Insights into the inhibition of platelet activation by omega-3 polyunsaturated fatty acids: beyond aspirin and clopidogrel

Objectives

We sought to examine the effects of escalating doses of omega-3 polyunsaturated fatty acid (PUFA) supplements on platelet function using light transmission aggregometry (LTA) and electrophoretic quasi-elastic light scattering technology (EQELS).

Background

PUFA may inhibit platelet function through fatty acid substitution in the platelet membrane by changing the surface charge density and causing decreased production of thromboxane A2. EQELS can measure platelet surface charge density and determine whether the platelet is in resting or activated state.

Methods

A total of 30volunteers were divided in 3 groups of 10 as follows: Group A, no antiplatelet agent; Group B, daily aspirin only, and Group C, daily aspirin and clopidogrel. All patients received escalating doses of omega-3PUFA from 1 to 8 g daily over 24 weeks. Platelet function was measured by template bleeding time, LTA, and EQELS at baseline and at 6, 12, 18 and 24 weeks.

Results

Mean bleeding time increased in a dose-dependent manner with escalating omega-3 PUFA doses. LTA confirmed expected antiplatelet effects of aspirin and clopidogrel, but did not detect any additional antiplatelet effects of omega-3 PUFA. EQELS showed a significant increase in the negative resting platelet charge compared to baseline and an attenuated response to arachidonic acid mediated platelet activation. No bleeding events were observed.

Conclusions

In this pilot study we were able to successfully measure platelet surface charge variation as a measure of omega-3 PUFA effect on platelets. Our results suggest that omega-3 PUFA increase the total platelet surface charge and, therefore, attenuate platelet activation, even among patients taking aspirin or aspirin plus clopidogrel. Further studies are needed to determine the clinical significance of these measured effects and EQELS results.     

Response to antiplatelet therapy is independent of endogenous thrombin generation potential

Background

Thrombin is the most potent platelet activator, and achieves rapid platelet activation even in the presence of antiplatelet therapy. Since activated platelets respond stronger to additional stimuli, the extent of endogenous thrombin generation may in part be responsible for the reported response variability to aspirin and clopidogrel therapy.

Patients and methods

Thrombin generation potential was measured with a commercially available assay, and platelet reactivity was assessed with the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, light transmission aggregometry (LTA), the VerifyNow aspirin and P2Y12 assays, and multiple electrode aggregometry (MEA) in 316 patients on dual antiplatelet therapy undergoing angioplasty and stenting.

Results

Peak thrombin, the lag phase and the area under the curve of thrombin generation correlated poorly with on-treatment platelet reactivity by all test systems. High on-treatment residual platelet reactivity (HRPR) in response to arachidonic acid was seen in 33 (10.5%), 41 (13%), and 79 (25.7%) patients by LTA, the VerifyNow aspirin assay, and MEA, respectively. HRPR in response to adenosine diphosphate was seen in 150 (48.1%), 48 (15.3%), 106 (33.7%), and 118 (38.3%) patients by the VASP assay, LTA, the VerifyNow P2Y12 assay, and MEA, respectively. Peak thrombin generation did not differ between patients without and with HRPR by the VASP assay, LTA, the VerifyNow P2Y12 assay and MEA. In the VerifyNow aspirin assay, patients without HRPR had higher peak thrombin generation than patients with HRPR (p = 0.01). Finally, patients without and with high peak thrombin generation exhibited similar on-treatment platelet reactivity by all test systems, and high peak thrombin generation occurred to a similar extent in patients without and with HRPR.

Conclusion

Response to antiplatelet therapy with aspirin and clopidogrel is not associated with thrombin generation potential.     

Impact of the proton pump inhibitors and CYP2C19*2 polymorphism on platelet response to clopidogrel as assessed by four platelet function assays

Background

Previous studies suggested a possible negative interference of proton pump inhibitors (PPIs) on clopidogrel’s antiplatelet effect because of the competitive inhibition of the CYP 2C19 isoenzyme. Moreover, carriers of the loss-of-function allele of CYP2C19 polymorphism (CYP2C19*2) display significantly lower responses to clopidogrel. In this study, we investigated the association between CYP2C19*2 genotype, PPI intake and clopidogrel resistance in patients with coronary artery disease (CAD) and their effect on clinical outcome.

Methods

We recruited 95 patients with CAD receiving chronic clopidogrel therapy in combination with aspirin. Platelet reactivity was simultaneously assessed by INNOVANCE PFA-100 P2Y, ADP-induced light transmission aggregometry (LTA), flow-cytometric vasodilator-stimulated phosphoprotein (VASP)-phosphorylation assay and multiple electrode aggregometry (Multiplate). Cardiovascular outcomes were recorded during 1-year follow-up period.

Results

Only platelet reactivity assessed by measuring platelet phosphorylated-VASP demonstrated a significant higher platelet reactivity in carriers of CYP2C19*2 (p = 0.023). The other methods displayed higher - but not statistically significant - platelet reactivity in patients carrying the CYP2C19*2 variant as compared with non-carriers. Patients on PPIs demonstrated almost similar suppression of platelet reactivity in comparison with those not treated with PPIs by all platelet function assays. In logistic regression analysis none of the platelet function assays measurements were related with clinical outcomes. Similarly neither CYP2C19*2 genetic variant nor PPI treatment were associated with adverse clinical events.

Conclusions

PPI co-administration did not influence clopidogrel’s antiplatelet effect on laboratory testing by all platelet function assays used. On the contrary, patients carrying CYP2C19*2 genotype had significantly higher residual platelet reactivity as estimated by VASP-phosphorylation assay.     

The effect of antiplatelet drugs clopidogrel and aspirin is less immediately after stent implantation

Introduction

A decreased effect of clopidogrel or aspirin on platelets corresponds to an increased risk of major adverse coronary events. The aim was to investigate if the inhibition of platelet function by clopidogrel and aspirin is equal at two different time points: immediately after percutaneous coronary intervention (PCI) and one day thereafter.

Materials and methods

Platelet function was assessed by the Vasodilator Stimulated Phosphoprotein (VASP) phosphorylation assay, Impedance Aggregometry, Platelet Function Analyzer and the Cone and Platelet Analyzer in 30 patients on chronic treatment with clopidogrel and aspirin.

Results

Inhibition of platelets by clopidogrel and aspirin was less post PCI than one day after PCI as measured with the VASP assay and aggregometry: the platelet reactivity index, the adenosine diphosphate/prostaglandin and the arachidonic acid -induced platelet aggregation were 23% (p = 0.009), 75% (p = 0.001) and 127% (p < 0.001) higher post PCI than one day after PCI, respectively. The collagen/adenosine diphosphate closure time was 30% higher after PCI compared to one day thereafter (p = 0.047), which could in part be due to a two-fold increase in von Willebrand factor-ristocetin cofactor activity one day after PCI (p = 0.001).

Conclusion

Inhibition of platelets by clopidogrel and aspirin was less immediately post PCI as compared to one day thereafter. This indicates that the time point of platelet function testing is important for the determination of cut-off points and the definition of nonresponsiveness to antiplatelet drugs.     

Anti-Platelet Drug Resistance in the Prediction of Thromboembolic Complications after Neurointervention

Objective

The aim of this study was to analyze the correlation between thromboembolic complications and antiplatelet drugs before and after neurointervention.

Methods

Blood samples and radiographic data of patients who received a neurointervention (coil embolization, stent placement or both) were collected prospectively. Rapid platelet function assay-aspirin (RPFA-ASA) was used to calculate aspirin resistance in aspirin reaction units (ARU). For clopidogrel resistance, a P2Y12 assay was used to analyze the percentage of platelet inhibition. ARU > 550 and platelet inhibition < 40% were defined as aspirin and clopidogrel resistance, respectively.

Results

Both aspirin and clopidogrel oral pills were administered in fifty-three patients before and after neurointerventional procedures. The mean resistance values of all patients were 484 ARU and < 39%. Ten (17.0%) of 53 patients showed resistance to aspirin with an average of 597 ARU, and 33 (62.3%) of 53 patients showed resistance to clopidogrel with an average of < 26%. Ten patients demonstrated resistance to both drugs, 5 of which suffered a thromboembolic complication after neurointervention (mean values : 640 ARU and platelet inhibition < 23%). Diabetic patients and patients with hypercholesterolemia displayed mean aspirin resistances of 513.7 and 501.8 ARU, and mean clopidogrel resistances of < 33.8% and < 40.7%, respectively.

Conclusion

Identifying individuals with poor platelet inhibition using standard regimens is of great clinical importance and may help prevent cerebral ischemic events in the future. Neurointerventional research should focus on ideal doses, timing, choices, safety, and reliable measurements of antiplatelet drug therapy, as well as confirming the clinical relevance of aggregometry in cerebrovascular patients.     

Cervical artery dissection: Pathology, epidemiology and management

Background

Cervical artery dissection is often treated with anticoagulants to prevent ischemic stroke. The risk-benefit ratio of anticoagulation versus antiplatelet therapy is unclear.

Objectives

To provide an educational review of current data on the disease to explain the rationale for the treatment options and to explore the results of management studies in order to determine if anticoagulation is justified.

Methods

We searched the databases MEDLINE and EMBASE as well as bibliographies for information on anticoagulants and antiplatelet agents in cervical, i.e. carotid and/or vertebral artery, dissection.

Results

There are no randomized controlled trials on the treatment. One systematic review from 2003 identified 20 case series or cohort studies. We identified 9 additional studies with a total of 1,033 patients. Of those, 731 received anticoagulation sometimes followed by platelet inhibition vs. 282 patients treated with antiplatelet agents alone. The rate of ischemic stroke was 2.3% vs. 6.9% and bleeding complications were reported in 0.7% vs. 0%.

Conclusion

It cannot be excluded that there is a net benefit from anticoagulant therapy in cervical dissection, but the studies are flawed by considerable bias. Very ill patients at a high risk of ischemic stroke may have been given aspirin due to fear of hemorrhagic complications. A randomized controlled trial is planned and will be crucial to resolve this issue.     

Determination of cut-off levels for on-clopidogrel platelet aggregation based on functional CYP2C19 gene variants in patients undergoing elective percutaneous coronary intervention

Introduction

Carriers of reduced-function CYP2C19 allele on antiplatelet therapy show diminished platelet inhibition and higher rate of clinical risk. The purpose of this study was to determine cut-off levels of VerifyNow P2Y12 system associated with effective inhibition of on-clopidogrel platelet aggregation to predict carriers of CYP2C19 reduced-function allele among patients undergoing percutaneous coronary intervention (PCI).

Materials and Methods

We enrolled 202 consecutive patients with stable coronary artery disease (CAD) undergoing PCI and treated with clopidogrel. All patients underwent CYP2C19 genotyping and measurement of residual platelet aggregation by VerifyNow system.

Results

Carriers of CYP2C19 reduced-function allele constituted 131 (65%) of 202 CAD patients. Platelet inhibition measured by P2Y12 reaction units (PRU) and %inhibition was diminished in carriers compared with noncarriers (PRU: 290.0 ± 81.2 vs 217.6 ± 82.4, p < 0.001, %inhibition: 17.9 ± 17.8 vs 35.5 ± 22.8, p < 0.001, respectively). Multiple logistic regression analysis identified PRU and %inhibition as significant predictors of carrier state [odds ratio (OR) 4.95; 95% confidence interval (95%CI): 2.49 to 9.85; p < 0.001, OR 5.55; 95%CI: 2.80 to 10.99; p < 0.001, respectively]. Receiver-operating characteristic analysis showed that PRU and %inhibition were significant predictors of carrier state [area under the curve (AUC) 0.736 (95%CI: 0.664 to 0.808; p < 0.001), AUC 0.727 (95%CI: 0.651 to 0.803; p < 0.001), respectively]. The cut-off levels of PRU and %inhibition were 256 and 26.5% for the identification of carriers.

Conclusions

Our results suggested that the cut-off levels of PRU and %inhibition to discriminate carriers of CYP2C19 reduced-function allele from noncarriers are potentially useful clinically to provide optimal clopidogrel therapy in patients with stable CAD undergoing PCI.     

Reduced platelet response to aspirin in patients with coronary artery disease and type 2 diabetes mellitus

Introduction

Diabetes mellitus is complicated by accelerated atherosclerosis, resulting in an increased risk of coronary artery disease (CAD) and thrombosis. Despite the proven benefits of aspirin, previous studies indicate a reduced cardiovascular protection from aspirin in diabetic patients. We aimed to investigate whether diabetes mellitus influenced the platelet response to aspirin in patients with CAD.

Materials and Methods

Platelet aggregation and activation were evaluated during aspirin treatment in 85 diabetic and 92 non-diabetic patients with CAD. Adherence to aspirin was carefully controlled. All patients had CAD verified by coronary angiography and were taking 75 mg non-enteric coated aspirin daily.

Results

Diabetic patients showed significantly higher levels of platelet aggregation compared to non-diabetic patients evaluated by VerifyNow^® Aspirin (p = 0.03) and Multiplate^® aggregometry using arachidonic acid (AA) 0.5 mM (p = 0.005) and 1.0 mM (p = 0.009). In addition, platelet activation determined by soluble P-selectin was significantly higher in diabetics compared to non-diabetics (p = 0.005). The higher AA-induced aggregation was associated with higher levels of HbA_1c. Compliance was confirmed by low levels of serum thromboxane B₂ (below 7.2 ng/mL). Diabetics had significantly higher levels of serum thromboxane B₂ (p < 0.0001).

Conclusions

Diabetic patients with CAD had significantly higher levels of both platelet aggregation and activation compared to non-diabetic patients with CAD despite treatment with the same dosage of aspirin. These findings may partly explain the reduced cardiovascular protection from aspirin in diabetic patients.     

Evaluation of laboratory methods routinely used to detect the effect of aspirin against new reference methods

Background

Aspirin, a commonly used antiplatelet agent, blocks platelet thromboxane A₂ (TXA₂) formation from arachidonic acid (AA) by acetylating platelet cyclooxygenase-1 (COX-1). Laboratory methods currently used to detect this antiplatelet effect of aspirin provide variable results. We have reported three methods that assess platelet COX-1 acetylation (inactivation) by aspirin and its direct consequences. The first and second assays use monoclonal anti-human-COX-1 antibodies that only detect acetylated (inactivated) COX-1 and active (non-acetylated) COX-1, respectively. The third method measures platelet production of TXB₂ (the stable metabolite of TXA₂) in vitro in response to AA. We compared the results of these three reference methods with other routinely used methods for assessing the functional consequences aspirin treatment.

Methods

108 healthy volunteers were treated with low-dose aspirin for 7 days. On day 7 following aspirin treatment COX-1 in the platelets was fully acetylated whereas only non-acetylated COX-1 was present in the day 0 platelets. Further, TXB₂ production by day 7 platelets was completely blocked. The following tests were performed on the samples obtained from study participants before and after seven days of aspirin treatment: PFA-100 closure time with collagen/epinephrine cartridge, VerifyNow® (VN) Aspirin Assay, platelet aggregation and ATP secretion using AA, ADP, epinephrine and collagen as agonists.

Results

Comparing the pre-treatment and day 7 values, methods that use AA as platelet agonist (AA-induced platelet aggregation/secretion and VN Aspirin Assay) showed high discriminative power. In contrast, results of the other tests showed considerable overlap between day 7 and day 0 values.

Conclusions

Only assays that clearly distinguish between acetylated and non-acetylated platelet COX-1 are useful for establishing the antiplatelet effect of aspirin. The other tests are not suitable for this purpose.     

The GPIIIa PlA polymorphism and the platelet hyperactivity in Tunisian patients with stable coronary artery disease treated with aspirin

Background

Various genetic polymorphisms have been proposed to explain the persistent platelet hyperactivity (HPR) under aspirin treatment. PlA polymorphism of platelet GPIIIa receptor has been largely studied. However, its influence on platelet sensitivity to aspirin remains controversial.

Objectives

The aim of this prospective study is to investigate whether this PlA polymorphism is associated with a greater prevalence of HPR in stable coronary artery disease patients Material and Methods: 188 stable coronary artery disease patients were included. Platelet aspirin inhibitory effect was determined with PFA-100 using Collagen/Epinephrine closure time (CEPI-CT). A CEPI-CT<160 sec was defining the HPR status. GPIIIa PlA polymorphism was established using polymerase chain reaction and classical restriction fragments length polymorphism.

Results

The observed frequencies of different genotypes were not different from those predicted by the Hardy-Weinberg equilibrium: PlA1/lA1 (55.3%), PlA1/PlA2 (39.4%) and PlA2/PlA2 (5.3%). HPR patients with inadequate aspirin inhibition were significantly more often homozygous PlA1/A1 (65.4% vs. 47.7%, p = 0.015). After multivariate analysis, PlA1/A1 genotype was the only independent risk factor for persistent HPR (OR: 2.07; 95% CI [1.14 to 3.76; p = 0.016).

Conclusion

In CAD patients receiving daily low dose of aspirin, there is a significant and independent association between the expression of GPIIIa PlA1 allele and the occurrence of persistent HPR detected with PFA-100.     

Initial experiences with Multiplate for rapid assessment of antiplatelet agent activity in neurosurgical emergencies

Objective

As the population ages, physicians encounter a growing number of patients who are treated with antiplatelet agents and present with severe conditions requiring urgent neurosurgical therapy. Standard laboratory investigations are insufficient to evaluate platelet activity and furthermore, it is difficult to evaluate effects of haemostatic measures on platelet function. In this article we report our initial experiences with the point-of-care device Multiplate^® for assessment of platelet activity in neurosurgical emergencies on patients with a reported intake of antiplatelet medication.

Methods

Multiplate^® assessment of antiplatelet activity was carried out in 21 non-consecutive patients with a reported intake of antiplatelet medication (aspirin: n = 21, clopidogrel: n = 3, ticragrelor: n = 1) and urgent admission to our hospital because of conditions such as intracranial haemorrhage requiring urgent neurosurgical therapy. Analysis was repeated in order to evaluate the effectiveness of haemostatic drugs and platelet concentrate transfusion on platelet activity in six patients.

Results

No technical difficulties occurred and in all cases, results were obtained within 15 min. On admission, patients’ arachidonic acid induced platelet activity was reduced by 44.4 ± 33.5% (range: −79.7% to +44.3%) compared to the lower reference limit. Two patients had a normal platelet activity despite a reported intake of aspirin. Haemostatic measures significantly increased arachidonic acid induced platelet activity by 100 ± 66% (p < 0.005).

Conclusion

The Multiplate^® device allowed rapid assessment of antiplatelet agent activity and evaluation of haemostatic measures on platelet activity. Further studies with larger patient numbers are needed, but this device may represent a valuable tool to improve treatment modalities in patients treated with antiplatelet medication and conditions requiring urgent neurosurgical therapy.     

Evaluation of the platelet count drop method for assessment of platelet function in comparison with “gold standard” light transmission aggregometry

Introduction

Hyporesponsiveness to antiplatelet agents has been linked to an increased risk of major adverse cardiovascular events. However, light transmission aggregometry (LTA), the gold standard methodology for assessing platelet function, requires expertise and is labour-intensive, which render its use in clinical settings impractical. We assessed whether platelet count drop (PCD), a technique widely available in any haematology laboratory, could replace LTA in testing for inhibition of platelet aggregation induced by antiplatelet agents.

Materials and methods

One hundred and sixty-one coronary artery disease patients taking aspirin alone and 91 patients taking a combination of aspirin and clopidogrel were enrolled. Platelet aggregation was measured by LTA and PCD stimulated with 1.6 mM of arachidonic acid (AA) for aspirin and 5 and 20 μM of adenosine diphosphate (ADP) for clopidogrel.

Results

Correlation between AA-induced LTA and PCD was inexistent (r = - 0.043, p = 0.587), while correlation between ADP-induced LTA and PCD was low (r = 0.374, p < 0.0001 for ADP 5 μM and r = 0.402, p < 0001 for ADP 20 μM). PCD, whether stimulated with AA or ADP, overestimated platelet aggregation as assessed by LTA, by 13-18%. The wide 95% limits of agreement suggest that the assays can disagree significantly in individual patients.

Conclusions

Although the PCD method is widely available in non-specialized laboratories, our results demonstrate that there is poor correlation with the current gold standard, i.e. LTA. Thus, PCD should not be used in replacement of LTA to assess antiplatelet responsiveness.     

Pharmacodynamic assessment of a novel P2Y12 receptor antagonist in Japanese patients with coronary artery disease undergoing elective percutaneous coronary intervention

Introduction

Numerous reports have shown that prasugrel shows a rapid and consistent antiplatelet effect among European and US patients. Previous studies suggest that prasugrel might be expected to achieve an adequate antiplatelet effect in healthy Asian subjects, even at lower doses than those assessed in the TRITON-TIMI 38 study. In this study, the antiplatelet effect of prasugrel was evaluated in Japanese coronary artery disease (CAD) patients undergoing percutaneous coronary intervention (PCI).

Methods and results

Eighty-four patients were randomized into four treatment groups: prasugrel 10/2.5 mg (loading dose [LD]/maintenance dose [MD]), 15/3.75 mg or 20/5 mg, and clopidogrel 300/75 mg. The LD of each regimen was administered the day before PCI, followed by 28-day MD on aspirin background therapy (81-100 mg). Antiplatelet effects were evaluated by light transmission aggregometry and VASP assay.The mean inhibition of platelet aggregation (IPA) induced by 20 μM of adenosine diphosphate at 4 hours after LD was higher among the prasugrel 10/2.5 mg, 15/3.75 mg and 20/5 mg groups compared with the clopidogrel group (12.3%, 20.9%, 29.8% vs. 8.4%, respectively). The proportion of subjects with an IPA of < 10% on Day 28 was lower among the prasugrel 15/3.75 mg, and 20/5 mg groups than in the clopidogrel group (0%, 6.3% vs. 15.8%, respectively). No “major” or “clinically relevant non-major” bleeding was observed.

Conclusions

Prasugrel 15 mg LD/3.75 mg MD or higher doses was well tolerated and achieved a more rapid, higher and consistent antiplatelet effect than clopidogrel in Japanese CAD patients undergoing PCI.     

Effects of additional treatment of sarpogrelate to aspirin therapy on platelet aggregation and plasma plasminogen activator inhibitor activity in patients with stable effort angina

Introduction

Serotonin is secreted from platelets at sites of endothelial injury, where it promotes thrombogenic reactions. Serotonin is reported to be associated with not only coronary artery disease but also cardiac events.

Materials and Methods

We studied 33 patients with stable effort angina (SEA) (11 patients with multivessel disease (MVD) and 22 patients with singlevessel disease (SVD)) and 25 patients with chest pain syndrome (CPS). Sarpogrelate was administered to 22 of 33 patients with SEA in addition to aspirin therapy, and platelet aggregation, plasma serotonin concentration, and plasma plasminogen activator inhibitor (PAI) activity were measured before and 1 week after administration.

Results and Conclusions

Serotonin level was higher in patients with MVD than in those with SVD (p < 0.05) and in those with CPS (p < 0.001). The formation of small-sized platelet aggregates was significantly higher in the high serotonin group than in the low serotonin group of SEA patients. The formation of large-sized platelet aggregates was significantly decreased by administration of sarpogrelate (P < 0.05). The formation of small- or medium-sized aggregates was not significantly decreased. Plasma PAI activity decreased significantly (P < 0.05) although the plasma serotonin concentration did not show significant change by administration of sarpogrelate. Plasma serotonin level is increased in relation to severity of coronary artery disease and plasma serotonin level is associated with increased platelet aggregation. Administration of sarpogrelate in addition to aspirin therapy reduces the increased platelet aggregation and PAI activity, and it may indicate that additional administration of sarpogrelate is useful for patients with SEA.     

Surgery for carpal tunnel syndrome under antiplatelet therapy

Objective

Antiplatelet therapy is often instituted after cardiovascular or neurological ischemic events. In general, discontinuation of the antiplatelet medication for several days is warranted previous to surgery. However, discontinuation can lead to ischemic events. For some forms of surgery, the risks of an ischemic event, and especially, its consequences do not outweigh the benefit of discontinuation of the antiplatelet therapy. Retrospective analysis was done of a cohort of patients treated for carpal tunnel syndrome with special emphasis on postoperative hemorrhage in combination with antiplatelet medication.

Methods

Retrospective analysis of cohort consisting of 362 consecutive patients treated for carpal tunnel syndrome in the Neurosurgical Centre, Nijmegen was done.

Results

In 362 patients 423 operations on carpal tunnel release were done. Thirty-one patients were on antiplatelet therapy, of which 6 did not discontinue the medication before surgery. The remaining patients stopped at least seven days before surgery. A postoperative hemorrhage did not occur in any of the 423 operations.

Conclusion

There seems no reasonable evidence that discontinuation of aspirin for carpal tunnel syndrome is justified. Bleeding complications are considered rare, moreover the impact of an ischemic cardiovascular or a cerebral event would be far more severe than that of postoperative hemorrhage in the wrist.     

Patent foramen ovale closure versus medical therapy in cases with cryptogenic stroke,meta-analysis of randomized controlled trials

Background

PFO is more common in cases with cryptogenic stroke compared to cases with no stroke or stroke of identified etiology. Several randomized controlled trials (RCTs) comparing PFO closure with medical therapy have been published with controversial findings.

Methods

PubMed, Embase and Cochrane library databases were searched for RCT comparing PFO closure with medical therapy including antiplatelet therapy (aspirin or clopidogrel or combination) or anticoagulation. We identified 5 trials, including 3627 cases. The mean duration of follow-up was 4 years. Relative risk (RR) and 95% confidence intervals (CI) were calculated using fixed and random-effects models.

Results

There was a significant reduction in the incidence of stroke among the PFO closure group compared to medical therapy group, 2.0 versus 4.2%, RR 0.48; 95% CI (0.3, 0.7), p < 0.001. The incidence of AF was higher in the PFO closure group compared to medical therapy group, 4.2 versus 0.7%, respectively, RR 5.9, 95% CI (3, 11), p < 0.001. After exclusion of oral anticoagulants cases (19%), analysis showed a lower incidence of stroke in the PFO closure group (2%) compared to antiplatelet therapy (5.2%), RR 0.4; 95% CI (0.3, 0.6), p < 0.001. There was no significant difference between both groups in the incidence of transient ischemic attacks or all-cause deaths.

Conclusion

PFO closure results in a significant reduction in the recurrence of ischemic stroke compared to medical therapy alone, primarily antiplatelet, among cases with PFO and cryptogenic stroke.

     

Influence of renal function and platelet turnover on the antiplatelet effect of aspirin

Introduction

Kidney disease predisposes to cardiovascular events. This study investigated the influence of renal function and platelet turnover on the antiplatelet effect of aspirin in patients with coronary artery disease.

Materials and Methods

We included 124 aspirin-treated patients with coronary artery disease and normal to moderately reduced renal function. All tests were performed one hour after aspirin ingestion. Renal function was assessed using creatinine, estimated glomerular filtration rate (eGFR), and cystatin C. The antiplatelet effect of aspirin was evaluated using the VerifyNow® Aspirin assay and multiple electrode aggregometry (MEA, Multiplate®) induced by collagen (1.0 μg/mL) and arachidonic acid (1.0 mmol/L). Von Willebrand factor was measured as a marker of endothelial dysfunction. Platelet turnover was evaluated by measurements of immature, reticulated platelets.

Results

Renal function did not influence the antiplatelet effect of aspirin evaluated by MEA (r = − 0.2-0.09, p = 0.03-0.77) or the VerifyNow® (r = − 0.12-0.11, all p-values > 0.1). In contrast, renal function correlated inversely with von Willebrand factor levels (r_creatinine = 0.48, p < 0.0001; r_eGFR = − 0.46, p < 0.001; r_{cystatin C} = 0.54, p < 0.0001). The number of immature platelets correlated with platelet aggregation according to MEA (r = 0.20-0.39, all p-values < 0.03), but not according to VerifyNow® (r = − 0.07, p = 0.50).

Conclusions

A reduced antiplatelet effect of aspirin may be explained by an increased number of immature platelets. Moderately impaired renal function was associated with high levels of von Willebrand factor, but not with a reduced antiplatelet effect of aspirin.     

Effect of increased aspirin dose after stenting in association with ClOpidogrel: the FIASCO randomized study

Background

Increased doses of antiplatelet therapy have been proposed to overcome the variability of response. However, the chronic dose of aspirin after DES remains controversial.

Methods and results

We assessed in a prospective and randomized study the benefit of higher dose of aspirin, in association with clopidogrel, on aspirin response and non COX-specific platelet testing in patients receiving Drug Eluting Stent (DES) for stable angina pectoris. 50 consecutive patients receiving DES for stable angina pectoris were prospectively included. They received loading dose of 250 mg aspirin and 600 mg clopidogrel and antiplatelet response was assessed with Arachidonic Acid-induced aggregation (AA-Ag) and ADP-induced aggregation (ADP-Ag) for aspirin and clopidogrel response respectively. Patients were randomized to either 75 or 160 mg of aspirin with 150 mg clopidogrel and platelet testing were repeated one month after hospital discharge. The two groups (aspirin “75 mg” or “160 mg”) had no difference for aspirin response: AA-Ag (5.2 ± 1.7% vs 6 ± 2%, p = 0.75) and non COX-specific pathway testing: ADP-Ag (47 ± 3% vs 49 ± 4%, p = 0.61).

Conclusion

The present study did not show any benefit of higher dose of aspirin neither on aspirin responsiveness, nor on inhibition of non COX-specific pathway. These data does not support use of higher dose than 75 mg of aspirin in association with clopidogrel in patients receiving DES, especially while higher doses have been associated with increased bleeding risk.     

The effect of clopidogrel besylate and clopidogrel hydrogensulfate on platelet aggregation in patients with coronary artery disease: a retrospective study

Background

Recently several alternative forms of the original clopidogrel hydrogensulfate (CHS) were spread worldwide. A large amount of such drugs turned out to be clopidogrel besylate (CB). Only three studies, involving healthy volunteers, investigated the antiplatelet effect of CB, whereas its attribute remained unexplored in the case of patients with cardiovascular diseases. This retrospective study aimed to evaluate the difference between the antiplatelet effects of two clopidogrel formulas, CHS and CB, on patients with coronary artery diseases.

Methods

Data of 150 patients with previous CHS treatment were investigated. According to the documentations, the CHS therapy was shifted to CB. 94 patients of the selected population received dual antiplatelet therapy, clopidogrel and aspirin. The antiplatelet effects of CHS and CB were compared by ADP induced platelet aggregation measurements using light transmission aggregometry.

Results

Irrespective of the therapeutic combinations the performed statistical investigations failed to show significant difference (p = 0.30) between the effect of CB (AGGmax_CB: 27.6 ± 13.7%) or CHS (AGGmax_CHS: 29.0 ± 15.3%) on the ADP induced platelet aggregation. Insignificant deviations were found in both forms of clopidogrel salts, either in the lack (AGGmax_CB : 32.5 ± 14,2%; AGGmax_CHS: 34,0 ± 16,1%; p = 0,29) or in the presence of aspirin (AGGmax_CB: 24.7 ± 12,5%; AGGmax_CHS: 26,0 ± 14,1%; p = 0,31).

Conclusion

Our results indicated that both CB and CHS had an identical inhibitory effect on ADP induced platelet aggregation in patients with cardiovascular diseases. Moreover their efficiency showed no overall significant difference in the case of dual antiplatelet therapy with aspirin as well. However there might be an inter- and intraindividual variability between the two clopidogrel formulas.     

In vitro and in vivo analysis of the antithrombotic and toxicological profile of new antiplatelets N-acylhydrazone derivatives and development of nanosystems: Determination of novel NAH derivatives antiplatelet and nanotechnological approach

Background

Cardiovascular diseases are the most frequent cause of morbidity and mortality worldwide. Among the most important cardiovascular diseases are atherothrombosis and venous thromboembolism that present platelet aggregation as a key event. Currently, the commercial antiplatelet agents display several undesirable effects, which prompt the search for new compounds with better therapeutic index, more efficient body distribution and mechanism.

Methods

In this work we characterized in vivo and in vitro the antithrombotic and toxicological profiles of novel antiplatelet N-substituted-phenylamino-5-methyl-1H-1,2,3-triazole-4-carbohydrazides derivatives also comparing them with aspirin. In addition we also analyzed the stability of the more active compound after encapsulation in PLGA or PCL nanoparticles and the release profile of these new nanosystems.

Results

The biological results revealed not only the selective effect against arachidonic acid-induced platelet aggregation mainly for compounds 2c, 2e and 2 h but also their in vivo active profile on thromboembolism pulmonary animal model with better survival rates (e.g. 82%) than aspirin (33%). The overall toxicological profile was determined by in vitro (MTT reduction tests, neutral red uptake in kidney VERO cells and hemolysis assays) and in vivo (pulmonary embolism) assays that pointed 2c as the most promising derivative with potential as a lead compound. By using the nanoprecipitation technique 2c was loaded into PLGA and PCL nanoparticles showing controlled release profile over 21 days according to our drug release tests.

Conclusion

According to our results compound 2c is the most interesting derivative for further studies as it showed the best activity and toxicological profile also allowing the nanoencapsulation process. Thus 2c may assist in determining a new potential therapy with favorable pharmacokinetics for treatment of thrombotic disorders.