Clopidogrel discontinuation and platelet reactivity following coronary stenting

No rebound effect after a course of clopidogrel in patients with acute TIA or minor stroke

BACKGROUND AND PURPOSE

Previous studies demonstrated that discontinuation of clopidogrel in patients after ACS was associated with a rebound increase in risk of recurrent events. In this study, we aimed to investigate the rebound effect after discontinuation of clopidogrel therapy in patients with TIA or stroke.

METHODS

All patients with minor stroke or TIA were recruited from the Clopidogrel in High-Risk Patients With Acute Nondisabling Cerebrovascular Events (CHANCE) trial. Patients were divided into two groups: patients who discontinued clopidogrel and switched to aspirin therapy   (Clopidogrel Discontinuation Group) and patients who continued one mono-antiplatelet therapy (non-Clopidogrel Discontinuation Group) during 90-180  days. The outcomes included risks of recurrent ischemic stroke, recurrent TIA, and composite events during 90-180  days. The prevalence of each outcome was compared between two groups for every 30 days. Further subgroup analysis was conducted in patients with and without CYP2C19 loss-of-function alleles.

RESULTS

Among the 3456 patients included, a total of 10 patients in the Clopidogrel Discontinuation Group and 11 patients in the non-Clopidogrel Discontinuation Group presented ischemic stroke recurrence during the 90-180-day period. The inter-group comparisons were not significant in each 30 days. Similar results were found for recurrent stroke, recurrent TIA, and composite events in these two groups, which were also found in CYP2C19 subgroup analysis.

CONCLUSIONS

No rebound increase in the risk of ischemic stroke and composite events was found during the 90 days after discontinuation of clopidogrel therapy in patients with TIA or minor stroke in the CHANCE trial.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00979589.

Immature cell fractions after cessation of chronic P2Y12-inhibition in patients with coronary artery diseases

Changes in circulating cell populations may promote ischemic events that occur soon after discontinuation of P2Y₁₂-inhibition. The aim of the study was to track the course of thrombopoietic and erythropoietic cells in patients with coronary artery diseases (CAD) after planned and physician-driven cessation of chronic P2Y₁₂-inhibition (clopidogrel 75 mg OD, or prasugrel 10 mg OD, or ticagrelor 90 mg BID). Cell fractions were determined in 62 patients at baseline (the last day of P2Y₁₂-inhibitor intake), on day-10, day-30, and day-180 thereafter. Immature platelet fraction (IPF), immature reticulocyte fraction (IRF), reticulocyte hemoglobin content (Ret-Hb) and red blood cell count (RBC) significantly increased from baseline to day-180 (IPF: p = .003; IRF: p = .013; Ret-Hb: p < .001; RBC: p = .044). Platelet count, leucocyte count and immature granulocyte fraction did not change over time (p = .561, p = .869, and p = .161, respectively). Fibrinogen levels significantly declined over time (p = .011), thrombopoietin levels increased in a non-significant manner (p = .379). We did not observe any significant interaction with choice of P2Y₁₂-inhibitor, therefore suggesting a drug class-effect. Our data shows, that discontinuation of dual antiplatelet therapy is associated with raised thrombopoietic and erythropoietic activity in the bone marrow, without significant upregulation of thrombopoietin. This provides further evidence for a direct stimulation of precursor cells by P2Y_12-inhibitors.

The effect of cessation of 2nd generation P2Y12 inhibitor therapy on platelet reactivity in patients 1 year after acute myocardial infarction

To assess the effect of cessation of dual antiplatelet therapy (DAPT) regimens containing 2nd generation P₂Y₁₂ inhibitors on platelet reactivity, in patients who completed 12 months of DAPT following an acute myocardial infarction. Clinical data has shown an increased cardiovascular risk in the 90 days following cessation of DAPT. One possible explanation is a transient platelet hyper-reactivity after cessation of treatment. Data from patients treated with 2nd generation P₂Y₁₂ inhibitors is scarce. Patients who completed 12 month DAPT with prasugrel/ticagrelor underwent serial assessment of platelet reactivity (on DAPT and 1, 4 and 12 weeks post cessation). The primary outcome was platelet reactivity, expressed as platelet reactivity units (PRU) at each time point. 41 participants were included in this study, (23 ticagrelor, 18 prasugrel). There was no statistically significant differences in baseline characteristics between prasugrel/ticagrelor treated patients . The pattern of platelet reactivity recovery after DAPT cessation differed between the ticagrelor and prasugrel: with ticagrelor, after the initial PRU increase from baseline, the PRU remained stable, while with prasugrel, there was a further increase in PRU between 1 and 4 weeks, with a return to the 1 week level by 12 weeks (p = 0.034 for the time × treatment interaction between ticagrelor and prasugrel). Our results suggest there is a transient platelet hyper-reactivity after cessation of ADP receptor blockers therapy with prasugrel, but not ticagrelor. Further research is required to elucidate the pathophysiologic mechanisms behind these findings and to evaluate potential strategies to prevent or overcome this "rebound" effect.

Risk of Early Adverse Events After Clopidogrel Discontinuation in Patients Undergoing Short-Term Dual Antiplatelet Therapy: An Individual Participant Data Analysis

OBJECTIVES

The study sought to evaluate the presence of a clinically relevant rebound phenomenon after dual antiplatelet therapy (DAPT) discontinuation in randomized trials.

BACKGROUND

It is currently unknown whether clopidogrel discontinuation after short-term DAPT is associated with an early hazard of ischemic events.

METHODS

The authors performed an individual participant data analysis and aggregate meta-analysis. The primary outcome was major adverse cardiac and cerebrovascular events (MACCE), defined as the composite of cardiac death, myocardial infarction (MI), or stroke.

RESULTS

The study included 11,473 PCI patients with individual participant data from 6 randomized trials comparing short-term DAPT (3 or 6 months) versus long-term DAPT (12 months or more). During the first 90 days following clopidogrel discontinuation, there was no significant increase in the risk of MACCE between patients randomized to short-term DAPT compared with long-term DAPT (hazard ratio [HR]: 1.18; 95% confidence interval [CI]: 0.71 to 1.98; p = 0.52; absolute risk difference 0.10%; 95% CI: -0.16% to 0.36%). The risk of MI or stent thrombosis was similar among patients randomized to short-term DAPT versus long-term DAPT (HR: 0.93; 95% CI: 0.46 to 1.90; p = 0.85). In the aggregate data meta-analysis of 11 trials including 38,919 patients, a higher risk of early MACCE was observed after long-term (≥12 months) DAPT duration (HR: 2.28; 95% CI: 1.69 to 3.09; p < 0.001) but not short-term (<12 months) DAPT duration (HR: 1.08; 95% CI: 0.67 to 1.74; p for interaction = 0.036).

CONCLUSIONS

Among patients undergoing PCI with predominantly new-generation DES, discontinuation of clopidogrel after 3 or 6 months DAPT duration was not associated with an early increase in adverse clinical events. An early increase in MACCE was observed after long-term (≥12 months) DAPT exposure.

96-well plate-based aggregometry

While there are many bench and bedside tests to assess platelet reactivity, ex vivo light transmission aggregometry (LTA) remains the gold standard. LTA, however, is expensive, time-consuming and requires dedicated equipment and staff, making it impractical in many situations. In addition, there is significant variability between data generated at different testing sites meaning that tests often need to be repeated if a patient is transferred to the care of a different hospital. As such, there is clearly an unmet need for standardization of platelet testing. Using the principles of LTA, aggregometry can be conducted in 96-well plates with readings being made in a standard plate reader. This approach allows for the assessment of multiple concentrations of agonists, since the volume of platelets required for each test is significantly lower than for LTA. Furthermore, the lyophilization of a set panel of agonists to a 96-well plate to produce a stable assay substrate allows the production of portable, standardized plates that can be used to generate reproducible tests at multiple sites. In this review, we will discuss the methods and uses of 96-well plate aggregometry for both research and the clinic.

Platelets, inflammation and anti-inflammatory effects of antiplatelet drugs in ACS and CAD

Platelets play a pivotal role in chronic inflammation leading to progression of atherosclerosis and acute coronary events. Recent discoveries on novel mechanisms and platelet-dependent inflammatory targets underpin the role of platelets to maintain a chronic inflammatory condition in cardiovascular disease. There is strong and clinically relevant crosslink between chronic inflammation and platelet activation. Antiplatelet therapy is a cornerstone in the prevention and treatment of acute cardiovascular events. The benefit of antiplatelet agents has mainly been attributed to their direct anti-aggregatory impact. Some anti-inflammatory off-target effects have also been described. However, it is unclear whether these effects are secondary due to inhibition of platelet activation or are caused by direct distinct mechanisms interfering with inflammatory pathways. This article will highlight novel platelet associated targets that contribute to inflammation in cardiovascular disease and elucidate mechanisms by which currently available antiplatelet agents evolve anti-inflammatory capacities, in particular by carving out the differential mechanisms directly or indirectly affecting platelet mediated inflammation. It will further illustrate the prognostic impact of antiplatelet therapies by reducing inflammatory marker release in recent cardiovascular trials.

Clopidogrel Versus Aspirin as an Antiplatelet Monotherapy After 12-Month Dual-Antiplatelet Therapy in the Era of Drug-Eluting Stents

BACKGROUND

The use of dual-antiplatelet therapy (DAPT) exceeding 12 months may increase a bleeding risk despite a lower risk of ischemic events. There is no study to compare clinical outcomes in patients treated with a single-antiplatelet drug after DAPT in the era of drug-eluting stents (DES). We sought to investigate the efficacy and safety of clopidogrel versus aspirin monotherapy after 12-month DAPT after DES implantation using an institutional registry.

METHODS AND RESULTS

This observational study was conducted on consecutive patients receiving DES between January 2003 and December 2010. A total of 3243 patients receiving 12-month DAPT after DES implantation without adverse clinical outcomes were divided into 2 groups based on prescribed antiplatelet status: aspirin (n=2472) and clopidogrel (n=771). Clinical, angiographic, and procedural characteristics revealed more comorbidities and more complex lesions in the clopidogrel group than in the aspirin group. At 36 months after initiation of antiplatelet monotherapy, clopidogrel was associated with a reduction in risk for a composite of cardiac death, myocardial infarction, or stroke (aspirin versus clopidogrel; 3.8% versus 2.6%; hazard ratio, 0.54; 95% confidence interval, 0.32-0.92; P=0.02). The risk of cardiac death was lower with clopidogrel monotherapy than with aspirin monotherapy (1.4% versus 0.5%; hazard ratio, 0.31; 95% confidence interval, 0.11-0.93; P=0.04). Thrombolysis in myocardial infarction major bleeding occurred similarly between both groups (0.9% versus 1.3%; hazard ratio, 1.03; 95% confidence interval, 0.46-2.32; P=0.95).

CONCLUSIONS

After 12-month DAPT, clopidogrel monotherapy, when compared with aspirin monotherapy, might be associated with a reduced risk of recurrent ischemic events in patients receiving DES.

Viable pregnancies beyond 28 weeks gestation in women with a history of unexplained recurrent miscarriage have reduced platelet function

OBJECTIVE

The aim of this study was to characterize platelet function in pregnant patients with a history of unexplained recurrent miscarriage (RM) in the third trimester of a subsequent viable pregnancy, a time at which platelet dysfunction may be associated with an increased obstetric risk.

STUDY DESIGN

A prospective study was performed comparing 30 viable pregnancies that had reached at least 28 weeks' gestation amongst patients who had a background history of unexplained RM, with 30 healthy pregnant controls at a similar gestational age. Platelet function was determined by means of platelet aggregation in response to 5 different agonists at multiple concentrations.

RESULTS

Amongst the 30 RM patients with ongoing viable pregnancies, we demonstrated significantly reduced platelet aggregation compared to the pregnant controls in the third trimester. For three out of five agonists, we demonstrated statistically significantly decreased platelet aggregation and for all five agonists we demonstrated significantly decreased platelet aggregation in the postnatal period. There were no obvious differences in obstetric outcomes.

CONCLUSION

This study shows that women with a history of unexplained RM have reduced platelet function after 28 weeks' gestation in their subsequent pregnancies compared to healthy pregnant controls, but without this difference leading to any obvious increase in adverse obstetric risk.

Coming safely to a stop: a review of platelet activity after cessation of antiplatelet drugs

The platelet P2Y12 antagonists are widely used, usually in combination with aspirin, to prevent atherothrombotic events in patients with acute coronary syndromes during percutaneous coronary intervention and after placement of arterial stents. Inhibition by clopidogrel or prasugrel lasts for the lifetime of the affected platelets and platelet haemostatic function gradually recovers after stopping the drug, as new unaffected platelets are formed. The optimal durations for dual antiplatelet therapy are prescribed by clinical guidelines. Continuation beyond the recommended duration is associated with an increased mortality, mainly associated with major bleeding. Fear of a 'rebound' of prothrombotic platelet activity on stopping the drug has provoked much discussion and many studies. However, review of the available literature reveals no evidence for production of hyper-reactive platelets after cessation of clopidogrel in patients who are stable. Any increase in acute coronary and other vascular events after stopping seems most likely therefore to be due to premature discontinuation or disruption of treatment while thrombotic risk is still high. No difference in rebound was found with the newer P2Y12 inhibitors, although ticagrelor and prasugrel are more potent platelet inhibitors than clopidogrel. Recent randomized controlled trials confirm it is safe to stop the thienopyridine and continue with aspirin alone in most patients after the duration of treatment recommended by the guidelines. Decisions on when to stop therapy in individuals, however, remain challenging and there is a growing rationale for platelet testing to assist clinical judgement in certain situations such as patients stopping dual antiplatelet therapy before surgery or in individuals at highest bleeding or thrombotic risk.

Gradual increase in thrombogenicity of juvenile platelets formed upon offset of prasugrel medication

In patients with acute coronary syndrome, dual antiplatelet therapy with aspirin and a P2Y12 inhibitor like prasugrel is prescribed for one year. Here, we investigated how the hemostatic function of platelets recovers after discontinuation of prasugrel treatment. Therefore, 16 patients who suffered from ST-elevation myocardial infarction were investigated. Patients were treated with aspirin (100 mg/day, long-term) and stopped taking prasugrel (10 mg/day) after one year. Blood was collected at the last day of prasugrel intake and at 1, 2, 5, 12 and 30 days later. Platelet function in response to ADP was normalized between five and 30 days after treatment cessation and in vitro addition of the reversible P2Y12 receptor antagonist ticagrelor fully suppressed the regained activation response. Discontinuation of prasugrel resulted in the formation of an emerging subpopulation of ADP-responsive platelets, exhibiting high expression of active integrin αIIbβ3. Two different mRNA probes, thiazole orange and the novel 5'Cy5-oligo-dT probe revealed that this subpopulation consisted of juvenile platelets, which progressively contributed to platelet aggregation and thrombus formation under flow. During offset, juvenile platelets were overall more reactive than older platelets. Interestingly, the responsiveness of both juvenile and older platelets increased in time, pointing towards a residual inhibitory effect of prasugrel on the megakaryocyte level. In conclusion, the gradual increase in thrombogenicity after cessation of prasugrel treatment is due to the increased activity of juvenile platelets.

Platelet function in patients with a history of unexplained recurrent miscarriage who subsequently miscarry again

OBJECTIVE

This study was designed to evaluate platelet aggregation in pregnant women with a history of unexplained recurrent miscarriage (RM) and to compare platelet function in such patients who go on to have either another subsequent miscarriage or a successful pregnancy.

STUDY DESIGN

A prospective longitudinal study was performed to evaluate platelet function in a cohort of patients with a history of unexplained RM. Platelet reactivity testing was performed at 4-7 weeks gestation, to compare platelet aggregation between those with a subsequent miscarriage and those who had successful live birth outcomes. Platelet aggregation was calculated using a modified assay of light transmission aggregometry with multiple agonists at different concentrations.

RESULTS

In a cohort of 39 patients with a history of RM, 30 had a successful pregnancy outcome while nine had a subsequent miscarriage again. Women with subsequent miscarriage had reduced platelet aggregation in response to adenosine diphosphate (P value 0.0012) and thrombin receptor activating peptide (P value 0.0334) when compared to those with successful pregnancies. Women with subsequent miscarriages also had a trend towards reduced platelet aggregation in response to epinephrine (P value 0.0568).

CONCLUSION

Patients with a background history of unexplained RM demonstrate reduced platelet function if they have a subsequent miscarriage compared to those who go on to have a successful pregnancy.

Evidence of platelet sensitization to ADP following discontinuation of clopidogrel therapy in patients with stable coronary artery disease

Epidemiological studies have linked clopidogrel discontinuation with an increased incidence of ischemic events. This has led to the hypothesis that clopidogrel discontinuation may result in a pharmacological rebound. We evaluated the impact of clopidogrel discontinuation on platelet function. Platelet aggregation was measured by light transmission aggregometry (LTA) in response to adenosine diphosphate (ADP) 0.5, 1, 1.5, 2.5, 5 and 10 µM and by VerifyNow® P2Y12, in 37 clinically stable coronary artery disease (CAD) patients scheduled to discontinue clopidogrel treatment, and 37 clinically stable CAD patients not taking clopidogrel. Platelet function was assessed the day before clopidogrel cessation and 1, 3, 7, 14, 21 and 28 days after. Clopidogrel had been initiated a median of 555 days (ranging from 200 to 2280 days) before the treating cardiologist recommended its discontinuation. All participants were taking aspirin, most commonly 80 mg daily although a minority was prescribed 325 mg daily. Following clopidogrel discontinuation, VerifyNow® P2Y12 did not detect any rebound platelet activity, but ADP-induced LTA showed platelet sensitization to ADP, particularly at low ADP levels. Increased platelet activity was detectable seven days after clopidogrel cessation and remained higher than in controls 28 days after discontinuation. No clinical event occurred in any of the participants during the 28 days following clopidogrel cessation. In conclusion, platelet sensitization to ADP as a consequence of chronic clopidogrel administration may partially explain the recrudescence of ischemic events following clopidogrel discontinuation in otherwise stable coronary artery patients.

Randomised, double-blind trial on the value of tapered discontinuation of clopidogrel maintenance therapy after drug-eluting stent implantation. Intracoronary Stenting and Antithrombotic Regimen: CAUTION in Discontinuing Clopidogrel Therapy--ISAR-CAUTION

There is little evidence on the optimal mode of clopidogrel discontinuation. Epidemiological studies observed clustering of thrombotic events after cessation of chronic clopidogrel therapy. The underlying mechanism has been ascribed to transient platelet hyper-reactivity. Gradual tapering of clopidogrel may have the potential to attenuate this phenomenon. The objective of the present study was to assess whether in patients with drug-eluting stents (DES) gradual discontinuation of clopidogrel maintenance therapy is superior to conventional, abrupt discontinuation. Patients with planned discontinuation of chronic clopidogrel therapy after DES implantation were randomised in a double-blinded fashion to either gradual discontinuation (according to a tapering schema over four weeks) or abrupt discontinuation (after continued clopidogrel therapy for additional four weeks). The primary endpoint was the composite of cardiac death, myocardial infarction, stroke, stent thrombosis, major bleeding or rehospitalisation due to an acute coronary syndrome at 90 days. Enrollment of 3,000 patients was planned. The study was stopped prematurely due to slow recruitment after enrollment of 782 patients. At 90 days, nine of 392 patients (2.3%) with tapered cessation reached the primary endpoint compared to five of 390 patients (1.3%) with abrupt cessation (p=0.284). The composite of death or myocardial infarction occurred in three patients with tapered and three patients with abrupt discontinuation (p=0.764). In conclusion, tapered discontinuation of chronic clopidogrel therapy is not superior to abrupt discontinuation regarding the primary endpoint in this study. However, the results must be interpreted in view of the premature termination of the trial and low event rates.

Testing platelet function

Platelet function tests have been traditionally used to aid in the diagnosis and management of patients with bleeding problems. Given the role of platelets in atherothrombosis, several dedicated platelet function instruments are now available that are simple to use and can be used as point-of-care assays. These can provide rapid assessment of platelet function within whole blood without the requirement of sample processing. Some tests can be used to monitor antiplatelet therapy and assess risk of bleeding and thrombosis, although current guidelines advise against this. This article discusses the potential utility of tests/instruments that are available.

A randomized controlled trial of platelet activity before and after cessation of clopidogrel therapy in patients with stable cardiovascular disease

OBJECTIVES

The aim of this randomized placebo-controlled trial was to determine if withdrawing clopidogrel therapy leads to increased platelet activity compared with pre-treatment values in patients with stable coronary artery or peripheral arterial disease.

BACKGROUND

Reports of increased cardiovascular events after planned cessation of clopidogrel therapy have raised concerns over the possible existence of a rebound in platelet activity.

METHODS

In all, 171 patients receiving established aspirin therapy were randomly assigned to placebo or clopidogrel (75 mg daily) for 28 days. Blood samples were taken at pre-treatment baseline, on treatment just before discontinuation of study drug, and on days 7, 14, and 28 after discontinuation. The primary outcome measure was adenosine diphosphate (ADP)-stimulated platelet fibrinogen binding. Six secondary outcomes were assessed: ADP-stimulated platelet P-selectin, unstimulated platelet fibrinogen binding, and light transmission aggregometry with ADP 5 and 10 μmol/l recorded at maximum and at 6 min.

RESULTS

The ADP-stimulated platelet fibrinogen binding, P-selectin expression, and platelet aggregation were lower on treatment with clopidogrel compared with baseline (p < 0.0001), but returned to baseline levels by 7 days after discontinuation. Mixed model analyses excluding the on-treatment timepoint showed no overall differences between the clopidogrel and placebo groups (p > 0.05). Furthermore, there was no evidence of an interaction between platelet inhibition over time and treatment allocation.

CONCLUSIONS

This trial found no evidence for rebound of platelet activity to above baseline after stopping clopidogrel in patients with stable coronary artery disease or peripheral arterial disease. (Is Cessation of Clopidogrel Therapy Associated With Rebound of Platelet Activity in Stable Vascular Disease Patients?; ISRCTN77887299/77887299).

Platelet reactivity changes significantly throughout all trimesters of pregnancy compared with the nonpregnant state: a prospective study

OBJECTIVE

Platelets play an important role in the pathophysiology of uteroplacental disease and platelet reactivity may be an important marker of uteroplacental disease activity. However, platelet reactivity has not been evaluated comprehensively in normal pregnancy. We sought to evaluate platelet reactivity using a number of agonists at defined time points in pregnancy using a novel platelet assay and compare these with a nonpregnant cohort.

DESIGN

Prospective longitudinal study.

SETTING

Outpatient department of a large tertiary referral centre.

SAMPLE

Eighty participants with 30 nonpregnant women and 50 pregnant women assessed longitudinally.

METHODS

This was a prospective cohort study performed longitudinally throughout uncomplicated singleton pregnancies with participants recruited before 15 weeks of gestation. They were controlled for a number of factors known to affect platelet reactivity. Blood samples were obtained in each trimester. Thirty nonpregnant healthy female volunteers also had a platelet assay performed. A modification of standard light transmission aggregometry was used to assess platelet function, with light absorbance measured following the addition of five different agonists at submaximal concentrations. Dose-response curves were plotted for each agonist for the nonpregnant cohort and in each trimester for the pregnant cohort.

MAIN OUTCOME MEASURES

Dose-response curves and median effective concentration.

RESULTS

When compared with the nonpregnant controls a significant reduction was demonstrated in platelet reactivity to collagen during the first trimester of pregnancy (P < 0.0001). Platelet aggregation increased significantly from the first to third trimesters in response to collagen and arachidonic acid.

CONCLUSION

Platelet reactivity varies according to pregnancy state, gestational age and agonist. The finding that platelet reactivity is reduced in the first trimester of pregnancy may be useful for the interpretation of further studies examining the role of platelet reactivity in the first trimester of pregnancies that develop uteroplacental disease.

Dual antiplatelet therapy with aspirin and clopidogrel: what is the risk in noncardiac surgery? A narrative review

Clopidogrel is one of the most commonly prescribed medications and is currently recommended along with aspirin as treatment to be used for 1 year in all patients without contraindications following an acute coronary syndrome. Patients who are committed to clopidogrel therapy due to recent coronary artery stent implantation may require noncardiac surgery during this recommended period of dual antiplatelet therapy (DAPT). Due to differing rates of endothelialization, patients who undergo bare-metal stent implantation generally require ≥ 1 month of uninterrupted DAPT, and those who undergo drug-eluting stent implantation require ≥ 12 months. Many surgeons ask their patients to stop taking clopidogrel in advance of their procedure to decrease perioperative bleeding. This practice is based largely on anecdotal experience and extrapolated from limited data in cardiac surgery. Premature cessation of aspirin and/or clopidogrel following coronary artery stenting, however, has been associated with acute stent thrombosis, myocardial infarction, and death. We searched PubMed for English language articles published from 1960 to 2012, using the keywords aspirin, clopidogrel, surgery, general, vascular, genitourinary, thoracic, orthopedic, ophthalmologic, dermatologic, endoscopy, colonoscopy, cardiac device implantation, pacemaker, defibrillator, bronchoscopy, bridging, bleeding complications, and transfusion, including various combinations. s were reviewed to confirm relevance, and then the full articles were extracted. References from extracted articles were also reviewed for relevant articles. Literature regarding perioperative clopidogrel continuation is predominantly composed of small, nonrandomized data, but suggests that most noncardiac surgeries or procedures can be performed safely while patients are taking clopidogrel. In this article, we review the current best evidence on the risk for bleeding with clopidogrel therapy in noncardiac surgery, summarize recent guidelines on appropriate duration of DAPT, and make recommendations on the management of perioperative DAPT.

Discontinuation of long-term clopidogrel therapy is associated with death and myocardial infarction after saphenous vein graft percutaneous coronary intervention

OBJECTIVES

This study sought to examine the pattern of death and myocardial infarction (MI) after clopidogrel cessation in patients undergoing percutaneous coronary intervention (PCI) of the saphenous vein graft (SVG).

BACKGROUND

The timing and incidence of adverse events by different durations of clopidogrel therapy after SVG PCI remain unknown.

METHODS

This is a cohort study of patients undergoing SVG PCI between 2000 and 2009, followed for all-cause mortality or MI after stopping clopidogrel. Incidence rates were calculated across different time periods after clopidogrel cessation. Adjusted incidence rate ratios (IRR) were calculated with multivariable regression (piecewise exponential and Poisson).

RESULTS

There were 603 patients who underwent SVG PCI, of which 411 were event-free at the time of clopidogrel cessation. The incidence rate (95% confidence interval: [CI])/1,000 person-days of death or MI after stopping clopidogrel in the time intervals of 0 to 90 days, 91 to 365 days, and 1 to 2 years were 1.26 (95% CI: 0.93 to 1.70), 0.41 (95% CI: 0.30 to 0.56), and 0.41 (95% CI: 0.30 to 0.55), respectively. In multivariable analyses, the overall IRR (95% CI) for death or MI in the 0- to 90-day interval after stopping clopidogrel compared with the 91- to 365-day interval was 2.58 (95% CI: 1.64 to 4.07). Similar results were observed over a broad range of clopidogrel treatment durations (<6 months, 6 months to 1 year, 1 to 2 years, or >2 years). The results were also consistent across subgroups, including sex, stent type, stent diameter, PCI period, and diabetes status. When death alone was evaluated, there remained a significant increase in the event rate in the 0- to 90-day interval compared with the 91- to 365-day interval (IRR: 2.33; 95% CI: 1.32 to 4.11).

CONCLUSIONS

A clustering of events was observed in the initial 0 to 90 days after clopidogrel cessation in all treatment durations of clopidogrel investigated after SVG PCI. These results might have important implications in high-risk cohorts undergoing PCI. Additional studies are needed to elucidate the mechanisms underlying the early clustering of events after clopidogrel cessation.

Platelet reactivity in type 2 diabetes mellitus: a comparative analysis with survivors of myocardial infarction and the role of glycaemic control

Patients with type 2 diabetes mellitus exhibit considerable platelet dysfunction, though this is poorly characterized in patients with diabetes taking aspirin for the primary prevention of cardiovascular events. We sought to compare platelet function in this patient population with that of a high-risk group of non-diabetic subjects with a history of previous myocardial infarction (MI), and to assess whether glycaemic control impacts on platelet function.

METHODS

Platelet aggregation was measured in response to incremental concentrations of five platelet agonists using light transmission aggregometry. All patients were taking aspirin, and aspirin insensitivity was defined as ≥ 20% arachidonic acid (AA) mediated aggregation. Patients with diabetes were divided according to glycaemic control (HbA(1c)): optimal ≤ 6.5, good 6.6-7.4 and suboptimal ≥ 7.5%.

RESULTS

In total, 85 patients with type 2 diabetes and 35 non-diabetic patients with previous MI were recruited. Compared to MI patients, diabetes patients had increased aggregation in response to multiple concentrations of epinephrine, collagen, adenosine diphosphate and AA. Aspirin insensitivity was more common in type 2 diabetes (15% vs. 0%, p=0.037). Platelet aggregation was increased in response to several agonists patients with suboptimal glycaemic control compared to patients with optimal control. Aspirin insensitivity was also more common in patients with suboptimal glycaemic control compared to those with good or optimal control (26.0% vs. 8.3% vs. 4%, p=0.04).

CONCLUSION

Patients with type 2 diabetes mellitus, without proven vascular disease, exhibit platelet dysfunction and have increased platelet aggregation and aspirin insensitivity compared to non-diabetic patients with previous MI. Platelet dysfunction in diabetes is more severe in patients with suboptimal glycaemic control.

Role of newly formed platelets in thrombus formation in rat after clopidogrel treatment: comparison to the reversible binding P2Y₁₂ antagonist ticagrelor

Platelet P2Y₁₂ receptors play an important role in arterial thrombosis by stimulating thrombus growth. Both irreversibly (clopidogrel) and reversibly binding (ticagrelor, AZD6140) P2Y₁₂ antagonists are clinically used for restricted periods, but possible differences in platelet function recovery after drug cessation have not been investigated. We treated WKY rats with a single, high dose of 200 mg/kg clopidogrel or 40 mg/kg ticagrelor. Blood was collected at different time points after treatment. Flow cytometry confirmed full platelet protection against ADP-induced αIIbβ₃ activation shortly after clopidogrel or ticagrelor treatment. At later time points after clopidogrel treatment, a subpopulation of juvenile platelets appeared that was fully responsive to ADP. Addition of ticagrelor to clopidogrel-treated blood reduced αIIbβ₃ activation of the unprotected platelets. In contrast, at later time points after ticagrelor treatment, all platelets gradually lost their protection against ADP activation. Perfusion experiments showed abolishment of thrombus formation shortly after clopidogrel or ticagrelor treatment. Thrombus formation on collagen was determined under high shear flow conditions. At later time points, large thrombi formed in the clopidogrel but not in the ticagrelor group, and unprotected, juvenile platelets preferentially incorporated into the formed thrombi. However, platelets from both groups were still similarly reduced in assays of whole blood aggregation. Conclusively, recovery of rat platelet function after ticagrelor differs mechanistically from that after clopidogrel. This difference is masked by conventional platelet aggregation methods, but is revealed by thrombus formation measurement under flow. Juvenile platelets formed at later time points after clopidogrel treatment promoted thrombus formation.

Abrupt cessation of one-year clopidogrel treatment is not associated with thrombotic events

We aimed to examine the rate of thrombotic events after discontinuation of one year clopidogrel therapy in patients with implanted coronary stent, and to determine platelet aggregability by multiple electrode analyzer after cessation of clopidogrel. This prospective, multicenter study enrolled 200 patients subjected to coronary stent implantation and treated with aspirin + clopidogrel one year after the stent placement. Platelet aggregation was measured using 3 agonists [adenosine diphosphate with PGE(1) (ADPHS), arachidonic-acid (ASPI), and thrombin receptor activating peptide (TRAP)] on the day of cessation of clopidogrel and at 10, 45, and 90 days after clopidogrel was stopped. Two thrombotic events were registered during the 6-months follow up (one ischemic stroke and one myocardial infarction; incidence of 1%). The mean values of ADP + PGE(1)- and ASPI-induced aggregation 10 - 90 days after the cessation of clopidogrel were significantly higher than values obtained before the termination of the drug (P < 0.001, all). Cessation of clopidogrel did not influence the TRAP-induced aggregation, which reached the plateau in all measurements. In conclusion, the incidence of thrombotic events after the cessation of one-year clopidogrel treatment might be lower than expected in patients with implanted coronary stent.