Platelet testing in flow diversion: a review of the evidence

Hyperacute in-Stent Thrombosis Causing Large Vessel Occlusion after Stent-Assisted Aneurysm Coiling Secondary to Complete Clopidogrel and Prasugrel Resistance: a Case Report

Dual antiplatelet therapy (DAPT) is standard treatment for endoluminal stent insertion, and complete resistance to DAPT is rare. A case of in-stent thrombosis occurring 3 hours after stent-assisted coiling of internal carotid artery aneurysm is presented despite compliance with DAPT. Platelet function tests (PFTs) revealed complete clopidogrel and prasugrel resistance.

Clopidogrel Hyperresponsiveness and Hemorrhagic Complications Using On-Label Clopidogrel Dosing after Pipeline Embolization

Introduction: Clopidogrel hyperresponsiveness is a timely topic, with wide ranging reports of hemorrhagic complications, using various clopidogrel dosing strategies following neuroendovascular procedures. This study serves to investigate hemorrhagic complications using standard clopidogrel doses and timing of these complications in relation to the procedure. Materials and Methods: Retrospective cohort of consecutive adult patients undergoing flow diversion with Pipeline Embolization Device (PED) at an academic medical center, receiving on-label clopidogrel doses. Patients with clopidogrel hyperresponsiveness (VerifyNowTM P2Y12 reaction unit (PRU) ≤ 70) were compared to those who were normoresponsive. The primary outcome is the rate of hemorrhagic complications between groups. Results: Of 148 included patients, 54 (36.5%) were identified as clopidogrel hyperresponsive (PRU ≤ 70) and 94 (63.5%) as clopidogrel normoresponsive (PRU 71 - 194). There were no hemorrhagic complications observed in patients who were clopidogrel hyperresponsive, with 5 occurring in patients who were normoresponsive (P = 0.09). Three (60%) of the hemorrhages were intracranial with most occurring intra-procedure or within the first week of the procedure. Age > 60 years was the only candidate predictor for hemorrhagic complications (P = 0.004). Conclusion: Our findings are contradictory, with lower hemorrhagic complications in clopidogrel hyperresponders than prior literature, and most occurring intra-op or in the immediate acute post-op phase.

Thromboembolic Events in the Posterior Circulation After Flow Diversion-A Closer Look at Coverage of the Posterior Cerebral Artery

BACKGROUND

Flow diversion for bifurcation aneurysms requires excluding one of the branches from the parent artery, raising concern for ischemic events. We evaluated thromboembolic events and their relationship with covering the origin of the posterior cerebral artery (PCA).

METHODS

This retrospective analysis included patients with confirmed basilar and proximal PCA aneurysms treated with flow diversion between 2013 and 2023. Procedures were classified according to the coverage of the origin of the PCA. Thromboembolic events associated with the excluded PCA were evaluated.

RESULTS

Of the total 28 aneurysms included, 7 were at the basilar tip, 16 in the basilar trunk, and 5 in the first segment of the PCA; 15 were treated by excluding one of the PCAs. Dual antiplatelet therapy included aspirin and ticagrelor (57.1%), aspirin and clopidogrel (35.7%), or aspirin and prasugrel (3.57%). Complete and near-complete aneurysm occlusion was achieved in 80.8% of the aneurysms treated at a median follow-up of 12.31 months. Thromboembolic complications occurred in 3 patients (2 with basilar perforator stroke and 1 with basilar in-stent thrombosis). However, the difference in these events was not statistically significant between patients with PCA coverage and those without (P = 0.46). Diminished flow and a lack of flow was seen in 8 and 7 of the covered vessels, respectively. A modified Rankin scale score of ≤2 was reported for 89.3% of patients at a median clinical follow-up of 5.5 months.

CONCLUSIONS

The incidence of thromboembolic events is high in distal basilar and proximal PCA aneurysms; however, PCA coverage was not associated with their occurrence. There was no difference in postprocedural disability between patients whose aneurysms were treated by excluding one of the PCAs and those who were not.

Efficacy and safety of low dose intravenous cangrelor in a consecutive cohort of patients undergoing neuroendovascular procedures

BACKGROUND

Cangrelor is an intravenous P2Y12 inhibitor with rapid onset and fast offset of antiplatelet action. Dose adjusted cangrelor based on platelet function testing is suggested to be advantageous for use during neuroendovascular procedures. In this study, we aimed to assess the efficacy and safety of this strategy.

METHODS

This retrospective study included consecutive patients who received low dose intravenous cangrelor (5 µg/kg; infusion 1 µg/kg/min) for ruptured (RIA) and unruptured (UIA) intracranial aneurysms, and acute ischemic stroke (AIS). Indications were acute stenting or intraluminal thrombus. Outcomes were assessed at 24 hours by brain CT and CT angiography. The primary efficacy outcome was the rate of stent occlusion or persistent intraluminal thrombus. The primary safety outcome was the rate of major hemorrhages.

RESULTS

101 patients (56 men; median age (IQR) 59 (51-70) years) received low dose cangrelor for acute stenting (79/101 (78%)) and intraprocedural thrombus (22/101 (22%)). Overall, 5 (4.9%) patients experienced stent occlusion within 24 hours (RIA 3/28; AIS 2/52). There were no cases of failure among UIA patients. Stent mis-opening (fish mouthing or stenosis >50%) was significantly associated with stent occlusion (P<0.001). The overall rate of major hemorrhage was 2% (2/101), which occurred in AIS patients. Platelet reactivity unit (PRU) values were lower in those presenting with major hemorrhage (PRU 4 (SD 1.4) vs PRU 60 (SD 63); P=0.043). Mortality rate after cangrelor related hemorrhage was 1%.

CONCLUSIONS

Low dose cangrelor appears to be effective in preventing stent thrombosis and arterial patency with a low hemorrhagic risk.

Discordance in tests used to detect inhibition of the P2Y12 receptor in patients undergoing interventional neuroradiology procedures

BACKGROUND

Clopidogrel is an inhibitor of the P2Y12 platelet receptor but testing to demonstrate a drug effect is controversial since there are often discordant results between different tests methods.

METHODS

Samples from patients taking clopidogrel prior to intracranial flow-diversion procedures were tested using light transmission aggregometry (LTA), whole blood impedance aggregometry (WBIA) and the VerifyNow device (VND). Samples were classified as concordant if all test results were either responsive (inhibition) or resistant. Discordant results were separated using the VND into those with a responsive versus a resistant test result.

RESULTS

Samples from 96 patients were studied. Concordance for all three tests was seen in 53/96 (55%) of samples, of which 41 (43%) were responsive and 12 (12%) were resistant. Discordance was observed in 43 samples (45%), 37 (28%) of which were caused by responsive VND and either a resistant WBIA or LTA and 6 (7%) of which were caused by a resistant VND but a responsive test result using either WBIA or LTA. These two discordant groups differed in both platelet count and hematocrit, but no such difference was present between the two concordant groups.

CONCLUSION

Discordance in P2Y12 inhibition testing may be partly explained by sample platelet count and hematocrit.

Role of neuromodulation in acute pain settings

Peripheral nerve stimulation (PNS), a type of neuromodulatory technique, is increasingly used to treat chronic pain syndromes. PNS has also recently gained popularity as a viable adjunct analgesic modality in acute pain settings, where the practice primarily relies on using boluses or infusion of local anesthetics for nerve blockade, followed by stimulation to extend the analgesia. There is some early promise in PNS for perioperative analgesic control, but considerable obstacles must be addressed before it can be implemented into standard practice. In this daring discourse, we explore the possibilities and constraints of using the PNS paradigm in acute pain.

Comparison of Clopidogrel, Prasugrel and Ticagrelor Response of Patients by PFA-100-Innovance Test Results

Devices such as stents and flow diverters require the use of safe and fast antiplatelet therapy. We aimed to compare the responses to clopidogrel, prasugrel, and ticagrelor by assessing the Platelet Function Analysis (PFA-100)-Innovance test results of patients undergoing endovascular stenting to determine their resistance rates. Sixty-one women and 55 men, aged 18-87 years, were included in this study. Patients were divided into three groups: clopidogrel treatment, prasugrel treatment, and ticagrelor treatment. The systemic diseases of the patients, especially hypertension and diabetes, were recorded. The test results were evaluated according to the results for the collagen/epinephrine (COL-EPI), collagen/adenosine (COL-ADP), and P2Y results. The PFA-100-Innovance results for COL-EPI and P2Y were significantly higher for patients treated with prasugrel and ticagrelor compared with patients treated with clopidogrel (COL-EPI, p = 0.001; P2Y, p = 0.001). Clopidogrel resistance was identified in 31 patients (26.7%), and prasugrel resistance was identified in 4 patients (3.4%). Ticagrelor resistance was not detected. Therefore, 30.1% of patients were classified as drug-resistant. Perioperative bleeding was not detected in any patient. Hypertension was the most common disease recorded for patients being treated for cerebral aneurysm, and diabetes was the most common disease recorded for patients who underwent peripheral artery stenting (p = 0.002). Potent antiplatelet agents, such as prasugrel and ticagrelor, have a low rate of resistance but are associated with an increased bleeding risk. Thus, the choice of a suitable drug during the treatment window remains a critical factor when determining treatment strategies.

Endovascular treatment of unruptured intracranial aneurysms with flow diverters: A retrospective long-term single center analysis

PURPOSE

The introduction of flow diverters (FDs) in 2007 greatly enhanced the treatment of intracranial aneurysms. Here, we present our long-term clinical experience in treating unruptured intracranial aneurysms with FDs.

METHODS

107 patients with unruptured aneurysms and treated with an FD between 2010 and 2019 were retrospectively reviewed. Aneurysm occlusion, procedural complications, and clinical outcome were evaluated.

RESULTS

Angiographic follow-up was available for 93 patients with a mean long-term follow-up time of 28.4 ± 21.6 months. Additional coiling was performed in 15.1% of patients (n = 14). Adequate aneurysm occlusion (Kamran grades 3 and 4) at long-term follow-up was achieved in 94.6% of patients (n = 88). 3.2% (n = 3) required endovascular retreatment since the last follow-up showed a lack of aneurysm occlusion (Kamran grade 0) due to a foreshortening of the FD. Incomplete opening of the FD and parent vessel occlusion was seen in 1.1% (n = 1) and 3.2% (n = 3) of patients, respectively. In-stent stenosis was observed in 57% (n = 53) of cases at short-term follow-up and 22.6% (n = 21) at long-term, which were moderate and asymptomatic overall. In-stent stenosis decreased significantly between short- and long-term follow-ups (31.4 ± 17.0% vs 9.7 ± 13.6%, respectively; p ≤ 0.001). Thromboembolic and hemorrhagic events occurred in 7.5% (n = 7) and 1.1% (n = 1) of patients, respectively. Good clinical outcome (modified Rankin scale: 0-2) was obtained in 97.8% (n = 91) leading to an overall treatment-related morbidity of 2.2% (n = 2). There was no procedural mortality.

CONCLUSION

Our study shows that FD treatment of unruptured intracranial aneurysms is effective and safe with high occlusion rates and low rates of permanent morbidity at long-term follow-up.

A Sticky Situation: Variable Agreement Between Platelet Function Tests Used to Assess Anti-platelet Therapy Response

Background

Platelet function testing to monitor antiplatelet therapy is important for reducing thromboembolic complications, yet variability across testing methods remains challenging. Here we evaluated the agreement of four different testing platforms used to monitor antiplatelet effects of aspirin (ASA) or P2Y₁₂ inhibitors (P2Y12-I).

Methods

Blood and urine specimens from 20 patients receiving dual antiplatelet therapy were analyzed by light transmission aggregometry (LTA), whole blood aggregometry (WBA), VerifyNow PRUTest and AspirinWorks. Result interpretation based on pre-defined cutoff values was used to calculate raw agreement indices, and Pearson's correlation coefficient determined using individual units of measure.

Results

Agreement between LTA and WBA for P2Y12-I-response was 60% (r = 0.65, high-dose ADP; r = 0.75, low-dose ADP). VerifyNow agreed with LTA in 75% (r = 0.86, high-dose ADP; r = 0.75, low-dose ADP) and WBA in 55% (r = 0.57) of cases. Agreement between LTA and WBA for ASA-response was 45% (r = 0.09, high-dose collagen WBA; r = 0.19, low-dose collagen WBA). AspirinWorks agreed with LTA in 60% (r = 0.32) and WBA in 35% (r = 0.02, high-dose collagen WBA; r = 0.08, low-dose collagen WBA) of cases.

Conclusions

Overall agreement varied from 35 to 75%. LTA and VerifyNow demonstrated the highest agreement for P2Y12-I-response, followed by moderate agreement between LTA and WBA. LTA and AspirinWorks showed moderate agreement for aspirin response, while WBA showed the weakest agreement with both LTA and AspirinWorks. The results from this study support the continued use of LTA for monitoring dual antiplatelet therapy, with VerifyNow as an appropriate alternative for P2Y12-I-response. Integration of results obtained from these varied testing platforms with patient outcomes remains paramount for future studies.

Flow diversion for acutely ruptured intracranial aneurysms treatment: A retrospective study and literature review

OBJECTIVE

Flow diversion is becoming an increasingly established practice for the treatment of acutely ruptured intracranial aneurysms. In this study the authors present a literature review and meta-analysis, adding a retrospective review of institutional registry on emergency treatment of aRIA with flow diverter stent.

MATERIALS AND METHODS

A systematic search of PubMed, SCOPUS, Ovid MEDLINE, and Ovid EMBASE was performed on April 20^th, 2021, extrapolating 35 articles. R language 'meta' and 'metafor' packages were used for data pooling. The DerSimonian-Laird model was used to calculate the pooled effect. The I² value and Q statistic evaluated study heterogeneity. Additionally, the authors retrospectively reviewed their institutional database for the treatment and outcomes of all patients with acutely ruptured intracranial aneurysms treated with flow diverter stent placement from May 2010 to November 2020 was performed.

RESULTS

From the systematic literature review and meta-analysis, the pooled proportion of complete aneurysm occlusion was 78%, with a pooled rate of 79%, 71%, 80%, and 50% for dissecting, saccular, fusiform, and mycotic aneurysms, respectively. The pooled proportion of aneurysm rebleeding and intrastent stenosis was 12% and 15% respectively, for a total of 27% rate. The analysis of authors retrospective register showed an overall mortality rate of 16.7% (3/18), with a low but not negligible postprocedural rebleeding and intrastent thrombosis rates (5.6% and 11.1% respectively).

CONCLUSION

Although increasingly utilized in the management of selected patients with acutely ruptured intracranial aneurysms, flow diversion for acutely ruptured intracranial aneurysms treatment presents rebleeding and intrastent stenosis rates not negligible.

First Experience of Three Neurovascular Centers With the p64MW-HPC, a Low-Profile Flow Diverter Designed for Proximal Cerebral Vessels With Antithrombotic Coating

Background: In the last decade, flow diversion (FD) has been established as hemodynamic treatment for cerebral aneurysms arising from proximal and distal cerebral arteries. However, two significant limitations remain—the need for 0.027” microcatheters required for delivery of most flow diverting stents (FDS), and long-term dual anti-platelet therapy (DAPT) in order to prevent FDS-associated thromboembolism, at the cost of increasing the risk for hemorrhage. This study reports the experience of three neurovascular centers with the p64MW-HPC, a FDS with anti-thrombotic coating that is implantable via a 0.021” microcatheter.

Materials and methods: Three neurovascular centers contributed to this retrospective analysis of patients that had been treated with the p64MW-HPC between March 2020 and March 2021. Clinical data, aneurysm characteristics, and follow-up results, including procedural and post-procedural complications, were recorded. The hemodynamic effect was assessed using the O'Kelly–Marotta Scale (OKM).

Results: Thirty-two patients (22 female, mean age 57.1 years) with 33 aneurysms (27 anterior circulation and six posterior circulation) were successfully treated with the p64MW-HPC. In 30/32 patients (93.75%), aneurysmal perfusion was significantly reduced immediately post implantation. Follow-up imaging was available for 23 aneurysms. Delayed aneurysm perfusion (OKM A3: 8.7%), reduction in aneurysm size (OKM B1-3: 26.1%), or sufficient separation from the parent vessel (OKM C1-3 and D1: 65.2%) was demonstrated at the last available follow-up after a mean of 5.9 months. In two cases, device thrombosis after early discontinuation of DAPT occurred. One delayed rupture caused a caroticocavernous fistula. The complications were treated sufficiently and all patients recovered without permanent significant morbidity.

Conclusion: Treatment with the p64MW-HPC is safe and feasible and achieves good early aneurysm occlusion rates in the proximal intracranial circulation, which are comparable to those of well-established FDS. Sudden interruption of DAPT in the early post-interventional phase can cause in-stent thrombosis despite the HPC surface modification. Deliverability via the 0.021” microcatheter facilitates treatment in challenging vascular anatomies.

Ticagrelor versus Clopidogrel in the Dual Antiplatelet Regimen for Intracranial Stenting or Flow-Diverter Treatment for Unruptured Cerebral Aneurysms: A Single-Center Cohort Study

BACKGROUND AND PURPOSE

Ticagrelor is a novel P2Y12 antagonist, and little is known about its efficacy and safety in the endovascular treatment of aneurysms. This study evaluated the efficacy and safety of ticagrelor versus clopidogrel for stent-assisted coiling or flow-diversion treatment in patients with unruptured cerebral aneurysms.

MATERIALS AND METHODS

From November 2003 to February 2019, two hundred one patients (mean age, 57.5 years; 156 women) with 233 unruptured aneurysms underwent stent-assisted coiling or flow-diversion treatment. All patients received antiplatelet therapy of aspirin plus clopidogrel (clopidogrel group, 121 patients with 140 aneurysms) or aspirin plus ticagrelor (ticagrelor group, 80 patients with 93 aneurysms). The clinical and radiologic data in each group were retrospectively reviewed and compared.

RESULTS

Two hundred thirty-six procedures were performed, including stent-assisted coiling (n = 101) and flow diversion (n = 135). At 90 days, the primary outcome-a composite of any stroke and death-occurred in 9.9% of the clopidogrel group and 8.6% of the ticagrelor group (P = .822). Ischemic stroke occurred in 10 (7.0%) of the clopidogrel group and 7 (7.5%) of the ticagrelor group (P > .999). Disabling stroke occurred in 4 (2.8%) in the clopidogrel group and in 4 (4.3%) in the ticagrelor group (P = .716). Ninety-day death occurred in 3 (2.1%) in the clopidogrel group and 1 (1.1%) in the ticagrelor group (P > .999). Any bleeding at 90 days occurred in 13 (9.2%) in the clopidogrel group and 6 (6.5%) in the ticagrelor group (P = .479).

CONCLUSIONS

Ticagrelor appears to be as effective and safe as clopidogrel in stent-assisted coiling or flow-diversion treatment for unruptured cerebral aneurysms.

Retrospective analysis of intracranial aneurysms after flow diverter treatment including color-coded imaging (syngo iFlow) as a predictor of aneurysm occlusion

PURPOSE

Flow Diverters (FD) have immensely extended the treatment of cerebral aneurysms in the past years. Complete aneurysm occlusion is a process that often takes a certain amount of time and is usually difficult to predict. Our aim was to investigate different syngo iFlow parameters in order to predict aneurysm occlusion.

METHODS

Between 2014 and 2018 patients with unruptured cerebral aneurysms treated with a FD were reviewed. Aneurysm occlusion and complication rates have been assessed.In addition, various quantitative criteria were assessed using syngo iFlow before, after the intervention, and after short and long-term digital subtraction angiography (DSA).

RESULTS

A total of 66 patients hosting 66 cerebral aneurysms were included in this study. 87.9% (n = 58) aneurysms in the anterior and 12.1% (n = 8) in the posterior circulation were treated. Adequate aneurysm occlusion at long-term follow-up (19.05 ± 15.1 months) was achieved in 90.9% (n = 60). Adequately occluded aneurysm revealed a significantly greater peak intensity delay (PI-D, p = 0.008) and intensity decrease ratio (ID-R, p < 0.001) compared to insufficiently occluded aneurysms. Increased intra-aneurysmal contrast agent intensity (>100%) after FD implantation resulted in an ID-R < 1, which was associated with aneurysm growth during follow-up DSA. Retreatment with another FD due to foreshortening and/or aneurysm growth was performed in 10.6% (n = 7). Overall morbidity and mortality rates were 1.5% (n = 1) and 0%.

CONCLUSION

The applied syngo iFlow parameters were found to be useful in predicting adequate aneurysm occlusion and foresee aneurysm growth, which might indicate the implantation of another FD.

Use of pCONUS HPC for the treatment of unruptured wide-necked bifurcation aneurysms: early clinical experience using single antiplatelet therapy

BACKGROUND

In recent years, a growing number of stents and stent-like devices have become available to facilitate the treatment of challenging aneurysms. However, the need for dual antiplatelet therapy can limit their use, especially in ruptured aneurysms. The hydrophilic polymer coating (pHPC, phenox) is a novel glycan-based multilayer polymer that reduces platelet adhesion. This study aims to report our initial experience using the pCONUS HPC device for the treatment of unruptured wide-necked bifurcation aneurysms (WNBA) using acetylsalicylic acid (ASA) as single antiplatelet therapy (SAPT).

METHODS

We retrospectively identified all patients who were treated with the pCONUS HPC for unruptured WNBA in a multi-staged procedure using ASA as SAPT. Records were made of periprocedural complications, clinical outcome and angiographic and clinical follow-up.

RESULTS

We identified 15 patients with 15 WNBA. The average age was 69 years old (range, 41-76). Seven aneurysms were located in the middle cerebral artery, five in the anterior communicating artery, two at the basilar tip and one in the posterior communicating artery. Immediate post-treatment angiography showed five aneurysms with modified Raymond-Roy classification (mRRC) grade I and four aneurysms with mRRC grade II. There were no haemorrhagic complications. Four patients developed thrombus formation during the second treatment session, all of them completely resolving after administration of glycoprotein IIb/IIIa antagonists. Angiographic follow-up data were available for 10 patients and showed adequate occlusion (mRRC I or II) in eight aneurysms (80%). In-stent stenosis was observed in one patient whereas two patients showed de novo stenosis in one of the efferent branches.

CONCLUSIONS

This early experience on the use of the pCONUS HPC device suggests that it can be useful for treating unruptured WNBA under ASA as SAPT. Further investigation with a randomised treatment registry and larger cohort is needed.

Cangrelor dose titration using platelet function testing during cerebrovascular stent placement

BACKGROUND

Optimal antiplatelet inhibition is vital during cerebrovascular stenting procedures, yet no standardized recommendation exists for antithrombotic therapy in these scenarios. Cangrelor is an intravenous P2Y12 inhibitor with a favorable pharmacokinetic profile for use during neuroendovascular stenting.

METHODS

A retrospective review of all neuroendovascular patients who underwent stenting between 1 January 2019 and 22 March 2020 and were treated with cangrelor was conducted. Thirty-seven patients met inclusion criteria.

RESULTS

All patients were administered a bolus of 5 mcg/kg of cangrelor followed by a maintenance infusion. Antiplatelet effects of cangrelor were monitored using platelet reactivity units (PRU). Based on the initial PRU, seven patients' doses were adjusted with subsequent PRUs in or near the goal range of 50-150. One patient experienced an acute intraprocedural occlusion likely related to a subtherapeutic PRU which subsequently resolved with cangrelor dose adjustment and intra-arterial tirofiban administration, and one patient experienced a post-procedure stent occlusion which required a thrombectomy and intra-arterial tirofiban administration. No hemorrhagic complications occurred.

DISCUSSION

Cangrelor utilization during neuroendovascular stenting with maintenance doses of <2 mcg/kg/min with dose adjustments based on platelet function testing has not been previously described. Cangrelor presents many advantages compared to standard therapy in patients undergoing stent placement related to its pharmacokinetic profile, rapid onset of action, ease of transition to oral P2Y₁₂ antiplatelet agents, and measurability.

CONCLUSION

Cangrelor is a promising alternative to currently available therapies, especially in patients with a high hemorrhagic risk.

A 70-Year-Old Female with Unexpected Platelet Function Testing Results

A 70-year-old female with a history of hypertension and left A2 segment aneurysm was scheduled for pipeline embolization device (PED) placement. Preinterventional antiplatelet prophylaxis included aspirin and ticagrelor. Unexpectedly, after 13 days of treatment, VerifyNow showed a P2Y12 reaction unit (PRU) value of 216, approximately >5 times the mean PRU of other patients on aspirin and ticagrelor. We confirmed platelet reactivity and ticagrelor resistance with light transmission aggregometry. Antiplatelet therapy was switched to prasugrel, and aspirin was continued. Eight days later, the P2Y12 reaction value (PRU) was 164. PED was placed without complications. Unlike clopidogrel, ticagrelor is a direct P2Y12 inhibitor that does not require metabolism to an active metabolite. Ticagrelor resistance is very rarely reported. To the best of our knowledge, there has been no case of ticagrelor resistance reported in the context of pre-PED placement prophylaxis.

Antiplatelet Therapy in Flow Diversion

Dual antiplatelet therapy is typically employed as a means to mitigate thromboembolic complications after deployment of flow diverters, most commonly consisting of aspirin with either clopidogrel, prasugrel, or ticagrelor. Recent studies have demonstrated at least similar efficacy for ticagrelor as compared to clopidogrel in the form of periprocedural complications and angiographic results. Though controversial, systematic reviews of platelet function assay usage have demonstrated greater rates of thrombotic complications in antiplatelet hyporesponders and greater rates of hemorrhagic complications in hyperresponders. Though in its infancy, the management of antiplatelet therapy for acutely ruptured aneurysms treated with flow diversion is not yet standardized, with approaches including intravenous glycoprotein IIb-IIIa inhibitors and subsequent antiplatelet loading vs antiplatelet loading, response assessment, and subsequent treatment.

Outcome of intracranial flow diversion according to the antiplatelet regimen used: a systematic review and meta-analysis

Background

Thromboembolic complications are not uncommon in patients undergoing neurointerventional procedures. The use of flow diverting stents is associated with higher risks of these complications despite current dual antiplatelet regimens.

Objective

To explore contemporary evidence on the safety of emerging dual antiplatelet regimens in flow diverting stenting procedures.

Methods

We performed a systematic review and meta-analysis to identify relevant articles in electronic databases, and relevant references. Studies reporting the complications and mortality of flow diverting stenting procedures using acetyl salicylic acid (ASA) + ticagrelor or ASA + prasugrel compared with ASA + clopidogrel were included.

Results

Of 452 potentially relevant studies, we identified 49 studies (2526 patients) which reported the safety of ticagrelor or prasugrel for pooled analysis, and five studies (1005 patients) for meta-analysis. The pooled overall mortality in all studies was 2.14%, ischemic complications 6.89%, and hemorrhagic complications 3.68%. The use of ticagrelor or prasugrel was associated with a lower risk of mortality compared with clopidogrel (RR=4.57, 95% CI 1.23 to 16.99; p=0.02). Considering ischemic events, ASA + clopidogrel was as safe as ASA + prasugrel (RR=0.55, 95% CI 0.11 to 2.74; p=0.47) and ASA + ticagrelor (RR=0.74, 95% CI 0.32 to 1.74; p=0.49). ASA +ticagrelor was not associated with a higher risk of hemorrhagic complications (RR=0.92, 95% CI 0.27 to 3.16; p=0.89).

Conclusions

Evidence suggests that dual antiplatelet regimens including ticagrelor or prasugrel are safe for patients undergoing flow diversion procedures. Regimens using ticagrelor were associated with better survival than those using clopidogrel in the included studies.

Predictors of Clinical Outcome After Treatment of Intracranial Aneurysms with the Pipeline Embolization Device

BACKGROUND

Flow-diverting stents have revolutionized the endovascular treatment of intracranial aneurysms. The purpose of this study is to identify predictors of adverse outcomes associated with the pipeline embolization device (PED).

METHODS

A retrospective analysis of all patients treated with PED at a single high-volume center from January 2014 to September 2018. Patient outcomes, neurologic morbidity/mortality, and other clinical variables were analyzed.

RESULTS

We treated 204 aneurysms in 170 patients with PED. Mean length of follow-up was 11 months. Most (181) aneurysms (89%) were located in the anterior circulation, and 23 (11%) were found in the posterior circulation. Most aneurysms were saccular (82%), followed by fusiform (11%), blister (4%), and dissecting pseudoaneurysms (3%). Mean aneurysm size was 8.2 + 5.7 mm with 145 (71%) small aneurysms (≤10 mm), 53 (26%) large aneurysms (between 10 and 25 mm), and 6 (3%) giant aneurysms (≥25 mm). Ninety-two percent of aneurysms were unruptured, and 8% were ruptured. The overall major neurologic morbidity/mortality was 4.7% and 1.8%, respectively. The all-cause mortality was 2.9%. Predictors of neurologic morbidity/mortality included the baseline modified Rankin Scale (P = 0.001), aneurysm neck size (P = 0.003), aneurysm size (P = 0.006), anterior versus posterior location (P = 0.02), and rupture at presentation (0.006). The P2Y12 Reactivity Unit, parent vessel diameter, and patient age did not correlate with adverse events.

CONCLUSIONS

The PED has a satisfactory safety profile in both on- and off-label indications. A poor clinical patient baseline, wider aneurysm neck or larger size, and rupture predict an increased risk of an unfavorable outcome.

Anti-thrombogenic coatings for devices in neurointerventional surgery: Case report and review of the literature

BACKGROUND

Stent-assisted coiling and extra-saccular flow diversion require dual anti-platelet therapy due to the thrombogenic properties of the implants. While both methods are widely accepted, thromboembolic complications and the detrimental effects of dual anti-platelet therapy remain a concern. Anti-thrombogenic surface coatings aim to solve both of these issues. Current developments are discussed within the framework of an actual clinical case.

CASE DESCRIPTION

A 33-year-old male patient lost consciousness while doing sport and was administered 500 mg acetylsalicylic acid on site. Computed tomography revealed a massive subarachnoid haemorrhage, and digital subtraction angiography showed an aneurysm of the right middle cerebral artery. Stent-assisted coiling using a neck bridging device with a hydrophilic coating (pCONUS_HPC) was considered as an appropriate approach. Another 500 mg acetylsalicylic acid IV was given. After the single anti-platelet therapy was seen to be effective, a pCONUS_HPC was implanted, and the aneurysm sac subsequently fully occluded using coils. No thrombus formation was encountered. During the following days, 2 × 500 mg acetylsalicylic acid IV daily were required to maintain single anti-platelet therapy, monitored by frequent response testing. Follow-up digital subtraction angiography after 13 days confirmed the occlusion of the aneurysm and the patency of the middle cerebral artery.

CONCLUSION

A variety of ways to reduce the thrombogenicity of neurovascular stents is discussed. Hydrophilic surface coatings are a valid concept to improve the haemocompatibility of neurovascular implants while avoiding the use of dual anti-platelet therapy. Phosphorylcholine and phenox hydrophilic polymer coating are currently the most promising candidates. This concept is supported by anecdotal experience. However, formalised registries and randomised trials are currently being established.

Treatment of intracranial vertebral artery dissecting aneurysms involving the posterior inferior cerebellar artery origin

Background

Vertebral artery dissecting aneurysm (VADA) involving the origin of the posterior inferior cerebellar artery (PICA) is a complex disease entity in which the dual goals of preventing future rebleeding and maintaining perfusion of the lateral medulla must be considered. We present an illustrative case and review the literature surrounding treatment strategies.

Case Description

We report a patient presenting with extensive subarachnoid hemorrhage due to rupture of an intracranial VADA involving the PICA origin. After consideration of the patient's cerebral vasculature and robustness of collaterals, a flow-diverting stent was placed with angiographic resolution of the lesion and maintenance of antegrade PICA flow. Ultimately, the patient experienced a contralateral intraparenchymal hemorrhage leading to death. Review of the literature identified 124 cases of VADA involving the PICA origin described over the past decade. The methods of surgical and endovascular treatment of these cases were reviewed, with particular focus on the rationale of treatment, outcomes, and complications.

Conclusion

Numerous treatment options for VADA involving PICA have been reported with different risk and benefit profiles. Flow-diverting stents appear to offer the most favorable balance of securing the aneurysm and avoiding medullary infarction, but the risks and optimal anti-thrombotic treatment strategy are incompletely understood. In select cases, in which the surgical risk is low or in which the anatomy is favorable (e.g., nondominant parent vessel or robust collateral circulation in the involved territories), parent artery trapping with or without microsurgical revascularization can be considered.

A computational model for prediction of clot platelet content in flow-diverted intracranial aneurysms

Treatment of intracranial aneurysms with flow-diverting stents is a safe and minimally invasive technique. The goal is stable embolisation that facilitates stent endothelialisation, and elimination of the aneurysm. However, it is not fully understood why some aneurysms fail to develop a stable clot even with sufficient levels of flow reduction. Computational prediction of thrombus formation dynamics can help predict the post-operative response in such challenging cases. In this work, we propose a new model of thrombus formation and platelet dynamics inside intracranial aneurysms. Our novel contribution combines platelet activation and transport with fibrin generation, which is key to characterising stable and unstable thrombus. The model is based on two types of thrombus inside aneurysms: red thrombus (fibrin- and erythrocyte-rich) can be found in unstable clots, while white thrombus (fibrin- and platelet-rich) can be found in stable clots. The thrombus generation model is coupled to a CFD model and the flow-induced platelet index (FiPi) is defined as a quantitative measure of clot stability. Our model is validated against an in vitro phantom study of two flow-diverting stents with different sizing. We demonstrate that our model accurately predicts the lower thrombus stability in the oversized stent scenario. This opens possibilities for using computational simulations to improve endovascular treatment planning and reduce adverse events, such as delayed haemorrhage of flow-diverted aneurysms.

Predictive value of platelet reactivity unit (PRU) value for thrombotic and hemorrhagic events during flow diversion procedures: a meta-analysis

BACKGROUND AND PURPOSE

Platelet function testing prior to flow diversion procedures, although initially heavily debated, has seen a substantial increase in its adoption to assess the risk of operative and perioperative thrombotic and hemorrhagic events. This meta-analysis was conducted to assess platelet function testing, particularly the VerifyNow Platelet Reactivity Unit (PRU) assay, for a relationship between the reported assay PRU value and thrombotic and hemorrhagic events.

MATERIALS AND METHODS

The currently available literature (2013-2018) was surveyed with PubMed and Google Scholar searches. Included studies were those for which there were at least 30 cases during the study period, for which VerifyNow platelet reactivity unit values were obtained prior to the procedures and for which intraoperative and perioperative adverse events were noted. PRU value cut-offs ranging from >200 to >240 comprised the hyporesponse group while values ranging from <60 to <70 comprised the hyper-response group. The data were subject to statistical analysis to assess the relationship between PRU values and thrombotic and hemorrhagic events. The collected data were subsequently statistically analyzed to assess for publication bias.

RESULTS

The searches yielded 27 studies, of which 12 met the inclusion criteria for the meta-analysis. The meta-analysis included data from 1464 reported Pipeline cases. The study included 273 men and 1177 women with a mean age across the analyzed procedures of 58 years (range 25-85). After loading with antiplatelet medications, preprocedural platelet hyper-responsiveness was associated with a greater incidence of hemorrhagic events with an increased absolute risk of 12%, but showed no relationship with thrombotic events. Preprocedural platelet hyporesponsiveness was associated with a greater incidence of thrombotic events with an absolute risk of 15%, but showed no relationship with hemorrhagic events.

CONCLUSIONS

VerifyNow PRU values that correspond to platelet hyporesponse or hyper-response to dual antiplatelet therapy are associated with a higher risk of thrombotic and hemorrhagic events, respectively. Thus, the PRU value may offer some predictive value for these events.

Pipeline-assisted coil embolization of a large middle cerebral artery pseudoaneurysm in a 9-month-old infant: experience from the youngest flow diversion case

Intracranial aneurysms in the pediatric population are rare entities. The authors recently treated a 9-month-old infant with a 19-mm recurrent, previously ruptured, and coil-embolized left middle cerebral artery (MCA) pseudoaneurysm, which was treated definitively with single-stage Pipeline-assisted coil embolization. The patient was 5 months old when she underwent resection of a left temporal Grade 1 desmoplastic infantile ganglioglioma at an outside institution, which was complicated by left MCA injury with a resultant 9-mm left M1 pseudoaneurysm. Within a month, the patient had two aneurysmal rupture events and underwent emergency craniectomy for decompression and evacuation of subdural hematoma. The pseudoaneurysm initially underwent coil embolization; however, follow-up MR angiography (MRA) revealed aneurysm recanalization with saccular enlargement to 19 mm. The patient underwent successful flow diversion-assisted coil embolization at 9 months of age. At 7 months after the procedure, follow-up MRA showed complete aneurysm occlusion without evidence of in-stent thrombosis or stenosis. Experience with flow diverters in the pediatric population is still in its early phases, with the youngest reported patient being 22 months old. In this paper the authors report the first case of such a technique in an infant, whom they believe to be the youngest patient to undergo cerebral flow diversion treatment.

Antiplatelet therapy and the risk of ischemic and hemorrhagic complications associated with Pipeline embolization of cerebral aneurysms: a systematic review and pooled analysis

BACKGROUND

Pipeline embolization devices (PEDs) are increasingly used in the treatment of cerebral aneurysms. Yet, major ischemic or hemorrhagic complications after PED treatment associated with antiplatelet regimens are not well-established.

OBJECTIVE

To investigate the risk of ischemic and hemorrhagic complications associated with common antiplatelet regimens following PED treatment, and to examine whether platelet function testing (PFT) is associated with a lower risk of these complications.

METHODS

We searched Medline, Embase, and Cochrane from 2009 to 2017. Twenty-nine studies were included that had reported a uniform antiplatelet regimen protocol and had provided data on major ischemic and hemorrhagic complications following PED treatment. Random-effect meta-analysis was used to pool overall ischemic and hemorrhagic event rates across studies. The rate of these complications with respect to the antithrombotic regimen and PFT was assessed by χ² proportional tests.

RESULTS

Overall, 2002 patients (age 55.9 years, 76% female) were included. A low-dose acetylsalicylic acid (ASA) regimen before and after PED treatment was associated with a higher rate of late ischemic complications than with high-dose ASA therapy (2.62 (95% CI 1.46 to 4.69) and 2.56 (1.41 to 4.64), respectively). Duration of post-procedure clopidogrel therapy <6 months was associated with greater rates of ischemic complications (1.56, 95% CI 1.11 to 2.20) than a clopidogrel regimen of ≥6 months. Performing PFT before PED treatment was not associated with the risk of ischemic complications (1.27, 95% CI 0.77 to 2.10).

CONCLUSION

High-dose ASA therapy and clopidogrel treatment for at least 6 months were associated with a reduced incidence of ischemic events, without affecting the risk of hemorrhagic events.

Transient in-stent stenosis at mid-term angiographic follow-up in patients treated with SILK flow diverter stents: incidence, clinical significance and long-term follow-up

BACKGROUND

Little is known about in-stent stenosis (ISS) in patients with aneurysms treated with flow diverter (FD) stents. The reported incidence in the literature varies significantly.

OBJECTIVE

The aim of this study was to assess the incidence, severity, distribution, clinical significance, and possible predictors for ISS.

METHODS

Between July 2012 and June 2016 we retrospectively reviewed all patients treated with SILK FDs in our center. Only cases with short-term (4±2 months) and long-term (>1 year) follow-ups with digital subtraction angiograms were included. ISS was graded as mild (<25%), moderate (25-50%) or severe (>50%). The following predictors for ISS were assessed: gender, age, the presence of subarachnoid hemorrhage, aneurysm size, location, occlusion status, and post-stenting angioplasty.

RESULTS

Thirty-six patients met the inclusion criteria. At mid-term follow-up, ISS was observed in 16/36 patients (44%). Eleven patients (69%) had mild ISS, three (19%) moderate, and two (12%) severe ISS. ISS was diffuse in 11 patients (69%) and focal in five patients (31%). All patients were asymptomatic. Thirteen patients were maintained on dual antiplatelet therapy and three on aspirin alone. At long-term follow-up, complete ISS resolution was seen in 11 patients, improvement in three and worsening in two patients. No de novo ISS occurrence was observed. On univariate analysis there was no significant predictor for ISS.

CONCLUSIONS

Transient ISS after FD deployment is a common asymptomatic finding on mid-term angiographic follow-up. Complete resolution or improvement at long-term follow-up is seen in most patients who are maintained on dual antiplatelet therapy.

Stent and flow diverter assisted treatment of acutely ruptured brain aneurysms

OBJECTIVE

We present our experience with stent techniques in the management of acutely ruptured aneurysms, focusing on aneurysm occlusion rates, intraprocedural complications, and late outcomes.

METHODS

We retrospectively reviewed the clinical records of patients treated by stent techniques during the early acute phase of aneurysmal rupture, from June 2011 to June 2016. Patients who underwent stenting for the management of unruptured aneurysms, or in a delayed fashion for a ruptured lesion, were excluded.

RESULTS

47 patients met inclusion criteria, including 46 with subarachnoid hemorrhage (SAH). There were 27 men and 20 women, mean age 38 years (range 23-73). They harbored 71 aneurysms, including 56 treated in the acute phase. Aneurysmal dome and neck width averaged 4.7 mm (range 1.7-12.1) and 3.2 mm (range 1.5-7.1), respectively. Single stent techniques were used in 39 patients and dual stent techniques in 17. External ventricular drains (EVDs) were placed before embolization in 35 patients (92%) and after in 3. Intraprocedure thromboembolic complications due to a hyporesponse to antiplatlets in 4 patients (8.5%) were successfully managed with intra-arterial antiplatelet agents. In 45 surviving patients (96%), there was complete aneurysm occlusion at the 9-12 month follow-up in 26/29 aneurysms treated by stent-assisted coiling (90%), in 2/3 aneurysms treated by flow diverter-assisted coiling (66%), and in 19/22 aneurysms treated by flow diverter alone (86%); 42/45 patients (93%) presented with a modified Rankin Scale score of 0-2.

CONCLUSION

Stenting techniques in ruptured aneurysms can be performed with good technical success; however, procedural thromboembolic complications related to the antiplatelet strategy merit investigation. EVD placement before stenting must be considered.

Procedural complexity independent of P2Y12 reaction unit (PRU) values is associated with acute in situ thrombosis in Pipeline flow diversion of cerebral aneurysms

Background

Acute in situ thrombosis is an ischaemic phenomenon during Pipeline embolisation device (PED) procedures with potentially high morbidity and mortality. There is controversy regarding the role of platelet function testing with P2Y12 assay as a predictor of intraprocedural thromboembolic events. There is limited knowledge on whether procedural complexity influences these events.

Methods

Data were collected retrospectively on 742 consecutive PED cases at a single institution. Patients with intraprocedural acute thrombosis were compared with patients without these events.

Results

A cohort of 37 PED cases with acute in situ thrombosis (mean age 53.8 years, mean aneurysm size 8.4 mm) was matched with a cohort of 705 PED cases without intraprocedural thromboembolic events (mean age 56.4 years, mean aneurysm size 6.9 mm). All patients with in situ thrombosis received intra-arterial and/or intravenous abciximab. The two groups were evenly matched in patient demographics, previous treatment/subarachnoid hemorrhage (SAH) and aneurysm location. There was no statistical difference in postprocedural P2Y12 reaction unit (PRU) values between the two groups, with a mean of 156 in the in situ thrombosis group vs 148 in the control group (p=0.5894). Presence of cervical carotid tortuosity, high cavernous internal carotid artery grade, need for multiple PED and vasospasm were not significantly different between the two groups. The in situ thrombosis group had statistically significant longer fluoroscopy time (60.4 vs 38.4 min, p<0.0001), higher radiation exposure (3476 vs 2160 mGy, p<0.0001), higher rates of adjunctive coiling (24.3% vs 8.37%, p=0.0010) and higher utilisation of balloon angioplasty (37.8% vs 12.2%, p<0.0001). Clinically, the in situ thrombosis cohort had higher incidence of major and minor stroke, intracerebral haemorrhage and length of stay.

Conclusions

Predictors of procedural complexity (higher radiation exposure, longer fluoroscopy time, adjunctive coiling and need for balloon angioplasty) are associated with acute thrombotic events during PED placement, independent of PRU values.

Rescue Therapy for Procedural Complications Associated With Deployment of Flow-Diverting Devices in Cerebral Aneurysms

Flow diverting devices (FDDs) have revolutionized the treatment of morphologically complex intracranial aneurysms such as wide-necked, giant, or fusiform aneurysms. Although FDDs are extremely effective, they carry a small yet significant risk of intraprocedural complications. As the implementation of these devices increases, the ability to predict and rapidly treat complications, especially those that are iatrogenic or intraprocedural in nature, is becoming increasingly more necessary.

Our objective in this paper is to provide a descriptive summary of the various types of intraprocedural complications that may occur during FDDs deployment and how they may best be treated. A systematic and qualitative review of the literature was conducted using electronic databases MEDLINE and Google Scholar. Searches consisted of Boolean operators “AND” and “OR” for the following terms in different combinations: “aneurysm,” “endovascular,” “flow diverter,” “intracranial,” and “pipeline.”

A total of 94 papers were included in our analysis; approximately 87 of these papers dealt with periprocedural endovascular (mainly related to FDDs) complications and their treatment; 7 studies concerned background material. The main categories of periprocedural complications encountered during deployment of FDDs are failure of occlusion, parent vessel injury and/or rupture, spontaneous intraparenchymal hemorrhage, migration or malposition of the FDDs, thromboembolic or ischemic events, and side branch occlusion

Periprocedural complications occur mainly due to thromboembolic events or mechanical issues related to device deployment and placement. With increasing use and expanding versatility of FDDs, the understanding of these complications is vital in order to effectively manage such situations in a timely manner.