Risk Factors for Ischemic Complications following Pipeline Embolization Device Treatment of Intracranial Aneurysms: Results from the IntrePED Study

BACKGROUND AND PURPOSE

Risk factors for acute ischemic stroke following flow-diverter treatment of intracranial aneurysms are poorly understood. Using the International Retrospective Study of Pipeline Embolization Device (IntrePED) registry, we studied demographic, aneurysm, and procedural characteristics associated with postoperative acute ischemic stroke following Pipeline Embolization Device (PED) treatment.

MATERIALS AND METHODS

We identified patients in the IntrePED registry with post-PED-treatment acute ischemic stroke. The rate of postoperative acute ischemic stroke was determined by demographics, comorbidities, aneurysm characteristics, and procedure characteristics (including anticoagulation use, platelet testing, number of devices used, sheaths, and so forth). Categoric variables were compared with χ(2) testing, and continuous variables were compared with the Student t test. Odds ratios and 95% confidence intervals were obtained by using univariate logistic regression. Multivariate logistic regression analysis was used to determine which factors were independently associated with postoperative stroke.

RESULTS

Of 793 patients with 906 aneurysms, 36 (4.5%) patients had acute ischemic stroke. Twenty-six (72.2%) strokes occurred within 30 days of treatment (median, 3.5 days; range, 0-397 days). Ten patients died, and the remaining 26 had major neurologic morbidity. Variables associated with higher odds of acute ischemic stroke on univariate analysis included male sex, hypertension, treatment of MCA aneurysms, treatment of fusiform aneurysms, treatment of giant aneurysms, and use of multiple PEDs. However, on multivariate analysis, the only one of these variables independently associated with stroke was treatment of fusiform aneurysms (OR, 2.74; 95% CI, 1.11-6.75; P = .03). Fusiform aneurysms that were associated with stroke were significantly larger than those not associated with stroke (mean, 24.5 ± 12.5 mm versus 13.6 ± 6.8 mm; P < .001).

CONCLUSIONS

Ischemic stroke following PED treatment is an uncommon-but-devastating complication. Fusiform aneurysms were the only variable independently associated with postoperative stroke.

Prevalence of Intracranial Aneurysms in Patients with Aortic Aneurysms

BACKGROUND AND PURPOSE

Previous studies have suggested an association between aortic aneurysms and intracranial aneurysms with a higher prevalence of intracranial aneurysms in patients with aortic aneurysms. The aims of the present study were to evaluate the incidence of intracranial aneurysms in a large cohort of patients with aortic aneurysms and to identify potential risk factors for intracranial aneurysms in this population.

MATERIALS AND METHODS

We included all patients with aortic aneurysms (either abdominal and/or thoracic) who had available cerebral arterial imaging and were seen at our institution during a 15-year period. We identified patients with intracranial aneurysms. Patient demographics, comorbidities, and aortic aneurysm and intracranial aneurysm sizes and locations were analyzed. Univariate analysis was performed with a χ(2) test for categoric variables and a Student t test or ANOVA for continuous variables.

RESULTS

A total of 1081 patients with aortic aneurysms were included. Of them, 440 (40.7%) had abdominal aortic aneurysms, 446 (41.3%) had thoracic aortic aneurysms, and 195 (18.0%) had both abdominal aortic and thoracic aortic aneurysms. The overall prevalence of associated intracranial aneurysms in patients with aortic aneurysms was 11.8% (128/1081), with 12.7% (56/440), 10.8% (48/446), and 12.3% (24/195), respectively, in patients with abdominal aortic aneurysms, thoracic aortic aneurysms, and both thoracic aortic aneurysms and abdominal aortic aneurysms. Female patients had a higher risk of associated intracranial aneurysms (OR = 2.08; 95% CI, 1.49-3.03; P = .0002). There was a slight association between abdominal aortic aneurysm size and the prevalence of intracranial aneurysms (OR = 1.02; 95% CI, 1.01-1.03; P = .045). There was no significant association between the locations of the aortic and intracranial aneurysms (P = .93).

CONCLUSIONS

The prevalence of intracranial aneurysms is high in patients with aortic aneurysms. Further studies examining the role and cost-effectiveness of intracranial aneurysm screening in patients are warranted.

The association between carotid intraplaque hemorrhage and outcomes of carotid stenting: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

The purpose of this systematic review and meta-analysis was to determine whether carotid stenting patients with intraplaque hemorrhage (IPH) identified on preoperative MRI were more likely to suffer perioperative ischemic complications compared with patients without IPH.

METHODS

We conducted a comprehensive literature search of studies published between January 1, 2005 and December 31, 2015 reporting perioperative outcomes of carotid stenting among patients with and without IPH on hemorrhage sensitive carotid MRI sequences. Clinical outcomes included perioperative (≤30 days post-stenting) minor stroke, major stroke, death, and a composite outcome combining stroke, death, and myocardial infarction (MI). We also compared the rate of silent ischemia on diffusion weighted imaging (DWI) between groups. Statistical analysis was performed using a random effects meta-analysis.

RESULTS

9 studies with 491 unique patients (198 in the IPH group and 293 in the non-IPH group) were included. The rate of the composite outcome of any stroke, death, or MI within 30 days was 8.1% (13/160) in the IPH group and 2.1% (5/239) in the non-IPH group (OR=4.45, 95% CI 1.61 to 12.30, p<0.01). There were no significant differences between groups in the rates of minor stroke, major stroke, or death when considered individually. The rate of postoperative infarct on DWI was 49.7% (75/161) for the IPH group and 33.6% (81/241) for the non-IPH group (OR=2.01, 95% CI 1.31 to 3.09, p<0.01).

CONCLUSIONS

Our systematic review and meta-analysis demonstrated that patients with IPH on pre-carotid stenting MRI had higher rates of silent ischemia as well as of a composite outcome of perioperative stroke, death, and MI compared with those without IPH.

Efficacy and Safety of the Woven EndoBridge (WEB) Device for the Treatment of Intracranial Aneurysms: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Intrasaccular flow diverters are increasingly being used in the treatment of wide-neck and bifurcation aneurysms. We performed a systematic review and meta-analysis of existing literature on the Woven EndoBridge device in the treatment of intracranial aneurysms.

MATERIALS AND METHODS

A comprehensive literature search was performed through October 1, 2015. We extracted information on baseline aneurysm and patient characteristics. Outcomes studied included immediate and midterm (>3 month) angiographic outcomes (complete occlusion as well as adequate occlusion, defined as complete occlusion or neck remnant), aneurysm retreatment, intraoperative rupture, perioperative morbidity and mortality, thromboembolic complications, and treatment failure. Meta-analysis was performed by using the random-effects model.

RESULTS

Fifteen uncontrolled series were included in this analysis, including 565 patients with 588 aneurysms, of which 127 were ruptured. Initial complete and adequate occlusion rates were 27% (95% CI, 15%-39%) and 59% (95% CI, 39%-78%), respectively. Midterm complete and adequate occlusion rates after a median of 7 months were 39% (95% CI, 26%-52%) and 85% (95% CI, 78%-91%), respectively. Perioperative morbidity and mortality rates were 4% (95% CI, 1%-8%) and 1% (95% CI, 0%-2%), respectively. Midterm adequate occlusion rates for ruptured aneurysms were 85% (95% CI, 67%-98%), compared with 84% (95% CI, 72%-94%) for unruptured aneurysms (P = .89). Patients with ruptured aneurysm had similar rates of perioperative morbidity to patients with unruptured aneurysm (2%; 95% CI, 0%-26% versus 2%; 95% CI, 0%-6%, respectively; P = .35).

CONCLUSIONS

Early evidence derived from uncontrolled studies suggests that Woven EndoBridge treatment has a good safety profile and promising rates of adequate occlusion, especially given the complexity of aneurysms treated. Further prospective clinical trials are needed to confirm these results and better define the risks and benefits of use of the Woven EndoBridge device in treating wide-neck and wide-neck bifurcation aneurysms.

Neurovascular manifestations of connective-tissue diseases: A review

Patients with connective tissue diseases are thought to be at a higher risk for a number of cerebrovascular diseases such as intracranial aneurysms, dissections, and acute ischemic strokes. In this report, we aim to understand the prevalence and occurrences of such neurovascular manifestations in four heritable connective tissue disorders: Marfan syndrome, Ehlers-Danlos syndrome, Neurofibromatosis Type 1, and Loeys-Dietz syndrome. We discuss the fact that although there are various case studies reporting neurovascular findings in these connective tissue diseases, there is a general lack of case-control and prospective studies investigating the true prevalence of these findings in these patient populations. Furthermore, the differences observed in the manifestations and histology of such disease pathologies encourages future multi-center registries and studies in better characterizing the pathophysiology, prevalence, and ideal treatment options of neurovascular lesions in patents with connective tissue diseases.

Armband activity monitor data do not correlate with reported pain scores in patients receiving vertebroplasty

BACKGROUND

Prior research on the efficacy of vertebroplasty has focused primarily on subjective, patient-reported outcomes.

OBJECTIVE

To apply an armband activity monitor (SenseWear by BodyMedia Inc, USA) to patients presenting for consideration for vertebroplasty and to determine the correlation between patient-reported outcomes and quantitative activity metrics at baseline and 30 days after presentation.

MATERIALS AND METHODS

Nineteen patients were enrolled (15 receiving vertebroplasty, 4 not receiving vertebroplasty). Patients reported their average pain over the past 24 hours and completed the Roland-Morris disability questionnaire at baseline and 30 days. Patients wore the SenseWear Armband activity monitor for a median of 4 days at baseline and at the 30-day time period to assess steps, metabolic equivalents expended, sedentary activity time, moderate activity time, sleep efficiency, and total sleep time. Pain and disability scores were correlated with activity monitor metrics using linear regression analysis.

RESULTS

Changes in reported average pain in the past 24 hours and disability scores were not significantly different between vertebroplasty and non-vertebroplasty groups (p>0.05). Changes in activity monitor data were not significantly different between the vertebroplasty and non-vertebroplasty groups (p>0.05). None of the correlations between the reported pain or disability scores and the activity monitor data were significant.

CONCLUSIONS

Activity monitors can be used to objectively record changes in activity following vertebroplasty procedures. Patient-reported pain or disability scores do not correlate with activity monitor-measured activity or sleep metrics.

Wall Apposition Is a Key Factor for Aneurysm Occlusion after Flow Diversion: A Histologic Evaluation in 41 Rabbits

BACKGROUND AND PURPOSE

Robust wall apposition for flow-diverter stents may be important for endothelialization. Using a large series of experimental aneurysms treated with the Pipeline Embolization Device, the objectives of this study were to 1) assess interobserver agreement for the evaluation of wall apposition on posttreatment DSA and evaluate its association with aneurysm occlusion, and 2) measure the relationship between wall apposition assessed with histology and aneurysm occlusion rate after treatment.

MATERIALS AND METHODS

Saccular aneurysms were created in 41 rabbits and treated with the Pipeline Embolization Device. DSA was performed just after the deployment of the device and at follow-up. Three investigators independently graded wall apposition on posttreatment DSA as good or poor. A histopathologist blinded to the angiographic results graded the wall apposition on histologic samples. We examined the correlation between angiographic occlusion and wall apposition with histology and angiography.

RESULTS

Wall apposition evaluated on histology was strongly associated with saccular aneurysm occlusion. Sensitivity and specificity of wall apposition to predict complete occlusion at follow-up were 76.9% and 84.0%, respectively, with an overall accuracy of 81.6%. In this experimental study, DSA was suboptimal to assess flow-diverter apposition, with moderate interobserver agreement and low accuracy.

CONCLUSIONS

Good wall apposition is strongly associated with complete occlusion after flow-diverter therapy. In this study, DSA was suboptimal for assessing wall apposition of flow-diverter stents. These findings suggest that improved tools for assessing flow diverter-stent wall apposition are highly relevant.

Concomitant aneurysm detection in an intracranial dolichoectasia mouse model using a MicroFil polymer perfusion technique

OBJECTIVE

To assess the feasibility of using MicroFil polymer perfusion to detect concomitant saccular aneurysms in an intracranial arterial dolichoectasia (IADE) model in mice, and to report detailed histomorphometric features of these aneurysms.

MATERIALS AND METHODS

IADE models were created in C57/BL6 mice via microsurgical injection of 25 mU elastase into the cisterna magna. The cerebral vasculature was perfused with MicroFil polymer and harvested at 1, 3, and 7 days, and 2 and 4 weeks (n=8 for each group). IADE was defined by a tortuosity index >10 combined with a 25% increase in diameter of the A1 segment of the anterior cerebral artery (ACA), internal carotid artery (ICA), or basilar artery compared with the baseline of controls, which received heat-inactivated elastase. Saccular aneurysm occurrence rate, location, and morphological parameters were investigated using macroscopic and microscopic analysis.

RESULTS

IADE was present in 95% (36/38) of the subjects, with a mortality rate of 5% (2/40). Fifteen concomitant saccular aneurysms were detected in 8 (21%) of the 38 surviving mice, including 6 at the posterior communicating artery, 1 along the ACA, 2 along the anterior communicating artery complex, 3 along the ICA, and 3 along the middle cerebral artery. Rupture was confirmed in two aneurysms. Histological examination indicated that the aneurysms develop via arterial-wall remodelling, which is characterized by internal elastic lamina disruptions and muscular layer discontinuity in the media.

CONCLUSIONS

The proportion of subjects developing saccular aneurysms in addition to IADE in our mouse model is similar to the 15% of patients with IADE who have concomitant saccular aneurysms.

Treatment of ruptured complex and large/giant ruptured cerebral aneurysms by acute coiling followed by staged flow diversion

OBJECT

Flow-diversion treatment has been shown to be associated with high rates of angiographic obliteration; however, the treatment is relatively contraindicated in the acute phase following subarachnoid hemorrhage (SAH) as these patients require periprocedural dual antiplatelet therapy. Acute coiling followed by flow diversion has emerged as an intriguing and feasible treatment option for ruptured complex and giant aneurysms. In this study the authors report outcomes and complications of patients with ruptured aneurysms undergoing coiling in the acute phase followed by planned delayed flow diversion.

METHODS

This case series includes patients from 2 institutions. All patients underwent standard endovascular coiling in the acute phase after SAH with the intention and plan to proceed with flow diversion at a later date. Outcomes studied included angiographic occlusion, procedure-related complications, and long-term clinical outcome as measured using the modified Rankin Scale.

RESULTS

A total of 31 patients underwent coiling in the acute phase with the intention to undergo flow diversion at a later date. The mean aneurysm size was 15.8 ± 7.9 mm. Of the 31 patients undergoing coiling, 4 patients could not undergo further flow-diverter therapy: 3 patients (9.7%) died of complications of subarachnoid hemorrhage and 1 patient had permanent morbidity as a result of perioperative ischemic stroke (3.1%). Twenty-seven patients underwent staged placement of flow diverters after adequate recovery. The median time to treatment was 16 weeks. There was one case of aneurysm rebleeding following coil treatment. There were no cases of permanent morbidity or mortality resulting from flow-diverter treatment. Twenty-four patients underwent imaging follow-up; 18 of these patients had aneurysms that were completely or nearly completely occluded (58.1% on an intent-to-treat basis). At last follow-up (mean 18.3 months), 25 patients had mRS scores ≤ 2 (80.6% on an intent-to-treat basis).

CONCLUSIONS

Staged treatment of ruptured complex and giant intracranial aneurysms with coiling in the acute phase and flow-diverter treatment following recovery from SAH is both safe and effective. In this series, no cases of rebleeding occurred during the interval between coiling and flow diversion. This strategy should be considered as a valid option in patients presenting with these challenging ruptured aneurysms.

Comparing magnetic resonance angiography (MRA) and computed tomography angiography (CTA) with conventional angiography in the detection of distal territory cerebral mycotic and oncotic aneurysms

BACKGROUND

Mycotic and oncotic aneurysms may result in devastating neurologic sequelae if undetected. The objectives of this study were to examine interobserver variability and accuracy of cross-sectional imaging for the detection of distal territory mycotic and oncotic aneurysms.

METHODS

We searched our institutional database for all radiology reports from 2005 to 2015 with an indication or diagnosis of mycotic or oncotic aneurysm. Patients who underwent DSA and either CTA or MRA within 12 weeks of each other were identified. The cross-sectional images from each study were blinded and reviewed by two radiologists. If positive for aneurysm, location and number of aneurysms were reported. Sensitivity, specificity, positive predictive value, negative predictive value, and interobserver variability were determined for MRA and MRA/CTA.

RESULTS

Twenty-five patients were included in this study. Ten (40%) harbored distal aneurysms. Cross-sectional imaging had a sensitivity of 45.5%, specificity of 90.0%, and kappa value of 0.29 (0.00-0.69) for the detection of cerebral mycotic and oncotic aneurysms.

CONCLUSIONS

Because of the low sensitivity and high interobserver variability of cross-sectional imaging, DSA should remain the gold standard for evaluation of suspected oncotic and mycotic aneurysms. In cases in which cross sectional imaging is negative and there is a high clinical suspicion for mycotic aneurysm, DSA should be strongly considered.

Age-related outcomes following intracranial aneurysm treatment with the Pipeline Embolization Device: a subgroup analysis of the IntrePED registry

OBJECT

The association between age and outcomes following aneurysm treatment with flow diverters such as the Pipeline Embolization Device (PED) have not been well established. Using the International Retrospective Study of the Pipeline Embolization Device (IntrePED) registry, the authors assessed the age-related clinical outcomes of patients undergoing aneurysm embolization with the PED.

METHODS

Patients with unruptured aneurysms in the IntrePED registry were divided into 4 age groups: ≤ 50, 51–60, 61–70, and > 70 years old. The rates of the following postoperative complications were compared between age groups using chi-square tests: spontaneous rupture, intracranial hemorrhage (ICH), ischemic stroke, parent artery stenosis, cranial neuropathy, neurological morbidity, neurological mortality, combined neurological morbidity and mortality, and all-cause mortality. The association between age and these complications was tested in a multivariate logistic regression analysis adjusted for sex, number of PEDs, and aneurysm size, location, and type.

RESULTS

Seven hundred eleven patients with 820 unruptured aneurysms were included in this study. Univariate analysis demonstrated no significant difference in ICH rates across age groups (lowest 1.0% for patients ≤ 50 years old and highest 5.0% for patients > 70 years old, p = 0.097). There was no difference in ischemic stroke rates (lowest 3.6% for patients ≤ 50 years old and highest 6.0% for patients 50–60 years old, p = 0.73). Age > 70 years old was associated with higher rates of neurological mortality; patients > 70 years old had neurological mortality rates of 7.4% compared with 3.3% for patients 61–70 years old, 2.7% for patients 51–60 years old, and 0.5% for patients ≤ 50 years old (p = 0.006). On multivariate logistic regression analysis, increasing age was associated with higher odds of combined neurological morbidity and mortality (odds ratio 1.02, 95% confidence interval 1.00–1.05; p = 0.03).

CONCLUSIONS

Increasing age is associated with higher neurological morbidity and mortality after Pipeline embolization of intracranial aneurysms. However, the overall complication rates of PED treatment in this group of highly selected elderly patients (> 70 years) were acceptably low, suggesting that age alone should not be considered an exclusion criterion when considering treatment of intracranial aneurysms with the PED.

Smoking Does Not Affect Occlusion Rates and Morbidity-Mortality after Pipeline Embolization for Intracranial Aneurysms

BACKGROUND AND PURPOSE

Smoking is a major risk factor for patients with intracranial aneurysms, yet the effects of smoking on outcomes of aneurysm with flow-diverter treatment remain unknown. We studied the impact of smoking on long-term angiographic and clinical outcomes after flow-diverter treatment of intracranial aneurysms.

MATERIALS AND METHODS

We retrospectively reviewed data from patients treated with the Pipeline Embolization Device and included in the International Retrospective Study of the Pipeline Embolization Device, the Pipeline for Uncoilable or Failed Aneurysms Study, and the Aneurysm Study of Pipeline in an Observational Registry. Patients were stratified according to smoking status into 3 groups: 1) never smoker, 2) current smoker, and 3) former smoker. We studied angiographic and clinical outcomes. Outcomes were compared by using χ(2) and Student t tests. A multivariate analysis was performed to determine whether smoking was independently associated with poor outcomes.

RESULTS

Six hundred sixteen patients with 694 aneurysms were included. Current smokers had a smaller mean aneurysm size compared with the other 2 groups (P = .005) and lower rates of multiple Pipeline Embolization Device use (P = .015). On multivariate analysis, former smokers (OR, 1.08; 95% CI, 0.43-2.71; P = .57) and current smokers (OR, 0.70; 95% CI, 0.27-1.77; P = .38) had similar odds of long-term angiographic incomplete occlusion compared with never smokers. Former smokers (OR, 1.27; 95% CI, 0.64-2.52; P = .25) and current smokers (OR, 0.74; 95% CI, 0.37-1.46; P = .22) had similar odds of major morbidity and neurologic mortality compared with never smokers.

CONCLUSIONS

These results suggest that smoking is not associated with angiographic and clinical outcomes among patients treated with the Pipeline Embolization Device. Nonetheless, patients with intracranial aneurysms should continue to be counseled about the risks of tobacco smoking.

Current Trends and Results of Endovascular Treatment of Unruptured Intracranial Aneurysms at a Single Institution in the Flow-Diverter Era

BACKGROUND AND PURPOSE

During the past several years, the number of unruptured aneurysms treated with endovascular techniques has increased. Traditionally, coil embolization was the treatment of choice for these lesions; however, recently flow diversion has become a viable, and in some cases superior, treatment option. The current single-center study presents results and trends of endovascular treatment with flow diversion and coil embolization in an unselected group of patients with unruptured intracranial aneurysms in a "real world" setting during the flow-diverter era.

MATERIALS AND METHODS

Three hundred ten patients with 318 treated unruptured aneurysms from June 2009 to May 2015 were included. Patient demographics, clinical characteristics, aneurysm/treatment characteristics, and outcomes were collected prospectively. We studied the following: intensive care unit admission/reasons, perioperative and mid-/long-term complications, target aneurysm rupture, retreatment/recurrence rates, and long-term neurologic outcome using the mRS.

RESULTS

The flow-diverter group had a larger mean aneurysm size (12.3 ± 8.6 mm versus 8.7 ± 6.3 mm, P < .0001). There were no significant differences in the immediate (P = .43) and mid-/long-term complication rates (P = .54) between groups. Periprocedural neurologic morbidity and mortality rates were 2.1% and 0.5% in the coiling group and 2.5% and 1.6% in the flow-diverter group. Patients with coiling were more likely to be retreated than those with flow diversion (14.8% versus 5.7%, P = .009). Worsening of the mRS due to the target aneurysm was noted in only 3.2% of patients.

CONCLUSIONS

The endovascular treatment of unruptured aneurysms can be performed with very low rates of neurologic complications. Both flow-diverter and coil therapy were safe and effective.

Aneurysm Study of Pipeline in an Observational Registry (ASPIRe)

BACKGROUND AND OBJECTIVE

Few prospective studies exist evaluating the safety and efficacy of the Pipeline Embolization Device (PED) in the treatment of intracranial aneurysms. The Aneurysm Study of Pipeline In an observational Registry (ASPIRe) study prospectively analyzed rates of complete aneurysm occlusion and neurologic adverse events following PED treatment of intracranial aneurysms.

MATERIALS AND METHODS

We performed a multicenter study prospectively evaluating patients with unruptured intracranial aneurysms treated with PED. Primary outcomes included (1) spontaneous rupture of the Pipeline-treated aneurysm; (2) spontaneous nonaneurysmal intracranial hemorrhage (ICH); (3) acute ischemic stroke; (4) parent artery stenosis, and (5) permanent cranial neuropathy. Secondary endpoints were (1) treatment success and (2) morbidity and mortality at the 6-month follow-up. Vascular imaging was evaluated at an independent core laboratory.

RESULTS

One hundred and ninety-one patients with 207 treated aneurysms were included in this registry. The mean aneurysm size was 14.5 ± 6.9 mm, and the median imaging follow-up was 7.8 months. Twenty-four aneurysms (11.6%) were small, 162 (78.3%) were large and 21 (10.1%) were giant. The median clinical follow-up time was 6.2 months. The neurological morbidity rate was 6.8% (13/191), and the neurological mortality rate was 1.6% (3/191). The combined neurological morbidity/mortality rate was 6.8% (13/191). The most common adverse events were ischemic stroke (4.7%, 9/191) and spontaneous ICH (3.7%, 7/191). The complete occlusion rate at the last follow-up was 74.8% (77/103).

CONCLUSIONS

Our prospective postmarket study confirms that PED treatment of aneurysms in a heterogeneous patient population is safe with low rates of neurological morbidity and mortality. Patients with angiographic follow-up had complete occlusion rates of 75% at 8 months.

From bench to bedside: utility of the rabbit elastase aneurysm model in preclinical studies of intracranial aneurysm treatment

Preclinical studies are important in helping practitioners and device developers improve techniques and tools for endovascular treatment of intracranial aneurysms. Thus an understanding of the major animal models used in such studies is important. The New Zealand rabbit elastase induced arterial aneurysm of the common carotid artery is one of the most commonly used models in testing the safety and efficacy of new endovascular devices. In this review we discuss: (1) the various techniques used to create the aneurysm, (2) complications of aneurysm creation, (3) natural history of the arterial aneurysm, (4) histopathologic and hemodynamic features of the aneurysm, (5) devices tested using this model, and (6) weaknesses of the model. We demonstrate how preclinical studies using this model are applied in the treatment of intracranial aneurysms in humans. The model has similar hemodynamic, morphological, and histologic characteristics to human aneurysms, and demonstrates similar healing responses to coiling as human aneurysms. Despite these strengths, however, the model does have many weaknesses, including the fact that the model does not emulate the complex inflammatory processes affecting growing and ruptured aneurysms. Furthermore, the extracranial location of the model affects its ability to be used in preclinical safety assessments of new devices. We conclude that the rabbit elastase model has characteristics that make it a simple and effective model for preclinical studies on the endovascular treatment of intracranial aneurysms, but further work is needed to develop aneurysm models that simulate the histopathologic and morphologic characteristics of growing and ruptured aneurysms.

Hemodynamic differences between unstable and stable unruptured aneurysms independent of size and location: a pilot study

BACKGROUND

While clinical and angiographic risk factors for intracranial aneurysm instability are well established, it is reasonable to postulate that intra-aneurysmal hemodynamics also have a role in aneurysm instability.

OBJECTIVE

To identify hemodynamic characteristics that differ between radiologically unstable and stable unruptured intracranial aneurysms.

MATERIALS AND METHODS

12 pairs of unruptured intracranial aneurysms with a 3D rotational angiographic set of images and followed up longitudinally without treatment were studied. Each pair consisted of one stable aneurysm (no change on serial imaging) and one unstable aneurysm (demonstrated growth of at least 1 mm diameter or ruptured during follow-up) of matching size (within 10%) and locations. Patient-specific computational fluid dynamics models were created and run under pulsatile flow conditions. Relevant hemodynamic and geometric variables were calculated and compared between groups using the paired Wilcoxon test.

RESULTS

The area of the aneurysm under low wall shear stress (low shear stress area (LSA)) was 2.26 times larger in unstable aneurysms than in stable aneurysms (p=0.0499). The mean aneurysm vorticity was smaller by a factor of 0.57 in unstable aneurysms compared with stable aneurysms (p=0.0499). No statistically significant differences in geometric variables or shape indices were found.

CONCLUSIONS

This pilot study suggests there may be hemodynamic differences between unstable and stable unruptured cerebral aneurysms. In particular, the area under low wall shear stress was larger in unstable aneurysms. These findings should be considered tentative until confirmed by future larger studies.

Prevalence of Intracranial Aneurysms in Patients with Connective Tissue Diseases: A Retrospective Study

BACKGROUND AND PURPOSE

Few studies have examined the prevalence of intracranial aneurysms in connective tissue diseases such as Marfan syndrome, Ehlers-Danlos syndrome, neurofibromatosis type 1, and Loeys-Dietz syndrome. We studied the prevalence of intracranial aneurysms and other intracranial neurovascular pathologies such as arteriovenous malformations and intracranial dissections, in these 4 patient populations.

MATERIALS AND METHODS

We retrospectively reviewed all patients who had a clinical diagnosis of Marfan syndrome, Ehlers-Danlos syndrome, neurofibromatosis type 1, or Loeys-Dietz syndrome who underwent MRA, CTA, and/or DSA imaging of the intracranial circulation between January 1, 2005, and January 31, 2015. The presence, location, and maximum dimensions of intracranial aneurysms were catalogued. Other neurovascular findings studied included intracranial dissections and arteriovenous fistulas and shunts. Baseline data collected included demographic characteristics (sex, age, smoking history), imaging modality, and cardiovascular comorbidities.

RESULTS

The prevalence of intracranial saccular and fusiform aneurysms was as follows: 14% (8/59) among patients with Marfan syndrome, 12% (12/99) among patients with Ehlers-Danlos syndrome, 11% (5/47) among patients with neurofibromatosis type 1, and 28% (7/25) among patients with Loeys-Dietz syndrome. Intracranial dissections were found in 2 patients (3%) with Marfan syndrome and 1 patient (1%) with Ehlers-Danlos syndrome. No intracranial dissections were found in patients with neurofibromatosis type 1 or Loeys-Dietz syndrome.

CONCLUSIONS

Patients with connective tissue disorders, including Marfan syndrome, Ehlers-Danlos syndrome, neurofibromatosis type 1, and Loeys-Dietz syndrome, have a high prevalence of intracranial aneurysms.

Statins are not associated with short-term improved aneurysm healing in a rabbit model of unruptured aneurysms

Background

Owing to their anti-inflammatory effects and ability to stimulate production of extracellular matrix and chemotactic migration of mesenchymal progenitor cells, statins could potentially improve aneurysm healing after endovascular treatment.

Objective

To test the hypothesis that systemic administration of simvastatin would improve aneurysm healing in a rabbit model of unruptured intracranial aneurysms.

Methods

Experimental aneurysms were created in female rabbits and were embolized with platinum coils. Six rabbits served as controls and six rabbits received oral administration of simvastatin. Digital subtraction angiography was used to evaluate stability after embolization. Subjects were euthanized 4 weeks after coil embolization. Histologic samples were examined with a grading system (0–12) based on neck and dome features. Aneurysm occlusion data were compared using a Student t test.

Results

No significant differences in the mean aneurysm size were found between groups. No coil compaction occurred in either group. All aneurysms in both the statin and control groups showed stable occlusion. There were no significant differences in the histologic grade of occlusion in either group (statin group 2.6±0.8 vs control group 2.7±3.2, p=0.94).

Conclusions

Systemic statin administration after platinum coil embolization of unruptured aneurysms in a rabbit model does not improve aneurysm occlusion rates at 4 weeks.

Preclinical Testing of a Novel Thin Film Nitinol Flow-Diversion Stent in a Rabbit Elastase Aneurysm Model

BACKGROUND AND PURPOSE

Thin film nitinol can be processed to produce a thin microporous sheet with a low percentage of metal coverage (<20%) and high pore attenuation (∼70 pores/mm(2)) for flow diversion. We present in vivo results from the treatment of experimental rabbit aneurysms by using a thin film nitinol-based flow-diversion device.

MATERIALS AND METHODS

Nineteen aneurysms in the rabbit elastase aneurysm model were treated with a single thin film nitinol flow diverter. Devices were also placed over 17 lumbar arteries to model perianeurysmal branch arteries of the intracranial circulation. Angiography was performed at 2 weeks (n = 7), 1 month (n = 8), and 3 months (n = 4) immediately before sacrifice. Aneurysm occlusion was graded on a 3-point scale (grade I, complete occlusion; grade II, near-complete occlusion; grade III, incomplete occlusion). Toluidine blue staining was used for histologic evaluation. En face CD31 immunofluorescent staining was performed to quantify neck endothelialization.

RESULTS

Markedly reduced intra-aneurysmal flow was observed on angiography immediately after device placement in all aneurysms. Grade I or II occlusion was noted in 4 (57%) aneurysms at 2-week, in 6 (75%) aneurysms at 4-week, and in 3 (75%) aneurysms at 12-week follow-up. All 17 lumbar arteries were patent. CD31 staining showed that 75% ± 16% of the aneurysm neck region was endothelialized. Histopathology demonstrated incorporation of the thin film nitinol flow diverter into the vessel wall and no evidence of excessive neointimal hyperplasia.

CONCLUSIONS

In this rabbit model, the thin film nitinol flow diverter achieved high rates of aneurysm occlusion and promoted tissue in-growth and aneurysm neck healing, even early after implantation.

Experimental testing of the dual-layer Woven EndoBridge device using an elastase-induced aneurysm model in rabbits

The dual-layer Woven EndoBridge (WEB) device (WEB II) is designed to improve the performance of the first-generation WEB device. This study was performed to evaluate the acute and chronic performance of WEB II for aneurysm occlusion in an elastase-induced aneurysm model in rabbits. We implanted WEB II devices in 36 elastase-induced aneurysms and followed up for one, three, six, and 12 months. Degree of aneurysm occlusion at follow-up was graded on the Web Occlusion Scale (WOS): Grade A, complete aneurysm occlusion; Grade B, complete occlusion with recess filling; Grade C, residual neck filling; and Grade D, residual aneurysm filling. Hematoxylin and eosin staining was performed for histological assessment of aneurysm healing. Grades A, B, C, and D aneurysm occlusion at one-month follow-up were noted in three (17%), three (17%), eight (44%), and four (22%) of 18 cases, respectively. At the three-month time point Grades A, B, C, and D were shown in two (33%), two (33%), one (17%), and one (17%) aneurysms. Six months after treatment, one (17%), two (33%), two (33%), and one (17%) cases demonstrated Grades A, B, C, and D occlusion. At the 12-month time point, Grades B, C, and D were shown in three (50%), two (33%), and one (17%) aneurysms. Histologic evaluation showed progressive thrombus organization within aneurysm lumen from one to 12 months. These results indicated that the WEB II device can achieve high rates of aneurysm occlusion over time in experimental aneurysms.

Abstract WP11: Comparative Safety and Efficacy of the Trevo, Penumbra and Solitaire Devices in Treatment of Acute Ischemic Stroke

Background and Purpose: We performed a systematic review and meta-analysis comparing rates of recanalization, good neurological outcome, and mortality between patients treated with three modern devices used for endovascular treatment of acute ischemic stroke.

Materials and Methods: We performed a comprehensive literature search on studies reporting outcomes of endovascular treatment of acute ischemic stroke. We selected studies including≥30 patients treated with either the Trevo stent-retriever, Penumbra aspiration system or the Solitaire stent-retriever. Outcomes studied included mrs≤2, 90-day mortality, symptomatic and intracranial hemorrhage (sICH), recanalization. Outcomes were pooled across studies using a random-effects meta-analysis.

Results: 27 articles with 2666 patients were included (1514 Solitaire, 260 Trevo and 892 Penumbra). Rates of good neurological outcome (mRS≤2) were higher in the Solitaire group (54.0%, 95%CI=49.0-58.0%) than the Penumbra group (39.0%, 95%CI=31.0%-47.0%) (P<0.01). There was a trend towards higher rates of good neurological outcome in the Solitaire compared to the Trevo group (P=0.08). Rates of 90-day mortality were significantly lower in the Solitaire group (16.0%, 95%CI=11.0%-22.0%) than in the Penumbra group (27.0%, 95%CI=24.0%-30.0%) (P<0.01) and the Trevo group (23.0%, 95%CI=13.0-33.0)(P=0.01). Recanalization rates were similar between groups at 80.0% (95%CI=75.0%-84.0% for the Solitaire group, 82.0% (95%CI=75.0%-88.0%) for the Penumbra group (P=0.54) and 76.0% (95%CI=68.0-83.0) for the Trevo group (P=0.13 vs Penumbra and P=0.27 vs. Solitaire).

Conclusions: Meta-analysis of incidence rates in noncomparative series reporting on over 2500 patients suggests that the Solitaire device maybe associated with superior neurological outcomes and lower rates of 90-day mortality. Comparative studies are needed to confirm these observations.

Abstract TP31: Variability of Stroke Patients Meeting Endovascular Stroke Trial Criteria in a Non-clinical Trial Setting

Introduction: Five randomized trials proving the efficacy and safety of mechanical embolectomy for ischemic stroke patients used differing radiological methods to select patients for treatment.

Hypothesis: The percentage of patients evaluated in a non-clinical trial setting that would meet radiological criteria to be included in the five trials will differ substantially.

Methods: Retrospective study of consecutive ischemic stroke patients who were considered for endovascular stroke therapy based on confirmed intracranial large vessel occlusion (M1, M2, or carotid terminus) at an academic medical center from April 2010 - November 2014. All patients underwent CT perfusion and CT angiogram.

Results: The table shows baseline characteristics of 119 patients. Median age was 69 years (IQR 57-79) and median NIHSS 18 (IQR 14-21). Most patients had ASPECTS score ≥ 6 (n=105, 88.2%). The M1 segment of MCA was the most common vessel occluded (n=81, 68%). All 119 patients (100%) met radiological criteria for MR CLEAN while 105 (88.2%) met criteria for SWIFT-PRIME, 96 (80.7%) for REVASCAT, 80/116 (69.0%) for EXTEND IA, and 74 (62.2%) for ESCAPE. IV TPA was given to 58 patients (48.7%) and acute endovascular stroke therapy attempted in 66 (55.5%). Any intracranial hemorrhage was more common in the patients treated with endovascular therapy than in those who were not (36% vs. 17%, p=0.025). The frequency of symptomatic ICH did not significantly differ between these two groups (6.1% vs 3.8%, p=0.691).

Conclusions: The percentage of patients with acute stroke and large vessel occlusion that would qualify for endovascular stroke trials based on radiological criteria varies considerably (62%-100%) in a non-clinical trial cohort from an academic comprehensive stroke center. Additional individual patient characteristics influence treatment decisions in non-clinical trial settings.

Evaluation of the Angiographic Grading Scale in Aneurysms Treated with the WEB Device in 80 Rabbits: Correlation with Histologic Evaluation

BACKGROUND AND PURPOSE

The WEB Occlusion Score has been proposed to assess angiographic outcomes for intracranial aneurysms treated with the Woven EndoBridge (WEB) device. Using a large series of experimental aneurysms treated with the WEB, we had the following objectives: 1) to compare angiographic outcomes as measured by the WEB Occlusion Scale with histologic results, and 2) to assess interobserver and intraobserver agreement of the WEB Occlusion Scale.

MATERIALS AND METHODS

Intracranial aneurysms were created in 80 rabbits and treated with WEB devices. Animals were sacrificed at last follow-up for histologic evaluation. DSA was performed just after the deployment of the device and at follow-up. Four investigators independently and retrospectively graded the DSA twice according to the WEB Occlusion Scale. One histopathologist blinded to the angiographic results graded the occlusion according to a 4-point scale patterned on the WEB Occlusion Scale. Intra- and interobserver agreement were evaluated for DSA. Follow-up angiographic grading and histologic reference were compared to determine the WEB Occlusion Scale accuracy for complete (with or without recess filling) versus incomplete occlusion and adequate (complete occlusion or neck remnant) versus inadequate occlusion.

RESULTS

Inter- and intraobserver weighted κ for the angiographic WEB Occlusion Scale were, respectively, 0.76 and 0.76, indicating substantial agreement. The sensitivity and specificity of the WEB Occlusion Scale for complete occlusion at follow-up compared with the histologic reference standard were, respectively, 75% and 83.3%, with an overall accuracy of 80%. Similarly, for adequate occlusion at follow-up, sensitivity was 97.7%, specificity was 64.9%, and overall accuracy was 82.5%.

CONCLUSIONS

The WEB Occlusion Scale appears to be consistent, reliable, and accurate compared with a histologic reference standard.