4D Flow Cardiac Magnetic Resonance Research Articles

Evaluation of Cardiac Shunts With 4D Flow Cardiac Magnetic Resonance: Intra‐ and Interobserver Variability

Evaluation of Cardiac Shunts With 4D Flow Cardiac Magnetic Resonance: Intra‐ and Interobserver Variability

4D flow cardiac magnetic resonance in children and adults with congenital heart disease: Clinical experience in a high volume center

BackgroundCardiac magnetic resonance (CMR) imaging with velocity encoding along all three directions of flow, known as 4DFlow CMR, provides both anatomical and functional information. Few data are available on the usefulness of 4DFlow CMR in everyday practice. Here, our objective was to investigate the usefulness of 4DFlow CMR for assessing congenital heart disease (CHD) in everyday practice. MethodsFrom 2017 to 2019, consecutive patients who underwent 4DFlow CMR were included prospectively at a single high-volume centre. The parameters recommended by an expert's consensus statement for each diagnosis (congenital valvulopathy, septal defect, complex CHD, tetralogy of Fallot, aortic abnormalities) were assessed by two blinded experienced readers. 4DFlow CMRs that provided all recommended parameters were considered successful. Inter-observer and intra-observer agreement were investigated. ResultsWe included 187 adults and 60 children covering broad ranges of weight (4.5–142 kg) and age (0.1–67 years). 4DFlow CMR was always the second-line imaging modality, after inconclusive echocardiography, and was successful in 231/247 (91%) patients, with no significant difference between children and adults (54/60, 90%; and 177/187, 95%; respectively; p = .13). Longer time using 4DFlow CMR at our centre was associated with success; in children, older age was also associated with exam success. There was an about 12-month learning curve in children. The success rate was lowest in neonates. Inter-observer and intra-observer agreement were substantial. ConclusionOur results suggest that 4DFlow CMR usually provides a comprehensive assessment of CHD in adults and children. A learning curve exists for children and the investigation remains challenging in neonates.

Measuring atrial stasis during sinus rhythm in patients with paroxysmal atrial fibrillation using 4 Dimensional flow imaging: 4D flow imaging of atrial stasis

BackgroundParoxysmal atrial fibrillation (PAF) is associated with cardioembolic risk, however events may occur during sinus rhythm (SR). 4D-flow cardiac magnetic resonance (CMR) imaging allows visualisation of left atrial blood flow, to determine the residence time distribution (RTD), an assessment of atrial transit time. ObjectiveTo determine if atrial transit time is prolonged in PAF patients during SR, consistent with underlying atrial stasis. Method91 participants with PAF and 18 healthy volunteers underwent 4D flow analysis in SR. Velocity fields were produced RTDs, calculated by seeding virtual ‘particles’ at the right upper pulmonary vein and counting them exiting the mitral valve. An exponential decay curve quantified residence time of particles in the left atrium, and atrial stasis was expressed as the derived constant (RTDTC) based on heartbeats. The RTDTC was evaluated within the PAF group, and compared to healthy volunteers. ResultsPatients with PAF (n = 91) had higher RTDTC compared with gender-matched controls (n = 18) consistent with greater atrial stasis (1.68 ± 0.46 beats vs 1.51 ± 0.20 beats; p = .005). PAF patients with greater thromboembolic risk had greater atrial stasis (median RTDTC of 1.72 beats in CHA₂DS₂-VASc≥2 vs 1.52 beats in CHA₂DS₂-VASc<2; p = .03), only female gender and left ventricular ejection fraction contributed significantly to the atrial RTDTC (p = .006 and p = .023 respectively). ConclusionsAtrial stasis quantified by 4D flow is greater in PAF, correlating with higher CHA₂DS₂-VASc scores. Female gender and systolic dysfunction are associated with atrial stasis. RTD offers an insight into atrial flow that may be developed to provide a personalised assessment of thromboembolic risk.

4D Flow cardiac magnetic resonance quantification of mitral regurgitation, comparison with transthoracic echocardiography

Mitral valve regurgitation (MR) is primarily assessed by a multiparametric approach with transthoracic echocardiography (TTE) that can be further completed by 2D Cardiac Magnetic Resonance (2D CMR) in case of doubt or poor acoustic window. TTE and 2D CMR have nevertheless imperfect agreement for MR quantification. Time-resolved phase-contrast CMR with flow-encoding in three spatial directions (4D Flow CMR) could help in MR quantification. Compare 4D Flow CMR quantification of MR with TTE using a multiparametric approach. We conducted a prospective study at the Institut Mutualiste Montsouris in Paris between November 2016 and 2017 including patients with chronic primitive MR. MR was evaluated with a multiparametric approach by two cardiologists with TTE and quantitatively by two radiologists with 4D Flow CMR. MR was classified as mild, moderate or severe and evaluated blindly with consensus in case of disagreement. 4D Flow CMR quantified MR regurgitant volume (RV) and MR regurgitant fraction (RF). 4D anterograde mitral flow was compared to left ventricular stroke volume using 2D-cine CMR. Thirty-three patients were included. Inter-observer agreement was good in TTE (kappa = 0.75 95%CI [0.57–0.92]) and excellent in 4D Flow CMR (ICC = 0.94 95%CI [0.79–0.95]). Agreement with TTE was excellent using optimized thresholds (Mild: RV ≤ 20 mL RF ≤ 20%, Moderate: RV = 21–39 mL RF = 21–36%, Severe: RV ≥ 40 mL RF ≥ 37%): kappa = 0.93 95%CI [0.8–1] for RV and kappa = 0.90 95%CI [0.7–0.9] for RF. A validation cohort confirmed that the 4D flow thresholds as determined were accurate for MR grading. Agreement between 4D anterograde mitral flow and 2D-cine CMR left ventricular stroke volume was also excellent (ICC = 0.92 95%CI [0.85–0.96]). 4D Flow CMR is a reliable tool for MR quantification. Providing direct quantitative evaluation of MR with low inter-observer variability, it may therefore be used as a gatekeeper before therapeutic decisions such as surgery.

4d cardiac magnetic resonance flow in patients with pulmonary arterial hypertension associated with congenital heart disease

Right heart catheterization is an invasive exam that is currently the gold standard to assess pulmonary hemodynamics for diagnosis and follow-up of pulmonary arterial hypertension (PAH) associated with congenital heart diseases (CHD). Cardiac magnetic resonance 4D flow (4D CMR flow) emerges as a promising non-invasive imaging. We assess the accuracy of 4D CMR flow to measure pulmonary cardiac output (Qp). We prospectively included 28 patients (median age was 42 years old [35–52] with PAH and CHD (pre-tricuspid shunt n = 23, 82.1%, median mean pulmonary artery pressure 46 mmHg [40–58]; median pulmonary vascular resistance 15.0 WU.m 2 [7.5–25.6]). Qp was measured invasively using Fick principle (direct oxygen consumption measure) during a right heart catheterization (QpF) and compared to Qp measured by 2D (Qp2D) and 4D flow CMR (Qp4D) on the same day. 4D CMR flow analysis was feasible in all patients. Qp4D and QpF were strongly correlated (rho = 0.87, P < 0.0001; r 2 = 0.68, P < 0.0001). Using Bland Altman analysis, mean difference was 0.0 ± 1.0 L/min. Mean difference within two observers (interobserver variability) was 0.3 ± 0.4 L/min ( Fig. 1 ). Mean difference within one observer (intra-observer variability) was 0.1 ± 0.3 L/min. Qp2D and QpF were moderately correlated (rho = 0.54, P = 0.008; r 2 = 0.41, P = 0.0007). Using Bland Altman analysis, mean difference was 0.6 ± 2.3 L/min ( Fig. 1 ). Qp measured by 4D CMR flow is well correlated to QpF. Further studies are needed to explore other potential interests of using 4D CMR flow to assess PAH, including the derivation of additional hemodynamic parameters such as pulmonary artery compliance, wall shear stress and pulse wave velocities, which could provide further insights into pulmonary artery remodelling and interactions between pulmonary arterial stiffening and right ventricular dysfunction.

4D flow MRI versus conventional 2D for measuring pulmonary flow after Tetralogy of Fallot repair

BackgroundAfter tetralogy of Fallot (TOF) repair, pulmonary regurgitation and right ventricular function must be monitored. Conventional (2D) cardiac magnetic resonance (CMR) is currently the clinical reference method for measuring pulmonary regurgitation. However, 4DFlow CMR has been reported to provide a more comprehensive flow analysis than 2D CMR. We aimed to compare 4DFlow CMR to 2D CMR for assessing pulmonary regurgitation and flow, as well as aortic flow, in children and adults after surgical repair of TOF. MethodsRetrospective analysis of patients with repaired TOF admitted for cardiac MRI with 4DFlow acquisition from 2016 to 2018. Linear regression was used to assess correlations and Bland-Altman analyses were performed. ResultsThe 60 included patients had a mean age of 18.2 ± 10.4 years (range, 2–54 years).Significant correlations between the two techniques were found for pulmonary regurgitant fraction (R [2] = 0.6642, p < 0.0001), net pulmonary flow (R [2] = 0.6782, p < 0.0001), forward pulmonary flow (R [2] = 0.6185, p < 0.0001), backward pulmonary flow (R [2] = 0.8192, p < 0.0001), and aortic valve flow (R [2] = 0.6494, p < 0.0001). The Bland-Altman analysis showed no significant bias, narrow limits of agreement, and few scattered points. The correlation between pulmonary and aortic flow was better with 4DFlow CMR than with 2D CMR (R [2] = 0.8564, p < 0.0001 versus R [2] = 0.4393, p < 0,0001, respectively). Interobserver reliability was good. ConclusionThese results establish the feasibility and reliability of 4DFlow CMR for assessing pulmonary flow in a large paediatric and adult population with repaired TOF. 4DFlow CMR may be more reliable than 2D MRI for pulmonary flow assessment after TOF repair.

Abstract 736: Increased Cell Death in Regions of Elevated Aortic Wall Shear Stress in Bicuspid Valve Aortopathy

Bicuspid aortic valve (BAV) is a common congenital malformation associated with aortopathy and potential rupture. Identifying those patients at greatest risk for dissection is difficult at present. Abnormal hemodynamics in the ascending aorta creates regions of increased wall shear stress (WSS) which causes extracellular matrix dysregulation and may affect cell death. Dying cells release fragmented DNA into the blood and levels of aorta-specific cell-free DNA (cfDNA), identified by the presence of tissue-specific differentially methylated regions (DMRs), could be leveraged as a biomarker. Our objective was to determine if a relationship between elevated WSS and apoptosis in the ascending aorta existed and identify aorta-specific DMRs in the cfDNA of BAV patients. We hypothesized that areas of increased WSS would demonstrate increased cell death that would correlate with increases in aorta-specific cfDNA from patient blood. BAV patients undergoing 4D-flow cardiac magnetic resonance imaging (CMR) and surgery for ascending aorta dilation (range 36-63 mm) were recruited. Blood was collected from 23 patients at the time of CMR and used for the isolation of plasma cfDNA. Aortic wall samples (n = 30) corresponding to regions of high and low WSS were collected at surgery from 15 patients and stained for cell death using the TUNEL assay. Publicly-available methylomes and Metilene were used to identify aorta-specific DMRs in silico . Regions of elevated WSS were seen in all individuals regardless of absolute aortic dimension. These regions of elevated WSS by CMR showed significantly greater cell death when compared to the region of normal WSS in the ascending aorta (0.14 ± 0.05 vs. 0.08 ± 0.06, p=0.00006). Levels of cell death did not correlate with maximal aortic diameter. Twenty-three aorta-specific DMRs were identified. Of the four that were tested, three were found to be hypomethylated in genomic DNA from the aorta compared to 14 other tissues. Levels of aorta-specific cfDNA based on our DMRs did not correlate with maximal aortic diameter. Increased regional cell death corresponding to elevated WSS may implicate abnormal hemodynamic flow in the progression of aortopathy and provides a biological rationale for the use of cfDNA as a biomarker for aortopathy.

4D cardiac magnetic resonance flow in patients with pulmonary hypertension associated with congenital heart disease

Right heart catheterization is an invasive exam that is currently the gold standard to assess pulmonary hemodynamics for diagnosis and follow-up of pulmonary arterial hypertension (PAH) associated with congenital heart diseases (CHD). Cardiac magnetic resonance 4D flow (4D CMR flow) emerges as a promising non-invasive imaging. We assess the accuracy of 4D CMR flow to measure pulmonary cardiac output (Qp). We prospectively included 28 patients with PAH associated with CHD. Qp was measured invasively using Fick principle (direct oxygen consumption measure) during aright heart catheterization (QpF) and compared to Qp measured by 2D (Qp2D) and 4D flow CMR (Qp4D) on the same day. Twenty eight patients was included (median age was 42 years old [35–52]) with PAH and CHD (pre-tricuspid shunt n = 23, 82.1%, median mean pulmonary artery pressure 46 mmHg [40-58]; median pulmonary vascular resistance 15.0 WU.m 2 [7.5–25.6]) 4D CMR flow analysis were feasible in all patients. Qp4D and QpF were strongly correlated (rho = 0.87, P < 0.0001; r 2 = 0.68, P < 0.0001). Using Bland Altman analysis, mean difference was 0.0 ± 1.0 L/min. Mean difference within two observers (interobserver variability) was 0.3 ± 0.4 L/min. Mean difference within one observer (intra-observer variability) was 0.1 ± 0.3 L/min. Qp2D and QpF were moderately correlated (rho = 0.54, P = 0.008; r 2 = 0.41, P = 0.0007). Using Bland Altman analysis, mean difference was 0.6 ± 2.3 L/min ( Fig. 1 ). Qp measured by 4D CMR flow is well correlated to QpF. Further studies are needed to explore other potential interests of using 4D CMR flow to assess PAH, including the derivation of additional hemodynamic parameters such as pulmonary artery compliance, wall shear stress and pulse wave velocities, which could provide further insights into pulmonary artery remodeling and interactions between pulmonary arterial stiffening and right ventricular dysfunction.

The detection of retrograde flow from the left anterior descending artery into the main pulmonary artery by 4D-flow cardiac magnetic resonance in a patient with Bland-White-Garland syndrome

The detection of retrograde flow from the left anterior descending artery into the main pulmonary artery by 4D-flow cardiac magnetic resonance in a patient with Bland-White-Garland syndrome

P875Atrial stasis measured by cardiac magnetic resonance 4D flow particle tracing is present during sinus rhythm in patients with paroxysmal atrial fibrillation and is associated with higher stroke risk

P875Atrial stasis measured by cardiac magnetic resonance 4D flow particle tracing is present during sinus rhythm in patients with paroxysmal atrial fibrillation and is associated with higher stroke risk

The ventricular residence time distribution derived from 4D flow particle tracing: a novel marker of myocardial dysfunction.

4D flow cardiac magnetic resonance (CMR) imaging allows visualisation of blood flow in the cardiac chambers and great vessels. Post processing of the flow data allows determination of the residence time distribution (RTD), a novel means of assessing ventricular function, potentially providing additional information beyond ejection fraction. We evaluated the RTD measurement of efficiency of left and right ventricular (LV and RV) blood flow. 16 volunteers and 16 patients with systolic dysfunction (LVEF < 50%) underwent CMR studies including 4D flow. The RTDs were created computationally by seeding virtual 'particles' at the inlet plane in customised post-processing software, moving these particles with the measured blood velocity, recording and counting how many exited per unit of time. The efficiency of ventricular flow was determined from the RTDs based on the time constant (RTDc = - 1/B) of the exponential decay. The RTDc was compared to ejection fraction, T1 mapping and global longitudinal strain (GLS). There was a significant difference between groups in LV RTDc (healthy volunteers 1.2 ± 0.13 vs systolic dysfunction 2.2 ± 0.80, p < 0.001, C-statistic = 1.0) and RV RTDc (1.5 ± 0.15 vs 2.0 ± 0.57, p = 0.013, C-statistic = 0.799). The LV RTDc correlated significantly with LVEF (R = - 0.84, P < 0.001) and the RV RTDc had significant correlation with RVEF (R = - 0.402, p = 0.008). The correlation between LV RTDc and LVEF was similar to GLS and LVEF (0.926, p < 0.001). The ventricular residence time correlates with ejection fraction and can distinguish normal from abnormal systolic function. Further assessment of this method of assessment of chamber function is warranted.

Whole-heart 4D flow cardiac magnetic resonance in healthy dogs.

In cardiac magnetic resonance imaging (CMR), accurate flow measurements rely on perpendicular plane-alignment with flow direction. For 2D phase contrast (PC) cardiac magnetic resonance measurements, planes have to be defined during the examination of the heart, which is time consuming and error-prone. Collection of flow information of the entire volume of the heart by a 4D flow CMR postpones plane alignment to post-processing. Sampling of such a large amount of data requires acceleration of data acquisition with techniques such as SENSitivity Encoding (k-t SENSE) or Broad-use Linear Acquisition Speed-up Technique (k-t BLAST). Objectives of the study were to compare 4D flow CMR, accelerated with two different acceleration methods with the established 2D PC CMR based on assessment of stroke volume at all four cardiac valves. The values of stroke volume acquired with the 4D flow CMR SENSE did not differ significantly when compared to the 2D PC CMR SENSE at the left side of the heart (aortic and mitral valve). Significant differences between the techniques were seen at the pulmonic and tricuspid valves. Acceleration with k-t BLAST revealed significantly lower values of stroke volume at all cardiac valves, except at the mitral valve.

Atrial Stasis Measured by Cardiac Magnetic Resonance 4D Flow Particle Tracing is Present During Sinus Rhythm in Patients with Paroxysmal Atrial Fibrillation, and is Associated with Higher Cardio-Embolic Risk

Atrial Stasis Measured by Cardiac Magnetic Resonance 4D Flow Particle Tracing is Present During Sinus Rhythm in Patients with Paroxysmal Atrial Fibrillation, and is Associated with Higher Cardio-Embolic Risk

Utility of 4D Flow mapping in Eisenmenger syndrome with pulmonary atresia.

Management of patients with Eisenmenger syndrome with pulmonary atresia is challenging because of the complexity of the structure-function relationship of the components of the syndrome. Multi-modality imaging including cardiac magnetic resonance (CMR) 4D Flow offers unprecedented opportunities to unravel, at least in part, some of these components, and thus help in the management of these patients. In this study, we describe the use of these integrated methods with particular reference to CMR 4D Flow in a patient with Eisenmenger syndrome and pulmonary atresia and outline both the utility and the limitations. A comprehensive cardiac magnetic resonance (CMR) 4D Flow analysis was performed preoperatively and postoperatively, during peak systole, late systole, early diastole, and late diastole. The focus of the present study was to investigate the pattern of flow and dynamic changes at different levels of the aorta, as well as in the duct and the pulmonary arteries. Preoperatively, a right-handed helix and a vortex were observed in the dilated ascending aorta, and the duct flow was mainly dependent on reverse, upstream flow from the descending aorta, distal to the duct, during diastole, denoting low pulmonary vascular capacitance. Following repair, the flow in the ascending aorta and the descending aorta changed markedly. These changes included both timing and intensity of the right-handed helix, as well as the vortex in the ascending aorta. The significance of the observed changes in flow pattern and their influence on wall structure and function are discussed. Our study demonstrates the extremely powerful potential of CMR 4D Flow in the management of complex congenital anomalies.

Three-dimensional left atrial blood flow characteristics in patients with atrial fibrillation assessed by 4D flow CMR.

To apply 4D flow cardiac magnetic resonance (CMR) for the volumetric measurement of 3D left atrial (LA) blood flow to evaluate its potential to detect altered LA flow in patients with atrial fibrillation (AF) and to investigate associations of changes in systolic and diastolic LA flow with the current clinical risk score (CHA2DS2-VASc) used for the assessment of thromboembolic risk in AF. 4D flow CMR was performed in 40 patients with a history of AF (in sinus rhythm during CMR scan, age = 61 ± 11 years), 20 age-appropriate controls (59 ± 7 years), and 10 young healthy volunteers (24 ± 2 years) to measure in vivo time-resolved 3D LA blood flow. LA velocities were characterized with respect to atrial function and timing by calculating normalized LA flow velocity histograms during ventricular systole, early diastole, mid-late diastole, and the entire cardiac cycle. Mean, median, and peak LA velocity steadily decreased when comparing young volunteers, age-appropriate controls, and AF patients by 10-44% and 8-26% for early diastole and the entire cardiac cycle, respectively (P < 0.01 for all comparisons except median velocity for young vs. older volunteers and peak velocity for older volunteers and AF patients). There were moderate but significant inverse relationships between increased CHA2DS2-VASc score and reduced mean LA velocity (early diastole: r = -0.37, P < 0.001; entire RR-interval: r = -0.33, P = 0.005), median LA velocity (r = -0.33, P = 0.003; r = -0.25, P = 0.017), and peak velocity (r = -0.36, P = 0.001; r = -0.45, P < 0.001). LA flow indices also correlated significantly with age and LA volume (R2 = 0.44-0.62, P < 0.001), but not with left ventricular ejection fraction. Left atrial 4D flow CMR demonstrated significantly reduced LA blood flow velocities in patients with AF. Further study is needed to determine whether these measures can improve upon the CHA2DS2-VASc score for stroke risk prediction and enhance individual decisions on anticoagulation in patients with AF.

Vorticity is a marker of right ventricular diastolic dysfunction.

Right ventricular diastolic dysfunction (RVDD) is an important prognostic indicator in pulmonary arterial hypertension (PAH). RV vortex rings have been observed in healthy subjects, but their significance in RVDD is unknown. Vorticity, the local spinning motion of an element of fluid, may be a sensitive measure of RV vortex dynamics. Using four-dimensional (4D) flow cardiac magnetic resonance imaging (CMR), we investigated the relationship between right heart vorticity with echocardiographic indexes of RVDD. Thirteen (13) PAH subjects and 10 controls underwent same-day 4D flow CMR and echocardiography. RV diastolic function was assessed using trans-tricuspid valve (TV) early (E) and late (A) velocities, E/A ratio, and e' and a' tissue Doppler velocities. RV and right atrial (RA) integrated mean vorticity was calculated for E and A-wave filling periods using 4D datasets. Compared with controls, A-wave vorticity was significantly increased in RVDD subjects in both the RV [2343 (1,559-3,295) vs. 492 (267-2,649) 1/s, P = 0.028] and RA [30 (27-44) vs. 9 (5-27) 1/s, P = 0.005]. RA E vorticity was significantly decreased [13 (7-22) vs. 28 (15-31) 1/s, P = 0.038] in RVDD. E-wave vorticity correlated TV e', E-,and TV E/A (P < 0.05), and A-wave vorticity associated with both TV A and E/A (P < 0.02). RVDD is associated with alterations in E- and A-wave vorticity, and vorticity correlates with multiple echocardiographic markers of RVDD. Vorticity may be a robust noninvasive research tool for the investigation of RV fluid and tissue mechanical interactions in PAH.

Valve-Related Hemodynamics Mediate Human Bicuspid Aortopathy: Insights From Wall Shear Stress Mapping

BackgroundSuspected genetic causes for extracellular matrix (ECM) dysregulation in the ascending aorta in patients with bicuspid aortic valves (BAV) have influenced strategies and thresholds for surgical resection of BAV aortopathy. Using 4-dimensional (4D) flow cardiac magnetic resonance imaging (CMR), we have documented increased regional wall shear stress (WSS) in the ascending aorta of BAV patients. ObjectivesThis study assessed the relationship between WSS and regional aortic tissue remodeling in BAV patients to determine the influence of regional WSS on the expression of ECM dysregulation. MethodsBAV patients (n = 20) undergoing ascending aortic resection underwent pre-operative 4D flow CMR to regionally map WSS. Paired aortic wall samples (i.e., within-patient samples obtained from regions of elevated and normal WSS) were collected and compared for medial elastin degeneration by histology and ECM regulation by protein expression. ResultsRegions of increased WSS showed greater medial elastin degradation compared to adjacent areas with normal WSS: decreased total elastin (p = 0.01) with thinner fibers (p = 0.00007) that were farther apart (p = 0.001). Multiplex protein analyses of ECM regulatory molecules revealed an increase in transforming growth factor β-1 (p = 0.04), matrix metalloproteinase (MMP)-1 (p = 0.03), MMP-2 (p = 0.06), MMP-3 (p = 0.02), and tissue inhibitor of metalloproteinase-1 (p = 0.04) in elevated WSS regions, indicating ECM dysregulation in regions of high WSS. ConclusionsRegions of increased WSS correspond with ECM dysregulation and elastic fiber degeneration in the ascending aorta of BAV patients, implicating valve-related hemodynamics as a contributing factor in the development of aortopathy. Further study to validate the use of 4D flow CMR as a noninvasive biomarker of disease progression and its ability to individualize resection strategies is warranted.

Bioprosthetic mitral valve effective orifice area using 4D flow cardiac magnetic resonance derived time velocity integral. An in vitro comparison with Doppler Echocardiography

\Background 4D Flow Cardiac Magnetic Resonance (CMR) is a novel imaging modality to assess bioprosthetic mitral valve (BMV) function. We describe a new, 4D Flow derived velocity time integral (TVI) based method to assess effective orifice area (EOA) for BMVs. Methods In our MRI-compatible circulatory loop 4 stented porcine BMVs (27, 29, 31, 33mm) underwent CMR with a 1.5T Siemens scanner. The valves were evaluated at forward stroke volumes of 70, 90 and 110ml at a beat rate of 70bpm. We plotted instantaneous peak velocities and calculated TVI for each scenario. 4D CMR-EOA was

Variations in right atrial flow patterns in the normal heart a potential contributor to cryptogenic stroke in the setting of patent foramen ovale

Background Patent foramen ovale (PFO) occurs in a quarter of the population but half of those with cryptogenic stroke (CS). Difficulty in identifying the pathogenic PFO versus the innocent bystander has contributed to controversy surrounding outcomes following PFO closure. We aimed to investigate whether right atrial flow patterns could help define the mechanism for CS in the setting of PFO. Methods 4D flow cardiac magnetic resonance (CMR) was performed in 10 subjects (age 43±6 years, 4 male) with proven PFO and CS and in 10 controls (age 42±7years, 4 male) with normal trans-thoracic echocardiograms. CMR was performed at 3T (Achieva; Philips) with a 6-channel cardiac array. A retrospectively ECG-gated and respiratory-gated TFE sequence (TE/TR/flip:3.7/6.3ms/8°, VENC:150m/s, FOV:240mm(AP)x240mm(FH)x142mm (LR), spatial resolution:3mm 3 , temporal resolution:5055ms, 20 phases, SENSE, factor 2) was used. Analysis was performed with GTflow v2.0 (Gyrotools). Contours were placed manually in the superior vena cava (SVC) and inferior vena cava (IVC) in the axial plane at the junction with the right atrium. Net flow was assessed at these points. The relative position of the SVC and IVC at these points was measured. A pathline analysis of atrial flow was performed (SVC:red, IVC:green). Results

Turbulent kinetic energy in the ascending aorta is greater in bicuspid than tricuspid aortic valve stenosis

Background The main determinant of the haemodynamic significance of aortic stenosis (AS) is the irreversible pressure loss that is created by the stenosis. The majority of the pressure loss is caused by conversion/dissipation of turbulent kinetic energy (TKE) to heat. Recent developments in cardiac magnetic resonance 4D flow imaging have allowed the noninvasive assessment of TKE. Bicuspid aortic valve disease is known to be associated with a larger ascending aorta and disordered flow patterns, and we hypothesised that peak TKE would be higher in bicuspid AS than tricuspid AS. Methods 15 patients with bicuspid AS (mean age 63.6 years; mean aortic valve area 1.4cm 2 ; mean dimension of the ascending aorta at the level of the pulmonary artery 3.9cm) and no more than mild other valve disease were compared with 22 patients with tricuspid AS (mean age 72.9 years; mean aortic valve area 1.2cm 2 ; mean dimension of the ascending aorta at the level of the pulmonary artery 3.2cm) and no more than mild other valve disease. All subjects underwent time resolved, three dimensional cine magnetic resonance flow imaging at 3 Tesla, for the assessment of peak TKE. The peak TKE was obtained by integrating the TKE per voxel across the ascending aorta at each time frame of the cardiac cycle. Results