Platelet activation in patients after an acute coronary syndrome: results from the TIMI-12 trial. Thrombolysis in Myocardial Infarction

Point-of-care assessment of platelet reactivity in the emergency department may facilitate rapid rule-out of acute coronary syndromes: a prospective cohort pilot feasibility study

OBJECTIVE

Accurate, efficient and cost-effective disposition of patients presenting to emergency departments (EDs) with symptoms suggestive of acute coronary syndromes (ACS) is a growing priority. Platelet activation is an early feature in the pathogenesis of ACS; thus, we sought to obtain an insight into whether point-of-care testing of platelet function: (1) may assist in the rule-out of ACS; (2) may provide additional predictive value in identifying patients with non-cardiac symptoms versus ACS-positive patients and (3) is logistically feasible in the ED.

DESIGN

Prospective cohort feasibility study.

SETTING

Two urban tertiary care sites, one located in the USA and the second in Argentina.

PARTICIPANTS

509 adult patients presenting with symptoms of ACS.

MAIN OUTCOME MEASURES

Platelet reactivity was quantified using the Platelet Function Analyzer-100, with closure time (seconds required for blood, aspirated under high shear, to occlude a 150 µm aperture) serving as the primary endpoint. Closure times were categorised as 'normal' or 'prolonged', defined objectively as the 90th centile of the distribution for all participants enrolled in the study. Diagnosis of ACS was made using the standard criteria. The use of antiplatelet agents was not an exclusion criterion.

RESULTS

Closure times for the study population ranged from 47 to 300 s, with a 90th centile value of 138 s. The proportion of patients with closure times ≥138 s was significantly higher in patients with non-cardiac symptoms (41/330; 12.4%) versus the ACS-positive cohort (2/105 (1.9%); p=0.0006). The specificity of 'prolonged' closure times (≥138 s) for a diagnosis of non-cardiac symptoms was 98.1%, with a positive predictive value of 95.4%. Multivariate analysis revealed that the closure time provided incremental, independent predictive value in the rule-out of ACS.

CONCLUSIONS

Point-of-care assessment of platelet reactivity is feasible in the ED and may facilitate the rapid rule-out of ACS in patients with prolonged closure times.

Development of glycoprotein IIb–IIIa antagonists: translation of pharmacodynamic effects into clinical benefit

This article will review the development of glycoprotein IIb-IIIa antagonists, with particular emphasis on the characteristics and pharmacodynamic studies of each agent that is available for clinical use. Abciximab is a Fab fragment of the 7E3 antibody that has high affinity and a slow rate of dissociation from glycoprotein IIb-IIIa. In contrast, the small molecules eptifibatide and tirofiban, have a much more rapid rate of dissociation, with an off time of 10 to 15 s. Accordingly, the circulating pool of abciximab is predominantly associated with platelets, whereas maintenance of a consistent concentration of tirofiban and eptifibatide in the blood is critical in order to achieve and sustain their inhibitory effects. The affinity of abciximab and tirofiban for glycoprotein IIb-IIIa are substantially greater than that of eptifibatide, necessitating maintenance of greater molar concentrations of eptifibatide in blood in order to achieve effective inhibition of the binding of fibrinogen to the activated conformer of glycoprotein IIb-IIIa.

Combination of high on-treatment platelet aggregation and low deaggregation better predicts long-term cardiovascular events in PCI patients under dual antiplatelet therapy

High on-treatment platelet reactivity is associated with short-term major cardiovascular (CV) events in patients undergoing percutaneous coronary intervention (PCI). Maximum and final aggregation assessed by light transmission aggregometry (LTA) have both been used to predict short-term outcome after PCI, however their long-term prognostic impact remains controversial. There is currently no information regarding the prognostic role of deaggregation and its added value in combination with established aggregation parameters. About 1279 patients with symptomatic coronary artery disease (CAD) undergoing PCI were enrolled in this monocentric study. On-treatment platelet aggregation under clopidogrel maintenance therapy, as well as deaggregation was determined by maximum and final aggregation (5 min after adding of the agonist). Deaggregation was defined as slope of the tangent between Aggmax +0.5 min. Primary endpoints were the composite of myocardial infarction, stroke, and CV death or stent thrombosis according to the ARC criteria. Low deaggregation, defined as values in the lowest tertile (<1.5), was more frequent in patients with acute coronary syndromes (ACS) compared to patients with stable angina pectoris (SAP), ACS: 29.6% vs. SAP: 22.0%, p = 0.001. The combination of high on-treatment platelet reactivity, defined by the upper tertile of Aggmax and low deaggregation, was associated with significantly increased risk for combined long-term CV events. The combination of low deaggregation and high on-treatment platelet reactivity is associated with higher risk for recurrent events in patients with CAD undergoing PCI. Thus, deaggregation might be a more sensitive parameter providing added value in terms of risk prediction for long-term recurrent CV events in relation with established aggregation parameters.

Platelet glycoprotein IIIA PIA1/A2 polymorphism in young patients with ST elevation myocardial infarction and idiopathic ischemic stroke

It has been identified that platelet glycoprotein IIIa PIA1/A2 polymorphism plays an important role in atherothrombotic disease such as myocardial infarction and stroke, but results remain controversial. Here, we investigated whether the PIA2 allele is associated with ST myocardial infarction or idiopathic ischemic stroke in young individuals in two independent studies. In a case-control study 275 patients with ST elevation myocardial infarction ≤45 years of age and 278 controls were recruited. In a second study, 200 patients with idiopathic ischemic stroke ≤45 years of age and 200 controls were enrolled. In both studies cases and controls were matched by age and gender. The PIA1/A2 polymorphism was determined in all participants by a polymerase chain reaction-restriction fragment length polymorphism assay. There was a significant difference in the PIA1/A2 genotype distribution (P = 0.001) and allele frequency (P = 0.001), between ST elevation myocardial infarction and control groups, but not in the PIA1/A2 genotype distribution (P = 0.61) and allele frequency (P = 0.80), between idiopathic ischemic stroke. The allele PIA2 represented an independent risk for ST elevation myocardial infarction but not for idiopathic ischemic stroke. Hypertension, smoking, and family history of atherothrombotic disease were also associated with ST elevation myocardial infarction and idiopathic ischemic stroke. Our results suggest that PA2 allele represents a risk factor for ST elevation myocardial infarction in young Mexican individuals but not for idiopathic ischemic stroke.

Comparison of peri-procedural platelet inhibition with prasugrel versus adjunctive cilostazol to dual anti-platelet therapy in patients with ST segment elevation myocardial infarction

BACKGROUND

It has been well known that the inhibition of platelet aggregation (IPA) by anti-platelet agents was important to reduce the thrombo-embolic events in patients with ST segment elevation myocardial infarction (STEMI). However, the peri-procedural IPA by anti-platelet agents was not well known.

METHODS

We compared the peri-procedural IPA between prasugrel and adjunctive cilostazol to dual anti-platelet therapy (triple anti-platelet therapy; TAP) in patients with STEMI undergoing primary percutaneous coronary intervention (PCI). We prospectively randomized 70 consecutive clopidogrel-naive patients with STEMI planned PCI to either prasugrel [loading dose (LD) 60 mg; 37 patients] or TAP (LD aspirin 300 mg, clopidogrel 600 mg, and cilostazol 200mg; 33 patients). Primary end points of the study were the platelet reactivity unit (PRU) or % inhibition by the VerifyNow P2Y12 assay at pre-PCI and pre-discharge.

RESULTS

The drug loading to pre-PCI time was similar between prasugrel and TAP groups (25.4 ± 10.42 min vs. 25.5 ± 10.56 min, p=0.957). PRU at pre-PCI was significantly lower in prasugrel than in TAP (269.1 ± 71.69 vs. 306.5 ± 48.67, p=0.012). The lower PRU and greater % inhibition also observed in prasugrel than in TAP at pre-discharge (108.2 ± 60.51 vs. 238.1 ± 73.40; 63.6 ± 18.51% vs. 16.8 ± 17.91%, p<0.001 respectively). No differences in in-hospital bleeding complications between the two groups were observed.

CONCLUSION

Our study demonstrates that prasugrel could produce a significantly greater peri-procedural as well as in-hospital IPA compared with TAP in patients with STEMI undergoing primary PCI.

Efficacy of clopidogrel reloading in patients with acute coronary syndrome undergoing percutaneous coronary intervention during chronic clopidogrel therapy (from the Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty [ARMYDA-8 RELOAD-ACS] trial)

Whether an additional clopidogrel load in patients receiving chronic clopidogrel therapy and undergoing percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) is associated with clinical benefit has not been well characterized. The aim of the present study was to evaluate, in a randomized protocol, the safety and effectiveness of clopidogrel reload for patients with ACS undergoing PCI in the background of chronic clopidogrel therapy. A total of 242 patients with non-ST-segment elevation ACS with >10 days of clopidogrel therapy randomly received a 600-mg loading dose of clopidogrel 4 to 8 hours before PCI (n = 122) or placebo (n = 120). The primary end point was the 30-day incidence of major adverse cardiac events (death, myocardial infarction, target vessel revascularization). The primary end point occurred in 4.1% of patients in the reload arm versus 14.1% in the placebo arm (odds ratio 0.26, 95% confidence interval 0.10 to 0.73, p = 0.013). This benefit in the reload arm was mainly from the prevention of periprocedural myocardial infarction (4.1% vs 13%, p = 0.02) and was paralleled by lower periprocedural platelet reactivity. The aggregometry data were consistent with the clinical outcome. No difference was found in the bleeding outcomes between the 2 groups. In conclusion, the results from the Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty (ARMYDA-8 RELOAD-ACS) trial have shown a significant clinical benefit from reloading patients with ACS receiving chronic clopidogrel therapy before PCI. These data might be relevant in clinical practice, given the large number of patients with ACS who are still currently treated with clopidogrel during PCI.

Neutrophil-lymphocyte ratio and the platelet-lymphocyte ratio predict the limb survival in critical limb ischemia

BACKGROUND

The objective of this study was to evaluate whether admission neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR) might reflect amputation in patients with critical limb ischemia (CLI) who could not get surgical or radiological (percutaneous transluminal angioplasty) revascularization.

METHODS

A total of 104 patients with nonreconstructable CLI over a 5-year period were collected prospectively.

RESULTS

Admission NLR levels of ≥3.2 and a PLR of ≥160 were found to represent the optimal cutoff values to risk stratification of patients. If both levels were elevated, patients had a median overall limb survival of 22 months. For cases where both levels were less than the cutoff values, the median overall limb survival time was not reached but was greater than 60 months.

CONCLUSIONS

Admission NLR and PLR both merit further evaluation as prognostic indices in patients with CLI.

Platelet flow cytometry

Flow cytometry is a powerful and versatile tool which can be used to provide substantial phenotypic data on platelets by yielding quantitative information of their physical and antigenic properties. This includes surface expression of functional receptors, bound ligands, expression of granule components, interaction of platelets with other platelets via aggregation, or interaction with other blood components, such as leukocytes or the plasma coagulation system. Quantitative assessment of these parameters may facilitate the diagnosis of inherited or acquired platelet disorders, assist in the diagnosis of diseases associated with platelet activation, or assist in the monitoring of safety and efficacy of antiplatelet therapy.

Aspirin and platelet adenosine diphosphate receptor antagonists in acute coronary syndromes and percutaneous coronary intervention: role in therapy and strategies to overcome resistance

Platelet activation and aggregation are key components in the cascade of events causing thrombosis following plaque rupture. Antiplatelet therapy is essential in the treatment of patients with acute coronary syndromes (ACS) and for those requiring percutaneous coronary intervention (PCI). Aspirin (acetylsalicylic acid) is a well established antiplatelet therapy and is mandated for secondary prevention of cardiovascular events following ACS. In patients with ACS, the addition of clopidogrel to aspirin is more effective than aspirin alone. For patients undergoing PCI, dual antiplatelet therapy with aspirin and clopidogrel is warranted. Aspirin should be continued indefinitely after PCI. Pretreatment of patients with clopidogrel prior to PCI lowers the incidence of cardiovascular events, yet the optimum timing of drug administration and dose are still being investigated, as is the duration of therapy following PCI. Late-stent thrombosis with drug-eluting stents has pushed the recommendation for duration of clopidogrel therapy up to 1 year and perhaps beyond, in patients without risks for bleeding. The concepts of aspirin and clopidogrel resistance are important clinical questions. No uniform definition exists for aspirin or clopidogrel resistance. Measurements of resistance are often highly variable and do not necessarily correlate with clinical resistance. Noncompliance remains the most prominent mode of resistance. Screening of selected patient populations for resistance or pharmacologic intervention of those patients termed 'resistant' warrants further study.

The platelet fibrinogen receptor: from megakaryocyte to the mortuary

Platelets are integral to normal haemostatic function and act to control vascular haemorrhage with the formation of a stable clot. The fibrinogen receptor (glycoprotein IIb/IIIa [GPIIb/IIIa]) is the most abundant platelet integrin and, by binding fibrinogen, facilitates irreversible binding of platelets to the exposed extracellular matrix and enables the cross-linking of adjacent platelets. The vital role of GPIIb/IIIa requires tight control of both its synthesis and function. After transcription from distinct domains on chromosome 17, the two subunits of the heterodimer are carefully directed through organelles with intricate regulatory steps designed to prevent the cellular expression of a dysfunctional receptor. Similarly, exquisite control of platelet activation via bidirectional signalling acts to limit the inappropriate and excessive formation of platelet-mediated thrombus. However, the enormous diversity of genetic mutations in the fibrinogen receptor has resulted in a number of allelic variants becoming established. The Pro³³ polymorphism in GPIIIa is associated with increased cardiovascular risk due to a pathological persistence of outside-in signalling once fibrinogen has dissociated from the receptor. The polymorphism has also been associated with the phenomenon of aspirin resistance, although larger epidemiological studies are required to establish this conclusively. A failure of appropriate receptor function due to a diverse range of mutations in both structural and signalling domains, results in the bleeding diathesis Glanzmann's thrombasthaenia. GPIIb/IIIa inhibitors were the first rationally designed anti-platelet drugs and have proven to be a successful therapeutic option in high-risk primary coronary intervention. As our understanding of bidirectional signalling improves, more subtle and directed therapeutic strategies may be developed.

Thrombopoietin as biomarker and mediator of cardiovascular damage in critical diseases

Thrombopoietin (TPO) is a humoral growth factor originally identified for its ability to stimulate the proliferation and differentiation of megakaryocytes. In addition to its actions on thrombopoiesis, TPO directly modulates the homeostatic potential of mature platelets by influencing their response to several stimuli. In particular, TPO does not induce platelet aggregation per se but is able to enhance platelet aggregation in response to different agonists (“priming effect”). Our research group was actively involved, in the last years, in characterizing the effects of TPO in several human critical diseases. In particular, we found that TPO enhances platelet activation and monocyte-platelet interaction in patients with unstable angina, chronic cigarette smokers, and patients with burn injury and burn injury complicated with sepsis. Moreover, we showed that TPO negatively modulates myocardial contractility by stimulating its receptor c-Mpl on cardiomyocytes and the subsequent production of NO, and it mediates the cardiodepressant activity exerted in vitro by serum of septic shock patients by cooperating with TNF-α and IL-1β. This paper will summarize the most recent results obtained by our research group on the pathogenic role of elevated TPO levels in these diseases and discuss them together with other recently published important studies on this topic.

Influence of diabetes mellitus on clinical outcomes following primary percutaneous coronary intervention in patients with ST-segment elevation myocardial infarction

Patients with diabetes mellitus (DM) have a worse outcome after percutaneous coronary intervention (PCI) than nondiabetic patients. The purpose of this study was to compare rates of stent thrombosis, myocardial infarction (MI), target lesion revascularization (TLR), and death in diabetic and nondiabetic patients treated with primary PCI for ST-segment elevation MI (STEMI) in Western Denmark. From January 2002 through June 2005, 3,655 consecutive patients with STEMI treated with primary PCI and stent implantation (316 patients with DM, 8.6%; 3,339 patients without DM, 91.4%) were recorded in the Western Denmark Heart Registry. All patients were followed for 3 years. Cox regression analysis was used to compute hazard ratios (HRs), controlling for potential confounding. Three-year rates of definite stent thrombosis were 1.6% in the DM group and 1.5% in the non-DM group (adjusted HR 1.15, 95% confidence interval [CI] 0.50 to 2.67). The rate of MI was 12.3% in the DM group versus 5.6% in the non-DM group (adjusted HR 2.56, 95% CI 1.81 to 3.61). Rates of TLR were 12.1% in the DM group and 8.7% in the non-DM group (adjusted HR 1.55, 95% CI 1.14 to 2.11). All-cause mortality was 23.7% in patients with DM versus 12.7% in patients without DM (adjusted HR 2.03, 95% CI 1.59 to 2.59). In conclusion, stent thrombosis rate was similar in patients with and without DM and STEMI treated with primary PCI, whereas the presence of DM increased the risk of MI, TLR, and death.

A case-control study on platelet reactivity in patients with coronary stent thrombosis

BACKGROUND

The pathophysiology of stent thrombosis (ST) has evolved from the identification of single causative factors to a complex multifactorial model.

OBJECTIVES

The aim of the present study was to investigate whether patients with a history of ST exhibit heightened platelet reactivity to clopidogrel and aspirin.

PATIENTS/METHODS

Pretreatment and on-treatment platelet reactivity to clopidogrel and aspirin, as well as dual antiplatelet therapy resistance, was determined in 84 patients with a history of definite ST (cases: 41 early ST; 43 late ST) and in 103 control patients with a previously implanted coronary stent but no ST after the index procedure. Platelet function was evaluated with optical aggregometry, the VerifyNow P2Y12 and aspirin assays, the PFA-100 Innovance P2Y* cartridge, the flow cytometric vasodilator-stimulated phosphoprotein assay and urine 11-dehydrothromboxane B(2) measurement before and after the administration of a 600-mg loading dose of clopidogrel and 100 mg of aspirin. The study was registered at ClinicalTrials.gov, number NCT01012544.

RESULTS

Patients with a history of early ST clearly demonstrated higher on-clopidogrel platelet reactivity than controls. Patients with both early and late ST exhibited heightened on-aspirin platelet reactivity status, and dual antiplatelet therapy resistance was more frequent.

CONCLUSIONS

Patients with a history of early ST exhibit a poor response to clopidogrel. Furthermore, both early and late ST are strongly and independently associated with heightened on-aspirin platelet reactivity, and dual antiplatelet therapy resistance is more frequent.

The causes and outcomes of inadequate implementation of existing guidelines for antiplatelet treatment in patients with acute coronary syndrome: the experience from Taiwan Acute Coronary Syndrome Descriptive Registry (T-ACCORD Registry)

BACKGROUND

Benefits of antiplatelet agents in preventing future cardiovascular events have been well established. However, the prescription pattern of antiplatelet usage in patients with acute coronary syndrome (ACS) is rarely investigated. Hence, Taiwan ACute CORonary Syndrome Descriptive Registry (T-ACCORD Registry) aimed to evaluate medical practices in Taiwan in managing ACS patients.

HYPOTHESIS

The guidelines of antiplatelet treatment is not properly implanted in the management of ACS patients.

METHODS

This prospective observational study was performed between April 2004 and December 2006 in 27 hospitals in Taiwan. A total of 1331 patients with unstable angina or non-ST-elevation myocardial infarction (NSTEMI) discharged from hospitals was analyzed.

RESULTS

The patients with older age, lower hemoglobin levels, or previous cardiovascular ischemic diseases were less likely to receive aspirin at discharge, whereas patients with NSTEMI were less likely to receive clopidogrel at discharge. The prescription of dual antiplatelet agents declined rapidly from 61.8% at discharge to 12.6% at 12 months. The most common reason for clopidogrel discontinuation was recorded as physician's judgment. Dual antiplatelet treatment for 9 months or longer was associated with lower 1-year mortality. Percutaneous coronary intervention (PCI) was the only factor leading to dual antiplatelet therapy for at least 9 months.

CONCLUSIONS

Our registry showed that underlying medical conditions may affect antiplatelet prescriptions at discharge. During the first year following an ACS episode, the prescription rate of dual antiplatelet therapy declined over time, mainly due to physician's judgment leading to the discontinuation of clopidogrel. Adherence to dual antiplatelet treatment was associated with lower total mortality at 1 year.

Efficacy and safety of bivalirudin in patients receiving clopidogrel therapy after diagnostic angiography for percutaneous coronary intervention in acute coronary syndromes

OBJECTIVES

This study sought to investigate if the efficacy of bivalirudin monotherapy is similar to heparin plus GP IIb/IIIa inhibition in patients with acute coronary syndromes (ACS) treated with clopidogrel following diagnostic angiography.

BACKGROUND

Prior trials have demonstrated that peri-procedural bivalirudin therapy confers similar efficacy as heparin plus GP IIb/IIIa inhibitors, while lowering the risk of bleeding complications in ACS patients undergoing percutaneous coronary interventions (PCI). However, the incidence of adverse ischemic events post-PCI appeared to be higher in patients receiving bivalirudin without adequate pretreatment with clopidogrel.

METHODS

Using the 2004/2005 Cornell Angioplasty Registry, we evaluated 980 consecutive patients undergoing urgent PCI for UA/NSTEMI who were treated with either bivalirudin or UFH plus GP IIb/IIIa inhibitor. We excluded patients who were on chronic clopidogrel therapy or received clopidogrel pretreatment prior to angiography. All patients received a clopidogrel load (≥300-mg dose) immediately before or after the PCI. Long-term all-cause mortality was obtained for 100% of patients, with a mean follow-up of 24.6 ± 7.7 months.

RESULTS

Of the 980 study patients, 461 (47.0%) were treated with bivalirudin and 519 (53.0%) patients received UFH plus GP IIb/IIIa inhibitor. DES were used in 88% of PCI; 45% of patients presented with NSTEMI. The incidence of in-hospital death (0.4% vs. 0.2%, P = 0.604), post-procedural MI (6.9% vs. 5.4%, P = 0.351), and MACE including death, stroke, emergent CABG/PCI, and MI (7.6% vs. 5.8%, P = 0.304) were similar in patients treated with bivalirudin versus UFH plus GP IIb/IIIa inhibitors, respectively. The incidence of in-hospital stent thrombosis was similar (0.7% vs. 0%, P = 0.104), while major (0.9% vs. 2.9%, P = 0.034) and minor bleeding (10.4% vs. 18.9%, P < 0.001) was reduced in the bivalirudin-treated group. By two-years of follow-up, after propensity-score adjusted multivariate Cox regression analysis, there was no significant difference in long-term mortality between the two groups (HR 1.18; 95%CI 0.64-2.19, P = 0.598).

CONCLUSIONS

In patients presenting with ACS and receiving clopidogrel treatment after angiography (before or within 30 min of PCI), peri-procedural bivalirudin monotherapy suppresses acute and long-term adverse events to a similar extent as does UFH plus GP IIb/IIIa inhibitors, while significantly lowering the risk of bleeding complications.

Effectiveness of in-laboratory high-dose clopidogrel loading versus routine pre-load in patients undergoing percutaneous coronary intervention: results of the ARMYDA-5 PRELOAD (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty) randomized trial

OBJECTIVES

This study sought to evaluate safety and effectiveness of in-laboratory (in-lab) 600-mg clopidogrel loading pre-percutaneous coronary intervention (PCI) versus routine 6-h pre-load.

BACKGROUND

Clopidogrel pre-treatment significantly improves outcome in patients undergoing PCI; however, efficacy of an in-lab loading strategy before PCI after coronary angiography versus routine pre-load has not been fully characterized.

METHODS

A total of 409 patients (39% with acute coronary syndrome) were randomized to receive a 600-mg clopidogrel loading dose 4 to 8 h before PCI (pre-load group, n = 204) or a 600-mg loading dose given in the catheterization lab after coronary angiography, but prior to PCI (in-lab group, n = 205). Primary end point was 30-day incidence of major adverse cardiac events: cardiac death, myocardial infarction (MI), or unplanned target vessel revascularization.

RESULTS

There was no significant difference in primary end point between the 2 randomization arms (8.8% in-lab vs. 10.3% pre-load; p = 0.72); this was mainly driven by periprocedural MI (8.8% vs. 9.3%, p = 0.99). No increased risk of bleeding or vascular complications was observed in the pre-load arm (5.4% vs. 7.8%; p = 0.42). As determined by the VerifyNow assay (Accumetrics, San Diego, California), patients in the in-lab group showed higher platelet reactivity during PCI and 2 h after intervention versus those in the pre-load arm (p < or = 0.043).

CONCLUSIONS

ARMYDA-5 PRELOAD (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty) trial indicates that a strategy of 600-mg in-lab clopidogrel load pre-PCI may have similar clinical outcomes as routine 4- to 8-h pre-load. Thus, when indicated, in-lab clopidogrel administration can be a safe alternative to routine pre-treatment given before knowing patients' coronary anatomy.

Outcome in high risk patients with unprotected left main coronary artery stenosis treated with percutaneous coronary intervention

OBJECTIVE

We examined mortality, risk of myocardial infarction (MI), and target lesion revascularization (TLR) in high-risk patients with unprotected left main (LM) percutaneous coronary intervention (PCI) in Western Denmark.

BACKGROUND

PCI of left main coronary artery lesions may be an alternative to coronary artery bypass grafting in high-risk surgical patients.

METHODS

From January 2005 to May 2007, all patients who had unprotected LM PCI with stent implantation were identified in the Western Denmark Heart Registry. The indications for PCI were: (1) ST segment elevation MI (STEMI), (2) non-STEMI (NSTEMI) or unstable angina, and (3) stable angina. All patients were followed up for 18 months.

RESULTS

A total of 344 patients were treated with LM PCI (STEMI: 71, NSTEMI/unstable angina: 157, and stable angina: 116). In STEMI patients, the median logistic EuroSCORE was 22.5 (interquartile range 12.5-39.5), in non-STEMI (NSTEMI)/unstable angina patients 13.8 (4.8-23.9), and in stable angina patients 4.8 (2.2-10.4). Mortality after 18 months 38.0, 18.5, and 11.2% (P < 0.001) in patients with STEMI, NSTEMI/unstable angina, and stable angina, respectively. MI after 18 months was 9.9, 6.4, and 6.0% (P = ns), respectively. Four subacute and one late definite stent thrombosis were seen. TLR occurred in 5.6, 4.5, and 6.9% (P = ns) of patients, respectively.

CONCLUSION

After PCI, patients with STEMI and LM culprit lesion have a high-mortality risk, whereas long-term outcome for patients with NSTEMI and stable angina pectoris is comparable with other high surgical risk patients with unprotected left main lesion. Further, TLR rates and risk of stent thrombosis were low.

Efficacy of high-dose clopidogrel treatment (600 mg) less than two hours before percutaneous coronary intervention in patients with non-ST-segment elevation acute coronary syndromes

Current guidelines recommend pretreatment with a loading dose of clopidogrel before percutaneous coronary intervention (PCI) to reduce the incidence of periprocedural myocardial infarctions in patients undergoing PCI. However, because of concerns about postoperative bleeding, clopidogrel loading is frequently administered either immediately before or after PCI. Using the 2004/2005 Cornell Angioplasty Registry, we analyzed 1,041 consecutive patients undergoing urgent PCI for non-ST-elevation acute coronary syndrome. The patients were divided into 2 groups. The first group was the "preangiography clopidogrel therapy" group for those receiving chronic 75-mg clopidogrel therapy or receiving a clopidogrel loading dose (300 mg > or = 12 hours or 600 mg > or = 2 hours) before angiography according to the guidelines. The second group was the "in-laboratory 600-mg clopidogrel loading" group for the patients who received the clopidogrel loading dose <2 hours before PCI (immediately before or after PCI). The mean clinical follow-up was 23.8 + or - 7.6 months. Of the 1,041 study patients, 467 (44.9%) received clopidogrel before angiography and 574 (55.1%) received in-laboratory loading. The incidence of in-hospital death (0.4% vs 0.5%, respectively; p = 1.000), myocardial infarction (7.7% vs 6.8%, respectively; p = 0.630), and major adverse cardiovascular events (8.4% vs 7.1%, respectively; p = 0.484) were similar between the 2 groups. The Kaplan-Meier long-term survival rates were similar in the 2 groups (93.4% vs 95.8%, p log-rank = 0.152). After multivariate Cox regression analysis, administration of a 600-mg clopidogrel loading dose <2 hours before PCI did not have a significant effect on long-term mortality (hazard ratio 0.97, 95% confidence interval 0.54 to 1.75, p = 0.927). In conclusion, treatment with a 600-mg loading dose <2 hours before PCI is associated with similar short-term ischemic outcomes and long-term mortality compared to the currently recommended clopidogrel pretreatment regimen.

Mean platelet volume as a predictor of cardiovascular risk: a systematic review and meta-analysis

AIM

To determine whether an association exists between mean platelet volume (MPV) and acute myocardial infarction (AMI) and other cardiovascular events. Platelet activity is a major culprit in atherothrombotic events. MPV, which is widely available in clinical practice, is a potentially useful biomarker of platelet activity in the setting of cardiovascular disease.

METHODS AND RESULTS

We performed a systematic review and meta-analysis investigating the association between MPV and AMI, all-cause mortality following myocardial infarction, and restenosis following coronary angioplasty. Results were pooled using random-effects modeling. Pooled results from 16 cross-sectional studies involving 2809 patients investigating the association of MPV and AMI indicated that MPV was significantly higher in those with AMI than those without AMI [mean difference 0.92 fL, 95% confidence interval (CI) 0.67-1.16, P < 0.001). In subgroup analyses, significant differences in MPV existed between subjects with AMI, subjects with stable coronary disease (P < 0.001), and stable controls (P < 0.001), but not vs. those with unstable angina (P = 0.24). Pooled results from three cohort studies involving 3184 patients evaluating the risk of death following AMI demonstrated that an elevated MPV increased the odds of death as compared with a normal MPV (11.5% vs. 7.1%, odds ratio 1.65, 95% CI 1.12-2.52, P = 0.012). Pooled results from five cohort studies involving 430 patients who underwent coronary angioplasty revealed that MPV was significantly higher in patients who developed restenosis than in those who did not develop restenosis (mean difference 0.98 fL, 95% CI 0.74-1.21, P < 0.001).

CONCLUSIONS

Elevated MPV is associated with AMI, mortality following myocardial infarction, and restenosis following coronary angioplasty. These data suggest that MPV is a potentially useful prognostic biomarker in patients with cardiovascular disease. Whether the relationship is causal, and whether MPV should influence practice or guide therapy, remains unknown.

Mean platelet volume as a predictor of cardiovascular risk: a systematic review and meta-analysis

AIM

To determine whether an association exists between mean platelet volume (MPV) and acute myocardial infarction (AMI) and other cardiovascular events. Platelet activity is a major culprit in atherothrombotic events. MPV, which is widely available in clinical practice, is a potentially useful biomarker of platelet activity in the setting of cardiovascular disease.

METHODS AND RESULTS

We performed a systematic review and meta-analysis investigating the association between MPV and AMI, all-cause mortality following myocardial infarction, and restenosis following coronary angioplasty. Results were pooled using random-effects modeling. Pooled results from 16 cross-sectional studies involving 2809 patients investigating the association of MPV and AMI indicated that MPV was significantly higher in those with AMI than those without AMI [mean difference 0.92 fL, 95% confidence interval (CI) 0.67-1.16, P < 0.001). In subgroup analyses, significant differences in MPV existed between subjects with AMI, subjects with stable coronary disease (P < 0.001), and stable controls (P < 0.001), but not vs. those with unstable angina (P = 0.24). Pooled results from three cohort studies involving 3184 patients evaluating the risk of death following AMI demonstrated that an elevated MPV increased the odds of death as compared with a normal MPV (11.5% vs. 7.1%, odds ratio 1.65, 95% CI 1.12-2.52, P = 0.012). Pooled results from five cohort studies involving 430 patients who underwent coronary angioplasty revealed that MPV was significantly higher in patients who developed restenosis than in those who did not develop restenosis (mean difference 0.98 fL, 95% CI 0.74-1.21, P < 0.001).

CONCLUSIONS

Elevated MPV is associated with AMI, mortality following myocardial infarction, and restenosis following coronary angioplasty. These data suggest that MPV is a potentially useful prognostic biomarker in patients with cardiovascular disease. Whether the relationship is causal, and whether MPV should influence practice or guide therapy, remains unknown.

Triple Versus Dual Antiplatelet Therapy in Patients With Acute ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Background— Whether triple antiplatelet therapy is superior or similar to dual antiplatelet therapy in patients with acute ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention in the era of drug-eluting stents remains unclear.

Methods and Results— A total of 4203 ST-segment elevation myocardial infarction patients who underwent primary percutaneous coronary intervention with drug-eluting stents were analyzed retrospectively in the Korean Acute Myocardial Infarction Registry (KAMIR). They received either dual (aspirin plus clopidogrel; dual group; n=2569) or triple (aspirin plus clopidogrel plus cilostazol; triple group; n=1634) antiplatelet therapy. The triple group received additional cilostazol at least for 1 month. Various major adverse cardiac events at 8 months were compared between these 2 groups. Compared with the dual group, the triple group had a similar incidence of major bleeding events but a significantly lower incidence of in-hospital mortality. Clinical outcomes at 8 months showed that the triple group had significantly lower incidences of cardiac death (adjusted odds ratio, 0.52; 95% confidence interval, 0.32 to 0.84; P =0.007), total death (adjusted odds ratio, 0.60; 95% confidence interval, 0.41 to 0.89; P =0.010), and total major adverse cardiac events (adjusted odds ratio, 0.74; 95% confidence interval, 0.58 to 0.95; P =0.019) than the dual group. Subgroup analysis showed that older (>65 years old), female, and diabetic patients got more benefits from triple antiplatelet therapy than their counterparts who received dual antiplatelet therapy.

Conclusions— Triple antiplatelet therapy seems to be superior to dual antiplatelet therapy in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention with drug-eluting stents. These results may provide the rationale for the use of triple antiplatelet therapy in these patients.

The problem of persistent platelet activation in acute coronary syndromes and following percutaneous coronary intervention

Platelets play a central role in the atherosclerotic inflammatory response, thrombotic vascular occlusion, microembolization, vasoconstriction, and plaque progression. Persistent platelet activation poses a serious problem among patients with acute coronary syndromes (ACS) and those who have undergone percutaneous coronary intervention (PCI), placing them at risk for ischemic events and subacute stent thrombosis. Patients undergoing PCI are at risk for further ischemic events because of procedure-related platelet activation as well as the inherent persistent platelet hyperreactivity and enhanced thrombin generation associated with ACS. Persistent platelet activation following an acute coronary event and/or PCI supports incorporating antiplatelet strategies into the standard medical management of such patients. In this clinical setting, antiplatelet therapies are capable of improving outcomes. Aspirin, thienopyridines, and glycoprotein IIb/IIIa inhibitors, the 3 major pharmacologic approaches to persistent platelet activation, target various levels of the hemostatic pathways and thrombus formation.

Explicit risk in acute coronary syndrome management

At least implicitly, most clinical decisions represent an integration of disease and treatment-based risk assessments. Often, as is the case with acute coronary syndrome (ACS), these decisions need to be made quickly at a time when data elements are limited, and published risk models are very useful in clarifying time-dependent determinants of risk. The present review emphasizes the value of explicit risk assessment and reinforces the fact that patients at highest risk are often those most likely to benefit from newer and more invasive therapies. Suggested ways to incorporate published ACS risk models into clinical practice are included. In addition, the need to adopt a longer-term view of risk in ACS patients is stressed, with particular regard to the important role of heart failure prediction and treatment.

Contemporary issues on clopidogrel therapy

In this paper, data from available studies regarding some contemporary issues on clopidogrel therapy are analyzed. In particular, the following clinical questions have been considered and addressed: (a) Is early clopidogrel treatment needed in patients with acute coronary syndromes treated medically or undergoing percutaneous coronary intervention (PCI)? (b) What is the optimal clopidogrel loading dose in patients undergoing PCI? (c) Is pre-treatment with clopidogrel before PCI needed, or can clopidogrel loading be given in the catheter laboratory before intervention, but after coronary anatomy is known? (d) What is the optimal clopidogrel strategy in patients on chronic clopidogrel therapy undergoing PCI? (e) Does the degree of clopidogrel response influence clinical outcome in patients undergoing PCI?

Regulation of CD40L (CD154) and CD62P (p-selectin) surface expression upon GPIIb-IIIa blockade of platelets from stable coronary artery disease patients

INTRODUCTION

The aim of this study was to further characterize the effect of the antiplatelet agents, aspirin and eptifibatide, on the surface expression of CD40L and CD62P on platelets from patients with stable coronary artery disease.

MATERIALS AND METHODS

Platelet function was evaluated using standard light transmission aggregometry. Measurements of CD62P and CD40L were carried out by flow cytometry and ELISA assays.

RESULTS

All patients had the expected level of platelet aggregation inhibition in response to 20 muM ADP in the presence of increasing eptifibatide concentrations. Platelet activation by adenosine diphosphate (ADP) or thrombin agonist peptide (TRAP) increased CD62P and CD40L surface density in the presence of aspirin by 1.9 - 2.8 -fold. Aspirin treatment did not prevent either CD62P or CD40L expression. Eptifibatide pretreatment at pharmacologically relevant concentrations blocked agonist-induced increases in CD62P platelet surface density. A marked percentage of platelets still expressed low levels of surface CD62P suggesting slight platelet activation even with potent platelet inhibition. Eptifibatide also blocked agonist-induced increases in CD40L surface expression and decreased the percent of platelets positive for surface CD40L. Decreased expression of CD40L was due to an inhibition of CD40L translocation and not caused by enhanced shedding from the surface, as soluble CD40L (sCD40L). Eptifibatide concentrations that effectively blocked platelet aggregation correlated with total inhibition of increased CD62P and CD40L surface density.

CONCLUSION

Blockade of the GPIIb-IIIa receptor on platelets from coronary artery disease patients may have significant bearing on reducing proinflammatory and procoagulant events mediated by CD62P and sCD40L.

Two year follow-up after primary PCI with a paclitaxel-eluting stent versus a bare-metal stent for acute ST-elevation myocardial infarction (the PASSION trial): a follow-up study

AIMS

This follow-up study was performed to assess the long-term effects of paclitaxel-eluting stents (PES) compared with bare-metal stents (BMS) in patients who had undergone a percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

The PASSION trial randomly assigned 619 patients with STEMI to receive either a PES or BMS. The composite endpoint for the follow-up study was the occurrence of the combination of cardiac death, recurrent myocardial infarction, target lesion revascularisation (TLR) or stent thrombosis at two years. A trend towards a lower rate of the composite endpoint was observed in the PES compared to the BMS group (hazard ratio [HR] 0.70; 95% C.I. 0.45-1.09). This was driven by a reduced TLR in favour of PES (HR 0.60; 95% C.I. 0.34-1.09). Angiographically proven stent thrombosis at two years did not differ significantly between groups (2.1% in the PES group versus 1.4%; HR 1.48; 95% C.I. 0.42-5.23).

CONCLUSIONS

PES implantation for STEMI did not significantly improve clinical outcome at two years after the index event, although there was a trend towards a lower rate of target-lesion revascularisation. The rate of stent thrombosis did not differ significantly between groups.

Learning from the recently completed oral glycoprotein IIb/IIIa receptor antagonist trials

Although parenteral therapy with glycoprotein (GP) IIb/IIIa inhibitors has resulted in a reduced risk of death or myocardial infarction in patients with acute coronary syndromes and in patients undergoing percutaneous coronary intervention, the benefit is achieved only during the infusion period. Oral GP IIb/IIIa inhibitors may offer an opportunity to expand the application of this therapy to additional vascular indications and to extend therapy beyond the in-hospital period. A number of oral GP IIb/IIIa inhibiting agents have been evaluated; however, no benefit has been observed. Oral GP IIb/IIIa inhibitors have been associated with an increased incidence of bleeding, but additional experience may permit the design of dosing regimens that decrease this risk. The recent Orbofiban in Patients with Unstable Coronary Syndromes (OPUS/TIMI-16) trial showed a small but significant increase in mortality in orbofiban-treated patients. It appears that this agent, and perhaps other oral GP IIb/IIIa inhibitors including sibrafiban and xemilofiban, may have a pro-aggregatory effect. This may be caused by the drug dissociating from the GP IIb/IIIa receptor, leaving an activated receptor that can then bind fibrinogen and form a platelet aggregate. Further studies are needed to elucidate the mechanism of this effect and to evaluate whether the second-generation of oral GP IIb/IIIa inhibitors, which have tight binding and a longer duration of antiplatelet effect, will be of clinical benefit.

Changes in plasma von Willebrand factor-cleaving protease (ADAMTS13) levels in patients with unstable angina

INTRODUCTION

Increased plasma levels of von Willebrand factor (VWF) have been reported in acute myocardial infarction (AMI). Recently, we showed reduced activity of a VWF-cleaving protease (ADAMTS13) in AMI patients. However, there is no information as to whether ADAMTS13 affects the pathogenesis of unstable angina (UA). Thus, the purpose of this study was to examine changes in plasma VWF and ADAMTS13 levels in UA patients.

MATERIALS AND METHODS

Plasma VWF and ADAMTS13 levels (mU/ml) were measured in 45 patients with UA, 55 with stable exertional angina (SEA) and 47 with chest pain syndrome (CPS) at the time of coronary angiography. Levels were also measured in 15 UA patients after 6 months of follow-up.

RESULTS

VWF antigen levels (mU/ml) increased significantly in UA patients compared with SEA or CPS (2129.3+/-739.5, 1571.8+/-494.2 and 1569.5+/-487.0, respectively; P < 0.0001 in UA vs. SEA or CPS). ADAMTS13 antigen levels (mU/ml) were significantly lower in UA patients than SEA or CPS (737.3+/-149.5, 875.3+/-229.0 and 867.7+/-195.5, respectively; P < 0.01 in UA vs. SEA or CPS). Furthermore, there was a significant inverse correlation between VWF and ADAMTS13 antigen levels (r = -0.302, P = 0.0002). The antigen levels at 6 months of follow-up were not different compared to the acute phase in the 15 UA patients that had repeated blood sampling.

CONCLUSIONS

These findings suggest that there is prolonged thrombogenicity in UA patients represented as an imbalance between VWF and ADAMTS13 activity.

Platelet deposition in remote cardiac regions after coronary occlusion

BACKGROUND

Activated platelets might contribute to endothelial dysfunction in non-ischaemic territories during acute myocardial infarction. We assessed platelet deposition, coronary flow reserve and contractile function in remote cardiac regions after transient coronary occlusion and their association with systemic platelet activation.

MATERIALS AND METHODS

In 10 pigs (series A) subjected to 48-min occlusion of the left anterior descending coronary artery (LAD), 99mTc-platelet content in the right coronary artery (RCA) and its dependent myocardium was counted after reflow. In 10 pigs (series B) receiving the same occlusion of the RCA, the hyperaemic response at the LAD and systolic shortening in LAD-dependent myocardium were monitored after reperfusion. P-selectin expression on circulating platelets was assessed in both series by flow cytometry.

RESULTS

In series A, platelet counts in the RCA and non-ischaemic myocardium were correlated with platelet content, polymorphonuclear leukocyte infiltration and infarct size in the reperfused zone, as well as with the percentage of P-selectin-positive platelets after reflow. In series B, a transient reduction in peak hyperaemic response in the LAD and sustained contractile dysfunction in non-ischemic myocardium were observed after releasing the RCA occlusion, these changes being also correlated with platelet activation status.

CONCLUSIONS

Ischaemic injury triggers macro- and microvascular platelet deposition and causes an impairment in coronary flow reserve and contractile function in distant regions of the heart, which are related to activation of circulating platelets.

Combination of caregiving stress and hormone replacement therapy is associated with prolonged platelet activation to acute stress among postmenopausal women

OBJECTIVE

To investigate the combined effects of caregiving and hormone replacement therapy (HRT) on platelet hyperactivity to acute psychological stress. Both HRT and the chronic stress of caregiving have been associated with increased cardiovascular risk, potentially through a mechanism of platelet hyperactivity.

METHODS

A total of 78 elderly postmenopausal women (51 caregivers (CG) and 27 noncaregivers (NC)) were assessed for platelet activation in response to a laboratory speech test. Half the sample was taking HRT. Blood was sampled at baseline, post speech, and after 14 minutes of recovery. Platelet activation was assessed through whole blood flow cytometry assays of % aggregates (Agg), and expression of % fibrinogen receptors (FbR) and % P-selectin (P-sel) on platelet surface.

RESULTS

Multivariate repeated-measures analysis of variance revealed that CG taking HRT exhibited significantly prolonged platelet activation in response to acute stress. There was an interaction between HRT and CG on recovery from stress for Agg (F (1,71) = 5.260, p = .025), P-Sel (F(1,71 = 6.426, p = .013), and FbR (F(1,71 = 6.653, p = .012), controlling for age, cardiovascular disease, and aspirin. Among HRT users, regression analysis revealed that CG had delayed recovery of Agg (beta = 0.354, t(34) = 2.154, p = .038) and P-sel (beta = 0.498, t(34)=3.126, p = .004) from stress relative to NC. No caregiving effects on recovery were present among non-HRT users. In addition, these effects were maintained after controlling for health behaviors, medications, and medical conditions.

CONCLUSION

Chronic dementia caregiving stress in combination with HRT may impair recovery of platelet activation after acute mental stress (i.e., activation levels do not quickly return to resting levels), thereby potentially increasing cardiovascular risk among CG who take HRT.

Troponin level and efficacy of abciximab in patients with acute coronary syndromes undergoing early intervention after clopidogrel pretreatment

OBJECTIVE

We investigated how does troponin level (TnT) affect the benefit achieved by abciximab in patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI) after pretreatment with a high loading dose of clopidogrel.

METHODS

The Intracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment (ISAR-REACT 2) trial included 2,022 patients with non-ST elevation ACS undergoing PCI who were randomized to abciximab or placebo after pretreatment with 600 mg of clopidogrel. The patients were divided into groups with elevated TnT level (n = 1,049) and no elevated TnT level (n = 973). The primary end point of the trial was the composite of death, myocardial infarction and urgent reintervention at 30 days.

RESULTS

In patients with elevated TnT level the incidence of the primary end point was 13.1% in the abciximab group Vs. 18.3% in the placebo group [relative risk (RR): 0.70; 95% confidence interval (CI), 0.52-0.95, P = 0.02]. The combined incidence of death or myocardial infarction was 12.9% in the abciximab group vs. 17.9% in the placebo group (RR: 0.71; 95% CI, 0.52-0.96, P = 0.03). In contrast, the incidence of the primary end point in patients with no elevated TnT level was identical in both treatment groups (4.6%). The risk of bleeding was not related to TnT level.

CONCLUSIONS

Baseline troponin level affects the benefit of abciximab in patients with ACS undergoing PCI after pretreatment with a high loading dose of clopidogrel. Abciximab reduces the risk of ischemic events only in patients with ACS and elevated troponin level.

Circulating platelet and neutrophil activation correlates with the clinical course of unstable angina

Recent studies have suggested important roles of inflammation in the pathophysiology of unstable angina (UA). We investigated whether activation of the circulating platelets and neutrophils were implicated in inflammatory reactions associated with unstable angina Expressions of platelet P-selectin and neutrophil CD11b, and neutrophil-platelet aggregates were evaluated by flow cytometry in anticoagulated peripheral venous blood from 71 patients with UA and 22 patients with stable angina (SA). Expressions of platelet P-selectin and neutrophil CD11b, and neutrophil-platelet aggregates on the admission day were all significantly higher in 71 patients with UA than 22 with SA (median, mean fluorescence intensity [MFI]: 7.00 vs 4.51, P < 0.01, 64.68 vs 47.75, P = 0.0007; and % of 10 000 neutrophils: 7.84 vs 3.40, P = 0.0001, respectively). These three parameters in 43 patients with UA were significantly decreased (MFI: 4.23, P = 0.003, 50.82, P = 0.0003; and % of 10 000 neutrophils: 5.04, P = 0.0001, respectively) 7 days after the first measurement. These results indicate that circulating activated platelets and neutrophils are more strongly implicated in the acute phase of UA. These findings also suggest that thrombus formation after rupture of atherosclerotic plaques as well as plaque formation involves inflammatory reactions.

Platelet function in clopidogrel-treated patients with acute coronary syndrome

Percutaneous coronary intervention (PCI) in patients presenting with acute coronary syndrome (ACS) is associated with increased risk of thrombotic complications. ACS enhances platelet activation; whether pretreatment with clopidogrel is sufficient to suppress platelet function in patients with ACS is not known. This study assessed platelet function in patients with and without ACS prior to PCI and after pretreatment with a single dose of 600 mg clopidogrel. Blood samples of 402 patients prior to PCI with (n = 119) or without (n = 283) ACS were collected at least 2 h after 600 mg clopidogrel administration. Maximal platelet aggregation in response to ADP (5 and 20 micromol/l), collagen (4 microg/ml) and TRAP (25 micromol/l) was measured with optical aggregometry. Surface expression of glycoprotein IIb/IIIa and P-selectin was assessed with flow cytometry at baseline and after stimulation with 5 and 20 micromol/l ADP. Agonist-induced platelet aggregation did not differ significantly between patients with and without ACS (P > or = 0.15). Parameters of platelet activation (glycoprotein IIb/IIIa and P-selectin surface expression) were significantly higher in ACS patients at baseline and after 5 and 20 micromol/l ADP stimulation (P < 0.0001). Patients with ACS continue to exhibit increased platelet activation after pretreatment with 600 mg clopidogrel. This finding supports the need for additional platelet function inhibition during PCI in patients with ACS.

Elevated Plasma Fibrinogen Level Predicts Suboptimal Response to Therapy With Both Single- and Double-Bolus Eptifibatide During Percutaneous Coronary Intervention

OBJECTIVES

This study sought to determine the factors associated with suboptimal platelet inhibition (PI) with single- and double-bolus eptifibatide during percutaneous coronary intervention (PCI).

BACKGROUND

Although PI > or = 95% measured 10 min after glycoprotein IIb/IIIa inhibitor therapy is associated with improved outcomes following PCI, this level of PI often is not achieved.

METHODS

We prospectively studied 150 patients undergoing PCI with single-bolus eptifibatide (180 microg/kg) (n = 100) and double-bolus eptifibatide (180 microg/kg administered 10 min apart) (n = 50) followed by standard infusion (2 microg/kg/min). Measuring platelet aggregation at baseline and at 10 min and 30 to 45 min after eptifibatide bolus, patients were classified as optimal responders (OPT) (> or =95% PI) or suboptimal responders (sub-OPT) (<95% PI) based on 10-min PI after final bolus.

RESULTS

Suboptimal PI was achieved in 61% of patients with single-bolus eptifibatide and in 36% with double-bolus eptifibatide. In the single-bolus group, sub-OPT had higher fibrinogen levels (324 +/- 85 mg/dl vs. 259 +/- 49 mg/dl, p = 0.0002), platelet counts (221 +/- 70 vs. 186 +/- 47, p = 0.008), and white blood cell counts (7.7 +/- 2.3 vs. 6.6 +/- 1.9, p = 0.02). In the double-bolus group, sub-OPT also had higher fibrinogen levels (324 +/- 68 mg/dl vs. 278 +/- 53 mg/dl, p = 0.01) and were more likely to be smokers (38.9% vs. 9.4%, p = 0.01). Multivariable analysis showed that fibrinogen level was the only independent predictor of suboptimal PI, with fibrinogen cutoffs at 375 and 325 mg/dl predicting suboptimal PI (single-bolus: 100% and 90.0%, respectively; double-bolus: 100% and 60%, respectively) with both doses.

CONCLUSIONS

During PCI, both single- and double-bolus eptifibatide provide suboptimal PI in a substantial proportion of patients. A fibrinogen level >375 mg/dl is a strong predictor of suboptimal PI.

Thrombelastography: current clinical applications and its potential role in interventional cardiology

Thrombelastography is a bedside blood test used to assess patients' haemostatic status. It has a well-established role in hepatobiliary and cardiac surgery and is also used in obstetrics and trauma medicine to assess coagulation and identify the causes of post-operative bleeding. It is not routinely used in the diagnosis or treatment of thrombosis although recently it has been shown to predict thrombotic events post-operatively and after percutaneous intervention (PCI). In cardiovascular medicine the importance of the platelet in the pathophysiology of vascular events is increasingly apparent. As a result antiplatelet therapy is a cornerstone of the treatment for coronary disease, particularly in the setting of acute coronary syndromes. The increasing utilization of stents, particularly drug-eluting devices, in PCI has also necessitated widespread use of antiplatelet agents to minimize the risk of stent thrombosis. A quick, accurate and reliable test to measure the effect of platelet inhibition by antiplatelet agents on clotting in an individual patient would be of profound clinical value. The results from such a test could provide prognostic information, allow treatment with antiplatelet agents to be tailored to the individual and identify resistance to one or more of these agents. Optimization and tailoring of anti-platelet therapy in patients with cardiovascular disease, particularly those undergoing PCI, using such a test may reduce morbidity and mortality from thrombotic and haemorrhagic complications. Current methods of assessing platelet activity measure platelet count and function in isolation. Optical aggregation is the most widely used method for assessing platelet function but it is relatively time consuming, measures platelet function in isolation rather than in the context of clot formation and is not a bedside test. By contrast the modified thrombelastograph platelet mapping kit marketed by Haemoscope can be used to assess the effects of antiplatelet agents on ex vivo blood clotting, thus giving a measurement more relevant to in vivo responses. This represents a potentially powerful tool to assess response of individual patients to antiplatelet therapy, particularly in the context of PCI.

Platelets as Mediators of Inflammation

An expanding body of evidence continues to build on the central role of inflammation in the progression and clinical manifestations of atherosclerosis. Platelets, long thought to play only a reactionary role at the time of endothelial disruption, are now recognized as important mediators of the inflammatory process. Platelet activation, which is modulated by both inflammatory and hemostatic factors, can lead to the release of hundreds of proteins--many with known proinflammatory functions. Although compelling evidence is lacking that antiplatelet therapies directly lower markers of inflammation, there are intriguing, although preliminary, data suggesting that markers of inflammation predict the clinical benefit of antiplatelet therapies.

Thrombopoietin contributes to enhanced platelet activation in patients with unstable angina

OBJECTIVES

We sought to investigate the potential role of elevated levels of thrombopoietin (TPO) in platelet activation during unstable angina (UA).

BACKGROUND

Thrombopoietin is a humoral growth factor that does not induce platelet aggregation per se, but primes platelet activation in response to several agonists. No data concerning its contribution to platelet function abnormalities described in patients with UA are available.

METHODS

We studied 15 patients with UA and, as controls, 15 patients with stable angina (SA) and 15 healthy subjects. We measured TPO and C-reactive protein (CRP), as well as monocyte-platelet binding and the platelet expression of P-selectin and of the TPO receptor, c-Mpl. The priming activity of patient or control plasma on platelet aggregation and monocyte-platelet binding and the role of TPO in this effect also were studied.

RESULTS

Patients with UA showed higher circulating TPO levels, as well as increased monocyte-platelet binding, platelet P-selectin expression, and CRP levels, than those with SA and healthy control subjects. The UA patients also showed reduced platelet expression of the TPO receptor, c-Mpl. In vitro, the plasma from UA patients, but not from SA patients or healthy controls, primed platelet aggregation and monocyte-platelet binding, which were both reduced when an inhibitor of TPO was used.

CONCLUSIONS

Thrombopoietin may enhance platelet activation in the early phases of UA, potentially participating in the pathogenesis of acute coronary syndromes.