Effect of Pulsatility on the Transport of Thrombin in an Idealized Cerebral Aneurysm Geometry

Computational models of cerebral aneurysm thrombosis are designed for use in research and clinical applications. A steady flow assumption is applied in many of these models. To explore the accuracy of this assumption a pulsatile-flow thrombin-transport computational fluid dynamics (CFD) model, which uses a symmetrical idealized aneurysm geometry, was developed. First, a steady-flow computational model was developed and validated using data from an in vitro experiment, based on particle image velocimetry (PIV). The experimental data revealed an asymmetric flow pattern in the aneurysm. The validated computational model was subsequently altered to incorporate pulsatility, by applying a data-derived flow function at the inlet boundary. For both the steady and pulsatile computational models, a scalar function simulating thrombin generation was applied at the aneurysm wall. To determine the influence of pulsatility on thrombin transport, the outputs of the steady model were compared to the outputs of the pulsatile model. The comparison revealed that in the pulsatile case, an average of 10.2% less thrombin accumulates within the aneurysm than the steady case for any given time, due to periodic losses of a significant amount of thrombin-concentrated blood from the aneurysm into the parent vessel’s bloodstream. These findings demonstrate that pulsatility may change clotting outcomes in cerebral aneurysms.

Stereotactic direct-coiling of aneurysms—a feasibility study

Aim of the study Endovascular coiling has gained worldwide acceptance in the management of intracranial aneurysms. However, not all aneurysms can be coiled. Direct aneurysm puncture with aneurysm thrombosis has been performed, using coils for extracranial aneurysms and iron filings for intracranial aneurysms. Therefore, the feasibility of stereotactic aneurysm coiling with direct aneurysm puncture using Nester-coils was studied in an in vitro model. Methods and findings Twenty-eight aneurysms measuring 9–21 mm in diameters (median 14 mm) were made using 0.1 mm vinyl film that was connected to a monometer with 73 cm of water column. Twenty-three aneurysms were coiled through direct puncture of the aneurysms using a stereotactic frame. Five were coiled using a hand-held probe carrier. Statistical analysis of the data was conducted by data analysis feature of Microsoft Excel. Findings The study showed that needle puncture of the aneurysm and coiling of the aneurysm through the needle can be done with ease and without any significant fluid leak from the puncture site. It also shows that the coil will stay within the aneurysm without entering the neck. The study also shows that this method can be done using free-hand technique. Furthermore, it shows that the probe holder for the needle can also be used as an aneurysm stabilizer and as a tamponade.

Congenital coronary artery-to-pulmonary fistula with giant aneurysmal dilatation and thrombus formation: a case report and review of literature

Background Coronary artery-to-pulmonary artery fistula is a rare disorder characterized by abnormal vascular communication between the coronary artery and pulmonary artery. While most patients remain asymptomatic, some might exhibit symptoms of myocardial ischemia, congestive heart failure, or even sudden cardiac death if coronary aneurysm, thrombosis, infective carditis, or other congenital cardiac defects coexist. Case presentation We present a 66-year-old male complaining of angina pectoris with a history of hypertension and active smoking. He was diagnosed with a coronary aneurysm based on coronary computed tomography angiography. We subsequently identified a coronary artery-to-pulmonary artery fistula with giant aneurysmal dilation on coronary angiography. Ultimately we conducted surgery ligation and aneurysmorrhaphy. During surgery, we discovered newly formed thrombus within the aneurysmal cavity. Histological analysis of the aneurysmal wall supported the diagnosis of the congenital disorder. Our patient was successfully discharged and remained asymptomatic at two months of follow-up. Conclusion We presented a rare and complex combination of congenital coronary artery-to pulmonary artery fistula, giant coronary aneurysmal dilatation, and thrombosis through multi-modality evaluations.

Thrombin–Fibrinogen In Vitro Flow Model of Thrombus Growth in Cerebral Aneurysms

Cerebral aneurysms are balloon-like structures that develop on weakened areas of cerebral artery walls, with a significant risk of rupture. Thrombi formation is closely associated with cerebral aneurysms and has been observed both before and after intervention, leading to a wide variability of outcomes in patients with the condition. The attempt to manage the outcomes has led to the development of various computational models of cerebral aneurysm thrombosis. In the current study, we developed a simplified thrombin–fibrinogen flow system, based on commercially available purified human-derived plasma proteins, which enables thrombus growth and tracking in an idealized cerebral aneurysm geometry. A three-dimensional printed geometry of an idealized cerebral aneurysm and parent vessel configuration was developed. An unexpected outcome was that this phantom-based flow model allowed us to track clot growth over a period of time, by using optical imaging to record the progression of the growing clot into the flow field. Image processing techniques were subsequently used to extract important quantitative metrics from the imaging dataset, such as end point intracranial thrombus volume. The model clearly demonstrates that clot formation, in cerebral aneurysms, is a complex interplay between mechanics and biochemistry. This system is beneficial for verifying computational models of cerebral aneurysm thrombosis, particularly those focusing on initial angiographic occlusion outcomes, and will also assist manufacturers in optimizing interventional device designs.

Aspirin treatment prevents inflammation in experimental bifurcation aneurysms in New Zealand White rabbits

BackgroundAneurysm wall degeneration is linked to growth and rupture. To address the effect of aspirin (ASA) on aneurysm formation under various wall conditions, this issue was analyzed in a novel rabbit bifurcation model.MethodsBifurcation aneurysms created in 45 New Zealand White rabbits were randomized to vital (n=15), decellularized (n=13), or elastase-degraded (n=17) wall groups; each group was assigned to a study arm with or without ASA. At follow-up 28 days later, aneurysms were evaluated for patency, growth, and wall inflammation at macroscopic and histological levels.Results36 rabbits survived to follow-up at the end of the trial. None of the aneurysms had ruptured. Patency was visualized in all aneurysms by intraoperative fluorescence angiography and confirmed in 33 (92%) of 36 aneurysms by MRI/MRA. Aneurysm size was significantly increased in the vital (without ASA) and elastase-degraded (with and without ASA) groups. Aneurysm thrombosis was considered complete in three (50%) of six decellularized aneurysms without ASA by MRI/MRA. Locoregional inflammation of the aneurysm complex was significantly reduced in histological analysis among all groups treated with ASA.ConclusionASA intake prevented inflammation of both the periadventitial tissue and aneurysm wall, irrespective of initial wall condition. Although ASA prevented significant growth in aneurysms with vital walls, this preventive effect did not have an important role in elastase-degraded pouches. In possible translation to the clinical situation, ASA might exert a potential preventive effect during early phases of aneurysm formation in patients with healthy vessels but not in those with highly degenerative aneurysm walls.

Multilayer bare stent technique in treating intact mycotic suprarenal aortic aneurysm: a case report

Background Invasive aspergillosis (IA) related mycotic aortic aneurysm is rare in immunocompetent patient. The endovascular therapy remains controversial due to potential risk of graft infection, while the suprarenal cases might face catastrophic complications during open surgery. Case summary We presented an IA case with suprarenal abdominal aortic aneurysm confirmed by joint effusion. Multilayer bare stent technique was performed to preserve visceral blood flow and promote aneurysmal thrombus formation, along with antifungal treatment. Two years of follow-up revealed complete aneurysm thrombosis without evidence of infection. Discussion Fungal infection that affects the aorta is difficult to recognize due to often negative blood cultures. Close observation is recommended in case of suspicion of mycotic aneurysms. Multilayer bare stent technique can restore luminal laminar blood flow and reduce the risk of infection in intact mycotic suprarenal aortic aneurysm.