Publications by authors named "Frank J H Gijsen"

Endovascular thrombectomy (EVT) aims at restoring blood flow in case of acute ischemic stroke by removing the thrombus occluding a large cerebral artery. During the procedure with stent-retriever, the thrombus is captured within the device, which is then retrieved, subjecting the thrombus to several forces, potentially leading to its fragmentation. In silico studies, along with mechanical characterisation of thrombi, can enhance our understanding of the EVT, helping the development of new devices and interventional strategies.

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Article Synopsis
  • - The study investigates how red blood cell (RBC) and platelet content in blood clots affect CT imaging characteristics and mechanical properties, which could help predict the success of thrombectomy procedures.
  • - Researchers created blood clot analogues with varying RBC and platelet concentrations and used imaging techniques (NCCT and CECT) to assess clot densities and mechanical properties under stress.
  • - Findings suggest that while RBC content primarily determines non-contrast CT density, platelet content significantly impacts contrast-enhanced density and clot stiffness, indicating both components play unique roles in clot characteristics.
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Article Synopsis
  • - The study investigates the relationship between blood clot characteristics, such as composition and mechanical properties, and their visibility on CT imaging to improve endovascular thrombectomy outcomes.
  • - Five different red blood cell (RBC) volume suspensions created two distinct clot types: fibrin-rich (0% RBCs) and RBC-rich (>90% RBCs), revealing significant differences in density, stiffness, and contraction between them.
  • - Findings suggest that CT imaging can effectively indicate the RBC content of clots and may help predict their behavior, but further research is needed on clots with intermediate RBC and platelet levels.
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Endovascular thrombectomy procedures are significantly influenced by the mechanical response of thrombi to the multi-axial loading imposed during retrieval. Compression tests are commonly used to determine compressive ex vivo thrombus and clot analogue stiffness. However, there is a shortage of data in tension.

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Aims: Low wall shear stress (WSS) is acknowledged to play a role in plaque development through its influence on local endothelial function. Also, lipid-rich plaques (LRPs) are associated with endothelial dysfunction. However, little is known about the interplay between WSS and the presence of lipids with respect to plaque progression.

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The rupture of atherosclerotic plaques in coronary and carotid arteries is the primary cause of fatal cardiovascular events. However, the rupture mechanics of the heterogeneous, highly collagenous plaque tissue, and how this is related to the tissue's fibrous structure, are not known yet. Existing pipelines to study plaque mechanics are limited to obtaining only gross mechanical characteristics of the plaque tissue, based on the assumption of structural homogeneity of the tissue.

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Mechanical thrombectomy (MT) treatment of acute ischemic stroke (AIS) patients typically involves use of stent retrievers or aspiration catheters alone or in combination. For in silico trials of AIS patients, it is crucial to incorporate the possibility of thrombus fragmentation during the intervention. This study focuses on two aspects of the thrombectomy simulation: i) Thrombus fragmentation on the basis of a failure model calibrated with experimental tests on clot analogs; ii) the combined stent-retriever and aspiration catheter MT procedure is modeled by adding both the proximal balloon guide catheter and the distal access catheter.

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Shear stress (WSS) is involved in the pathophysiology of atherosclerotic disease and might affect plaque ulceration. In this case-control study, we compared carotid plaques that developed a ulcer during follow-up and plaques that remained silent for their exposure to time-dependent oscillatory shear stress parameters at baseline. Eighteen patients who underwent CTA and MRI of their carotid arteries at baseline and 2 years follow-up were included.

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Objective: Plaque rupture in atherosclerotic carotid arteries is a main cause of ischemic stroke and it is correlated with high plaque stresses. Hence, analyzing stress patterns is essential for plaque specific rupture risk assessment. However, the critical information of the multicomponent material properties of atherosclerotic carotid arteries is still lacking greatly.

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Wall shear stress (WSS), the frictional force of the blood on the vessel wall, plays a crucial role in atherosclerotic plaque development. Low WSS has been associated with plaque growth, however previous research used different approaches to define low WSS to investigate its effect on plaque progression. In this study, we used four methodologies to allocate low, mid and high WSS in one dataset of human coronary arteries and investigated the predictive power of low WSS for plaque progression.

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Acute ischemic stroke occurs when a thrombus obstructs a cerebral artery, leading to sub-optimal blood perfusion to brain tissue. A recently developed, preventive treatment is the endovascular stroke treatment (EVT), which is a minimally invasive procedure, involving the use of stent-retrievers and/or aspiration catheters. Despite its increasing use, many critical factors of EVT are not well understood.

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Treatment of acute ischemic stroke has been recently improved with the introduction of endovascular mechanical thrombectomy, a minimally invasive procedure able to remove a clot using aspiration devices and/or stent-retrievers. Despite the promising and encouraging results, improvements to the procedure and to the stent design are the focus of the recent efforts. Computational studies can pave the road to these improvements, providing their ability to describe and accurately reproduce a real procedure.

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Background And Purpose: Mechanical properties of thromboemboli play an important role in the efficacy of endovascular thrombectomy (EVT) for acute ischemic stroke. However, very limited data on mechanical properties of human stroke thrombi are available. We aimed to mechanically characterize thrombi retrieved with EVT, and to assess the relationship between thrombus composition and thrombus stiffness.

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Carotid atherosclerosis is a risk factor for ischemic stroke, one of the main causes of mortality and disability worldwide. The disease is characterized by plaques, heterogeneous deposits of lipids, and necrotic debris in the vascular wall, which grow gradually and may remain asymptomatic for decades. However, at some point a plaque can evolve to a high-risk plaque phenotype, which may trigger a cerebrovascular event.

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Objective: Atherosclerotic plaque rupture in carotid arteries is a major source of cerebrovascular events. Calcifications are highly prevalent in carotid plaques, but their role in plaque rupture remains poorly understood. This work studied the morphometric features of calcifications in carotid plaques and their effect on the stress distribution in the fibrous plaque tissue at the calcification interface, as a potential source of plaque rupture and clinical events.

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High wall shear stress (WSS) and near-infrared spectroscopy (NIRS) detected lipid-rich plaque (LRP) are both known to be associated with plaque destabilization and future adverse cardiovascular events. However, knowledge of spatial co-localization of LRP and high WSS is lacking. This study investigated the co-localization of LRP based on NIRS and high WSS.

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Atherosclerotic plaques prone to rupture may cause acute myocardial infarction (MI) but can also heal without causing an event. Certain common histopathological features, including inflammation, a thin fibrous cap, positive remodelling, a large necrotic core, microcalcification, and plaque haemorrhage are commonly found in plaques causing an acute event. Recent advances in imaging techniques have made it possible to detect not only luminal stenosis and overall coronary atherosclerosis burden but also to identify such adverse plaque characteristics.

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Despite advanced understanding of the biology of atherosclerosis, coronary heart disease remains the leading cause of death worldwide. Progress has been challenging as half of the individuals who suffer sudden cardiac death do not experience premonitory symptoms. Furthermore, it is well-recognized that also a plaque that does not cause a haemodynamically significant stenosis can trigger a sudden cardiac event, yet the majority of ruptured or eroded plaques remain clinically silent.

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Article Synopsis
  • The study tested a new dual-isotope imaging technique using SPECT/CT to assess inflammation in atherosclerotic plaques by focusing on specific leukocyte markers.
  • Human carotid plaque samples were stained and scanned, identifying areas of inflammation through the uptake of two radiotracers, which corresponded to specific inflammatory cell types.
  • Results showed that certain plaque types, especially fibrous cap atheromas, had higher tracer uptake, indicating a connection between imaging results and the presence of proinflammatory leukocytes.
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Aims: Bioresorbable scaffold (BRS) regions exposed to flow recirculation, low time-averaged wall shear stress (TAWSS) and high oscillatory shear index (OSI) develop increased neointima tissue. We investigated haemodynamic features in four different BRSs.

Methods And Results: Fantom (strut height [SH] = 125 µm), Fantom Encore (SH = 98 µm), Absorb (SH = 157 µm) and Magmaris (SH = 150 µm) BRSs were deployed in phantom tubes and imaged with microCT.

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Left ventricular (LV) blood flow is an inherently complex time-varying 3-D phenomenon, where 2-D quantification often ignores the effect of out-of-plane motion. In this study, we describe high frame rate 4-D echocardiographic particle image velocimetry (echo-PIV) using a prototype matrix transesophageal transducer and a dynamic LV phantom for testing the accuracy of echo-PIV in the presence of complex flow patterns. Optical time-resolved tomographic PIV (tomo-PIV) was used as a reference standard for comparison.

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Aims: Atherosclerotic plaque development has been associated with wall shear stress (WSS). However, the multidirectionality of blood flow, and thus of WSS, is rarely taken into account. The purpose of this study was to comprehensively compare five metrics that describe (multidirectional) WSS behaviour and assess how WSS multidirectionality affects coronary plaque initiation and progression.

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Aims: The aim of this study was to assess the acute performance of the 95 µm ArterioSorb oriented poly L-lactic acid (PLLA) scaffold in comparison with the XIENCE metallic drug-eluting stent (DES) in porcine coronary arteries.

Methods And Results: In 15 non-atherosclerotic Yucatan mini pigs, the ArterioSorb (3.0/14 mm) and XIENCE (3.

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Aims: The aim of this study was to validate novel software to calculate vessel fractional flow reserve (vFFR) based on 3D-QCA and to assess inter-observer variability in patients who underwent routine preprocedural FFR assessment for intermediate coronary artery stenosis.

Methods And Results: In vitro validation was performed in an experimental model. Clinical validation was performed in an observational, retrospective, single-centre cohort study.

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