Phase-contrast Cardiac Magnetic Resonance Research Articles

Assessment of pulmonary artery stiffness by multiparametric cardiac magnetic resonance-surrogate for right heart catheterization.

Cardiac magnetic resonance (CMR) imaging allows for multiparametric assessment of healthy pulmonary artery (PA) hemodynamics. Gender- and aging-associated PA stiffness and pressure alterations have remained clinically unestablished, however may demonstrate epidemiological differences in disease development. The aim of this study is to evaluate the role of CMR as a surrogate for catheter examinations by providing a comprehensive CMR assessment of sex- and age-related reference values for PA stiffness, flow, and pressure. PA hemodynamics were studied between gender and age groups (>/<50 years) using phase-contrast CMR. Corresponding correlation analyses were performed. 179 healthy volunteers with a median age of 32.6 years (range 11.3-68.2) were examined. Males demonstrated increased PA compliance (median [interquartile range] or mean ± standard deviation) (20.8 mm2/mmHg [16.6; 25.8] vs. 19.2 ± 7.1 mm2/mmHg; P < 0.033), higher pulse wave velocity (2.00 m/s [1.35; 2.87] vs. 1.73 m/s [1.19; 2.34]; P = 0.018) and a reduced full width half maximum (FWHM) (219 ± 22 ms vs. 235 ± 23 ms; P < 0.001) than females. Mean, systolic, diastolic PA pressure and pulmonary proportional pulse pressure were significantly elevated for males compared to females (P < 0.001). Older subjects (>50 years) exhibited reduced PA elasticity (41.7% [31.0; 52.9] vs. 66.4% [47.7; 83.0]; P < 0.001), reduced PA compliance (15.4 mm2/mmHg [12.3; 20.7] vs. 21.3 ± 6.8 mm2/mmHg; P < 0.001), higher pulse wave velocity (2.59 m/s [1.57; 3.59] vs. 1.76 m/s [1.24; 2.34]; P < 0.001) and a reduced FWHM (218 ± 29 ms vs. 231 ± 21 ms; P < 0.001) than younger subjects. Velocity-time profiles are dependent on age and gender. PA stiffness indices deteriorate with age. CMR has potential to serve as a surrogate for right heart catheterization.

Accuracy of pulmonary venous flow quantification by 2D phase contrast cardiac magnetic resonance

Abstract Funding Acknowledgements Type of funding sources: None. Background Determination of pulmonary venous flow by cardiac magnetic resonance (CMR) is frequently required in patients with complex congenital heart disease (CHD) lesions. Although new advanced imaging techniques like 4D flow are increasingly available, standard 2D phase contrast (2DPC) sequences remain the most frequently used method for quantification of flow. However, little is known on the accuracy of 2DPC flow measurements in the pulmonary veins. Purpose This study therefore aims to investigate the accuracy of pulmonary venous flow quantification by 2DPC. Methods Patients with CHD underwent a CMR on a 1.5T scanner. 2DPC flow sequences (typical temporal resolution 35–50ms, inplane spatial resolution 1.3–1.8 mm2, VENC 80–100) were acquired in the ascending aorta (AA), main, right and left pulmonary arteries (MPA, RPA, LPA), as well as left (LPV) and right (RPV) pulmonary veins. Pulmonary venous flow was compared to pulmonary arterial flow in all patients and to aortic flow in patients without left to right (L-R) shunt using Bland-Altman plots and Pearson’s correlations. Results Twenty CHD patients (age 27±3, range 7; 53 years, 7 women, tetralogy of Fallot N=7, Ross operation N=1; Fontan N=4, transposition of great arteries N=2, atrial septal defect N=2, Turner syndrome 1, Ebstein N=1, valvulopathies N=2) were included. Table 1 shows absolute flow values of the different vessels. Bland-Altman analyses and correlations (Table 2) showed a good agreement of total pulmonary venous (PV) to flow in the ascending aorta (group without shunt) and the sum of flow of both branch pulmonary arteries. However, agreement of total PV with MPA flow as well as of LPV and RPV with the respective branch pulmonary artery flow was reduced. Conclusions Total PV flow determined by 2DPC shows a good agreement with flow in the ascending aorta and the sum of the branch pulmonary arteries. Flow turbulences due to the pathologies of the right ventricular outflow tract probably contribute to the reduced agreement of total PV and MPA flow. However, the reduced agreement of the flow in left/right pulmonary veins and their respective branch pulmonary arteries underlines the need for newer advanced flow quantification techniques to improve accuracy of pulmonary venous flow measurements.

A computational study of aortic reconstruction in single ventricle patients.

Patients with hypoplastic left heart syndrome (HLHS) are born with an underdeveloped left heart. They typically receive a sequence of surgeries that result in a single ventricle physiology called the Fontan circulation. While these patients usually survive into early adulthood, they are at risk for medical complications, partially due to their lower than normal cardiac output, which leads to insufficient cerebral and gut perfusion. While clinical imaging data can provide detailed insight into cardiovascular function within the imaged region, it is difficult to use these data for assessing deficiencies in the rest of the body and for deriving blood pressure dynamics. Data from patients used in this paper include three-dimensional, magnetic resonance angiograms (MRA), time-resolved phase contrast cardiac magnetic resonance images (4D-MRI) and sphygmomanometer blood pressure measurements. The 4D-MRI images provide detailed insight into velocity and flow in vessels within the imaged region, but they cannot predict flow in the rest of the body, nor do they provide values of blood pressure. To remedy these limitations, this study combines the MRA, 4D-MRI, and pressure data with 1D fluid dynamics models to predict hemodynamics in the major systemic arteries, including the cerebral and gut vasculature. A specific focus is placed on studying the impact of aortic reconstruction occurring during the first surgery that results in abnormal vessel morphology. To study these effects, we compare simulations for an HLHS patient with simulations for a matched control patient that has double outlet right ventricle (DORV) physiology with a native aorta. Our results show that the HLHS patient has hypertensive pressures in the brain as well as reduced flow to the gut. Wave intensity analysis suggests that the HLHS patient has irregular circulatory function during light upright exercise conditions and that predicted wall shear stresses are lower than normal, suggesting the HLHS patient may have hypertension.

Machine learning for the automatic assessment of aortic rotational flow and wall shear stress from 4D flow cardiac magnetic resonance imaging.

Three-dimensional (3D) time-resolved phase-contrast cardiac magnetic resonance (4D flow CMR) allows for unparalleled quantification of blood velocity. Despite established potential in aortic diseases, the analysis is time-consuming and requires expert knowledge, hindering clinical application. The present research aimed to develop and test a fully automatic machine learning-based pipeline for aortic 4D flow CMR analysis. Four hundred and four subjects were prospectively included. Ground-truth to train the algorithms was generated by experts. The cohort was divided into training (323 patients) and testing (81) sets and used to train and test a 3D nnU-Net for segmentation and a Deep Q-Network algorithm for landmark detection. In-plane (IRF) and through-plane (SFRR) rotational flow descriptors and axial and circumferential wall shear stress (WSS) were computed at ten planes covering the ascending aorta and arch. Automatic aortic segmentation resulted in a median Dice score (DS) of 0.949 and average symmetric surface distance of 0.839 (0.632-1.071) mm, comparable with the state of the art. Aortic landmarks were located with a precision comparable with experts in the sinotubular junction and first and third supra-aortic vessels (p = 0.513, 0.592 and 0.905, respectively) but with lower precision in the pulmonary bifurcation (p = 0.028), resulting in precise localisation of analysis planes. Automatic flow assessment showed excellent (ICC > 0.9) agreement with manual quantification of SFRR and good-to-excellent agreement (ICC > 0.75) in the measurement of IRF and axial and circumferential WSS. Fully automatic analysis of complex aortic flow dynamics from 4D flow CMR is feasible. Its implementation could foster the clinical use of 4D flow CMR. • 4D flow CMR allows for unparalleled aortic blood flow analysis but requires aortic segmentation and anatomical landmark identification, which are time-consuming, limiting 4D flow CMR widespread use. • A fully automatic machine learning pipeline for aortic 4D flow CMR analysis was trained with data of 323 patients and tested in 81 patients, ensuring a balanced distribution of aneurysm aetiologies. • Automatic assessment of complex flow characteristics such as rotational flow and wall shear stress showed good-to-excellent agreement with manual quantification.

Four-dimensional flow cardiac magnetic resonance assessment of left ventricular diastolic function.

Left ventricular diastolic dysfunction is a major cause of heart failure and carries a poor prognosis. Assessment of left ventricular diastolic function however remains challenging for both echocardiography and conventional phase contrast cardiac magnetic resonance. Amongst other limitations, both are restricted to measuring velocity in a single direction or plane, thereby compromising their ability to capture complex diastolic hemodynamics in health and disease. Time-resolved three-dimensional phase contrast cardiac magnetic resonance imaging with three-directional velocity encoding known as ‘4D flow CMR’ is an emerging technology which allows retrospective measurement of velocity and by extension flow at any point in the acquired 3D data volume. With 4D flow CMR, complex aspects of blood flow and ventricular function can be studied throughout the cardiac cycle. 4D flow CMR can facilitate the visualization of functional blood flow components and flow vortices as well as the quantification of novel hemodynamic and functional parameters such as kinetic energy, relative pressure, energy loss and vorticity. In this review, we examine key concepts and novel markers of diastolic function obtained by flow pattern analysis using 4D flow CMR. We consolidate the existing evidence base to highlight the strengths and limitations of 4D flow CMR techniques in the surveillance and diagnosis of left ventricular diastolic dysfunction.

Phase contrast cardiac magnetic resonance imaging versus transoesophageal echocardiography for the evaluation of feasibility for transcatheter closure of atrial septal defects

BackgroundThis prospective study was aimed at comparing phase contrast cardiac magnetic resonance imaging (PC-CMR) with 2D transoesophageal echocardiography (TEE) for determining potential candidature for transcatheter closure in ostium secundum ASD (OS-ASD) patients. We included consecutive adult patients with OS-ASD for the evaluation of feasibility for transcatheter closure using 2D-TEE and PC-CMR over a period of 2 years. Patients who fulfilled the conventional criteria for transcatheter closure, i.e. maximum ASD diameter ≤ 34 mm, adequate rims (≥ 5 mm, except for anterosuperior rim), and normal pulmonary venous drainage on both imaging modalities, were taken for device closure. In patients where there was discrepancy in the measurements of ASD diameter or rim size, making them eligible for device closure on one imaging modality and ineligible on the other hand, provisional device closure was attempted. All patients who underwent transcatheter closure were followed up to 6 months to rule out any complications.ResultsA total of 58 patients (mean age 35.93 ± 10.59 years) were enrolled in the study. Overall, there was significant positive correlation between 2D-TEE and CMR measurements of maximal ASD diameter and rim size (p < 0.001). However, TEE significantly underestimated maximal ASD diameter and posteroinferior rim size in comparison with CMR (p = 0.013 and p = 0.023, respectively). 46 (79.3%) patients were suitable for transcatheter closure on CMR, while 44 (75.9%) were eligible on TEE. Transcatheter closure was attempted in 48 patients based on imaging findings and was successful in 46 (95.8%) patients. Device closure was unsuccessful in 2 patients with defect size < 34 mm on TEE but > 34 mm on CMR. Among 7 patients with deficient posteroinferior rim on TEE, 5 had sufficient rim on CMR and underwent successful transcatheter closure. CMR detected anomalous pulmonary venous drainage in one patient which was missed on TEE, hence excluding the patient from transcatheter closure. Mean device size was 28.3 ± 7.4 mm and correlated more strongly with the defect dimensions on PC-CMR (r = 0.85, p < 0.001) compared to TEE (r = 0.71, p = 0.02).ConclusionsPC-CMR may to be superior to 2D-TEE for the preprocedural planning and feasibility assessment for transcatheter closure in adult patients with ostium secundum ASD.

Impact of Variation in Interleaflet Triangle Height Between Fused Leaflets in the Functionally Bicuspid Aortic Valve on Hemodynamics and Tissue Biomechanics

AbstractThere is fusion between two leaflets in functionally bicuspid (bileaflet) aortic valves with trisinuate aortic root. The degree of fusion inversely correlates with variation in the interleaflet triangle height (“commissural height”). We aimed to determine the hemodynamics and biomechanical response in the thoracic aorta due to variations in the commissural height between fused leaflets in a bicuspid aortic valve with raphe. A three-dimensional (3D) aortic valve model was reconstructed using cardiac magnetic resonance (CMR) imaging from a patient with a normal trileaflet aortic valve. Fluid–structure interaction (FSI) simulations were used to investigate the effect of variation in commissural height between the coronary leaflets with leaflet fusion, and this was contrasted to a case with a normal trileaflet valve. Phase-contrast CMR was used for validation of the simulated hemodynamics. The aorta and leaflet tissues were treated as hyperelastic materials. In the normal trileaflet aortic valve, two counter-rotating vortex cores develop within the root at peak systole and interact with the walls of the ascending aorta. However, in the bicuspid aortic valve with fusion between the coronary leaflets, the vortex system becomes more asymmetric. This correlates with more recirculation of flow toward the fusion side of the aortic root. The peak velocity, pressure gradient, wall shear stress, and strain levels increase approximately linear with decreasing commissural height and increasing leaflet fusion. Decreasing interleaflet triangle height between the fused leaflets in bicuspid aortic valves with raphe results in linear elevation of wall shear stress at the sinutubular junction and proximal ascending aorta.

4D-flow cardiac magnetic resonance imaging after aortic root replacement with long-valved decellularized aortic homografts: comparison to valve-sparing aortic root replacement and healthy controls.

OBJECTIVESLong-valved decellularized aortic homografts (DAH) may be used in young patients to treat aortic valve disease associated with aortic root dilatation, thereby eliminating the need for prosthetic material and anticoagulation.METHODSThirty-three male subjects in 3 equally sized cohorts were compared: patients following DAH implantation with a median age of 29 years [interquartile range (IQR) 27.5–37.5], patients post-valve-sparing aortic root replacement (VSARR), median 44 years (IQR 31.5–49) and healthy controls, median 33 years (IQR 28–40, P = 0.228). Time-resolved three-dimensional phase-contrast cardiac magnetic resonance imaging was performed to assess maximum blood flow velocity, pulse wave velocity, mechanical energy loss (EL), wall shear stress and flow patterns (vorticity, eccentricity, helicity) in 5 different planes of the aorta.RESULTSThe mean time between surgery and cardiovascular magnetic resonance was 2.56 ± 2.0 years in DAH vs 2.67 ± 2.1 in VSARR, P = 0.500. No significant differences in maximum velocity and pulse wave velocity were found between healthy controls and DAH across all planes. Velocity in the proximal aorta was significantly higher in VSARR (182.91 ± 53.91 cm/s, P = 0.032) compared with healthy controls. EL was significantly higher in VSARR in the proximal aorta with 1.85 mW (IQR 1.39–2.95) compared with healthy controls, 1.06 mW (0.91–1.22, P = 0.016), as well as in the entire thoracic aorta. In contrast, there was no significant EL in DAH in the proximal, 1.27 m/W (0.92–1.53, P = 0.296), as well as in the thoracic aorta, 7.7 m/W (5.25–9.90, P = 0.114), compared with healthy controls. There were no significant differences in wall shear stress parameters for all 5 regions of the thoracic aorta between the 3 groups. DAH patients, however, showed more vorticity, helicity and eccentricity in the ascending aorta compared with healthy controls (P < 0.019).CONCLUSIONSDecellularized long aortic homografts exhibit near to normal haemodynamic parameters 2.5 years postoperatively compared with healthy controls and VSARR.

Integrating Novel Physiologic Data into Decision-Making in Congenital Heart Surgery.

Optimal decision-making to determine the type and timing of surgical intervention for various congenital heart disease (CHD) requires adequate understanding and interpretation of anatomic and physiologic data obtained from various imaging modalities. Cardiac magnetic resonance (CMR) has revolutionized the way we evaluate the anatomy and physiology of CHD. In addition to 2- and 3-dimensional anatomic data and volumetry, phase-contrast CMR allows quantitative measurements of cardiac output, pulmonary blood flow, pulmonary-to-systemic flow ratio, the amount of intracardiac shunt, valve regurgitation, and aortopulmonary collateral flows. This review article describes the utilization of CMR-derived flow data in surgical decision-making in three distinct subgroups: (1) patients with borderline left ventricle (LV) with emphasis on the ascending aortic flow and other physiologic parameters, (2) single ventricle patients who undergo bidirectional cavopulmonary shunt with emphasis on the impact of superior vena cava blood flow on postoperative physiology, and (3) patients with pulmonary atresia and major aortopulmonary collateral arteries with emphasis on the impact of total pulmonary blood flow and systemic-to-pulmonary flow ratio on clinical outcomes.

Prognostic value of depressed cardiac index after STEMI: a phase-contrast magnetic resonance study.

An invasively measured cardiac index (CI) of ≤2.2 L/min/m2 is one of the strongest prognostic indicators after ST-elevation myocardial infarction (STEMI), however, knowledge is mainly based on invasive evaluations performed in the pre-stent era. Velocity-encoded phase-contrast cardiac magnetic resonance (PC-CMR) allows non-invasive determination of CI. In this prospective study, CMR was performed in 406 stable and contemporarily revascularized patients a median of 3 days after STEMI. Forward stroke volume was assessed at the level of the ascending aorta by PC-CMR. Left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS) were determined by cine CMR. Major adverse cardiac events (MACE) were defined as the composite of death, myocardial infarction, or hospitalization for heart failure. Median CI was 2.52 L/min/m2 and 27% of patients had ≤2.2 L/min/m2. Median LVEF was 53% and median GLS was -12.2%. During a median follow-up of 14.2 [95% confidence interval (95% CI) 13.6-14.7] months, 41 patients (10.1%) experienced a MACE. A depressed CI was significantly associated with MACE after adjustment for LVEF, GLS, Thrombolysis in Myocardial Infarction (TIMI) risk score, and infarct size [hazard ratio = 3.15 (95% CI 1.53-6.47); P = 0.002] and led to significant discrimination improvement [net reclassification improvement 0.61 (95% CI 0.25-0.97); P < 0.001]. A CI of 2.2 L/min/m2 or less as measured by PC-CMR was present in 27% of clinically stable patients after STEMI and strongly and independently predicted medium-term MACE. The prognostic value of a depressed CI was superior and incremental to LVEF, GLS, TIMI risk score, and infarct size.

Determinants and prognostic relevance of aortic stiffness in patients with recent ST-elevation myocardial infarction

Abstract Background The association between aortic stiffness, cardiovascular risk factors and prognosis in patients with recent ST-elevation myocardial infarction (STEMI) is poorly understood. We analyzed the relationship between cardiovascular risk factors and arterial stiffening and assessed its prognostic significance in patients with recent STEMI. Methods We prospectively enrolled 408 consecutive patients who sustained a first STEMI and underwent primary percutaneous coronary intervention (PPCI). Aortic pulse wave velocity (PWV), a direct measure of aortic stiffness, was determined by the transit-time method using velocity-encoded, phase-contrast cardiac magnetic resonance imaging. Patient characteristics were acquired at baseline and major adverse cardiac and cerebrovascular events (MACCE) were assessed at 13 (interquartile range [IQR] 12–31) months. Cox regressionand logistic regression analysis were performed to explore predictors of PWV and MACCE. Results Median aortic PWV was 6.6 m/s (IQR 5.6–8.3m/s). In multivariable analysis, age (odds ratio [OR] 1.10, 95% confidence interval [CI], 1.08–1.14, p&amp;lt;0.001) and hypertension (OR 2.45, 95% CI, 1.53–3.91, p&amp;lt;0.001) were independently associated with increased PWV. Sex, diabetes, smoking status, dyslipidemia, and obesity were not significantly associated with PWV in adjusted analysis (all p&amp;gt;0.05). High PWV significantly and independently predicted occurrence of MACCE in adjusted analysis (hazard ratio [HR] 2.45, 95% CI 1.19–5.04, p=0.014). Conclusion In patients with recent STEMI, the impact of classical cardiovascular risk factors on aortic stiffness is mainly dependent on age and increased blood pressure. Increased aortic stiffness is associated with adverse clinical outcome post-STEMI, suggesting it as a relevant therapeutic target in this population. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Austrian Science Fund (FWF)Austrian Society of Cardiology Figure 1. Biorender.com

Flow vorticity relationships with right ventricular geometry in adult tetralogy of Fallot

Abstract Background Repaired tetralogy of Fallot adults (rToF) undergo right ventricular (RV) remodeling, in part due to volume overload of residual pulmonary regurgitation volume (PRV). Time-resolved phase-contrast cardiac magnetic resonance imaging (4D Flow MRI) enables the qualitative and quantitative measurement of altered blood flow patterns, including vorticity. Cardiac atlases allow for complex three-dimensional heart shapes to be expressed as morphometric scores. Those scores show the extent of geometrical shift and can help explore uncharted relationships between vorticity and architecture. Purpose We aimed to quantify vorticity, incorporating deep learning to enhance 4D Flow data, and correlate this with global cardiac parameters and morphometric scores. Methods 12 Adult rToF patients and 10 age-matched controls underwent 4D flow MRI and cine imaging. RV interventricular vorticity was calculated for outflow and inflow tracts. EDV, ESV and SV were computed from cines which were also used to build three-dimensional shape models. The biventricular models were projected onto an atlas generated from 95 rToF patients, and twenty-one principal component analysis shape modes were correlated with cardiac metrics and vorticity to identify global shape variations. Association between biventricular shape and vorticity was further analysed using multivariate multiple regression models. Results Strong correlation was found between PRV and the right ventricular outflow tract (RVOT) vorticity. PRV and RVOT vorticity both correlated with the same 3 shape modes (r=−0.55, −0.50 and 0.6 (p&amp;lt;0.05) respectively for PR and r=0.63, −0.82 and 0.60 (p&amp;lt;0.05) respectively for vorticity) i.e., the RV dilates with an increase in basal bulging, apical bulging and tricuspid annulus tilting with more severe regurgitation, as well as a smaller LV, and a paradoxical movement of the septum (Figure 1). However, RV vorticity correlated with 2 modes that did not correlate with PRV, (r=−0.62, −0.69, p&amp;lt;0.05). With higher vorticity the RV was longer, increased tilting of the tricuspid annulus and an increased basal bulge around the tricuspid area. The multivariate analysis model demonstrated that higher vorticity was associated with displacement of the pulmonary valve and change in the RVOT length and direction. A septal displacement towards the left ventricle was observed and increased apical flatness of the RV (Figure 1). Qualitatively, vorticity in rToF group was more heterogeneous than controls (Figure 2). Conclusions Vorticity is a novel marker based on the influence of blood motion providing new insight into early diagnosis and prognosis of cardiac disease. This is the first study to examine the relationships between vorticity and regional RV shape changes in rToF. Mode associations with vorticity were different to associations with PRV. More longitudinal studies are required for standardization of change in vorticity with the disease process. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): The New Zealand heart foundation Mode variations and morphometric modelVorticity visualization and analysis

Determinants and prognostic relevance of aortic stiffness in patients with recent ST-elevation myocardial infarction

The association between aortic stiffness, cardiovascular risk factors and prognosis in patients with recent ST-elevation myocardial infarction (STEMI) is poorly understood. We analyzed the relationship between cardiovascular risk factors and arterial stiffening and assessed its prognostic significance in patients with recent STEMI. We prospectively enrolled 408 consecutive patients who sustained a first STEMI and underwent primary percutaneous coronary intervention (PPCI). Aortic pulse wave velocity (PWV), the most widely used measure of aortic stiffness, was determined by the transit-time method using velocity-encoded, phase-contrast cardiac magnetic resonance imaging. Patient characteristics were acquired at baseline and major adverse cardiac and cerebrovascular events (MACCE) were assessed at 13 [interquartile range (IQR) 12–31] months. Cox regression- and logistic regression analysis were performed to explore predictors of aortic stiffness and MACCE. Median aortic PWV was 6.6 m/s (IQR 5.6–8.3 m/s). In multivariable analysis, age [odds ratio (OR) 1.10, 95% confidence interval (CI), 1.08–1.14, p < 0.001] and hypertension (OR 2.45, 95% CI, 1.53–3.91, p < 0.001) were independently associated with increased PWV. Sex, diabetes, smoking status, dyslipidemia, and obesity were not significantly associated with PWV in adjusted analysis (all p > 0.05). High PWV significantly and independently predicted occurrence of MACCE in adjusted analysis [hazard ratio (HR) 2.45, 95% CI 1.19–5.04, p = 0.014]. In patients with recent STEMI, the impact of classical cardiovascular risk factors on aortic stiffness is mainly dependent on age and increased blood pressure. Increased aortic stiffness is associated with adverse clinical outcome post-STEMI, suggesting it as a relevant therapeutic target in this population. Trial (NCT04113356).

Deep artifact suppression for spiral real-time phase contrast cardiac magnetic resonance imaging in congenital heart disease

PurposeReal-time spiral phase contrast MR (PCMR) enables rapid free-breathing assessment of flow. Target spatial and temporal resolutions require high acceleration rates often leading to long reconstruction times. Here we propose a deep artifact suppression framework for fast and accurate flow quantification. MethodsU-Nets were trained for deep artifact suppression using 520 breath-hold gated spiral PCMR aortic datasets collected in congenital heart disease patients. Two spiral trajectories (uniform and perturbed) and two losses (Mean Absolute Error -MAE- and average structural similarity index measurement -SSIM-) were compared in synthetic data in terms of MAE, peak SNR (PSNR) and SSIM. Perturbed spiral PCMR was prospectively acquired in 20 patients. Stroke Volume (SV), peak mean velocity and edge sharpness measurements were compared to Compressed Sensing (CS) and Cartesian reference. ResultsIn synthetic data, perturbed spiral consistently outperformed uniform spiral for the different image metrics. U-Net MAE showed better MAE and PSNR while U-Net SSIM showed higher SSIM based metrics.In-vivo, there were no significant differences in SV between any of the real-time reconstructions and the reference standard Cartesian data. However, U-Net SSIM had better image sharpness and lower biases for peak velocity when compared to U-Net MAE. Reconstruction of 96 frames took ~59 s for CS and 3.9 s for U-Nets. ConclusionDeep artifact suppression of complex valued images using an SSIM based loss was successfully demonstrated in a cohort of congenital heart disease patients for fast and accurate flow quantification.

Invasive validation of a novel approach to determine aortic valve area with phase-contrast cardiac magnetic resonance imaging

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Austrian Society of Cardiology Background. Echocardiography is considered the standard method for screening and diagnosing aortic valve stenosis. However, inaccuracies in the determination of stroke-volumes by the continuity equation might particularly make the evaluation of patients with low-flow states difficult. Phase-contrast cardiac magnetic resonance (PC-CMR) is a promising tool in overcoming these limitations by the simultaneous determination of flow volumes and velocities across the stenotic valve. Purpose The aim of this study is to validate a novel approach based on PC-CMR against the invasive determination of the aortic valve area (AVA). Methods. PC-CMR was performed in 50 patients with moderate or severe AS (n = 52; age 72 years [interquartile range (IQR) 66 - 78], 38% of patients with low-flow states). All of them were referred to invasive evaluation of aortic stenosis by cardiac catheterization. Additionally, transthoracic echocardiography (TTE) was performed. Aortic valve area (AVA) was determined by PC-CMR (AVAPC-CMR) via plotting momentary flow across the valve against momentary flow velocity. AVAPC-CMR at different time points over the entire cardiac cycle was compared to invasively determined AVA, calculated according to the Gorlin-formula. Stroke volumes (SV) were determined by the Fick-principle, pressure gradients according to the modified Bernoulli-equation. Results. Mean AVA during the whole systolic phase showed a good correlation (r: 0.544, p &amp;lt; 0.001) with invasive AVA with a small bias (AVACMR: 0.78 cm², IQR: [0.60-0.96] versus AVAINVASIVE: 0.70 cm², IQR: [0.52-0.87], bias: 0.08 cm², p = 0.017). Intermethodical correlation and bias of AVA as measured by TTE (AVATTE) and AVAINVASIVE were similar to AVAPC-CMR (AVATTE: 0.81 cm²; IQR: [0.64-0.96] versus AVAINVASIVE: 0.70 cm², IQR: [0.52-0.87] r: 0.580, p &amp;lt; 0.001, bias 0.11 cm², p &amp;lt; 0.001). SV by PC-CMR showed a good correlation with Cine-CMR with no significant bias (r: 0.730, p &amp;lt; 0.001; SVPC-CMR: 86 ± 31 ml; SVCine: 85 ± 19 ml). Maximum gradients determined by PC‑CMR were 65 ± 2 9mmHg and showed a good inverse correlation with AVAPC-CMR (r: ‑0.371; p = 0.008). Conclusion. PC-CMR with continuous determination of flow volumes and flow velocities is able to determine AVA in patients with severe aortic stenosis with a tendency to overestimate AVA compared to invasively determined AVA.

4D Flow analysis of intracavitary blood flow dynamics and energetics in the systemic right ventricle

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Italian Ministry of Health Background The systemic position of a morphologically right ventricle (SRV) makes it vulnerable to fail, leading to high incidence of heart failure and cardiac death [1]. Understanding SRV intracavitary blood flow dynamics and energetics could improve patient risk stratification. Purpose Testing the potential of three-dimensional time-resolved phase contrast cardiac magnetic resonance (4D Flow) in quantifying SRV blood flow dynamics and energetics. Methods 4D Flow prototype sequences were acquired on 3 patients (1 male, 2 females) with SRV in D-loop transposition of great arteries after atrial switch operation (D-TGA/ASO), 3 male patients with SRV in L-loop TGA (L-TGA) and healthy controls (2 males, 1 female). Kinetic energy (KE), viscous energy loss (EL), dissipation index (DI) calculated as EL to KE ratio, and hemodynamics forces (HFs) resulting from pressure gradients, were computed for the D-TGA/ASO and L-TGA SRVs, and for the control left ventricles (LVs) and right ventricles (RVs). HFs were decomposed in inferior-anterior, septal-lateral and basal-apical components (HFIA, HFSL, HFBA, respectively) Results Figure 1 reports the time-course of HF components and the general features of the enrolled subjects. In systole, all SRVs (Figure 1a-1b) presented a dominant HFIA and a minor HFSL, similarly to RVs (Figure 1c); however, HFSL had a positive peak, indicating septal contraction towards the SRV cavity, opposite to its normal motion. HFBA magnitude was similar to LVs (Figure 1d), suggesting that the shortening of the tricuspid anulus towards the apex is more pronounced than in RVs (Figure 1c). Over the whole cardiac cycle, DI values were highest in D-TGA/ASO SVRs (0.40-0.55); in L-TGA SRVs, DI values (0.24-0.45) were comparable to healthy LVs (0.22-0.37) and RVs (0.23-0.36). This difference may be related to the fact that in DTGA/ASO the left atrium is functionally replaced by a pulmonary venous baffle, which lacks efficient contraction, as highlighted by the absence of a distinctive A-wave in the KE time-course (Figure 2a). Due to the adaptation to systemic afterload, SRVs were hypertrophic (Figure 1a-1b), with indexed mass higher than normal RVs (Figure 1c), and presented reduced compliance to the diastolic filling, as suggested by increased KE E-wave slope in L-TGA (Figure 2b) compared to controls (Figure 2c-2d). Conclusions Intracavitary HFs in SRVs reveal a partial shift from a RV towards LV pattern. This occurs at the expenses of a higher energetic consumption in D-TGA/ASO than L-TGA, enlightening the crucial role of atrial contribution to impaired SRV diastolic filling. These findings corroborate the previous evidence that patients with D-TGA/ASO have abnormal decrease in stroke volume during exercise whereas L-TGA patients can reach values comparably to healthy controls [2].

Right atrium and cryptogenic ischaemic stroke in the young: a case–control study

BackgroundRecent studies suggest left atrial (LA) dysfunction in cryptogenic stroke. We studied the dynamics of right atrium (RA) and right atrial appendage (RAA) in young adults with cryptogenic stroke. We...

Prognostic value of depressed cardiac index after STEMI: a phase-contrast magnetic resonance study

Abstract Funding Acknowledgements Type of funding sources: None. Aims An invasively measured Cardiac Index (CI) of ≤2.2 l/min/m² is one of the strongest prognostic indicators after ST-elevation myocardial infarction, however knowledge is mainly based on invasive evaluations performed in the pre-stent era. Velocity-encoded Phase Contrast Cardiac Magnetic Resonance (PC-CMR) allows non-invasive determination of CI. Methods In this prospective study CMR was performed in 406 stable and contemporarily revascularized patients a median of 3 days after STEMI. Forward stroke volume was assessed at the level of the ascending aorta by PC-CMR. Left ventricular ejection fraction (LVEF) and global longitudinal strain (GLS) were determined by cine CMR. Major adverse cardiac events (MACE) were defined as the composite of death, myocardial infarction or hospitalization for heart failure. Results Median CI was 2.52 l/min/m², 27% of patients had ≤2.2 l/min/m². Median LVEF was 53%, median GLS was -12.2%. During a median follow-up of 13.6 (12.1;62.9) months, 38 patients (8.7%) experienced a MACE. A depressed CI was significantly associated with MACE after adjustment for GLS and LVEF (HR = 2.55 (95%CI 1.10—5.28); p = 0.01), markers of myocardial injury (HR = 2.18, 95%CI 1.10-4.30, p = 0.02) and clinical parameters (HR = 2.42, 95%CI 1.19-4.90, p = 0.01). Adding CI to a model including LVEF and GLS led to significant discrimination improvement (0.55 [95%CI 0.18 - 0.91]; p = 0.003). Conclusions A CI of 2.2 l/min/m² or less as measured by PC-CMR was present in 27% of clinically stable patients after STEMI, which strongly and independently predicted medium-term MACE. The prognostic value of a depressed CI was superior and incremental to LVEF and GLS. Abstract Figure. Graphical Abstract

CMR 4D flow underestimates peak systolic flow measurements in patients with severe aortic stenosis

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Helsinki University Hospital, Finland Background Aortic stenosis (AS) is the most prevalent valvular disease in the developed countries. 4D flow is an emerging cardiac magnetic resonance (CMR) imaging technique, which has been suggested to improve the evaluation of AS severity. The accuracy of peak flow measurement by 4D flow CMR in patients with severe AS has, however, remained unvalidated. Purpose We investigated the reliability of the novel 4D flow CMR technique in measuring transvalvular peak systolic flow in patients with severe aortic valve stenosis. Methods The study included 63 patients clinically evaluated for valve replacement due to severe symptomatic AS. All the patients underwent echocardiography, 2D phase-contrast and 4D flow CMR. CMR was performed on consecutive patients according to international guidelines. Mean age of the patients was 73.8 ± 11.5 years, mean aortic valve area 0.7 ± 0.2 cm², and 40 of the valves were tricuspid and 23 bicuspid. QFlow and QFlow 4D software were used for flow analyses. Bland-Altman analyses and Wilcoxon signed rank sum tests were performed using SPSS software. Results CMR 4D flow analyses underestimated peak flow values when compared with echocardiography (bias -1.1 m/s, limits of agreement ± 1.5 m/s) and with 2D flow analyses (bias -1.2 m/s, limits of agreement ± 1.7 m/s). The difference between values obtained by 4D flow (median 3.1 m/s, range 1.5 – 4.9 m/s) and echocardiography (median 4.3 m/s, range 2.1 – 6.1 m/s) as well as by 2D flow (median 4.3 m/s, range 2.0 – 8.4 m/s) were statistically significant (p &amp;lt; 0,001). The difference between 2D flow analyses and echocardiography remained statistically insignificant (bias 0.05 m/s, limits of agreement ± 1.6 m/s). Conclusions We found that 4D flow analysis significantly underestimates systolic peak flow values in patients with severe AS. This may be due to intra-voxel averaging of the narrow jets. In contrast to previous assumptions, traditional 2D flow technique may therefore outperform 4D flow in measuring valvular peak flow by CMR in patients with severe AS. This should be taken into consideration when assessing disease severity by CMR. Abstract Figure. Peak systolic flow in AS patients (n = 63)

Determinants and prognostic relevance of aortic stiffness in patients with recent ST-elevation myocardial infarction

Abstract Funding Acknowledgements Type of funding sources: None. Background The association between aortic stiffness, cardiovascular risk factors and prognosis in patients with recent ST-elevation myocardial infarction (STEMI) is poorly understood. Purpose We analyzed the relationship between cardiovascular risk factors and arterial stiffening and assessed its prognostic significance in patients with recent STEMI. Methods We prospectively enrolled 408 consecutive patients who sustained a first STEMI and underwent primary percutaneous coronary intervention (pPCI). Aortic pulse wave velocity (PWV), a direct measure of aortic stiffness, was determined by the transit-time method using velocity-encoded, phase-contrast cardiac magnetic resonance imaging. Patient characteristics were acquired at baseline and major adverse cardiac and cerebrovascular events (MACCE) were assessed at 13 (interquartile range [IQR] 12–31) months. Cox regression- and logistic regression analysis were performed to explore predictors of PWV and MACCE. Results Median aortic PWV was 6.6 m/s (IQR 5.6–8.3m/s). In multivariable analysis, age (odds ratio [OR] 1.10, 95% confidence interval [CI], 1.08–1.14, p &amp;lt; 0.001) and hypertension (OR 2.45, 95% CI, 1.53–3.91, p &amp;lt; 0.001) were independently associated with higher PWV. Gender, diabetes, smoking status, dyslipidemia, and obesity were not significantly associated with PWV in adjusted analysis (all p &amp;gt; 0.05). High PWV significantly and independently predicted occurrence of MACCE in adjusted analysis (hazard ratio [HR] 2.45, 95% CI 1.19–5.04, p = 0.014). Conclusion In patients with recent STEMI, the impact of classical cardiovascular risk factors on aortic stiffness is mainly dependent on age and increased blood pressure. Increased aortic stiffness is associated with adverse clinical outcome, suggesting it as a relevant therapeutic target in this population.