Citations

Flow diversion treatment of cerebral aneurysms has increasingly been considered, especially for large complex aneurysms with wide necks that are difficult to treat with coils of by clipping. However, the relationship between the hemodynamic environment created immediately after implantation of flow diverters (FD) and the subsequent aneurysm occlusion is poorly understood [1].

Since treatment of cerebral aneurysms with flow diverters (FD) has gained much attention in recent years, it is important to understand what is the effect of these devices on the flow through arteries jailed or crossed by these devices [1].

We present a quantified description of the fluid flow and a novel flowline-based meshing technique to create adaptive grids for Computational Fluid Dynamics (CFD) simulations in patient-specific intracranial aneurysms. The adaptive grid density is obtained such that it captures the fine geometrical details of the flow with high grid density, while smoother flow characteristics are calculated with a coarser grid density. The correlation between the topological characteristics of the flow and the element size of the adaptive grid results in a practical mathematical formula for calculating the element size using only one uniform base mesh and a user defined implementation in CFD post processors.

Background and Purpose— Angiographic revascularization grading after intra-arterial stroke therapy is limited by poor standardization, making it unclear which scale is optimal for predicting outcome. Using recently standardized criteria, we sought to compare the prognostic performance of 2 commonly used reperfusion scales. Methods— Inclusion criteria for this multicenter retrospective study were acute ischemic stroke attributable to middle cerebral artery M1 occlusion, intra-arterial therapy, and 90-day modified Rankin scale score. Post–intra-arterial therapy reperfusion was graded using the Thrombolysis in Myocardial Infarction (TIMI) and Modified Thrombolysis in Cerebral Infarction (mTICI) scales. The scales were compared for prediction of clinical outcome using receiver-operating characteristic analysis. Results— Of 308 patients, mean age was 65 years, and median National Institutes of Health Stroke Scale score was 17. The mean time from stroke onset to groin puncture was 305 minutes. There was no difference in the time to treatment between patients grouped by final TIMI (ie, 0 versus 1 versus 2 versus 3) or mTICI grades (ie, 0 versus 1 versus 2a versus 2b versus 3). Good outcome (modified Rankin scale, 0–2) was achieved in 32.5% of patients, and mortality rate was 25.3% at 90 days. There was a 6.3% rate of parenchymal hematoma type 2. In receiver-operating characteristic analysis, mTICI was superior to TIMI for predicting 90-day modified Rankin scale 0 to 2 (c-statistic: 0.74 versus 0.68; P <0.0001). The optimal threshold for identifying a good outcome was mTICI 2b to 3 (sensitivity 78.0%; specificity 66.1%). Conclusions— mTICI is superior to TIMI for predicting clinical outcome after intra-arterial therapy. mTICI 2b to 3 is the optimal biomarker for procedural success.

The Modeling and Analysis group in the Division of Engineering at Mayo Clinic, Rochester works in the area of numerical modeling and experimental validation of cerebral aneurysms. In our modeling we use patient-specific geometries from imaging studies provided by Dr. Kallmes. The CFD analysis is performed with commercial packages Mimics (Materialise, Leuven, Belgium), for segmentation and ANSYS (ANSYS Inc. Canonsburg, PA) for meshing, simulation and post-processing. The experiments are conducted using a tomographic Particle Image Velocimetry system from LaVision Inc. The group is led by Dan Dragomir-Daescu, PhD and David F. Kallmes, MD and consists of two postdoctoral fellows and three engineers. For this project, CFD simulations were performed by postdoctoral fellow Simona Hodis, using the finite volume based solver Fluent.

An intracranial aneurysm (IA) is a pathological condition of cerebral arteries characterized by local enlargements of the arterial wall, typically into a saccular shape. Rupture of the aneurysm sac can result in devastating cerebral hemorrhage. Hemodynamic factors are believed to play an important role in initiation, development and rupture of IAs [1–3]. However, the coupling between hemodynamics and aneurysm pathophysiology is complex and remains poorly understood. Patient specific diagnostics regarding risk of rupture can be substantially advanced by improving our understanding of the in-vivo response of the aneurysm wall to intra-saccular hemodynamic stresses. A mechanism for fundamental studies of the impact of chronically altered WSS on the intact vascular wall is provided by animal models. However, cerebral aneurysms have not been shown to occur naturally in animals. Thus, a number of animal models have been created for studying aneurysm pathogenesis including those in mice, rats, rabbits, canines, swine and primates. To make meaningful use of these models, it is important to evaluate their relevance to human biomechanics and pathophysiology.

Background and Purpose— Reversal of anticoagulation with protamine might predispose to a higher risk of stroke in patients with carotid stenting. We evaluated a national, multihospital patient database to examine the risk of stroke in patients with carotid stenting receiving protamine compared with those who did not. Methods— The Premier Perspective database was used to identify patients who were electively hospitalized for carotid stenting from 2006 through 2011. The incidence of in-hospital mortality and morbidity was compared between patients who did and did not receive protamine after propensity score adjustment via 1:1 matching to reduce selection bias. Results— Of 6664 patients with carotid stenting treated at 193 hospitals, 556 (8%) received protamine on the day of the procedure. After matching by propensity score, patients who received protamine had a similar likelihood of stroke or transient ischemic attack ( P =0.77), in-hospital mortality ( P =0.12), discharge to long-term care ( P =0.15), and access site complications ( P =0.90) as compared with patients who did not receive protamine. Conclusions— Protamine administration is not associated with additional risk of adverse events after carotid stenting.

Background and purpose A recent expansion of the neurointerventional workforce in the USA could lead to a trend toward cerebral aneurysms being increasingly treated at low volume centers. Such a trend could have a negative impact on patient care as higher volume centers are known to have better outcomes. Methods Using the Nationwide Inpatient Sample, we evaluated trends in aneurysm treatment in the USA from 2001 to 2010. Annual volumes of both ruptured and unruptured aneurysms were counted, as well as annual percentages of cases treated at high volume centers (≥50 aneurysms/year clipped or coiled). Results The number of ruptured aneurysms treated per year has fluctuated between 9000 and 12 000 from 2003 to 2010. In 2001–2002, 27.4% of intracranial aneurysm patients were treated with clipping or coiling at high volume centers, with a peak of 70.1% in 2007–2008. This proportion dropped to 61.8% in 2009–2010. The proportion of patients clipped at high volume centers was 23.3% in 2001–2002 and peaked at 65.0% in 2007–2008. In 2009–2010, the proportion dropped to 58.6%. For coiling patients, 46.4% were treated at high volume centers in 2001–2002, with a peak of 70.1% in 2007–2008, and a drop to 61.8% in 2009–2010. Conclusion A trend toward less cerebral aneurysms being treated in high volume centers in 2009 and 2010 is worrisome because high volume centers are known to tend to have better outcomes. This trend is likely due to recent expansion of the neurointerventional workforce.

Background and Purpose— Acute intraprocedural thrombus formation complicating endovascular cerebral aneurysm treatment is often treated with intra-arterial or intravenous administration of thrombolytic agents or glycoprotein IIb/IIIa (GpIIb/IIIa) inhibitors. We sought to evaluate the morbidity and mortality associated with such treatments using a large multihospital database. Methods— Using the Premier Perspective Database, we examined outcomes for patients receiving endovascular coiling for ruptured and unruptured aneurysms requiring rescue therapy, defined as treatment with GpIIb/IIIa inhibitors and fibrinolytic therapy. We compared discharge status, length of stay, and complication rates across 3 groups: (1) patients receiving GpIIb/IIIa inhibitors only, (2) patients receiving fibrinolytic therapy only, and (3) patients receiving both GpIIb/IIIa inhibitors and fibrinolytics. Student t test was used to compare continuous variables, and Fisher exact test was used to compare categorical variables. Results— Seven-percent (254/3627) of patients treated for unruptured aneurysms received rescue therapy. When compared with patients receiving GpIIb/IIIa inhibitors alone, patients receiving only fibrinolytics had significantly higher rates of discharge to institutions other than home (37.5% [9/24] versus 7.4% [15/201]; P <0.0001). Eight-percent of patients (338/4204) treated for ruptured aneurysms received rescue therapy. When compared with patients receiving GpIIb/IIIa inhibitors alone, patients receiving only fibrinolytics had significantly higher rates of mortality (26.0% [18/69] versus 14.5% [35/241]; P =0.02) and discharge to institutions other than home (59.4% [41/69] versus 36.5% [88/241]; P <0.0001). Conclusions— Pharmacological rescue therapy occurred in 7% to 8% of endovascular coiling patients with unruptured and ruptured intracranial aneurysms. Rescue therapy with thrombolytic agents resulted in significantly more morbidity and mortality than rescue therapy with GpIIb/IIIa inhibitors.