The influence of anti-platelet resistance on the development of cerebral ischemic lesion after carotid artery stenting

Multi-institutional patterns of clopidogrel response among patients undergoing transcarotid artery revascularization

OBJECTIVE

Current guidelines recommend dual antiplatelet therapy (DAPT) in patients undergoing carotid artery stenting. The most common DAPT regimen is aspirin and clopidogrel, a P2Y12 receptor antagonist; however, the prevalence of clopidogrel resistance (CR) in patients undergoing percutaneous coronary interventions may exceed 60%. Few studies have investigated the prevalence and impact of CR in patients undergoing extracranial carotid artery stenting, particularly transcarotid artery revascularization (TCAR).

METHODS

Consecutive high-risk patients ≥ 18 years who underwent TCAR for high grade (≥70%) and/or symptomatic (≥50%) carotid stenosis with preoperative P2Y12 testing between August 2019 and December 2021 were identified across five institutions. Preoperative platelet reactivity was measured with the VerifyNow P2Y12 Reaction Unit (PRU) Test (Instrumentation Laboratory, Bedford, MA), with CR defined as PRU ≥ 194 and hyper-response as PRU <70. Patients without preoperative P2Y12 testing within 30 days prior to TCAR or those on a non-clopidogrel P2Y12 inhibitor preoperatively were excluded. The primary outcome of interest was prevalence of CR. Secondary outcomes of interest included the incidence of ischemic and hemorrhagic complications.

RESULTS

Of 92 patients identified, the majority were male (59%) and Caucasian (75%) with a mean age of 75 years (±8, range 56-92). Preoperatively, 93% of patients were on aspirin, 100% on clopidogrel, and 13% on therapeutic anticoagulation. At presentation, 36% were symptomatic. The mean preoperative P2Y12 was 156 PRU (±76, range 6-349). In total, 30 (33%) patients met criteria for CR (mean PRU 240 ± 37; range 197-349), and 15 (16%) met criteria for hyper-responder (mean PRU 38 ± 20; range 6-68). There was no significant difference by clopidogrel response phenotype in terms of sex (p = 0.246), race (p = 0.384), or symptomatic presentation (p = 0.956). Postoperatively, the cumulative incidence of stroke and MI was 2.1%, with no statistically significant difference in the incidence of in-hospital stroke (PRU 238, p = 0.489) or MI (PRU 168, p = 1) between clopidogrel phenotypes. Three (3.3%) patients, one CR (PRU 240) and two responders (PRU 119 and PRU 189), experienced postoperative access site hematomas that required no subsequent intervention. No other index hospitalization hemorrhagic complications occurred.

CONCLUSIONS

Using preoperative P2Y12 testing with a threshold PRU ≥ 194 to define CR, we identified a high prevalence of CR in patients undergoing TCAR similar to that in the pre-existing coronary literature. We found no significant differences in postoperative ischemic or hemorrhagic complications by clopidogrel response phenotype, although complication rates in the overall study cohort were low. CR may be a spectrum from responder to partial responder to complete non-responder, and this may account for the differences in our CR cohort compared to the ROADSTER 2 protocol deviation cohort. Further investigation is warranted to determine if a quantitative assessment of CR is sufficient to identify patients at risk of developing secondary cerebrovascular ischemic events in this patient population.

Genotype-guided dual antiplatelet therapy in cerebrovascular disease: assessing the risk and benefits for ethnic populations

INTRODUCTION

Cerebrovascular disease is a leading cause of morbidity and mortality in the world and antiplatelet therapy is a main pharmacologic means of secondary prevention. Clinical information has accumulated about benefit of dual antiplatelet therapy in certain clinical scenarios, genetic causes of antiplatelet resistance and its effect on clinical outcomes, and ethnic and geographic distributions of genetic polymorphisms.

AREAS COVERED

This review covers literature related to the pharmacogenomics of antiplatelet agents with a focus on ethnic variability, antiplatelet resistance, and dual antiplatelet therapy in cerebrovascular disease.

EXPERT OPINION

Selecting patients for dual antiplatelet therapy and specific agents require consideration of multiple factors. Ethnic factors should be considered in certain circumstances, but additional research is needed to determine the generalizability of the findings.

Efficacy and safety of single versus dual antiplatelet therapy in carotid artery stenting

OBJECTIVE

Current guidelines recommend dual antiplatelet (AP) therapy (DAPT) before carotid artery stenting (CAS); however, the true clinical effect of single AP therapy vs DAPT is unknown. We examined the efficacy and safety of preoperative single AP therapy vs DAPT in patients who had undergone transfemoral CAS (tfCAS) or transcarotid artery revascularization (TCAR).

METHODS

We identified all patients who had undergone tfCAS or TCAR in the Vascular Quality Initiative database from 2016 to 2021. We stratified the patients by procedure and identified those who had received the following preoperative AP regimens: DAPT (acetylsalicylic acid [ASA] + P2Y12 inhibitor [P2Yi]), no AP therapy, ASA only, ASA + AP loading dose, P2Yi only, and P2Yi + AP loading dose. The AP loading dose was given within 4 hours of CAS. We generated propensity scores for each treatment regimen and assessed in-hospital outcomes using inverse probability weighted log binomial regression, with DAPT as the reference and adjusting for intraoperative protamine use. The primary efficacy outcome was a composite end point of stroke and death, and the primary safety outcome was access-related bleeding.

RESULTS

Of the 18,570 tfCAS patients, 70% had received DAPT, 5.6% no AP therapy, 10% ASA only, 8.0% ASA + AP loading dose, 4.6% P2Yi only, and 2.9% P2Yi + AP loading dose. The corresponding unadjusted rates of stroke/death were 2.2%, 6.8%, 4.1%, 5.1%, 2.4%, and 2.3%. After adjustment, compared with DAPT, the incidence of stroke/death was higher with no AP therapy (relative risk [RR], 2.3; 95% confidence interval [CI], 1.7-3.2), ASA only (RR, 1.6; 95% CI, 1.2-2.1), and ASA + AP loading dose (RR, 2.0; 95% CI, 1.5-2.7) but was similar with P2Yi only (RR, 0.99; 95% CI, 0.58-1.7) and P2Yi + AP loading dose (RR, 1.1; 95% CI, 0.49-2.5). Of the 25,459 TCAR patients, 81% had received DAPT, 2.0% no AP therapy, 5.5% ASA only, 3.5% ASA + AP loading dose, 4.9% P2Yi only, and 2.4% P2Yi + AP loading dose. The corresponding unadjusted rates of stroke/death were 1.5%, 3.3%, 3.3%, 2.9%, 1.2%, and 1.1%. After adjustment, compared with DAPT, the incidence of stroke/death was higher with no AP therapy (RR, 2.0; 95% CI, 1.2-3.3) and ASA only (RR, 2.2; 95% CI, 1.5-3.1), with a trend toward a higher incidence with ASA + AP loading dose (RR, 1.6; 95% CI, 0.99-2.6), and was similar with P2Yi only (RR, 0.98; 95% CI, 0.54-1.8) and P2Yi + AP loading dose (RR, 0.66; 95% CI, 0.27-1.6). No differences were found in the incidence of access-related bleeding between the treatment groups after tfCAS or TCAR.

CONCLUSIONS

Compared with DAPT, no AP therapy or ASA monotherapy was associated with higher rates of stroke/death after CAS and should be discouraged as unsafe practice. Meanwhile, P2Yi monotherapy was associated with similar rates of stroke/death. No differences were found in the incidence of bleeding complications, and adding an AP loading dose to ASA or P2Yi monotherapy within 4 hours of the procedure did not affect the outcomes. Overall, these findings support the current guidelines recommending DAPT before CAS but also suggest that P2Yi monotherapy might confer thromboembolic benefits similar to those with DAPT. However, an immediate preoperative AP loading dose might not provide additional thromboembolic benefits.

Efficacy and safety of perioperative dual antiplatelet therapy with ticagrelor versus clopidogrel in carotid artery stenting

BACKGROUND

Clopidogrel resistance is associated with increased periprocedural neurologic events after carotid artery stenting (CAS). Ticagrelor offers an improved resistance profile; however, its bleeding risk has not been assessed with CAS. Therefore, we examined the efficacy and safety of perioperative dual antiplatelet therapy with aspirin/ticagrelor vs aspirin/clopidogrel in patients undergoing transfemoral carotid artery stenting (tfCAS) or transcarotid artery revascularization (TCAR).

METHODS

We identified all patients who underwent tfCAS or TCAR in the Vascular Quality Initiative registry from January 2016 to March 2021. We stratified patients by procedure and assessed outcomes using 1:3 propensity score-matched cohorts of patients who received perioperative aspirin/ticagrelor vs aspirin/clopidogrel. The primary efficacy outcome was a composite endpoint of in-hospital stroke/death, and the primary safety outcome was access-related bleeding. As a secondary analysis, we assessed these outcomes after stratifying each cohort by intraoperative protamine use.

RESULTS

Among 17,731 tfCAS patients, 593 (3.3%) received aspirin/ticagrelor and 11,404 (64%) received aspirin/clopidogrel. For the 2065 matched patients, no significant differences were found in the composite endpoint of stroke/death (aspirin/ticagrelor, 4.1%; vs aspirin/clopidogrel, 2.6%; relative risk [RR],1.5; 95% confidence interval [CI], 0.88-2.7) or in the individual endpoints of stroke (2.9% vs 1.8%; RR, 1.6; 95% CI, 0.87-3.0) or death (1.7% vs 1.1%; RR, 1.6; 95% CI, 0.71-3.5). However, aspirin/ticagrelor was associated with a higher risk of bleeding (5.8% vs 2.8%; RR, 2.0; 95% CI, 1.2-3.2). In a subgroup analysis of 297 tfCAS patients (14%) who received intraoperative protamine, no differences remained in stroke/death (1.5% vs 3.9%; RR, 0.38; 95% CI, 0.05-3.0), and there was no longer a difference in bleeding (3.0% vs 2.6%; RR, 1.1; 95% CI, 0.24-5.5). Among 17,946 TCAR patients, 453 (2.5%) received aspirin/ticagrelor and 13,696 (76%) received aspirin/clopidogrel. For the 1618 matched patients, no differences were found in stroke/death (0.7% vs 1.4%; RR, 0.53; 95% CI, 0.16-1.8), stroke (0.2% vs 1.2%; RR, 0.20; 95% CI, 0.03-1.5), death (0.5% vs 0.2%; RR, 3.0; 95% CI, 0.42-21), or bleeding (1.2% vs 1.6%; RR, 0.75; 95% CI, 0.28-2.0). For the 1429 TCAR patients (88%) who received protamine, no differences were found in stroke/death (0.8% vs 1.2%; RR, 0.68; 95% CI, 0.20-2.4) or bleeding (0.6% vs 1.4%; RR, 0.39; 95% CI, 0.09-1.7).

CONCLUSIONS

Compared with aspirin/clopidogrel, aspirin/ticagrelor was associated with a potentially lower risk of stroke/death and bleeding complications after CAS in cases in which protamine was used but a higher risk of these outcomes in the absence of protamine. Given our limited sample size, our analysis should be repeated when more patients are available for study. However, our findings suggest that aspirin/ticagrelor could be a reasonable alternative to aspirin/clopidogrel for both tfCAS and TCAR when protamine is used.

Platelet Biomarkers in Patients with Atherosclerotic Extracranial Carotid Artery Stenosis: A Systematic Review

OBJECTIVE

The aim was to enhance understanding of the role of platelet biomarkers in the pathogenesis of vascular events and risk stratifying patients with asymptomatic or symptomatic atherosclerotic carotid stenosis.

DATA SOURCES

Systematic review conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

REVIEW METHODS

A systematic review collated data from 1975 to 2020 on ex vivo platelet activation and platelet function/reactivity in patients with atherosclerotic carotid stenosis.

RESULTS

Forty-three studies met the inclusion criteria; the majority included patients on antiplatelet therapy. Five studies showed increased platelet biomarkers in patients with ≥ 30% asymptomatic carotid stenosis (ACS) vs. controls, with one neutral study. Preliminary data from one study suggested that quantification of "coated platelets" in combination with stenosis severity may aid risk stratification in patients with ≥ 50% - 99% ACS. Platelets were excessively activated in patients with ≥ 30% symptomatic carotid stenosis (SCS) vs. controls (≥ 11 positive studies and one neutral study). Antiplatelet-High on Treatment Platelet Reactivity (HTPR), previously called "antiplatelet resistance", was observed in 23% - 57% of patients on aspirin, with clopidogrel-HTPR in 25% - 100% of patients with ≥ 50% - 99% ACS. Aspirin-HTPR was noted in 9.5% - 64% and clopidogrel-HTPR in 0 - 83% of patients with ≥ 50% SCS. However, the data do not currently support the use of ex vivo platelet function/reactivity testing to tailor antiplatelet therapy outside of a research setting. Platelets are excessively activated (n = 5), with increased platelet counts (n = 3) in recently symptomatic vs. asymptomatic patients, including those without micro-emboli on transcranial Doppler (TCD) monitoring (n = 2). Most available studies (n = 7) showed that platelets become more reactive or activated following carotid endarterectomy or stenting, either as an acute phase response to intervention or peri-procedural treatment.

CONCLUSION

Platelets are excessively activated in patients with carotid stenosis vs. controls, in recently symptomatic vs. asymptomatic patients, and may become activated/hyper-reactive following carotid interventions despite commonly prescribed antiplatelet regimens. Further prospective multicentre studies are required to determine whether models combining clinical, neurovascular imaging, and platelet biomarker data can facilitate optimised antiplatelet therapy in individual patients with carotid stenosis.

Risk factors for new ischemic cerebral lesions after carotid artery stenting: A systematic review and meta-analysis

BACKGROUND

New ischemic cerebral lesions (NICL) are commonly occur after carotid artery stenting (CAS) with an incidence rate ranging from 18-58% and are detected by diffusion-weighted imaging-magnetic resonance imaging (DWI-MRI). Numerous studies have reported that NICL could increase the risk of future cerebrovascular events and cognitive impairment. This systematic review and meta-analysis aimed to identify risk factors for NICL after CAS.

METHODS

Relevant literature reporting risk factors for NICL after CAS were searched. Randomized controlled trials, case-control studies, or cohort studies were included in accordance with the pre-specified eligibility criteria. The risk of bias was assessed using the Cochrane Collaboration criteria and the quality of evidence was assessed with the corresponding scale. Data were analyzed using the RevMan V. 5.3 analysis software.

RESULTS

The final analyses included a total of 21 studies and 1907 participants, including 764 NICL-positives and 1143 NICL-negatives. Determinants for NICL-positivity were age (mean deviation (MD): 2.60; 95% confidence interval (CI): [1.53-3.68]), symptomatic carotid lesions (odds ratio (OR): 1.77; 95% CI: [1.39-2.25]) and smoking (OR: 0.74; 95% CI: [0.58-0.94]). For symptomatic patients, risk factors for NICL-positive included diabetes mellitus (OR: 1.76; 95% CI: [1.09-2.82]), but smoking (OR: 0.54; 95% CI: [0.31-0.93]) was a protective factor. Risk factors for centers with high NICL incidence were age (MD: 2.05; 95% CI: [0.93-3.17]) and symptomatic carotid lesions (OR: 1.77; 95% CI: [1.29-2.45]).

CONCLUSIONS

Older age and symptomatic carotid lesions are associated with an increased risk of post-CAS NICL whereas smoking is associated with a decreased risk. Risk factors for NICL in symptomatic patients is diabetes mellitus, while those for patients at centers with high incidence are age and symptomatic carotid lesions. Systematic review registration: CRD42019121129.

Clinical importance of testing for clopidogrel resistance in patients undergoing carotid artery stenting-a systematic review

Dual antiplatelet therapy is frequently prescribed for patients undergoing carotid artery stenting (CAS), however clopidogrel resistance might cause thromboembolic complications. The role of testing for clopidogrel resistance in patients undergoing CAS is unclear. In this study, we aimed to review the periprocedural thromboembolic outcomes in clopidogrel resistant patients who underwent CAS. We conducted a review of PubMed, EMBASE, and the Cochrane Library up to October 7, 2020. Studies were included that investigated at least ten patients aged 18 years or older with a symptomatic carotid artery stenosis requiring CAS. Studies were excluded that investigated patients with a carotid artery dissection, case reports, case series of less than ten patients, reviews, commentaries, letters to the editors, and conference abstracts. The primary endpoint was the incidence of thromboembolic events. One hundred seventy-seven unique articles were identified of which three studies were included in our systematic review. The sample sizes ranged from 76 to 449 patients and the follow-up duration from 24 hours to 2 years postprocedural. Two retrospective observational studies determined clopidogrel resistance using measurement of P2Y12 reaction units, and one historical cohort study used genetic testing. Two studies concluded that clopidogrel resistance was a risk factor for thromboembolic complications, the other found higher values of P2Y12 reaction units in patients with thromboembolic events compared to those without. In conclusion, current literature supports a possible relationship between clopidogrel resistance and thromboembolic complications in patients who underwent CAS. Preprocedural testing for clopidogrel resistance might therefore be of additional value. Randomized studies using a valid, reliable clopidogrel resistance test and clinical endpoints, are however required to make a definitive statement and to determine the impact of the thromboembolic complications. This study was registered within PROSPERO (CRD42020197318).

Antiplatelet Loading Effects Prior to Endovascular Treatment: Carotid Artery Stenosis versus Unruptured Cerebral Aneurysms

Objective

Carotid artery stenosis and cerebral aneurism may have different platelet functions and antiplatelet responses because these diseases have different etiologies. In this study, we compared the antiplatelet loading effects prior to endovascular treatment between carotid artery stenosis and unruptured cerebral aneurysm (UCA) patients.

Methods

Nine patients with asymptomatic carotid artery stenosis (ACS), 14 with symptomatic carotid artery stenosis (SCS), and 20 with unruptured cerebral aneurysms were enrolled in this study. Antiplatelet (aspirin + clopidogrel) loading effects prior to endovascular treatment were evaluated using light transmission aggregometry and platelet aggregate detection methods.

Results

Although there are differences in the prevalence of atherosclerosis risk factors, maximum aggregation rates in light transmission aggregometry and platelet aggregation-prone properties were not different in the three disease groups.

Conclusion

Preoperative dual antiplatelet therapy with aspirin and clopidogrel may be appropriate for both carotid artery stenosis and cerebral aneurism patients even though their conditions and background factors differ.

Adjunctive treatment with low dose intra-arterial eptifibatide and intravenous aspirin during carotid stenting: A case series

PURPOSE

According to most guidelines, medical protocol for carotid stenting includes the administration of oral Aspirin and Clopidogrel at least four days before the procedure, with intraprocedural intravenous (IV) heparin. Some publications have also reported the safety of adding glycoprotein 2b/3a inhibitors to the protocol. In this retrospective study, we evaluate the safety of a new medication protocol that includes IV aspirin and intra-arterial Eptifibatide (glycoprotein 2b/3a inhibitor) during carotid stenting. All patients who underwent carotid stenting at Soroka University Medical Center between January 2015 and May 2020 were included (emergent cases were excluded). We divided patients into two groups-patients treated under the standard protocol, and patients treated under the new protocol. In the latter, patients received both the standard protocol regimen, as well as 150 mg IV aspirin immediately before stenting, and a slow intra-arterial injection of 2-3 mg Eptifibatide (glycoprotein 2b/3a antagonist) immediately after stenting. Forty-four patients were treated according to the standard protocol (group 1), and 41 patients were treated according to the new protocol (group 2). In group 1, six patients had complications, while in group 2, no complications of any kind were noted (p = 0.027). The safety and possible efficacy of this novel protocol was preliminarily demonstrated in the present study. Future studies are needed to prove the safety and efficacy of a specific drug regimen that will further reduce the complication rates of carotid stenting.

The role of heparin in preventing the early silent ischemia in carotid stenting

INTRODUCTION AND AIMS

Serebral silent ischemia is a complication of carotid stenting. If silent ischemia occurs 24 h later of carotid stenting, it called early serebral silent ischemia. The aim of this study was to evaluate the effect of heparin infusion on the prevention of early silent ischemia in patients who underwent carotid stenting.

MATERIALS AND METHODS

We included 26 patients who underwent carotid stenting. Patients who had carotid stenting, we randomized into two groups. The first group of patients were given continuously heparin infusion a maximum of 20,000 units for 24 h, and screened the aPTT value each 6 h. The aPTT value aimed a range of 2-3 times to up baseline. The second group didn't take heparin infusion. Diffusion weighted magnetic resonance imaging (DWI-MRI) and gradient echo (GRE) sequences performed in all patients at the 24 h of carotid stenting.

RESULTS

Early serebral silent ischemia was detected by DWI-MRI in 13 (50%) of 26 patients who underwent carotid stenting. Seven (53.80%) of 13 patients whit early serebral silent ischemia did not receive heparin treatment, while 6 (46.20%) received heparin treatment. There was no symptomatic or asymptomatic acute hemorrhage in patients who treated with heparin.

CONCLUSION

In our study, the continuation of anticoagulant therapy for 24 h to prevent early silent ischemia was not statistically significant. Also there is no reduction for count of serebral silent ischemia between two groups. However, due to the small number of patients in the study, future studies are required with more patients.

Relationship between 'on-treatment platelet reactivity', shear stress, and micro-embolic signals in asymptomatic and symptomatic carotid stenosis

BACKGROUND

Assessment of 'high on-treatment platelet reactivity (HTPR)' could enhance understanding of the pathophysiology of first or recurrent vascular events in carotid stenosis patients on antiplatelet therapy.

METHODS

This prospective, multi-centre study assessed antiplatelet-HTPR status and its relationship with micro-emboli signals (MES) in asymptomatic vs. symptomatic ≥ 50-99% carotid stenosis. Platelet function/reactivity was assessed under 'moderately high shear stress' with the PFA-100^® and 'low shear stress' with VerifyNow^® and Multiplate^® analysers. Bilateral 1-h transcranial Doppler ultrasound of the middle cerebral arteries classified patients as MES + ve or MES - ve.

RESULTS

Data from 34 asymptomatic patients were compared with 43 symptomatic patients in the 'early phase' (≤ 4 weeks) and 37 patients in the 'late phase' (≥ 3 months) after TIA/ischaemic stroke. Median daily aspirin doses were higher in early symptomatic (225 mg; P < 0.001), but not late symptomatic (75 mg; P = 0.62) vs. asymptomatic patients (75 mg). There was a lower prevalence of aspirin-HTPR in early (28.6%; P = 0.028), but not late symptomatic (38.9%; P = 0.22) compared with asymptomatic patients (56.7%) on the PFA-100^®, but not on the VerifyNow^® or Multiplate^® (P ≤ 0.53). Early symptomatic patients had a higher prevalence of aspirin-HTPR on the PFA-100^® (28.6%) vs. VerifyNow^® (9.5%; P = 0.049), but not Multiplate^® assays (11.9%, P = 0.10). There was no difference in aspirin-HTPR prevalence between any symptomatic vs. asymptomatic MES + ve or MES - ve subgroup.

DISCUSSION

Recently symptomatic moderate-severe carotid stenosis patients had a lower prevalence of aspirin-HTPR than their asymptomatic counterparts on the PFA-100^®, likely related to higher aspirin doses. The prevalence of antiplatelet-HTPR was positively influenced by higher shear stress levels, but not MES status.

Comparison of Clopidogrel and Ticlopidine/Ginkgo Biloba in Patients With Clopidogrel Resistance and Carotid Stenting

Background and Purpose: Patients undergoing carotid artery stenting (CAS) who show low responsiveness to clopidogrel may have a higher risk of peri-procedural embolic events. This study aimed to compare the effectiveness and safety of clopidogrel and ticlopidine plus Ginkgo biloba in clopidogrel-resistant patients undergoing CAS.

Methods: In this multi-center, randomized, controlled trial, we used platelet reactivity test to select patients undergoing CAS who showed clopidogrel resistance, and compared treatments using clopidogrel and ticlopidine plus ginkgo. The primary outcome was the incidence of new ischemic lesion in the ipsilateral hemisphere of CAS. Detection of microembolic signal on transcranial Doppler was the secondary outcome. The clinical outcomes were also monitored.

Results: This trial was discontinued after 42 patients were randomized after preplanned interim sample size re-estimation indicated an impractical sample size. The primary endpoint occurred in 12/22 patients (54.5%) in the clopidogrel group and 13/20 patients (65.0%) in the ticlopidine–ginkgo group (P = 0.610). No significant differences in the presence of microembolic signal (15.0 vs. 11.8%, P = 0.580), clinical outcomes (ischemic stroke or transient ischemic attack, 0.0 vs. 5.5%; acute myocardial infarction 0.0 vs. 0.0%; all-cause death, 4.5 vs. 0.0%), or incidence of adverse events were found in the two groups. In terms of resistance to clopidogrel, treatment with ticlopidine–ginkgo significantly increased the P2Y12 Reaction Units (difference, 0.0 [−0.3–3.0] vs. 21.0 [6.0–35.0], P < 0.001).

Conclusions: In patients who showed clopidogrel resistance, ticlopidine–ginkgo treatment was safe and increased P2Y12 Reaction Units; however, compared to clopidogrel, it failed to improve surrogate and clinical endpoints in patients undergoing CAS. This multimodal biomarker-based clinical trial is feasible in neurointerventional research.

Clinical Trial Registration:http://www.clinicaltrials.gov. Unique identifier: NCT02133989.

Acute Early Carotid Stent Thrombosis: A Case Series

BACKGROUND

Acute early carotid stent thrombosis (AcuteCST) is a rare complication after carotid artery stenting (CAS). The purpose of this retrospective study was to investigate the incidence, causes, and optimal management of AcuteCST.

METHODS

Medical records of all patients undergoing CAS between 2008 and 2016 were retrospectively reviewed. The time of thrombosis, grade of stenosis, lesion side, preprocedural and postprocedural anticoagulants, causes, symptoms, treatment, recanalization, and outcome were reviewed.

RESULTS

Overall, 674 patients were treated with CAS. Four cases of AcuteCST were identified (0.59%). In the first patient, the stent thrombosis was attributed to dissection caused by filter deployment within a distal internal carotid artery with 360° coiling. Notably, in 3 of the 4 cases of thrombosis a second overlapping stent had been deployed. In total, 41 patients of the cohort under investigation underwent overlapping stent deployment. The use of a second overlapping stent as a bail-out procedure due to dissection or malposition or due to long lesions was correlated with increased rate of thrombosis (3/41 [7.3%] vs. 1/633 [0.002%]). In 2 patients, carotid stents were thrombosed within 2 hr of the procedure. Endovascular thrombus aspiration and subsequent eversion carotid endarterectomy with stent explantation in the first patient and intrathrombus urokinase administration with thromboaspiration and additional stent placement in the second patient were followed. In the other 2 patients having their carotid stents thrombosed 3 and 4 days after the procedure, treatment with low weight molecular heparin and antiplatelet regimens was followed.

CONCLUSIONS

The use of overlapping stents in the carotid artery is a predisposing factor for AcuteCST. Prognostic factors of this potentially devastating complication are the initial clinical presentation expressing the grade of ischemic brain damage, the accurate and timely recognition of the thrombosis, and the prompt restoration of oxygenated blood flow into the viable tissue at risk of infarction.

Review of aspirin and clopidogrel resistance in peripheral arterial disease

OBJECTIVE

Aspirin resistance (AR) and clopidogrel resistance (CR) are terms used to describe a reduction in the medication's efficacy in inhibiting platelet aggregation despite regular dosing. This review gives context to the clinical role and implications of antiplatelet resistance in peripheral arterial disease (PAD).

METHODS

A review of English-language literature on AR and CR in PAD involving human subjects using PubMed and MEDLINE databases was performed in April 2017. A total of 2075 patients in 22 relevant studies were identified. To give this issue context, a review of the larger, more established literature on antiplatelet resistance in coronary disease was undertaken, identifying significant research associating resistance to major adverse cardiovascular events (MACEs).

RESULTS

Studies in the coronary arterial disease literature have strongly associated antiplatelet resistance with increased MACE. Prevalence of AR or CR in coronary disease appears to be >55% for each in some studies. Meta-analyses of >50 studies revealed that AR and CR are significantly associated with MACE (relative risk of 2.09 and 2.8, respectively). This adds further weight to the literature reporting antiplatelet resistance as an independent predictor of and a threefold risk factor for major adverse cardiovascular events. The prevalence of resistance in PAD in this review was comparable to that in the coronary disease literature, with AR and CR prevalence up to 60% and 65%, respectively. There is evidence that the adverse effects of antiplatelet resistance are significant in PAD. In fact, research directly studying stent thrombosis populations with either coronary arterial disease or PAD revealed more significantly impaired platelet responsiveness to clopidogrel and aspirin in PAD compared with similar individuals with coronary disease. AR in PAD was found in studies to be a significant risk factor for iliofemoral stent reocclusion (P = .0093) and stroke in patients with symptomatic carotid disease (P = .018). CR was found to be a significant, independent risk factor in predicting ischemic outcomes in several recent PAD studies (P < .0001). Loss-of-function carriers of enzyme CYP2C19, important in clopidogrel metabolism, have a 30% greater risk of ischemic events (P < .001). Importantly, less antiplatelet drug resistance may be encountered with newer antiplatelet agents, including ticagrelor and prasugrel, because of reduced enzymatic polymorphisms.

CONCLUSIONS

The limited research addressing AR and CR in PAD suggests that further research is required to clarify the role of platelet assays and potential for individualized antiplatelet therapy.

Acute Carotid Stent Thrombosis

Acute carotid stent thrombosis (ACST) is a rare complication that can lead to dramatic and catastrophic consequences. A rapid diagnosis and prompt recanalization of the internal carotid artery are needed to minimize the ischemic insult and the reperfusion injury. We reviewed the current literature on this devastating complication of CAS with the intention of investigating the potential causative factors and to define the appropriate management. According to our study discontinuation of antiplatelet therapy, resistance to antiplatelet agents and inherent or acquired thrombotic disorders are the main causes of thrombosis. Technical intraprocedural parameters such as dissection, atheroma prolapse, kinking of the distal part of internal carotid artery and embolic protection device occlusion can also result in early carotid stent thrombosis. Rapid reperfusion ensures an improved neurological outcome and a better prognosis in the short and long term. Thrombolysis, mechanical thrombectomy or thromboaspiration in combination with drug or thrombolytic therapy, surgical therapy and re-angioplasty are treatment options that have been used with encouraging results. In conclusion, optimal perioperative antiplatelet treatment as well as technical considerations regarding the carotid artery stenting plays a determinant role.

Antiplatelet effect of clopidogrel can be reduced by calcium-channel blockers

PURPOSE

Clopidogrel is metabolized by the hepatic cytochrome P450 (CYP) system into its active thiol metabolite. CYP3A4 is involved in the metabolism of both clopidogrel and dihydropyridine calcium channel blockers (CCBs). A few reports have suggested an inhibitory interaction between CCBs and clopidogrel. Accordingly, the aim of this study was to determine the effect of CCBs on the antiplatelet activity of clopidogrel by serial P2Y12 reaction unit (PRU) measurements.

MATERIALS AND METHODS

We assessed changes in antiplatelet activity in patients receiving both clopidogrel and CCBs for at least 2 months prior to enrollment in the study. The antiplatelet activity of clopidogrel was measured by VerifyNow P2Y12 assay in the same patient while medicated with CCBs and at 8 weeks after discontinuation of CCBs. After discontinuation of the CCBs, angiotensin receptor blockers were newly administered to the patients or dosed up for control of blood pressure.

RESULTS

Thirty patients finished this study. PRU significantly decreased after discontinuation of CCBs (238.1±74.1 vs. 215.0±69.3; p=0.001). Of the 11 patients with high post-treatment platelet reactivity to clopidogrel (PRU≥275), PRU decreased in nine patients, decreasing below the cut-off value in seven of these nine patients after 8 weeks. Decrease in PRU was not related to CYP2C19 genotype.

CONCLUSION

CCBs inhibit the antiplatelet activity of clopidogrel.