| 1. |
- Arvidsson, Per M., et al.
(author)
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Hemodynamic forces using four-dimensional flow MRI : An independent biomarker of cardiac function in heart failure with left ventricular dyssynchrony?
- 2018
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In: American Journal of Physiology - Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 315:6, s. 1627-1639
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Journal article (peer-reviewed)abstract
- Patients with heart failure with left ventricular (LV) dyssynchrony often do not respond to cardiac resynchronization therapy (CRT), indicating that the pathophysiology is insufficiently understood. Intracardiac hemodynamic forces computed from four-dimensional (4-D) flow MRI have been proposed as a new measure of cardiac function. We therefore aimed to investigate how hemodynamic forces are altered in LV dyssynchrony. Thirty-one patients with heart failure and LV dyssynchrony and 39 control subjects underwent cardiac MRI with the acquisition of 4-D flow. Hemodynamic forces were computed using Navier-Stokes equations and integrated over the manually delineated LV volume. The ratio between transverse (lateral-septal and inferior-anterior) and longitudinal (apical-basal) forces was calculated for systole and diastole separately and compared with QRS duration, aortic valve opening delay, global longitudinal strain, and ejection fraction (EF). Patients exhibited hemodynamic force patterns that were significantly altered compared with control subjects, including loss of longitudinal forces in diastole (force ratio, control subjects vs. patients: 0.32 vs. 0.90, P < 0.0001) and increased transverse force magnitudes. The systolic force ratio was correlated with global longitudinal strain and EF (P < 0.01). The diastolic force ratio separated patients from control subjects (area under the curve: 0.98, P < 0.0001) but was not correlated to other dyssynchrony measures (P > 0.05 for all). Hemodynamic forces by 4-D flow represent a new approach to the quantification of LV dyssynchrony. Diastolic force patterns separate healthy from diseased ventricles. Different force patterns in patients indicate the possible use of force analysis for risk stratification and CRT implantation guidance. NEW & NOTEWORTHY In this report, we demonstrate that patients with heart failure with left ventricular dyssynchrony exhibit significantly altered hemodynamic forces compared with normal. Force patterns in patients mechanistically reflect left ventricular dysfunction on the organ level, largely independent of traditional dyssynchrony measures. Force analysis may help clinical decision making and could potentially be used to improve therapy outcomes.
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| 2. |
- Arvidsson, Per M., et al.
(author)
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Left and right ventricular hemodynamic forces in healthy volunteers and elite athletes assessed with 4D flow magnetic resonance imaging
- 2017
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In: American Journal of Physiology - Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 312:2, s. 314-328
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Journal article (peer-reviewed)abstract
- Intracardiac blood flow is driven by hemodynamic forces that are exchanged between the blood and myocardium. Previous studies have been limited to 2D measurements or investigated only left ventricular (LV) forces. Right ventricular (RV) forces and their mechanistic contribution to asymmetric redirection of flow in the RV have not been measured. We therefore aimed to quantify 3D hemodynamic forces in both ventricles in a cohort of healthy subjects, using magnetic resonance imaging 4D flow measurements. Twenty five controls, 14 elite endurance athletes, and 2 patients with LV dyssynchrony were included. 4D flow data were used as input for the Navier-Stokes equations to compute hemodynamic forces over the entire cardiac cycle. Hemodynamic forces were found in a qualitatively consistent pattern in all healthy subjects, with variations in amplitude. LV forces were mainly aligned along the apical-basal longitudinal axis, with an additional component aimed toward the aortic valve during systole. Conversely, RV forces were found in both longitudinal and short-axis planes, with a systolic force component driving a slingshot-like acceleration that explains the mechanism behind the redirection of blood flow toward the pulmonary valve. No differences were found between controls and athletes when indexing forces to ventricular volumes, indicating that cardiac force expenditures are tuned to accelerate blood similarly in small and large hearts. Patients’ forces differed from controls in both timing and amplitude. Normal cardiac pumping is associated with specific force patterns for both ventricles, and deviation from these forces may be a sensitive marker of ventricular dysfunction. Reference values are provided for future studies. New & Noteworthy Biventricular hemodynamic forces were quantified for the first time in healthy controls and elite athletes (n = 39). Hemodynamic forces constitute a slingshot-like mechanism in the right ventricle, redirecting blood flow toward the pulmonary circulation. Force patterns were similar between healthy subjects and athletes, indicating potential utility as a cardiac function biomarker.
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| 3. |
- Arvidsson, Per Martin, et al.
(author)
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Quantification of left and right atrial kinetic energy using four-dimensional intracardiac magnetic resonance imaging flow measurements.
- 2013
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In: Journal of Applied Physiology. - : American Physiological Society. - 1522-1601 .- 8750-7587. ; 114:10, s. 1472-1481
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Journal article (peer-reviewed)abstract
- Kinetic energy (KE) of atrial blood has been postulated as a possible contributor to ventricular filling. Therefore, we aimed to quantify the left and right atrial blood KE using cardiac magnetic resonance (CMR). Fifteen healthy volunteers underwent CMR at 3T, including a four-dimensional phase contrast flow sequence. Mean left atrial (LA) KE was lower than right atrial (RA) KE (1.1±0.1 mJ vs 1.7±0.1 mJ, P<0.01). Three KE peaks were seen in both atria; one in ventricular systole, one during early ventricular diastole, and one during atrial contraction. The systolic LA peak was significantly smaller than the RA peak (P<0.001), and the early diastolic LA peak was larger than the RA peak (P<0.05). Rotational flow contained 46 ± 7% of total KE, and conserved energy better than non-rotational flow did. The KE increase in early diastole was higher in the LA (P<0.001). Systolic KE correlated with the combination of atrial volume and systolic velocity of the atrioventricular plane displacement (R2=0.57 for LA and R2=0.64 for RA). Early diastolic KE of the LA correlated with LV mass (R2=0.28), however no such correlation was found in the right heart. This suggests that LA KE increases during early ventricular diastole due to LV elastic recoil, indicating that LV filling is dependent on diastolic suction. RV relaxation does not seem to contribute to atrial KE. Instead, atrial KE generated during ventricular systole may be conserved in a hydraulic "flywheel" and transferred to the RV through helical flow, which may contribute to RV filling.
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| 4. |
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| 5. |
- Arvidsson, Per, et al.
(author)
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Vortex ring behavior provides the epigenetic blueprint for the human heart.
- 2016
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Journal article (peer-reviewed)abstract
- The laws of fluid dynamics govern vortex ring formation and precede cardiac development by billions of years, suggesting that diastolic vortex ring formation is instrumental in defining the shape of the heart. Using novel and validated magnetic resonance imaging measurements, we show that the healthy left ventricle moves in tandem with the expanding vortex ring, indicating that cardiac form and function is epigenetically optimized to accommodate vortex ring formation for volume pumping. Healthy hearts demonstrate a strong coupling between vortex and cardiac volumes (R(2) = 0.83), but this optimized phenotype is lost in heart failure, suggesting restoration of normal vortex ring dynamics as a new, and possibly important consideration for individualized heart failure treatment. Vortex ring volume was unrelated to early rapid filling (E-wave) velocity in patients and controls. Characteristics of vortex-wall interaction provide unique physiologic and mechanistic information about cardiac diastolic function that may be applied to guide the design and implantation of prosthetic valves, and have potential clinical utility as therapeutic targets for tailored medicine or measures of cardiac health.
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| 6. |
- Bidhult, Sebastian, et al.
(author)
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A new vessel segmentation algorithm for robust blood flow quantification from two-dimensional phase-contrast magnetic resonance images
- 2019
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In: Clinical Physiology and Functional Imaging. - : Wiley. - 1475-0961 .- 1475-097X. ; 39:5, s. 327-338
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Journal article (peer-reviewed)abstract
- Blood flow measurements in the ascending aorta and pulmonary artery from phase-contrast magnetic resonance images require accurate time-resolved vessel segmentation over the cardiac cycle. Current semi-automatic segmentation methods often involve time consuming manual correction, relying on user experience for accurate results. The purpose of this study was to develop a semi-automatic vessel segmentation algorithm with shape constraints based on manual vessel delineations for robust segmentation of the ascending aorta and pulmonary artery, to evaluate the proposed method in healthy volunteers and patients with heart failure and congenital heart disease, to validate the method in a pulsatile flow phantom experiment, and to make the method freely available for research purposes. Algorithm shape constraints were extracted from manual reference delineations of the ascending aorta (n=20) and pulmonary artery (n=20) and were included into a semi-automatic segmentation method only requiring manual delineation in one image. Bias and variability (bias±SD) for flow volume of the proposed algorithm versus manual reference delineations were 0·0±1·9ml in the ascending aorta (n=151; 7 healthy volunteers; 144 heart failure patients) and -1·7±2·9 ml in the pulmonary artery (n=40; 25 healthy volunteers; 15 patients with atrial septal defect). Inter-observer bias and variability were lower (p=0·008) for the proposed semi-automatic method (-0·1±0·9ml) compared to manual reference delineations (1·5±5·1ml). Phantom validation showed good agreement between the proposed method and timer-and-beaker flow volumes (0·4±2·7ml). In conclusion, the proposed semi-automatic vessel segmentation algorithm can be used for efficient analysis of flow and shunt volumes in the aorta and pulmonary artery. This article is protected by copyright. All rights reserved.
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| 7. |
- Bidhult, Sebastian, et al.
(author)
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Independent validation of metric optimized gating for fetal cardiovascular phase-contrast flow imaging
- 2019
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In: Magnetic Resonance in Medicine. - : Wiley. - 1522-2594 .- 0740-3194. ; 81:1, s. 495-503
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Journal article (peer-reviewed)abstract
- PURPOSE: To validate metric optimized gating phase-contrast MR (MOG PC-MR) flow measurements for a range of fetal flow velocities in phantom experiments. 2) To investigate intra- and interobserver variability for fetal flow measurements at an imaging center other than the original site.METHODS: MOG PC-MR was compared to timer/beaker measurements in a pulsatile flow phantom using a heart rate (∼145 bpm), nozzle diameter (∼6 mm), and flow range (∼130-700 mL/min) similar to fetal imaging. Fifteen healthy fetuses were included for intra- and interobserver variability in the fetal descending aorta and umbilical vein.RESULTS: Phantom MOG PC-MR flow bias and variability was 2% ± 23%. Accuracy of MOG PC-MR was degraded for flow profiles with low velocity-to-noise ratio. Intra- and interobserver coefficients of variation were 6% and 19%, respectively, for fetal descending aorta; and 10% and 17%, respectively, for the umbilical vein.CONCLUSION: Phantom validation showed good agreement between MOG and conventionally gated PC-MR, except for cases with low velocity-to-noise ratio, which resulted in MOG misgating and underestimated peak velocities and warranted optimization of sequence parameters to individual fetal vessels. Inter- and intraobserver variability for fetal MOG PC-MR imaging were comparable to previously reported values.
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| 8. |
- Bissell, Malenka M., et al.
(author)
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4D Flow cardiovascular magnetic resonance consensus statement : 2023 update
- 2023
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In: Journal of Cardiovascular Magnetic Resonance. - : BMC. - 1097-6647 .- 1532-429X. ; 25:1
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Research review (peer-reviewed)abstract
- Hemodynamic assessment is an integral part of the diagnosis and management of cardiovascular disease. Four-dimensional cardiovascular magnetic resonance flow imaging (4D Flow CMR) allows comprehensive and accurate assessment of flow in a single acquisition. This consensus paper is an update from the 2015 ‘4D Flow CMR Consensus Statement’. We elaborate on 4D Flow CMR sequence options and imaging considerations. The document aims to assist centers starting out with 4D Flow CMR of the heart and great vessels with advice on acquisition parameters, post-processing workflows and integration into clinical practice. Furthermore, we define minimum quality assurance and validation standards for clinical centers. We also address the challenges faced in quality assurance and validation in the research setting. We also include a checklist for recommended publication standards, specifically for 4D Flow CMR. Finally, we discuss the current limitations and the future of 4D Flow CMR. This updated consensus paper will further facilitate widespread adoption of 4D Flow CMR in the clinical workflow across the globe and aid consistently high-quality publication standards.
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| 9. |
- Bock, Jelena, et al.
(author)
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Validation and reproducibility of cardiovascular 4D-flow MRI from two vendors using 2 × 2 parallel imaging acceleration in pulsatile flow phantom and in vivo with and without respiratory gating
- 2018
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In: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455.
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Journal article (peer-reviewed)abstract
- Background: 4D-flow magnetic resonance imaging (MRI) is increasingly used. Purpose: To validate 4D-flow sequences in phantom and in vivo, comparing volume flow and kinetic energy (KE) head-to-head, with and without respiratory gating. Material and Methods: Achieva dStream (Philips Healthcare) and MAGNETOM Aera (Siemens Healthcare) 1.5-T scanners were used. Phantom validation measured pulsatile, three-dimensional flow with 4D-flow MRI and laser particle imaging velocimetry (PIV) as reference standard. Ten healthy participants underwent three cardiac MRI examinations each, consisting of cine-imaging, 2D-flow (aorta, pulmonary artery), and 2 × 2 accelerated 4D-flow with (Resp+) and without (Resp−) respiratory gating. Examinations were acquired consecutively on both scanners and one examination repeated within two weeks. Volume flow in the great vessels was compared between 2D- and 4D-flow. KE were calculated for all time phases and voxels in the left ventricle. Results: Phantom results showed high accuracy and precision for both scanners. In vivo, higher accuracy and precision (P < 0.001) was found for volume flow for the Aera prototype with Resp+ (–3.7 ± 10.4 mL, r = 0.89) compared to the Achieva product sequence (–17.8 ± 18.6 mL, r = 0.56). 4D-flow Resp− on Aera had somewhat larger bias (–9.3 ± 9.6 mL, r = 0.90) compared to Resp+ (P = 0.005). KE measurements showed larger differences between scanners on the same day compared to the same scanner at different days. Conclusion: Sequence-specific in vivo validation of 4D-flow is needed before clinical use. 4D-flow with the Aera prototype sequence with a clinically acceptable acquisition time (<10 min) showed acceptable bias in healthy controls to be considered for clinical use. Intra-individual KE comparisons should use the same sequence.
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| 10. |
- Carlsson, Marcus, et al.
(author)
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Quantification and visualization of cardiovascular 4D velocity mapping accelerated with parallel imaging or k-t BLAST: head to head comparison and validation at 1.5 T and 3 T
- 2011
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In: Journal of Cardiovascular Magnetic Resonance. - 1097-6647. ; 13:55
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Journal article (peer-reviewed)abstract
- Background: Three-dimensional time-resolved (4D) phase-contrast (PC) CMR can visualize and quantify cardiovascular flow but is hampered by long acquisition times. Acceleration with SENSE or k-t BLAST are two possibilities but results on validation are lacking, especially at 3 T. The aim of this study was therefore to validate quantitative in vivo cardiac 4D-acquisitions accelerated with parallel imaging and k-t BLAST at 1.5 T and 3 T with 2D-flow as the reference and to investigate if field strengths and type of acceleration have major effects on intracardiac flow visualization. Methods: The local ethical committee approved the study. 13 healthy volunteers were scanned at both 1.5 T and 3 T in random order with 2D-flow of the aorta and main pulmonary artery and two 4D-flow sequences of the heart accelerated with SENSE and k-t BLAST respectively. 2D-image planes were reconstructed at the aortic and pulmonary outflow. Flow curves were calculated and peak flows and stroke volumes (SV) compared to the results from 2D-flow acquisitions. Intra-cardiac flow was visualized using particle tracing and image quality based on the flow patterns of the particles was graded using a four-point scale. Results: Good accuracy of SV quantification was found using 3 T 4D-SENSE (r(2) = 0.86, -0.7 +/- 7.6%) and although a larger bias was found on 1.5 T (r(2) = 0.71, -3.6 +/- 14.8%), the difference was not significant (p = 0.46). Accuracy of 4D k-t BLAST for SV was lower (p < 0.01) on 1.5 T (r(2) = 0.65, -15.6 +/- 13.7%) compared to 3 T (r(2) = 0.64, -4.6 +/- 10.0%). Peak flow was lower with 4D-SENSE at both 3 T and 1.5 T compared to 2D-flow (p < 0.01) and even lower with 4D k-t BLAST at both scanners (p < 0.01). Intracardiac flow visualization did not differ between 1.5 T and 3 T (p = 0.09) or between 4D-SENSE or 4D k-t BLAST (p = 0.85). Conclusions: The present study showed that quantitative 4D flow accelerated with SENSE has good accuracy at 3 T and compares favourably to 1.5 T. 4D flow accelerated with k-t BLAST underestimate flow velocities and thereby yield too high bias for intra-cardiac quantitative in vivo use at the present time. For intra-cardiac 4D-flow visualization, however, 1.5 T and 3 T as well as SENSE or k-t BLAST can be used with similar quality.
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