Quantitative Assessment of In-Stent Stenosis After Pipeline Embolization Device Treatment of Intracranial Aneurysms: A Single-Institution Series and Systematic Review

Comprehensive Analysis of Post-Pipeline Endothelialization and Remodeling

BACKGROUND AND PURPOSE

Successful post-flow-diverter endoluminal reconstruction is widely believed to require endothelial overgrowth of the aneurysmal inflow zone. However, endothelialization/neointimal overgrowth is a complex process, over which we currently have very limited influence. Less emphasized is vascular remodeling of the target arterial segment, the dynamic response of the vessel to flow-diverter implantation. This process is distinct from flow modifications in covered branches. It appears that basic angiographic methods allow simple and useful observations. The purpose of this article was to quantitatively evaluate observable postimplantation changes in target vessels following deployment of Pipeline endoluminal constructs.

MATERIALS AND METHODS

One hundred consecutive adults with unruptured, previously untreated, nondissecting aneurysms treated with the Pipeline Embolization Device with Shield Technology and the availability of follow-up conventional angiography were studied with 2D DSA imaging. Target vessel size; Pipeline Embolization Device diameter; endothelial thickness; and various demographic, antiplatelet, and device-related parameters were recorded and analyzed.

RESULTS

The thickness of neointimal overgrowth (mean, 0.3 [SD, 0.1] mm; range, 0.1-0.7 mm) is inversely correlated with age and is independent of vessel size, smoking status, sex, and degree of platelet inhibition. The decrease in lumen diameter caused by neointimal overgrowth, however, appears counteracted by outward remodeling (dilation) of the target arterial segment. This leads to an increase in the diameter with a corresponding decrease in length (foreshortening) of the implanted Pipeline Embolization Device. This physiologic remodeling process affects optimally implanted devices and is not a consequence of stretching, device migration, vasospasm, and so forth. A direct, linear, statistically significant relationship exists between the degree of observed outward remodeling and the diameter of the implanted Pipeline Embolization Device relative to the target vessel. Overall, remodeled arterial diameters were reduced by 15% (SD, 10%) relative to baseline and followed a normal distribution. Clinically relevant stenosis was not observed.

CONCLUSIONS

Vessel healing involves both outward remodeling and neointimal overgrowth. Judicial oversizing could be useful in specific settings to counter the reduction in lumen diameter due to postimplant neointimal overgrowth; however, this overszing needs to be balanced against the decrease in metal coverage accompanying the use of oversized devices. Similar analysis for other devices is essential.

Angiographic Safety and Efficacy of the ReSolv Flow-Diverting Stent in a Rabbit Model

BACKGROUND

Bioresorbable polymer-based flow-diverting stents have potential benefits over existing metal devices. This study aimed to evaluate the safety and efficacy of the novel ReSolv device, which is a primarily polymer-based flow-diverting stent, using the in vivo rabbit sidewall saccular aneurysm model.

METHODS

ReSolv stents were deployed in 14 New Zealand White rabbits that had undergone aneurysm creation procedures. Animals were allocated to follow-up time points of 1, 3, 6, 9, 12, 16, or 18 months. Angiographic images were evaluated by an independent neurointerventionalist blinded to follow-up time points for (1) in-stent stenosis, (2) parent vessel and jailed side branch patency, (3) wall apposition, and (4) aneurysm occlusion using the Raymond-Roy Occlusion Classification (RROC), O'Kelly Marotta grading scale, and the 4F flow diversion predictive score. Primary efficacy outcome was defined as RROC Class I or II.

RESULTS

At a median follow-up time of 7.5 months, parent vessel (14/14) and jailed side (33/33) branches were patent in all cases. There was no development of thrombus on the stent or cases of significant in-stent stenosis, and all stents had good wall apposition. Adequate occlusion was found in 85.7% (n = 12) of animals, including an RROC Class I in 64.3% (n = 9) and RROC Class II in 21.4% (n = 3).

CONCLUSIONS

The ReSolv stent shows encouraging angiographic safety and efficacy outcomes after placement in a rabbit sidewall saccular aneurysm model. Longer term studies are ongoing to determine eventual fate of the aneurysm, parent vessel, and jailed side branches after absorption of the polymer component of the stent.

Role of optical coherence tomography in pipeline embolization device for the treatment of vertebral-basilar artery dissecting aneurysms

BACKGROUND

Vertebral-basilar artery dissecting aneurysms (VADAs) are an uncommon phenomenon in all fields of cerebrovascular disease. The flow diverter (FD) can be used as an endoluminal reconstruction device that promotes neointima formation at the aneurysmal neck and preserves the parent artery. To date, imaging examinations such as CT angiography, MR angiography, and DSA are the main methods used to evaluate the vasculature of patients. However, none of these imaging methods can reveal the situation of neointima formation, which is of great importance in evaluating occlusion of VADAs, especially those treated with a FD.

METHODS

Three patients were included in the study from August 2018 to January 2019. All patients underwent preprocedural, postprocedural, and follow-up evaluations with high resolution MRI, DSA, and optical coherence tomography (OCT), as well as the formation of intima on the surface of the scaffold at the 6 month follow-up.

RESULTS

Preprocedural, postoperative, and follow-up high resolution MRI, DSA, and OCT of all three cases successfully evaluated occlusion of the VADAs and occurrence of in stent stenosis from different views of intravascular angiography and neointima formation.

CONCLUSIONS

OCT was feasible and useful to further evaluate VADAs treated with FD from a near pathological perspective, which may contribute toward guiding the duration of antiplatelet medication and early intervention of in stent stenosis.

Long-term outcomes and dynamic changes of in-stent stenosis after Pipeline embolization device treatment of intracranial aneurysms

BACKGROUND

Flow diverters have revolutionized the treatment of intracranial aneurysms. However, the delayed complications associated with flow diverter use are unknown.

OBJECTIVE

To evaluate the incidence, severity, clinical outcomes, risk factors, and dynamic changes associated with in-stent stenosis (ISS) after treatment with a Pipeline embolization device (PED).

METHODS

Patients who underwent PED treatment between 2015 and 2020 were enrolled. The angiographic, clinical, and follow-up data of 459 patients were independently reviewed by four neuroradiologists to identify ISS. Binary logistic regression was conducted to determine ISS risk factors, and an ISS-time curve was established to demonstrate dynamic changes in ISS after PED implantation.

RESULTS

Of the 459 treated patients, 69 (15.0%) developed ISS. At follow-up, nine patients (2.0%) with ISS demonstrated reversal, while 18 (3.9%) developed parental artery occlusion. A total of 380 patients (82.8%) achieved complete aneurysm occlusion (O'Kelly-Marotta grade D). Patients with posterior-circulation aneurysm (OR=2.895, 95% CI (1.732 to 4.838; P<0.001) or balloon angioplasty (OR=1.992, 95% CI 1.162 to 3.414; P=0.037) were more likely to develop ISS. Patients aged >54 years (OR=0.464, 95% CI 0.274 to 0.785; P=0.006) or with a body mass index of >28 kg/m2 (OR=0.427, 95% CI 0.184 to 0.991; P=0.026) had a lower ISS risk. Intimal hyperplasia initiated by PED placement peaked within 1 year after the procedure, rarely progressed after 12 months, and tended to reverse within 24 months.

CONCLUSIONS

ISS is a common, benign, and self-limiting complication of PED implantation in the Chinese population.

Parent artery occlusion after pipeline embolization device implantation of intracranial saccular and fusiform aneurysms

BACKGROUND

Studies reporting parent artery occlusion (PAO) after pipeline embolization device (PED) implantation are limited. The aim of this study was to investigate the incidence rate and risk factors of PAO after PED implantation.

METHODS

In this retrospective study, we enrolled consecutive patients with intracranial saccular and fusiform aneurysms treated with PED implantation at our institution. Multivariate logistic regression analysis was subsequently performed to determine the risk factors for PAO.

RESULTS

A total of 588 saccular and fusiform aneurysms were finally enrolled in the study. PAO was found in 14 (2.38%) aneurysms. The aneurysm complete occlusion rate was 79.6%. Compared with the non-PAO group, aneurysms in the PAO group were larger in size (20.08 vs 9.61 mm; p<0.001), had a greater neck diameter (9.92 vs 6.15 mm; p=0.001), and had higher frequencies of adjunctive coils (64.3% vs 35.7%; p=0.028). In the multivariate logistic analysis, aneurysm size (OR 1.12, 95% CI 1.02 to 1.24; p=0.016) and the presence of poor wall apposition after balloon angioplasty (OR 7.74, 95% CI 1.28 to 46.82; p=0.026) were associated with PAO occurrence after adjusting for confounding factors.

CONCLUSIONS

In this study, the incidence rate of PAO following PED implantation was 2.38% in intracranial saccular and fusiform aneurysms. Aneurysm size and residual presence of poor wall apposition after balloon angioplasty were risk factors for PAO. Further research is required to better understand the mechanisms of PAO.

Morphological features predicting in-stent stenosis after pipeline implantation for unruptured intracranial aneurysm

Purpose

Elongation denotes the regularity of an aneurysm and parent artery. This retrospective research study was conducted to identify the morphological factors that could predict postoperative in-stent stenosis (ISS) after Pipeline Embolization Device (PED) implantation for unruptured intracranial aneurysms (UIAs).

Methods

Patients with UIA and treated with PED at our institute between 2015 and 2020 were selected. Preoperative morphological features including both manually measured shape features and radiomics shape features were extracted and compared between patients with and without ISS. Logistic regression analysis was performed for factors associated with postoperative ISS.

Results

A total of 52 patients (18 men and 34 women) were involved in this study. The mean angiographic follow-up time was 11.87 ± 8.26 months. Of the patients, 20 of them (38.46%) were identified with ISS. Multivariate logistic analysis showed that elongation (odds ratio = 0.008; 95% confidence interval, 0.001-0.255; p = 0.006) was an independent risk factor for ISS. The area under the curve (AUC) of the receiver operating characteristic curve(ROC) was 0.734 and the optimal cut-off value of elongation for ISS classification was 0.595. The sensitivity and specificity of prediction were 0.6 and 0.781, respectively. The ISS degree of elongation of less than 0.595 was larger than the ISS degree of elongation of more than 0.595.

Conclusion

Elongation is a potential risk factor associated with ISS after PED implantation for UIAs. The more regular an aneurysm and parent artery, the less likelihood of an ISS occurrence.

The incidence and predictors of in-stent stenosis after pipeline flow-diverter stenting for intracranial aneurysm treatment

Background and purpose

Data on in-stent stenosis (ISS) following the flow diverter (FD) implantation method are scarce and inconsistent. In the present study, we sought to determine the incidence of ISS and identify the factors that predict its severity via the use of ordinal logistic regression.

Methods

A retrospective review of our center's electronic database was conducted to identify all patients with intracranial aneurysms (IAs) who received pipeline embolization device (PED) implantation between 2016 and 2020. Patient demographics, aneurysm characteristics, procedural information, and clinical and angiographic outcomes were reviewed. ISS was quantitatively assessed on angiographic follow-ups and graded as mild (<25%), moderate (25-50%), or severe (>50%). Ordinal logistic regression was conducted to determine the predictors of stenosis severity.

Results

A total of 240 patients with 252 aneurysms treated in 252 procedures were enrolled in this study. ISS has been detected in 135 (53.6%) lesions, with a mean follow-up time of 6.53 ± 3.26 months. The ISS was mild in 66 (48.9%) cases, moderate in 52 (38.5%) cases, and severe in 17 (12.6%) cases. All patients were asymptomatic, except for two of them with severe stenosis who presented with symptoms of acute cerebral thrombosis. Ordinal logistic regression identified that younger age and a longer procedure duration were independent predictors of a higher likelihood of ISS.

Conclusion

ISS is a common angiographic finding after PED implantation for IAs and is presented as a largely benign course through long-term follow-up. Patients who were younger in age and had a longer procedure duration were found to be at a greater risk of developing ISS.

Effect of Stent Porosity, Platelet Function Test Usage, and Dual Antiplatelet Therapy Duration on Clinical and Radiographic Outcomes After Stenting for Cerebral Aneurysms: A Meta-Analysis

BACKGROUND

The use of stents with various porosities for treating cerebral aneurysms requires dual antiplatelet therapy (DAPT) without clear guidelines on the utility of platelet function tests (PFTs) and the duration of DAPT. We sought to determine the effects of stent porosity, PFT usage, and DAPT duration on the radiographic and clinical outcomes after stenting of cerebral aneurysms.

METHODS

PubMed was searched on March 29, 2021 for studies of cerebral aneurysm stenting that had specified the stent type and DAPT duration. A random effects meta-analysis was used to measure the prevalence of nonprocedural thrombotic and hemorrhagic events, clinical outcomes, aneurysm occlusion, and in-stent stenosis stratified by stent porosity, PFT usage, and DAPT duration.

RESULTS

The review yielded 105 studies (89 retrospective and 16 prospective) with 117 stenting cohorts (50 high porosity, 17 intermediate porosity, and 50 low porosity). In the high-, intermediate-, and low-porosity stenting cohorts, PFT usage was 26.0%, 47.1%, and 62.0% and the mean DAPT duration was 3.51 ± 2.33, 3.97 ± 1.92, and 5.18 ± 2.27 months, respectively. The intermediate-porosity stents showed a reduced incidence of hemorrhagic events (π = 0.32%) compared with low-porosity stents (π = 1.36%; P = 0.01) and improved aneurysm occlusion (π = 6.18%) compared with high-porosity stents (π = 14.42%; P = 0.001) and low-porosity stents (π = 11.71%; P = 0.04). The prevalence of in-stent stenosis was lower for the intermediate-porosity (π = 0.57%) and high-porosity (π = 1.51%) stents than for the low-porosity stents (π = 3.30%; P < 0.05). PFT use had resulted in fewer poor clinical outcomes (π = 3.54%) compared with those without PFT use (π = 5.94%; P = 0.04). The DAPT duration had no effect on the outcomes.

CONCLUSIONS

In the present meta-analysis, which had selected for studies of cerebral aneurysm stenting that had reported the DAPT duration, intermediate-porosity stents and PFT use had resulted significantly improved outcomes. No effect of DAPT duration could be detected.

Effect on ophthalmic imaging findings of flow-diverting stent treatment covering the origin of the ophthalmic artery

BACKGROUND

Flow-diverting stents are devices that are increasingly used in the treatment of intracranial aneurysms and expand the spectrum of endovascular treatment. The patency of side branches and perforators is a major concern about flow-diverting stent (FDS) treatment.

METHODS

From 2011 to 2020, seventy-eight patients in whom the orifice of the ophthalmic artery was covered during FDS treatment were evaluated in this study. Bilateral retinal vascular parameters of study subjects were evaluated with OCT and OCTA. The FDS implanted-side eyes of the patients were defined as the procedure group, and the fellow eyes were considered as the control group.

RESULTS

Twenty-seven patients who were treated with FDS covering the ostium of the ophthalmic artery and who could undergo full ophthalmologic examination were included in the study. There was no statistically significant difference found in terms of visual acuity, retinal vascular parameters, and choroidal thickness between the procedure group and the control group (p>0.05). However, in one case, recanalized retinal artery branch occlusion was detected on the side where the FDS was implanted.

CONCLUSION

The orifice of the ophthalmic artery is often covered during FDS treatment for carotid-ophthalmic aneurysms; however, this treatment approach has no significant effect on ophthalmic vascular parameters.

Factors associated with in-stent stenosis after cerebral aneurysm embolization using a Pipeline embolization device

BACKGROUND

Flow-diverting (FD) stents, with or without coiling, are a mainstay in endovascular treatment of intracranial aneurysms (IAs). One observed complication from flow diverter stent (FDS) insertion has been in-stent stenosis. Though previously studied in the short-term period, the long-term history of this complication has yet to be described.

METHODS

We performed a retrospective cohort study of consecutive IAs treated with Pipeline Embolization Device (PED), with or without coiling, at our centre between September 2014 and December 2018 that had at least one digital subtraction angiogram (DSA) during follow-up. In-stent stenosis was measured from DSA images, and associated patient and procedural characteristics were analysed.

RESULTS

94 patients treated with PED for IA were identified. On initial DSA during follow-up, 52 patients (55.3%) had in-stent stenosis within the PED. Of these 52 patients, 17 had a second DSA during follow-up. In this 2nd DSA, improvement and/or stable in-stent stenosis was seen 16 patients (94.1%). One patient in this group had worsening in-stent stenosis had a vertebrobasilar junction FD stent. Of the patients without in-stent stenosis on initial DSA, 15 had a second DSA during follow-up. Only one of these patients (6.7%) had new appearance of in-stent stenosis (measuring 5%). Multivariate analysis found statin use to be predictive of in-stent stenosis (p = 0.020, Odds ratio = 0.279 and 95% confidence interval = 0.095-0.821).

CONCLUSIONS

In-stent stenosis after FDS placement was seen in 53.2% of cases, which had between 1-50% of stenosis. 82.4% had resolution/improvement of their stenosis. Statin use was protective of in-stent stenosis.

Pipeline for the treatment of distal cerebral circulation aneurysms: A multicenter study focusing on periprocedural Complications

BACKGROUND AND AIM

Distal cerebral circulation aneurysms (DCCAs) remain treatment challenges for neurointervention. The off-label use of the pipeline embolization device (PED) for these aneurysms remains controversial. This study aimed to evaluate the safety and efficacy of PED for DCCAs in a multicenter cohort of patients.

METHODS

Between March 2016 and June 2021, we retrospectively analyzed the neurointerventional data on the clinical and radiological records of all patients undergoing PED treatment of DCCAs at three medical centers.

RESULTS

A total of 53 consecutive patients with 53 DCCAs were treated with PED. The mean aneurysm size was 12.3 ± 5.7 mm. In total, 75.4% (40/53) were fusiform and 24.5% (13/53) were saccular. Of these, 17.0% (9/53) were recurrent aneurysms that were previously treated with endovascular or microsurgical approaches. The technical success rate was 100%, among which 81.1% (43/53) procedures were completed with a single PED, and the rest (10/53, 18.8%) required telescoping with two devices. Angiographic follow-up data were available for 51 patients, with a median follow-up time of 12 months. At the latest follow-up, 46/51 (90.2%) aneurysms showed complete obliteration, and 4/51 (7.8%) showed reduced filling. Periprocedural complications such as hemorrhage were observed in two patients with MCA aneurysms (3.8%, 2/53), and ischemic events occurred in six patients (11.3%, 6/53). The overall mortality and morbidity rates were 7% (4/53).

CONCLUSIONS

PED is a viable option for treating DCCAs, especially for recurrent aneurysms. Coverage of bifurcation branches and perforator may increase the risk of complications.

Stent-alone treatment of unruptured vertebral artery fusiform aneurysms: A comparison of flow diverter and conventional stents

Background

Treatment of vertebral artery fusiform aneurysms (VAFAs) is complex and controversial. This study aimed to compare the safety and efficacy between flow diverter and conventional stents in patients with VAFAs undergoing endovascular stent-alone treatment (SAT).

Methods

Thirty-six patients with 36 VAFAs who underwent SAT between January 2014 and December 2018 were retrospectively analyzed. Patient and aneurysm characteristics, procedural details, complications, and angiographic and clinical outcomes were compared between flow diverter stent patients (n = 22) and conventional stent patients (n = 14).

Results

More branches covered with stent were found in the conventional stent group (88.9 vs. 33.3%; p = 0.008). The number of stents placed was significantly higher in the conventional stent group (1.57 ± 0.76 vs. 1.09 ± 0.29; p = 0.016). The proportion of patients with significant or moderate stasis within the aneurysm immediately after stent placement was higher in the flow diverter stent group (95.5 vs. 57.1%; p = 0.004). The proportion of patients with complete obliteration or only a residual neck on follow-up angiography was significantly higher in the flow diverter stent group (86.3 vs 50.0%; p = 0.047). However, the incidence of parent artery stenosis or occlusion was also higher in the flow diverter stent group (27.3% vs. zero; p = 0.032). The rate of complications did not significantly differ between the groups.

Conclusions

SAT was safe and effective in patients with VAFAs. Flow diverter stents are associated with a significantly better complete occlusion rate than conventional stents; however, they are also associated with an increased risk of parent artery stenosis.

Management of In-Stent Stenosis with Dual Antiplatelet Therapy Following Pipeline Embolization of Intracranial Aneurysms

OBJECTIVE

Flow diversion of intracranial aneurysms with the pipeline embolization device (PED) may produce angiographically apparent stenosis within the PED, which can lead to secondary ischemic complications. In-stent stenosis can be treated medically with dual antiplatelet therapy (DAPT), but the safety and efficacy of this approach are unknown. In this work, we review the safety and efficacy of DAPT to prevent progression of in-stent stenosis or development of cerebral ischemia.

METHODS

Clinical and angiographic data from eligible patients were assessed from a prospectively maintained neurointerventional database. Details surrounding in-stent stenosis and DAPT were extracted. Patients were included in this study if in-stent stenosis was detected at any angiographic follow-up and managed with DAPT. The primary efficacy endpoint was lack of angiographic progression of in-stent stenosis or new ipsilateral infarct following initiation of medical therapy.

RESULTS

In total, 23 PED constructs developed in-stent stenosis and were managed with DAPT. Follow-up angiography was available for 19 constructs. Eighty-nine percent (17/19) of PED constructs achieved the primary endpoint of lack of stenosis progression and lack of new ipsilateral ischemic events. Of the 2 PED constructs that failed to achieve the primary endpoint of this study, one demonstrated worsening of in-stent stenosis from 55% to 76% over 16 months, while the other developed ipsilateral ischemic stroke 4 months after detection of in-stent stenosis. In addition, one patient experienced intracranial hemorrhage 9 months after the initiation of DAPT.

CONCLUSIONS

Progression of in-stent stenosis and new ipsilateral ischemic events are limited in the presence of DAPT. However, hemorrhagic events related to DAPT may occasionally occur.

Time Line of Occlusion for Intracranial Aneurysms Treated with the Pipeline Embolization Device

BACKGROUND

Rates of aneurysm occlusion following treatment with flow-diverting stents have been quantified at predefined time points in clinical trials, but data characterizing the continuous temporal progression of aneurysm occlusion are lacking. This study used real-world variability in timing of angiographic follow-up to characterize the time line of aneurysm occlusion following treatment with the Pipeline embolization device (PED).

METHODS

All aneurysms treated with a PED at our institution between 2011 and 2020 were screened. Nonsaccular or ruptured aneurysms were excluded. Aneurysm occlusion status and time since treatment were recorded for each follow-up angiogram. Aneurysm occlusion was characterized using Kaplan-Meier and Cox proportional hazards analysis after censoring at last follow-up or subsequent treatment.

RESULTS

There were 290 aneurysms in 222 patients analyzed. The median time of observed aneurysm occlusion was 7.5 months, and overall rate of aneurysm occlusion was 77.9%. Larger aneurysms demonstrated a longer median time to occlusion and lower rate of aneurysm occlusion (P = 0.029). There were no observed differences in the time line of occlusion for aneurysms treated with a single PED or multiple PEDs (P = 0.889) or without or with adjunctive coiling (P = 0.771).

CONCLUSIONS

Aneurysms treated with a PED had a median time to observed occlusion of 7.5 months. Occlusion of larger aneurysms occurred more slowly than occlusion of smaller aneurysms following flow diversion. The number of PEDs deployed or the use of adjunctive coiling did not affect the time line or likelihood of aneurysm occlusion. These findings may guide optimal timing of follow-up after treatment with a PED.

North American multicenter experience with the Flow Redirection Endoluminal Device in the treatment of intracranial aneurysms

OBJECTIVE

Flow diverters have revolutionized the endovascular treatment of intracranial aneurysms. Here, the authors present the first large-scale North American multicenter experience using the Flow Redirection Endoluminal Device (FRED) in the treatment of cerebral aneurysms.

METHODS

Consecutive cerebral aneurysms treated with FRED at 7 North American centers between June 2020 and November 2021 were included. Data collected included patient demographic characteristics, aneurysm characteristics, periprocedural and long-term complications, modified Rankin Scale (mRS) scores, and radiological follow-up.

RESULTS

In total, 133 aneurysms in 116 patients were treated with 123 FRED deployment procedures and included in this study. One hundred twenty-six aneurysms (94.7%) were unruptured, 117 (88.0%) saccular, and 123 (92.5%) located in anterior circulation. The mean (range) aneurysm maximal width and neck width sizes were 7.2 (1.5-42.5) mm and 4.1 (1.0-15.1) mm, respectively. Successful FRED deployment was achieved in 122 procedures (99.2%). Adjunctive coiling was used in 4 procedures (3.3%). Radiological follow-up was available for 101 aneurysms at a median duration of 7.0 months. At last follow-up, complete occlusion was observed in 55.4% of patients, residual neck in 8.9%, and filling aneurysm in 35.6%; among cases with radiological follow-up duration > 10 months, these values were 21/43 (48.8%), 3/43 (7.0%), and 19/43 (44.2%), respectively. On multivariate regression analysis, age (OR 0.93, p = 0.001) and aneurysm neck size (OR 0.83, p = 0.048) were negatively correlated with odds of complete occlusion at latest follow-up. The retreatment rate was 6/124 (4.8%). The overall complication rate was 31/116 (26.7%). Parent vessel occlusion, covered branch occlusion, and in-stent stenosis were detected in 9/99 (9.1%), 6/63 (9.5%), and 15/99 (15.2%) cases, respectively. The FRED-related, symptomatic, thromboembolic, and hemorrhagic complication rates were 22.4%, 12.9%, 6.9%, and 0.9% respectively. The morbidity rate was 10/116 patients (8.6%). There was 1 death due to massive periprocedural internal carotid artery stroke, and 3.6% of the patients had an mRS score > 2 at the last follow-up (vs 0.9% at baseline).

CONCLUSIONS

As the first large-scale North American multicenter FRED experience, this study confirmed the ease of successful FRED deployment but suggested lower efficacy and a higher rate of complications than reported by previous European and South American studies on FRED and other flow-diverting devices. The authors recommend judicious use of this device until future studies can better elucidate the long-term outcomes of FRED treatment.

Machine learning to predict in-stent stenosis after Pipeline embolization device placement

Background

The Pipeline embolization device (PED) is a flow diverter used to treat intracranial aneurysms. In-stent stenosis (ISS) is a common complication of PED placement that can affect long-term outcome. This study aimed to establish a feasible, effective, and reliable model to predict ISS using machine learning methodology.

Methods

We retrospectively examined clinical, laboratory, and imaging data obtained from 435 patients with intracranial aneurysms who underwent PED placement in our center. Aneurysm morphological measurements were manually measured on pre- and posttreatment imaging studies by three experienced neurointerventionalists. ISS was defined as stenosis rate >50% within the PED. We compared the performance of five machine learning algorithms (elastic net (ENT), support vector machine, Xgboost, Gaussian Naïve Bayes, and random forest) in predicting ISS. Shapley additive explanation was applied to provide an explanation for the predictions.

Results

A total of 69 ISS cases (15.2%) were identified. Six predictors of ISS (age, obesity, balloon angioplasty, internal carotid artery location, neck ratio, and coefficient of variation of red cell volume distribution width) were identified. The ENT model had the best predictive performance with a mean area under the receiver operating characteristic curve of 0.709 (95% confidence interval [CI], 0.697–0.721), mean sensitivity of 77.9% (95% CI, 75.1–80.6%), and mean specificity of 63.4% (95% CI, 60.8–65.9%) in Monte Carlo cross-validation. Shapley additive explanation analysis showed that internal carotid artery location was the most important predictor of ISS.

Conclusion

Our machine learning model can predict ISS after PED placement for treatment of intracranial aneurysms and has the potential to improve patient outcomes.

Comparison of Pipeline Embolization Device and Traditional Endovascular Therapeutic Approaches in Distal Cerebral Circulation Aneurysms Using Propensity Score Matching Analysis

Background

Coiling and stent-assisted coiling remain the first-line treatments for distal cerebral circulation aneurysms (DCCAs). The off-label use of the pipeline embolization device (PED) for these aneurysms has been explored recently but remains controversial.

Objective

To compare traditional endovascular therapeutic approaches (coiling and stent-assisted coiling) and PED for DCCAs in a multicenter cohort of patients.

Methods

A multicenter, retrospective cohort comparison study was conducted that included consecutive patients with unruptured DCCAs treated with either traditional endovascular therapeutic approaches or PED placement at three centers between 2016 and 2020. Propensity score matching analysis was applied to adjust for baseline risk factors between the PED and TET groups. Matching was based on age, sex, aneurysm size, location, morphology, adjunctive coiling, treatment history, and preoperative mRS score.

Results

In total, 209 patients with DCCAs treated with PED or traditional endovascular therapeutic approaches were identified. Thirty-seven patients underwent PED treatment, and 172 patients underwent traditional endovascular therapeutic approaches. After propensity score matching, 37 aneurysm pairs were matched, and the baseline characteristics of the patients were balanced between the groups. The complete occlusion rate between PED and traditional endovascular therapeutic approach in both matched cohorts (91.7 vs. 92.3%, p > 0.78) was similar. The rate of periprocedural treatment-related complications in both the PED and traditional endovascular therapeutic groups was 13.5%. Univariate analysis identified average parent vessel diameter as the only predictor of complete occlusion (p = 0.038).

Conclusions

PED is a viable option for treating DCCAs by providing occlusion and complication rates similar to those of traditional endovascular therapeutic approaches. A rigid patient selection procedure and proper planning should be undertaken to reduce treatment-related complications.

Bifurcated Aneurysm Location Predicts In-Stent Stenosis After Neuroform-EZ Stent-Assisted Coiling for Intracranial Aneurysm

Background and Purpose

The Neuroform EZ stent system (Boston Scientific Corporation, Fremont, CA, United States) is a fourth-generation intracranial aneurysm stent designed specifically for the cerebrovasculature to support aneurysm treatment. In this study, we analyzed our consecutive series of patients with aneurysm treated with the Neuroform EZ stent, with special attention to the occurrence of in-stent stenosis (ISS).

Methods

A retrospective review of our center's electronic database was conducted to identify all patients with intracranial aneurysms who underwent aneurysm treatment with the Neuroform EZ stent between January 2016 and October 2018. Patients with at least one digital subtraction angiography (DSA) follow-up in our hospital were enrolled in this study. In-stent stenosis (ISS) was graded as mild (<2–5%), moderate (25–50%), or severe (>50%).

Results

The study included 114 patients (78 women, 68.4%; median age 57.2 ± 9 years) with a total of 116 aneurysms. Of the 116 lesions, 20 were identified with ISS (17.2%) at a mean follow-up of 6.9 ± 1.7 months, and ISS was mild in 30% (6/20), moderate in 50% (10/20), and severe in 20% (4/20). No patients were symptomatic or required further intervention. Patients who developed ISS were younger than those without ISS (52.6 ± 7.8 vs. 57.9 ± 9; p = 0.016). The proportion of aneurysms located at the artery bifurcation was significantly higher in patients with stenosis than located at the sidewall artery (37.9 vs. 10.3%; p = 0.002). In the multivariable analysis, the patients' age (OR = 0.94; 95% CI 0.88–0.998; p = 0.02) and bifurcated aneurysm location (OR = 4.59; 95% CI 1.54–13.67; p = 0.006) were independent predictors of ISS.

Conclusions

In this retrospective study, the incidence of ISS after Neuroform EZ stent placement was 17.2%, and all the ISS cases were asymptomatic. Patients with younger age and bifurcated aneurysm location are more likely to develop ISS. Although Neuroform EZ stent is particularly suitable for bifurcated aneurysms, the ISS for this location should be focused upon.

Diversion-p64: results from an international, prospective, multicenter, single-arm post-market study to assess the safety and effectiveness of the p64 flow modulation device

BACKGROUND

The use of flow diversion to treat intracranial aneurysms has increased in recent years.

OBJECTIVE

To assess the safety and angiographic efficacy of the p64 flow modulation device.

METHODS

Diversion-p64 is an international, prospective, multicenter, single-arm, study conducted at 26 centers. The p64 flow modulation device was used to treat anterior circulation aneurysms between December 2015 and January 2019. The primary safety endpoint was the incidence of major stroke or neurologic death at 3-6 months, with the primary efficacy endpoint being complete aneurysm occlusion (Raymond-Roy Occlusion Classification 1) on follow-up angiography.

RESULTS

A total of 420 patients met the eligibility criteria and underwent treatment with the p64 flow modulation device (mean age 55±12.0 years, 86.2% female). Mean aneurysm dome width was 6.99±5.28 mm and neck width 4.47±2.28 mm. Mean number of devices implanted per patient was 1.06±0.47, with adjunctive coiling performed in 14.0% of the cases. At the second angiographic follow-up (mean 375±73 days), available for 343 patients (81.7%), complete aneurysm occlusion was seen in 287 (83.7%) patients. Safety data were available for 413 patients (98.3%) at the first follow-up (mean 145±43 days) with a composite morbidity/mortality rate of 2.42% (n=10).

CONCLUSIONS

Diversion-p64 is the largest prospective study using the p64 flow modulation device. The results of this study demonstrate that the device has a high efficacy and carries a low rate of mortality and permanent morbidity.

Utility of quantitative magnetic resonance angiography and non-invasive optimal vessel analysis for identification of complications and long-term hemodynamic changes in post-pipeline embolization patients

INTRODUCTION

Quantitative magnetic resonance angiography and non-invasive optimal vessel analysis serve as powerful tools to collect and analyze hemodynamic data from pipeline embolization patients. At our institution, patients receive post-embolization quantitative magnetic resonance angiography within 24 h of treatment and within 6 months for follow-up to evaluate pipeline patency. Here, we aim to elucidate the long-term hemodynamic changes following pipeline embolization device placement and report two cases in which in-stent stenosis was detected.

METHODS

Medical records of patients who underwent pipeline embolization device placement for an internal carotid artery aneurysm between 2017 and 2019 were reviewed. Patients who received post-procedure NOVA and follow-up NOVA were included in the study (n = 32). Location and size of aneurysm, number of pipeline embolization device deployed, and complications were collected along with the non-invasive optimal vessel analysis report (flow volume rate (ml/min), mean, systolic, and diastolic flow velocities (cm/s), and vessel diameter (mm)). Internal carotid artery vessel flow rate was measured proximal to the pipeline embolization device. Derivations of hemodynamic parameters (pulsatility index, Lindegaard ratio, and wall shear stress) were calculated.

RESULTS

The middle cerebral artery mean and diastolic flow velocities were significantly lower on the follow-up NOVA compared to the post-procedure NOVA. Moreover, follow-up NOVA demonstrated lower middle cerebral artery wall shear stress on the side with flow diversion compared to the post-procedure NOVA. In-stent stenosis, requiring intervention, was detected in two patients on follow-up NOVA. One patient had a successful balloon angioplasty of the stented internal carotid artery that resolved her stenosis. However, the second patient developed progressive stenosis and expired despite intervention.

CONCLUSION

Long-term hemodynamic adaptations post-pipeline embolization device demonstrate decreased wall shear stress and decreased mean and diastolic flow velocities in the distal middle cerebral artery, which suggest decreasing velocity of blood flow with endothelialization of the device. Furthermore, follow-up NOVA is a useful tool for detecting potential flow-related complications such as in-stent stenosis.

The value of long-term angiographic follow-up following Pipeline embolization of intracranial aneurysms

BACKGROUND

Flow diversion of intracranial aneurysms with the Pipeline Embolization Device (PED) is commonly performed, but the value of long-term angiographic follow-up has not been rigorously evaluated. Here we examine the prevalence of actionable findings of aneurysm recurrence and development of in-stent stenosis in a cohort of patients that underwent long-term angiographic follow-up at multiple time points.

METHODS

Angiographic data from eligible patients were retrospectively assessed for aneurysm occlusion, in-stent stenosis, and aneurysm regrowth or recurrence. Patients were included in this study if they underwent angiographic imaging at 6 months post-treatment and at least one later time point.

RESULTS

100% (132/132) of aneurysms occluded at 6 months remained occluded at final follow-up. 85.7% (6/7), 56.3% (27/48), and 25% (6/24) of aneurysms with entry remnant, subtotal filling, and total filling, respectively, at 6 months were completely occluded at final follow-up. 98.7% (147/149) of PED constructs that demonstrated no stenosis at 6 months demonstrated no stenosis at final angiography, while 44.4% (8/18) of PED constructs demonstrating in-stent stenosis at 6 months had resolution of stenosis on final angiography.

CONCLUSIONS

Among patients who undergo treatment of intracranial aneurysms with PED, the value of long-term angiography in patients demonstrating complete aneurysm occlusion and no in-stent stenosis on 6 month post-treatment angiography is low.

Incidence of Neo-Intimal Hyperplasia in Anterior Circulation Aneurysms Following Pipeline Flow Diversion

INTRODUCTION

Flow diversion of the distal anterior circulation cerebral vasculature may be used for management of wide necked aneurysms not amenable to other endovascular approaches. Follow-up angiography sometimes demonstrates neo-intimal hyperplasia within or adjacent to the stent, however there is limited evidence in the literature examining the incidence in MCA and ACA aneurysms. We present our experience with flow diversion of the distal vasculature and evaluate the incidence of neo-intimal hyperplasia.

MATERIALS AND METHODS

Retrospective review of patients who underwent Pipeline embolization device (PED) treatment for ruptured and unruptured anterior circulation aneurysms.

RESULTS

A total of 251 anterior circulation aneurysms were treated by pipeline flow diversion, of which 175 were ICA aneurysms, 14 were ACA aneurysms and 18 were MCA aneurysms. 6-month follow-up angiography was available in 207 patients. The incidence of neo-intimal hyperplasia was 15.9%, 21.4%, and 61.1% in ICA, ACA, and MCA aneurysms, respectively. MCA-territory aneurysms developed neo-intimal hyperplasia at a significantly higher rate than aneurysms in other vessel territories. Rates of aneurysmal occlusion did not significantly differ from those patients who did not exhibit intimal hyperplasia on follow-up angiography.

CONCLUSION

In our experience, flow diversion of distal wide-necked MCA and ACA aneurysms is a safe and effective treatment strategy. The presence of neo-intimal hyperplasia at 6-month angiography is typically clinically asymptomatic. Given the statistically higher rate of neo-intimal hyperplasia in MCA aneurysms at 6-month angiography, we propose delaying initial follow-up angiography to 12-months and maintaining dual antiplatelet therapy during that time.

Institutional experience of in-stent stenosis after pipeline flow diverter implantation: A retrospective analysis of 6 isolated cases out of 118 patients

Pipeline embolization devices (PLEDs) are flow diverting stents that have exhibited be safe and efficient in the treatment of complex aneurysms. Nevertheless, in-stent stenosis (ISS) has been reported as one of the cardinal complications associated with PLED. The association of wall malapposition and ISS in patient treated with PLED has not been reported.A retrospective study was conducted to identify patients with ISS after implantation of PLED as treatment for intracranial aneurysms from April 25, 2018 to April 24, 2019. Incidence of ISS and its associated causes such as sharp change of the PLED, distal wall malapposition, inconsistent compliance between parent artery as well as the PLED occlusion due to intimal hyperplasia and vessel tortuosity. Assessment of conservative treatment and retreatment outcomes of ISS were documented.In all, 6 ISS cases were identified by 2 independent neurointerventionalists out of 118 aneurysm patients treated with PLED. Thus, the incidence rate of ISS in patients treated with PLED was as low as 5% at our institution compared to other studies. The follow-up time for detection of ISS ranged from 6 to 12 months after implantation. Several combinations of reasons such as sharp change of the PLED, distal wall malapposition, inconsistent compliance between parent arteries as well as PLED occlusion due to intimal hyperplasia and vessel tortuosity accounted for the causes of ISS during our analysis. Conservative treatment with a combination of antiplatelet during follow-ups did not resolve the ISS in our study probably due to associated underlying factors above.

Pipeline Embolization Device Versus Stent-Assisted Coiling for Intracranial Aneurysm Treatment: A Retrospective Propensity Score-Matched Study

BACKGROUND

Pipeline embolization device (PED; Medtronic) and stent-assisted coiling (SAC) are established modalities for treatment of intracranial aneurysms.

OBJECTIVE

To comparatively assess the efficacy of these techniques.

METHODS

We conducted a retrospective analysis of patients with aneurysms treated at our institution with either PED from 2013 to 2017 or SAC from 2009 to 2015. All large (>10 mm), ruptured, fusiform, anterior communicating artery, posterior circulation aneurysms, and patients with no available follow-up imaging were eliminated before running the propensity score matching (PSM). Patients were matched using nearest neighbor controlling for: age, gender, smoking, exact location, maximal diameter, and presence of multiple aneurysms. Total hospital costs for equipment and implants were calculated from procedure product and hospital billing records, and compared between the propensity-matched pairs.

RESULTS

Out of 165 patients harboring 202 aneurysms; 170 (84.2%) were treated with the PED, and 32 (15.8%) were treated using SAC. PSM resulted in 23 matched pairs; with significantly longer follow up in the SAC group (mean 29.8 vs 14.1 mo; P = .0002). Complete occlusion rates were not different (82.6 vs 87%; P = .68), with no difference between the groups for modified Rankin Scale on last clinical follow-up, procedural complications or retreatment rates. Average total costs calculated from the hospital records, including equipment and implants, were not different between propensity-score matched pairs (P = .48).

CONCLUSION

PED placement and SAC offer equally efficacious occlusion rates, functional outcomes, procedural complication rates, and cost profiles for small unruptured anterior circulation saccular aneurysms which do not involve the anterior communicating artery.

Technical aspects of combined intrasaccular and endoluminal flow diversion

INTRODUCTION

The concurrent use of endoluminal flow diversion with coils is a viable option when treating complex or large aneurysms. Alternatives to coil embolization as an adjunctive treatment are currently limited. The Food and Drug Administration recently approved the Woven EndoBridge (WEB) device (Microvention, Aliso Viejo, California) as an intrasaccular flow diverter for wide-neck bifurcation aneurysms. We present the technical aspects of combined WEB device plus endoluminal flow diversion for the treatment of complex wide-necked intracranial aneurysms.

METHODS

A retrospective chart review of all patients treated via intrasaccular flow diversion at a single institution over the last 12 months was performed.

RESULTS

In total, seven patients underwent treatment of eight aneurysms via combined intrasaccular and endoluminal flow diversion. Of the seven patients, six were treated in a single setting. The most common aneurysm location was the posterior communicating artery. The majority of the aneurysms required steam shaping of the Via deployment catheter to place the WEB device orthogonally to the aneurysm dome. There were no complications.

CONCLUSIONS

We believe this is one of the first series reporting the combined use of the WEB device and endoluminal flow diversion for the treatment of intracranial aneurysms. This series demonstrates that the concurrent use of the WEB device with endoluminal flow diversion is safe for achieving immediate aneurysm treatment and may enhance the long-term durability in complex aneurysms.

Pipeline Embolization device for intracranial aneurysms in a large Chinese cohort: factors related to aneurysm occlusion

Background and Purpose:

The Pipeline Embolization Device (PED, Covidien/Medtronic) is widely used to treat intracranial aneurysms. This PED in China post-market multi-center registry study (PLUS) investigated safety and effectiveness of the PED for intracranial aneurysms in the Chinese population.

Methods:

This was a panoramic, consecutive, real-world cohort registry study. Patients treated with PED with or without coils between November 2014 and October 2019 at 14 centers in China were included, and those treated by parent vessel occlusion or other stents were excluded. Study outcomes included angiographic evaluation of aneurysm occlusion, complications, in-stent stenosis, and predictors of aneurysm occlusion. A central committee reviewed all imaging and endpoint events.

Results:

In total, 1171 patients with 1322 intracranial aneurysms were included. The total occlusion rate was 81.4% (787/967) at mean follow-up of 8.96 ± 7.50 months, with 77.1% (380/493) occlusion in the PED alone and 85.9% (407/474) in the PED plus coiling group. On multi-variate analysis, female sex, hyperlipidemia, vertebral aneurysms, PED plus coiling, and blood flow detained to venous phase were significant predictors of aneurysm occlusion. In posterior circulation cohort, there was no variable associated with aneurysm occlusion. In-stent stenosis predictors included current smoking and cerebral sclerosis/stenosis.

Conclusion:

In the largest series on PED of multi-center date of China, data suggest that treatment with the flow-diverting PED in intracranial aneurysms was efficacious. The treatment of PED combined coiling and blood flow detained to venous phase after PED implant were associated with aneurysmal occlusion. The occlusion rate of vertebral aneurysms was higher than other location aneurysms.

Clinical Trial Registration:

ClinicalTrials.gov identifier: NCT03831672.

Role of transcranial Doppler ultrasonography in assessing stenosis after flow diversion

INTRODUCTION

Patients after implantation of flow diverters (FD) due to intracranial aneurysms require radiological and clinical follow-up in view of in-stent stenosis. The aim of the study was to evaluate transcranial Doppler ultrasonography (TCD) as an alternative to more invasive digital subtraction angiography in monitoring patients with FD.

PATIENTS AND METHODS

Twenty-five patients after FD deployment due to internal carotid artery (ICA) aneurysms were reviewed. The degree stenosis found on TCD was compared with the results of catheter angiography. The TCD examinations were recorded from two sides at the extracranial ICA and the most proximal and distal segment of intracranial ICA. Analyzed TCD factors included: peak systolic blood flow velocity, end diastolic velocity, mean velocity, pulsatility index, and resistivity index. The side-to-side differences and ratios between particular TCD indices were calculated.

RESULTS

The cumulative frequency of angiographic in-stent stenosis was 5 of 25 (20 %). The analysis showed that pulsatility index measured on the most proximal intracranial segment of ICA is a predictor for angiographic instent stenosis (AUC = 0.854; p = 0.04; 95 % CI 0.59-1.00). The threshold of pulsatility index separating stenosis and non-stenosis groups was 1.05 with a sensitivity of 50 % and a specificity of 100 %. As the cut-off threshold of PI was set 0.75 the sensitivity and specificity was 100 % and 16.7 %, respectively.

CONCLUSIONS

The increased TCD-derived pulsatility index measured on the most proximal intracranial segment of ICA is associated with in-stent stenosis demonstrated on angiograms.

A Patient with a Large Aneurysm Complicated by Stenosis of the Internal Carotid Artery Distal to the Aneurysm in Whom Treatment Using a Pipeline Flex Was Performed

Objective

We report a case of in-stent stenosis as a complication at 6 months after the deployment of Pipeline Flex. This case necessitated retreatment for parent artery occlusion.

Case Presentation

A 55-year-old woman with right-side visual disorder was referred to our hospital for the deployment of Pipeline Flex. Cerebral digital subtraction angiography (DSA) demonstrated a large right-side paraclinoid aneurysm in combination with severe internal carotid artery (ICA) stenosis just beyond the aneurysm. We deployed Pipeline Flex under general anesthesia. After deployment, we performed angioplasty through the Pipeline. Six months after deployment, this patient exhibited exacerbation of visual disorder. Follow-up DSA revealed in-stent stenosis at 6 months after the deployment of Pipeline Flex. Therefore, we performed parent artery occlusion. Right-side visual disorder was improved in this patient.

Conclusion

If Pipeline is deployed for patients with ICA stenosis just beyond an aneurysm, we need to be aware of in-stent stenosis after deployment.