Imperial College London

Dr Omar Jarral

Faculty of MedicineDepartment of Surgery & Cancer

Honorary Clinical Research Fellow
 
 
 
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o.jarral

 
 
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Queen Elizabeth the Queen Mother Wing (QEQM)St Mary's Campus

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Summary

 

Publications

Publication Type
Year
to

74 results found

Jarral OA, Jensen CW, Doberne JW, Downey PS, Serfas JD, Vekstein AM, Hughes GCet al., 2023, Mid-term outcomes of aortic valve repair using an anatomically shaped internal annuloplasty ring., Eur J Cardiothorac Surg, Vol: 64

OBJECTIVES: The Hemispherical Aortic Annuloplasty Reconstructive Technology (HAART) ring is a rigid, internal and geometric device. The objective of this article is to assess the mid-term outcomes of aortic valve repair (AVr) using this prosthesis. METHODS: A prospectively maintained database was used to obtain outcomes for adult patients undergoing AVr using the HAART ring between September 2017 and June 2023. All aortic patients at our institution undergo life-long surveillance with regular assessment and valve imaging. RESULTS: Seventy-one patients underwent AVr using the HAART device: 53 had a trileaflet valve and 18 a bicuspid valve. The median age was 54 years, and most were male (79%). Many required concomitant intervention: 46% had a root procedure and 77% an arch repair. There were no in-hospital deaths, and the median postoperative stay was 5 days. At a mean follow-up of 3.9 (±1.1) years, freedom from reoperation was 94%. Late imaging demonstrated: zero trace (25%), 1+ (54%), 2+ (15%) and 4+ (6%) aortic insufficiency (AI). Eleven patients have ≥moderate AI under surveillance, all of whom have a trileaflet valve (21% of trileaflet patients). Four patients required reoperation: 3 for ring dehiscence and 1 for endocarditis. CONCLUSIONS: Although early results using the HAART device are encouraging, mid-term results raise concern as 21% of trileaflet patients developed recurrent ≥moderate AI by 4 years post-repair. We experienced 3 incidences of ring dehiscence requiring reoperation. Based on this, we recommend caution using the sub-annular approach for stabilization in patients with trileaflet aortic valves. Long-term results are needed to assess outcomes against established techniques.

Journal article

Hanna L, Gibbs RGJ, London Aortic Mechanobiology Working Group, 2023, Type II Endoleaks and Culprit Vessels: Will 4D MRI Change the Paradigm?, Eur J Vasc Endovasc Surg, Vol: 66

Journal article

Salmasi MY, Pirola S, Mahuttanatan S, Fisichella SM, Sengupta S, Jarral OA, Oo A, O'Regan D, Xu XY, Athanasiou Tet al., 2023, Geometry and flow in ascending aortic aneurysms are influenced by left ventricular outflow tract orientation: Detecting increased wall shear stress on the outer curve of proximal aortic aneurysms, JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY, Vol: 166, Pages: 11-+, ISSN: 0022-5223

Journal article

Salmasi MY, Alwis S, Cyclewala S, Jarral OA, Mohamed H, Mozalbat D, Nienaber CA, Athanasiou T, Morris-Rosendahl D, Members of the London Aortic Mechanobiology Working Groupet al., 2023, The genetic basis of thoracic aortic disease: The future of aneurysm classification?, Hellenic Journal of Cardiology, Vol: 69, Pages: 41-50, ISSN: 1109-9666

The expansion in the repertoire of genes linked to thoracic aortic aneurysms (TAA) has revolutionised our understanding of the disease process. The clinical benefits of such progress are numerous, particularly helping our understanding of non-syndromic hereditary causes of TAA (HTAAD) and further refinement in the subclassification of disease. Furthermore, the understanding of aortic biomechanics and mechanical homeostasis has been significantly informed by the discovery of deleterious mutations and their effect on aortic phenotype. The drawbacks in genetic testing in TAA lie with the inability to translate genotype to accurate prognostication in the risk of thoracic aortic dissection (TAD), which is a life-threatening condition. Under current guidelines, there are no metrics by which those at risk for dissection with normal aortic diameters may undergo preventive surgery. Future research lies with more advanced genetic diagnosis of HTAAD and investigation of the diverse pathways involved in its pathophysiology, which will i) serve to improve our understanding of the underlying mechanisms, ii) improve guidelines for treatment and iii) prevent complications for HTAAD and sporadic aortopathies.

Journal article

Salmasi MY, Morris-Rosendahl D, Jarral OA, Rosendahl U, Asimakopoulos G, Raja S, Aragon-Martin JA, Child A, Pepper J, Oo A, Athanasiou Tet al., 2022, Determining the genetic contribution in patients with non-syndromic ascending thoracic aortic aneurysms: Correlation with findings from computational pathology, INTERNATIONAL JOURNAL OF CARDIOLOGY, Vol: 366, Pages: 1-9, ISSN: 0167-5273

Journal article

Sasidharan S, Salmasi MY, Pirola S, Jarral OAet al., 2022, Relevance of machine learning to cardiovascular imaging, Research Anthology on Improving Medical Imaging Techniques for Analysis and Intervention, Pages: 589-605, ISBN: 9781668475447

Artificial intelligence (AI) broadly concerns analytical algorithms that iteratively learn from big datasets, allowing computers to find concealed insights. These encompass a range of operations comprising several terms, including machine learning(ML), cognitive learning, deep learning, and reinforcement learning-based methods that can be used to incorporate and comprehend complex biomedical and healthcare data in scenarios where traditional statistical approaches cannot be implemented. For cardiovascular imaging in particular, machine learning guarantees to be a transformative tool that can address many unmet needs for patient-specific management, accurate prediction of disease progression, and the tracking of identifiable biomarkers of disease processes. In this chapter, the authors discuss fundamentals of machine learning algorithms for image analysis in the cardiovascular system by evaluating the need for ML in this field and examining the potential obstacles and challenges of implementation in the context of three common imaging modalities used in cardiovascular medicine.

Book chapter

Zientara A, Hussein N, Bond C, Jacob KA, Naruka V, Doerr F, Nagele F, Polzl L, Eid M, Jarral O, Cerqueira R, Haunschild J, Sadaba JR, Gollmann-Tepekoylu Cet al., 2022, Basic principles of cardiothoracic surgery training: a position paper by the European Association for Cardiothoracic Surgery Residents Committee, INTERACTIVE CARDIOVASCULAR AND THORACIC SURGERY, Vol: 35, ISSN: 1569-9293

Journal article

Salmasi MYB, Morris-Rosendahl D, Jarral O, Rosendahl U, Asimakopoulos G, Aragon-Martin J, Child A, Pepper J, Oo A, Athanasiou Tet al., 2022, Determining the genetic contribution in patients with non-syndromic ascending thoracic aortic aneurysms: Correlation with findings from computational pathology, International Journal of Cardiology, ISSN: 0167-5273

Journal article

Trahanas JM, Jarral OA, Hughes GC, 2022, A dissection … of the Dacron?, JTCVS Tech, Vol: 13, Pages: 4-6

Journal article

Trahanas JM, Jarral OA, Long C, Hughes GCet al., 2022, Management of chronic type B aortic dissection, Vessel Plus, Vol: 6

The standard of care first-line therapy for uncomplicated acute type B aortic dissection is medical therapy. As a result, many of these dissections progress to become chronic type B aortic dissections (CTBAD). In the following manuscript, we will outline the natural history of these lesions and review what constitutes a CTBAD by anatomy and chronology. We will also describe the long-term medical management and surveillance of these lesions, what constitutes high-risk features, and when intervention should be considered. Endovascular, open and hybrid management strategies, potential complications, and subsequently required surveillance will also be discussed. With proper medical management, surveillance, and intervention, CTBAD can be managed effectively and downstream morbidity minimized.

Journal article

Tan MKH, Jarral OA, Salmasi Y, Sabetai M, Athanasiou Tet al., 2022, Thoracic Aortic Surgery, Patient Reported Outcomes and Quality of Life in Cardiovascular Interventions, Pages: 49-81, ISBN: 9783031098147

Operating on the thoracic aorta is a challenging task, with historically high morbidity and mortality. While outcomes are improving in recent times, there is increased focus on patient-reported outcome measures, principle of which is health-related quality of life (HRQoL), a development beyond isolated markers of operative morbidity or mortality. This concept is especially relevant to aortic surgery due to the number of asymptomatic patients which are operated on (for prognostic reasons) and rapidly developing endovascular techniques that require more holistic assessment. This book chapter aims to provide an overview on the current literature describing HRQoL in patients undergoing both open and endovascular interventions on the thoracic aorta. While certain aspects of the literature were lacking, for example the lack of baseline HRQoL measurements in the majority of studies, most studies confirm that HRQoL after major elective and emergency aortic surgery is acceptable and is comparable to age- and gender-matched populations. This chapter also provides strategies for improving HRQoL in aortic surgery, including the requirement for operating surgeons to carefully plan cerebral protection methods (to avoid post-operative neurological complications) and operative strategies to avoid reoperation or reintervention, as these are risk factors which are associated with deterioration of long-term HRQoL. Future research should include randomised studies with baseline and follow-up HRQoL measured at specific predefined timepoints, with potential for other innovative research areas including correlation of HRQoL with biomarkers or aortic biomechanics such as aortic stiffness or wall shear stress to characterise disease progression and prognosis.

Book chapter

Tan MKH, Jarral OA, 2022, Transcatheter Mitral Valve Procedures, Patient Reported Outcomes and Quality of Life in Cardiovascular Interventions, Pages: 155-170, ISBN: 9783031098147

Health-related quality of life (HRQoL) is increasingly used as an outcome measure in surgery. This concept is of particular importance to intervention on the mitral valve (MV), in view of guidelines recommending early intervention on patients even if they are asymptomatic. Transcatheter MV procedures are continuously evolving and requires robust assessment, of which HRQoL is an important parameter. This chapter reviews all available literature surrounding HRQoL outcomes in patients undergoing transcatheter MV interventions. While certain aspects of the literature were lacking, for example the lack of baseline HRQoL measurements in the majority of studies, most studies confirm that HRQoL benefits of transcatheter MV interventions is generally acceptable, with certain populations showing better HRQoL when compared to age- and gender-matched normal populations. This chapter also provides ideas for future research into HRQoL in transcatheter MV interventions, including establishing a common HRQoL instrument for disease-specific use, running randomised studies with baseline and follow-up HRQoL measured at specific predefined timepoints, and other innovative research areas including correlation of HRQoL with physical activity monitors, physiological biomarkers and radiological markers (e.g. leaflet stress from MRI and echocardiography) used as innovative markers of functional outcome.

Book chapter

Salmasi MYB, Pirola S, Sasidharan S, Fisichella S, Redaelli A, Jarral O, O'Regan D, Oo A, Moore Jr J, Xu XY, Athanasiou Tet al., 2021, High wall shear stress can predict wall degradation in ascending aorticaneurysms: an integrated biomechanics study, Frontiers in Bioengineering and Biotechnology, Vol: 9, Pages: 1-13, ISSN: 2296-4185

Background: Blood flow patterns can alter material properties of ascending thoracic aortic aneurysms (ATAA) via vascular wall remodeling. This study examines the relationship between wall shear stress (WSS) obtained from image-based computational modelling with tissue-derived mechanical and microstructural properties of the ATAA wall using segmental analysis.Methods: Ten patients undergoing surgery for ATAA were recruited. Exclusions: bicuspid aortopathy, connective tissue disease. All patients had pre-operative 4-dimensional flow magnetic resonance imaging (4D-MRI), allowing for patient-specific computational fluid dynamics (CFD) analysis and anatomically precise WSS mapping of ATAA regions (6–12 segments per patient). ATAA samples were obtained from surgery and subjected to region-specific tensile and peel testing (matched to WSS segments). Computational pathology was used to characterize elastin/collagen abundance and smooth muscle cell (SMC) count.Results: Elevated values of WSS were predictive of: reduced wall thickness [coef −0.0489, 95% CI (−0.0905, −0.00727), p = 0.022] and dissection energy function (longitudinal) [−15,0, 95% CI (−33.00, −2.98), p = 0.048]. High WSS values also predicted higher ultimate tensile strength [coef 0.136, 95% CI (0 0.001, 0.270), p = 0.048]. Additionally, elevated WSS also predicted a reduction in elastin levels [coef −0.276, 95% (CI −0.531, −0.020), p = 0.035] and lower SMC count ([oef −6.19, 95% CI (−11.41, −0.98), p = 0.021]. WSS was found to have no effect on collagen abundance or circumferential mechanical properties.Conclusions: Our study suggests an association between elevated WSS values and aortic wall degradation in ATAA disease. Further studies might help identify threshold values to predict acute aortic events.

Journal article

Sef D, Brown S, Jarral OA, Hussain A, Haslam E, Rajakaruna C, McAloon CJet al., 2021, Subtle aortic dissection in a patient with severe aortic regurgitation and undiagnosed bicuspid aortic valve: A case report with a literature review, JOURNAL OF CARDIAC SURGERY, Vol: 36, Pages: 3417-3420, ISSN: 0886-0440

Journal article

Salmasi MY, Jarral OA, Athanasiou T, 2021, What can we learn from outliers in cardiac surgery?, JOURNAL OF CARDIAC SURGERY, Vol: 36, Pages: 1832-1834, ISSN: 0886-0440

Journal article

Cerqueira RJ, Heuts S, Gollmann-Tepekoeylue C, Syrjaelae SO, Keijzers M, Zientara A, Jarral OA, Jacob KA, Haunschild J, Ariyaratnam P, Durko AP, Muller P, Myers PO, Sadaba JR, Lehtinen MLet al., 2021, Challenges and satisfaction in Cardiothoracic Surgery Residency Programmes: insights from a Europe-wide survey, INTERACTIVE CARDIOVASCULAR AND THORACIC SURGERY, Vol: 32, Pages: 167-173, ISSN: 1569-9293

Journal article

Olchanyi MD, Sadikov A, Frattolin J, Sasidharan S, Salmasi MY, Edgar LT, Jarral O, Athanasiou T, Moore JEet al., 2020, Validation of markerless strain-field optical tracking approach for soft tissue mechanical assessment., Journal of Biomechanics, Vol: 116, Pages: 1-11, ISSN: 0021-9290

Strain measurement during tissue deformation is crucial to elucidate relationships between mechanical loading and functional changes in biological tissues. When combined with specified loading conditions, assessment of strain fields can be used to craft models that accurately represent the mechanical behavior of soft tissue. Inhomogeneities in strain fields may be indicative of normal or pathological inhomogeneities in mechanical properties. In this study, we present the validation of a modified Demons registration algorithm for non-contact, marker-less strain measurement of tissue undergoing uniaxial loading. We validate the algorithm on a synthetic dataset composed of artificial deformation fields applied to a speckle image, as well as images of aortic sections of varying perceptual quality. Initial results indicate that Demons outperforms recent Optical Flow and Digital Image Correlation methods in terms of accuracy and robustness to low image quality, with similar runtimes. Demons achieves at least 8% lower maximal deviation from ground truth on 50% biaxial and shear strain applied to aortic images. To illustrate utility, we quantified strain fields of multiple human aortic specimens undergoing uniaxial tensile testing, noting the formation of strain concentrations in areas of rupture. The modified Demons algorithm captured a large range of strains (up to 50%) and provided spatially resolved strain fields that could be useful in the assessment of soft tissue pathologies.

Journal article

Salmasi M, Jarral OA, Pirola S, Sasidharan S, Pepper J, Oo A, Moore J, Xu XY, Athanasiou Tet al., 2020, In-vivo blood flow parameters can predict at-risk aortic aneurysms and dissection: a comprehensive biomechanics model, EUROPEAN HEART JOURNAL, Vol: 41, Pages: 2339-2339, ISSN: 0195-668X

Journal article

Sasidharan S, Salmasi MY, Pirola S, Jarral OAet al., 2020, Relevance of machine learning to cardiovascular imaging, Deep Learning Applications in Medical Imaging, Pages: 78-99, ISBN: 9781799850717

Artificial intelligence (AI) broadly concerns analytical algorithms that iteratively learn from big datasets, allowing computers to find concealed insights. These encompass a range of operations comprising several terms, including machine learning(ML), cognitive learning, deep learning, and reinforcement learning-based methods that can be used to incorporate and comprehend complex biomedical and healthcare data in scenarios where traditional statistical approaches cannot be implemented. For cardiovascular imaging in particular, machine learning guarantees to be a transformative tool that can address many unmet needs for patient-specific management, accurate prediction of disease progression, and the tracking of identifiable biomarkers of disease processes. In this chapter, the authors discuss fundamentals of machine learning algorithms for image analysis in the cardiovascular system by evaluating the need for ML in this field and examining the potential obstacles and challenges of implementation in the context of three common imaging modalities used in cardiovascular medicine.

Book chapter

Lucchese G, Jarral OA, Redwood S, Prendergast Bet al., 2020, Calcium Assessment, Correct Sizing, and Care With Balloons: Three Commandments to Prevent Annular Rupture Post-TAVR., JACC Case Rep, Vol: 2, Pages: 1859-1861

Journal article

Zargaran D, Ashraf M, Zargaran A, El-Hilly A, Jarral O, Baig K, Sabetai Met al., 2020, Restructuring and Optimising the Transfer of Aortic Dissections: A 48 Patient Analysis, International Surgical Conference of the Association-of-Surgeons-in-Training, Publisher: WILEY, Pages: 38-38, ISSN: 0007-1323

Conference paper

Salmasi MY, Al-Saadi N, Hartley P, Jarral OA, Raja S, Hussein M, Redhead J, Rosendahl U, Nienaber CA, Pepper JR, Oo AY, Athanasiou Tet al., 2020, The risk of misdiagnosis in acute thoracic aortic dissection: a review of current guidelines, HEART, Vol: 106, Pages: 885-891, ISSN: 1355-6037

Journal article

Jarral OA, Tan MKH, Salmasi MY, Pirola S, Pepper JR, O'Regan DP, Xu XY, Athanasiou Tet al., 2020, Phase-contrast magnetic resonance imaging and computational fluid dynamics assessment of thoracic aorta blood flow: a literature review, European Journal of Cardio-Thoracic Surgery, Vol: 57, Pages: 438-446, ISSN: 1010-7940

The death rate from thoracic aortic disease is on the rise and represents a growing global health concern as patients are often asymptomatic before acute events, which have devastating effects on health-related quality of life. Biomechanical factors have been found to play a major role in the development of both acquired and congenital aortic diseases. However, much is still unknown and translational benefits of this knowledge are yet to be seen. Phase-contrast cardiovascular magnetic resonance imaging of thoracic aortic blood flow has emerged as an exceptionally powerful non-invasive tool enabling visualization of complex flow patterns, and calculation of variables such as wall shear stress. This has led to multiple new findings in the areas of phenotype-dependent bicuspid valve flow patterns, thoracic aortic aneurysm formation and aortic prosthesis performance assessment. Phase-contrast cardiovascular magnetic resonance imaging has also been used in conjunction with computational fluid modelling techniques to produce even more sophisticated analyses, by allowing the calculation of haemodynamic variables with exceptional temporal and spatial resolution. Translationally, these technologies may potentially play a major role in the emergence of precision medicine and patient-specific treatments in patients with aortic disease. This clinically focused review will provide a systematic overview of key insights from published studies to date.

Journal article

Salmasi MY, Hartley P, Hussein M, Jarral O, Pepper J, Nienaber C, Athanasiou Tet al., 2020, Diagnosis and management of acute Type-A aortic dissection in emergency departments: Results of a UK national survey, INTERNATIONAL JOURNAL OF CARDIOLOGY, Vol: 300, Pages: 50-59, ISSN: 0167-5273

Journal article

Lucchese G, Jarral OA, 2019, Endoscopic vein harvest: benefits beyond (a) reasonable doubt?, JOURNAL OF THORACIC DISEASE, Vol: 11, Pages: S1342-S1345, ISSN: 2072-1439

Journal article

Berry A, Jarral O, Dawes T, Statton B, Quinlan M, Athanasiou T, O'Regan Det al., 2019, Aortic root surgery is associated with deterioration in left ventricular function and physical quality of life, SCMR 22nd Annual Scientific Sessions

Conference paper

Tan K, Wong J, Bakrania K, Abdullahi Y, Harling L, Casula RP, Rowlands AV, Athanasiou T, Jarral OAet al., 2018, Can activity monitors predict outcomes in patients with heart failure? A systematic review, European Heart Journal - Quality of Care and Clinical Outcomes, Vol: 5, Pages: 11-21, ISSN: 2058-5225

Actigraphy is increasingly incorporated into clinical practice to monitor intervention effectiveness and patient health in congestive heart failure (CHF). We explored the prognostic impact of actigraphy-quantified physical activity (AQPA) on CHF outcomes. PubMed and Medline databases were systematically searched for cross-sectional studies, cohort studies or randomised controlled trials from January 2007 to December 2017. We included studies that used validated actigraphs to predict outcomes in adult HF patients. Study selection and data extraction were performed by two independent reviewers. A total of 17 studies (15 cohort, 1 cross-sectional, 1 randomised controlled trial) were included, reporting on 2,759 CHF patients (22–89 years, 27.7% female). Overall, AQPA showed a strong inverse relationship with mortality and predictive utility when combined with established risk scores, and prognostic roles in morbidity, predicting cognitive function, New York Heart Association functional class and intercurrent events (e.g. hospitalisation), but weak relationships with health-related quality of life scores. Studies lacked consensus regarding device choice, time points and thresholds of PA measurement, which rendered quantitative comparisons between studies difficult. AQPA has a strong prognostic role in CHF. Multiple sampling time points would allow calculation of AQPA changes for incorporation into risk models. Consensus is needed regarding device choice and AQPA thresholds, while data management strategies are required to fully utilise generated data. Big data and machine learning strategies will potentially yield better predictive value of AQPA in CHF patients.

Journal article

Iqbal Y, Jarral OA, Tsipas P, Samiotis I, Kratimenos T, Kokotsakis J, Athanasiou Tet al., 2018, Single stage repair for aortic root aneurysm in a patient with coexisting coarctation incorporating the Cabrol technique: a case report, Journal of Cardiothoracic Surgery, Vol: 13, ISSN: 1749-8090

BackgroundA 44 year old man who presented with a history of chest pain and dyspnoea was found to have an aneurysm of the aortic root, aortic valve insufficiency, and coarctation of the aorta.Case presentationThe patient underwent a single stage procedure to treat the aortic root, valve and coarctation with a composite valved conduit and extra-anatomic bypass of the coarctation. The modified Cabrol technique was necessary to attach the coronary buttons due to grossly abnormal anatomy. The patient made a remarkable recovery and was discharged on the 8th post-operative day.ConclusionThis case report highlights the feasibility and efficacy of performing a single stage procedure on complex coarctation with associated cardiac defects. To the best of our knowledge, this is the first report of the modified Cabrol technique being used in this particular setting.

Journal article

Xu XY, Pirola S, Jarral O, O'Regan D, Asimakopoulos G, Anderson JR, Pepper J, Athanasiou Tet al., 2018, Computational study of aortic hemodynamics for patients with an abnormal aortic valve: the importance of secondary flow at the ascending aorta inlet, APL Bioengineering, Vol: 2, Pages: 026101-1-026101-14, ISSN: 2473-2877

Blood flow in the aorta is helical, but most computational studies ignore the presence of secondary flow components at the ascending aorta (AAo) inlet. The aim of this study is to ascertain the importance of inlet boundary conditions (BCs) in computational analysis of flow patterns in the thoracic aorta based on patient-specific images, with a particular focus on patients with an abnormal aortic valve. Two cases were studied: one presenting a severe aortic valve stenosis and the other with a mechanical valve. For both aorta models, three inlet BCs were compared; these included the flat profile and 1D through-plane velocity and 3D phase-contrast magnetic resonance imaging derived velocity profiles, with the latter being used for benchmarking. Our results showed that peak and mean velocities at the proximal end of the ascending aorta were underestimated by up to 41% when the secondary flow components were neglected. The results for helical flow descriptors highlighted the strong influence of secondary velocities on the helical flow structure in the AAo. Differences in all wall shear stress (WSS)-derived indices were much more pronounced in the AAo and aortic arch (AA) than in the descending aorta (DAo). Overall, this study demonstrates that using 3D velocity profiles as inlet BC is essential for patient-specific analysis of hemodynamics and WSS in the AAo and AA in the presence of an abnormal aortic valve. However, predicted flow in the DAo is less sensitive to the secondary velocities imposed at the inlet; hence, the 1D through-plane profile could be a sufficient inlet BC for studies focusing on distal regions of the thoracic aorta.

Journal article

Pirola S, Cheng Z, Jarral OA, O'Regan DP, Pepper JR, Athanasiou T, Xu XYet al., 2017, On the choice of outlet boundary conditions for patient-specific analysis of aortic flow using computational fluid dynamics, Journal of Biomechanics, Vol: 60, Pages: 15-21, ISSN: 1873-2380

Boundary conditions (BCs) are an essential part in computational fluid dynamics (CFD) simulations of blood flow in large arteries. Although several studies have investigated the influence of BCs on predicted flow patterns and hemodynamic wall parameters in various arterial models, there is a lack of comprehensive assessment of outlet BCs for patient-specific analysis of aortic flow. In this study, five different sets of outlet BCs were tested and compared using a subject-specific model of a normal aorta. Phase-contrast magnetic resonance imaging (PC-MRI) was performed on the same subject and velocity profiles extracted from the in vivo measurements were used as the inlet boundary condition. Computational results obtained with different outlet BCs were assessed in terms of their agreement with the PC-MRI velocity data and key hemodynamic parameters, such as pressure and flow waveforms and wall shear stress related indices. Our results showed that the best overall performance was achieved by using a well-tuned three-element Windkessel model at all model outlets, which not only gave a good agreement with in vivo flow data, but also produced physiological pressure waveforms and values. On the other hand, opening outlet BCs with zero pressure at multiple outlets failed to reproduce any physiologically relevant flow and pressure features.

Journal article

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