Pulsatile hemodynamics in patient-specific thoracic aortic dissection models constructed from computed tomography angiography

Computational fluid dynamics modelling of hemodynamics in aortic aneurysm and dissection: a review

Hemodynamic analysis based on computational fluid dynamics (CFD) modelling is expected to improve risk stratification for patients with aortic aneurysms and dissections. However, the parameter settings in CFD simulations involve considerable variability and uncertainty. Additionally, the exact relationship between hemodynamic features and disease progression remains unclear. These challenges limit the clinical application of aortic hemodynamic models. This review presents a detailed overview of the workflow for CFD-based aortic hemodynamic analysis, with a focus on recent advancements in the field. We also conducted a systematic review of 27 studies with large sample sizes (n > 5) that examine the hemodynamic characteristics of aortic aneurysms and dissections. Some studies identified consistent relationships between hemodynamic features and disease progression, reinforcing the potential for clinical application of aortic hemodynamic models. However, limitations such as small sample sizes and oversimplified patient-specific models remain. These findings emphasize the need for larger, more detailed studies to refine CFD modelling strategies, strengthen the connection between hemodynamics and diseases, and ultimately facilitate the clinical use of aortic hemodynamic models in disease management.

Comparison of thrombosis risk in an abdominal aortic dissection aneurysm with a double false lumen using computational fluid dynamic simulation method

BACKGROUND: Aneurysms are associated with a mortality rate of 81% or more in cases of rupture. OBJECTIVE: To analyse the haemodynamic indices and compare the thrombosis risk in a double false lumen abdominal aortic dissection aneurysm using computational fluid dynamics (CFD). METHODS: Computer tomography angiography (CTA) imaging data were collected from a patient with a double false lumen abdominal aortic dissection aneurysm, and three different lesion morphology aneurysm models were established, double false lumen abdominal aortic dissection aneurysm, single false lumen abdominal aortic dissection aneurysm and saccular abdominal aortic aneurysm, in order to analyse the flow velocity, time-averaged shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT) of blood flow, and endothelial cell activation potential (ECAP). RESULTS: All three aneurysms were in a low-flow state within the body, and the low-flow velocity flow in the proximal vessel wall extended to the right common iliac artery; the vortex intensity was more intense in the abdominal aortic dissection aneurysm than in the saccular abdominal aortic aneurysm. The risk area for thrombosis was concentrated in the expansion part of the aneurysm and the false lumen. The RRT and ECAP maxima of the double false lumen abdominal aortic dissection aneurysm were much greater than those of the single false lumen dissection aneurysm and saccular aortic aneurysm. CONCLUSION: Low-velocity blood flow, high OSI, low TAWSS, high RRT, and high ECAP regions correlate with the risk of thrombosis. The double false lumen type of abdominal aortic dissection aneurysm had some specificity in this case. The risk of thrombosis in the patient was extremely high, and the largest risk zone was within the smaller false lumen, which could be because the smaller false lumen was connected to the true lumen by only one breach. The results of the study provide some guidance in the early screening and development of treatment plans.

MRI in CFD for chronic type B aortic dissection: Ready for prime time?

OBJECTIVES

Better tools are needed for risk assessment of Type B aortic dissection (TBAD) to determine optimal treatment for patients with uncomplicated disease. Magnetic resonance imaging (MRI) has the potential to inform computational fluid dynamics (CFD) simulations for TBAD by providing individualised quantification of haemodynamic parameters, for assessment of complication risks. This systematic review aims to present an overview of MRI applications for CFD studies of TBAD.

METHODS

Following PRISMA guidelines, a search in Medline, Embase, and the Scopus Library identified 136 potentially relevant articles. Studies were included if they used MRI to inform CFD simulation in TBAD.

RESULTS

There were 20 articles meeting the inclusion criteria. 19 studies used phase contrast MRI (PC-MRI) to provide data for CFD flow boundary conditions. In 12 studies, CFD haemodynamic parameter results were validated against PC-MRI. In eight studies, geometric models were developed from MR angiography. In three studies, aortic wall or intimal flap motion data were derived from PC/cine MRI.

CONCLUSIONS

MRI provides complementary patient-specific information in CFD haemodynamic studies for TBAD that can be used for personalised care. MRI provides structural, dynamic and flow data to inform CFD for pre-treatment planning, potentially advancing its integration into clinical decision-making. The use of MRI to inform CFD in TBAD surgical planning is promising, however further validation and larger cohort studies are required.

Computational numerical analysis of different cannulation methods during cardiopulmonary bypass of type A aortic dissection model based on computational fluid dynamics

Background

The aim of the present study was to use a numerical simulation based on computational fluid dynamics (CFD) to analyze the difference of different cannulation methods on hemodynamics characteristic in a type A aortic dissection (TAAD) model.

Methods

A finite-element analysis based on the CFD model of a TAAD patient was used, and axillary artery cannulation (AAC), innominate artery cannulation (IAC), and femoral artery cannulation (FAC) were analyzed under different situations, including a cardiac output (CO) of 2.5 L/min and cardiopulmonary bypass (CPB) of 2.5 L/min (partial CPB before cross-clamping aorta, defined as condition A), and a CO of 0 L/min and CPB of 5 L/min (aortic cross-clamping phase, defined as condition B). The insertion of an 8-mm cannula into the different models was simulated. Hemodynamic characteristics, including wall shear stress, wall stress, blood flow, and velocity were analyzed.

Results

In condition A, the total flow of branches of the aortic arch was 2,009.5 mL/min (AAC), 1,855.47 mL/min (IAC), and 1,648.03 mL/min (FAC). All cannulation methods improved left renal blood perfusion. However, in relation to blood flow in the right renal artery, FAC showed the highest blood flow (105 mL/min). The results in condition B were similar to those of condition A. The velocity, shear stress, and stress of entry tear via AAC and IAC decreased in condition B compared with condition A. The velocity, shear stress, stress of tear via AAC was lower than that of IAC.

Conclusions

Different cannulation modes have an effect on the hemodynamic characteristic of the tear, but this effect is related to different states of CPB. AAC was found to superior to IAC, especially in reducing velocity, stress, and shear stress of site of tear. However, IAC and AAC are more conductive to blood supply than FAC in branch vessels of the aortic arch without being affected by the CPB state.

Multilayer flow modulator enhances vital organ perfusion in patients with type B aortic dissection

Management of aortic dissections (AD) is still challenging, with no universally approved guideline among possible surgical, endovascular, or medical therapies. Approximately 25% of patients with AD suffer postintervention malperfusion syndrome or hemodynamic instability, with the risk of sudden death if left untreated. Part of the issue is that vascular implants may themselves induce flow disturbances that critically impact vital organs. A multilayer mesh construct might obviate the induced flow disturbances, and it is this concept we investigated. We used preintervention and post-multilayer flow modulator implantation (PM) geometries from clinical cases of type B AD. In-house semiautomatic segmentation routines were applied to computed tomography images to reconstruct the lumen. The device was numerically reconstructed and adapted to the PM geometry concentrically fit to the true lumen centerline. We also numerically designed a pseudohealthy case, where the geometry of the aorta was extracted interpolating geometric features of preintervention, postimplantation, and published representative healthy volunteers. Computational fluid dynamics methods were used to study the time-dependent flow patterns, shear stress metrics, and perfusion to vital organs. A three-element Windkessel lumped parameter module was coupled to a finite-volume solver to assign dynamic outlet boundary conditions. Multilayer flow modulator not only significantly reduced false lumen blood flow, eliminated local flow disturbances, and globally regulated wall shear stress distribution but also maintained physiological perfusion to peripheral vital organs. We propose further investigation to focus the management of AD on both modulation of blood flow and restoration of physiologic end-organ perfusion rather than mere restoration of vascular lamina morphology. NEW & NOTEWORTHY The majority of aortic dissection modeling efforts have focused on the maintenance of physiological flow using minimally invasive placed grafts. The multilayer flow modulator is a complex mesh construct of wires, designed to eliminate flow disruptions in the lumen, regulate the physiological wall stresses, and enhance endothelial function and offering the promise of improved perfusion of vital organs. This has never been fully proved or modeled, and these issues we confirmed using a dynamic framework of time-varying arterial waveforms.