flowrate from 1.5 to 0.3. This model provides a realistic platform and framework for developing and evaluating left heart procedures and interventions.

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.

Denoising four-dimensional flow magnetic resonance imaging data using a split-and-overlap approach via singular value decomposition

Four-dimensional flow magnetic resonance imaging (4D flow MRI) offers a powerful tool for visualizing fluid flows, critical for both diagnosing cardiovascular diseases and analyzing engineering fluid dynamics. Despite its potential in medical research, the clinical applicability of 4D flow MRI often faces challenges due to inherent noise. To mitigate this, we introduce the split-and-overlap singular value decomposition (SOSVD) filter, a distinctive noise reduction approach. Unlike traditional singular value decomposition methods, the SOSVD filter partitions the primary data matrix into overlapping subdomains and then applies singular value decomposition to each subdomain, preserving only the dominant mode for noise attenuation. Evaluations on simulated and experimental flow data within a square duct revealed a significant decrease in root mean square noise metrics. Moreover, when applied to in vivo aortic data, the SOSVD filter enhanced various flow determinants, including divergence, velocity gradients, streamlines, and velocity coherence. Thus, the SOSVD method presents a promising avenue for augmenting noise reduction in 4D flow MRI, potentially elevating diagnostic accuracy and enriching cardiovascular disease research.

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.

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).

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 predictors of negative false lumen remodeling after frozen elephant trunk for acute aortic dissection.

We evaluated the blood flow within the downstream aortic false lumen after frozen elephant trunk repair for acute aortic dissection and identified hemodynamic predictors of false lumen expansion and negative false lumen remodeling using four-dimensional flow magnetic resonance imaging. Thirty-one patients (Stanford type A, n = 28; Stanford type B, n = 3) with patent false lumen who underwent frozen elephant trunk procedures for acute aortic dissection were included in this observational study. Each patient underwent computed tomography during the follow-up period and four-dimensional flow magnetic resonance imaging within 3 postoperative months. The false lumen volumetric expansion rate was calculated using computed tomography data. The direction and the rate of flow in the lower descending aortic false lumen were analyzed. Negative false lumen remodeling was defined as a volumetric increase of > 10% from the baseline volume. Negative false lumen remodeling had developed in 6 of the 31 patients during the observation period. Most of the false lumen flows were biphasic during systole. The range between peak and nadir flow rates was associated with the false lumen volumetric expansion rate (β coefficient = 6.77; p < 0.01, R2 = 0.43). The range between peak and nadir flow rates may serve as a hemodynamic predictor of negative false lumen remodeling, enabling further treatment for patients at risk of expansion in the downstream aorta.

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

Abstract 16638: 4D Flow MRI Analysis of the Left Atrial Hemodynamics After Atrial Fibrillation Surgery

Introduction: Postoperative anticoagulation therapy after atrial fibrillation (AF) surgery remains a controversial topic because left atrial (LA) blood flow velocity and pattern remain unclear. This study utilizes four-dimensional (4D) flow magnetic resonance imaging (MRI) to analyze postoperative LA hemodynamics following various atrial fibrillation surgeries. Methods: This retrospective study included nine patients (mean age, 73 ± 8 years; range, 56-83 years) who underwent AF surgeries from August 2021 to June 2022. Maze surgery was performed in 3, pulmonary vein isolation (PVI) and left atrial appendage closure (LAAC) in 3, and the LAAC alone in 3 patients. Postoperative 4D flow MRI scans of the left atrium were performed, and image analysis was conducted. Blood flow velocity in the left atrium was measured, with velocities below 10 cm/s considered flow stasis. The percentage of flow stasis within one systolic-diastolic cycle was evaluated as % stasis. Furthermore, the presence or absence of a physiological vortex flow was assessed from the flow images. Results: Sinus rhythm was postoperatively maintained in 6 patients, and 3 patients were analyzed in AF. The left atrial % stasis was significantly low in the sinus rhythm group (46.0 ± 22.7 in the sinus rhythm group vs. 100 in the AF group, p=0.027). The absence of vortex flow was observed during sinus rhythm in one patient after Maze surgery. Conversely, vortex flow was identified during AF in the patient after LAAC, being accompanied by moderate mitral regurgitation. Conclusions: Any type of AF surgery does not always provide physiological LA blood flow. Further, 4D flow MRI analysis contributes to our understanding of the discrepancy between ideals and reality which may or may not require anticoagulant therapy regardless of postoperative rhythm.

Abstract 14190: Simultaneous Analysis of Myocardial Flow Reserve and Intra-Ventricular 4D Flow Using Hybrid 13 N-ammonia Positron Emission Tomography/Magnetic Resonance Imaging in Patients With Coronary Artery Disease

Introduction: Intra-left ventricular (LV) blood flow dynamics is closely related to wall kinetics and myocardial perfusion. 4D flow magnetic resonance imaging (MR) has been developed to simulate and quantify intra-LV blood flow. We aimed to evaluate the usefulness of simultaneous analysis of myocardial flow reserve (MFR) and intra-LV 4D flow measured by hybrid 13 N-ammonia positron emission tomography (PET)/MR in patients with coronary artery disease (CAD). Methods: Forty patients (mean 65±18 years, male 32) with CAD who underwent pharmacological stress PET/MR were enrolled. MFR was calculated from a series of dynamic rest-stress PET scans. Simultaneously, 4D flow MR acquisition was performed during the stress PET scan. The intra-LV 4D flow was visually assessed, where the smooth flow was defined as normal pattern, and random, or reverse flow was defined as abnormal (Figure A). The velocity of LV inflow and outflow were measured. Results: A normal flow pattern was found in 22 patients, while abnormal pattern was found in 18. MFR showed a significant correlation with the velocity of LV inflow and outflow (inflow: R = 0.552, P &lt; 0.001; outflow: R = 0.563, P &lt; 0.001). MFR was significantly lower in the abnormal flow compared to the normal flow (1.484 ± 0.559 vs. 1.931 ± 0.775, P = 0.041, Figure B). Additionally, when analyzing MFR in coronary artery territories, MFR in the left anterior descending artery was significantly lower in the abnormal flow compared to the normal flow (1.405 ± 0.526 vs. 1.881 ± 0.791, P = 0.029, Figure C). Conclusion: Simultaneous analysis of MFR and intra-LV 4D flow has a potential to serve as a novel indicator for assessing the severity of ischemia in patients with CAD.