Outcome Comparison of 600- and 300-mg Loading Doses of Clopidogrel in Patients Undergoing Primary Percutaneous Coronary Intervention for ST-Segment Elevation Myocardial Infarction

Effect on Platelet Reactivity From a Prasugrel Loading Dose After a Clopidogrel Loading Dose Compared With a Prasugrel Loading Dose Alone

Background—

Adding a prasugrel loading dose (LD) to a clopidogrel LD could be desirable because clopidogrel may fail to provide adequate levels of platelet inhibition in patients with acute coronary syndrome undergoing percutaneous coronary intervention.

Methods and Results—

The pharmacodynamic response of prasugrel 60 mg LD alone was compared with prasugrel 60 mg or 30 mg added ≤24 hours to clopidogrel 600 mg in Transferring from Clopidogrel Loading Dose to Prasugrel Loading Dose in Acute Coronary Syndrome Patients study—a multicenter, randomized, double-blind, double-dummy, 3-arm, parallel, active-comparator controlled study. Two hundred eighty-two patients were randomized to 3 LD strategies: placebo plus prasugrel 60 mg, clopidogrel 600 mg plus prasugrel 60 mg, or clopidogrel 600 mg plus prasugrel 30 mg. Platelet function was assessed using VerifyNow P2Y12 Reaction Units (PRU) immediately before prasugrel LD, and 2, 6, 24, and 72 hours after prasugrel LD in 149 patients with evaluable platelet function studies. At 6 hours after the prasugrel 60 mg LD, the least squares mean (95% confidence interval) difference between placebo/prasugrel 60 mg and clopidogrel 600 mg/prasugrel 60 mg (primary outcome) was 22.2 (−11.0 to 55.5; P =0.19; least squares mean PRU 57.9 versus 35.6, respectively). For clopidogrel 600 mg/prasugrel 30 mg (least squares mean PRU, 53.9), the difference was 3.9 (−28.2 to 36.1; P =0.81) versus placebo/prasugrel 60 mg. No significant differences in PRU were observed at any time point across the 3 groups. There were few bleeding events observed regardless of treatment.

Conclusions—

Platelet reactivity with prasugrel 60 mg LD added to clopidogrel 600 mg LD was not significantly different compared with prasugrel 60 mg LD alone in acute coronary syndrome patients undergoing percutaneous coronary intervention.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01115738.

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.

Two classes of anti-platelet drugs reduce anatomical infarct size in monkey hearts

BACKGROUND

Recent studies in rabbits have demonstrated that platelet P2Y12 receptor antagonists are cardioprotective, and that the mechanism is surprisingly not related to blockade of platelet aggregation but rather to triggering of the same signal transduction pathway seen in pre- and postconditioning. We wanted to determine whether this same cardioprotection could be documented in a primate model and whether the protection was limited to P2Y12 receptor antagonists or was a class effect.

METHODS

Thirty-one macaque monkeys underwent 90-min LAD occlusion/4-h reperfusion.

RESULTS

The platelet P2Y12 receptor blocker cangrelor started just prior to reperfusion significantly decreased infarction by an amount equivalent to that seen with ischemic postconditioning (p < 0.001). For any size of risk zone, infarct size in treated hearts was significantly smaller than that in control hearts. OM2, an investigational murine antibody against the primate collagen receptor glycoprotein (GP) VI, produced similar protection (p < 0.01) suggesting a class effect. Both cangrelor and OM2 were quite effective at blocking platelet aggregation (94 % and 97 %, respectively).

CONCLUSIONS

Thus in a primate model in which infarct size could be determined directly platelet anti-aggregatory agents are cardioprotective. The important implication of these investigations is that patients with acute myocardial infarction who are treated with platelet anti-aggregatory agents prior to revascularization may already be in a postconditioned state. This hypothesis may explain why in recent clinical trials postconditioning-mimetic interventions which were so protective in animal models had at best only a modest effect.

Predictive values of post-clopidogrel platelet reactivity assessed by different platelet function tests on ischemic events in East Asian patients treated with PCI

Abstract An accumulating number of studies are revealing that platelet reactivity above specific cut-off scores leads to exponentially increased rates of post-percutaneous coronary intervention (PCI) ischemic events. To evaluate the optimal predictive values for three different platelet function measurement assays of platelet reactivity on early clinical outcomes in Korean patients undergoing PCI, we enrolled 228 patients receiving clopidogrel prior to PCI. Platelet reactivity was measured by light transmittance aggregometry (LTA), VerifyNow P2Y12 assay, and multiple electrode platelet aggregometry (MEA). The primary endpoint was the 30-day occurrence of ischemic events after PCI. MACE occurred in 36 patients (15.8%), including 35 patients (15.4%) with periprocedural MI and the death of one patient (0.4%). ADP-induced LTA and VerifyNow values (pre- and post-PCI) were significantly higher in patients with the subsequent occurrence of periprocedural MI, but the MEA assay data (PCI and post-PCI) displayed no significant differences (pre-PCI p=0.25 and post-PCI p=0.33). ROC curve analysis demonstrated HPR values for LTA (pre-PCI, >66% and post-PCI, >53 %, all p<0.001), VerifyNow (pre-PCI, >347 PRU and post-PCI >272 PRU, all p<0.001) and MEA (pre-PCI, >50 U and post-PCI >39 U, all p>0.05). The platelet reactivity measurements by LTA and the VerifyNow assay can discriminate the risk of 30-day ischemic events after PCI. The predictive cut-off values for adverse events are dependent on sampling time.

Glycoprotein IIb/IIIa inhibitors with or without thienopyridine pretreatment improve outcomes after primary percutaneous coronary intervention in high-risk patients with ST elevation myocardial infarction--a meta-regression of randomized controlled trials

BACKGROUND

Recent studies have casted a doubt on usefulness of routine glycoprotein IIb/IIIA inhibitors (GPI) in patients, pretreated with aspirin and clopidogrel, undergoing primary percutaneous coronary intervention (PCI) for ST elevation myocardial infarction (STEMI).

OBJECTIVE

We aimed to investigate the effect of relevant factors, particularly thienopyridine pretreatment, on clinical benefit from GPI in randomized controlled trials (RCT).

METHODS

We searched electronic databases for RCT comparing GPI to control in patients with STEMI undergoing primary PCI. Relevant study covariates and clinical outcomes were extracted. A random effect cumulative and subgroup analyses (thienopyridine non-pretreated studies vs. pretreated studies) were performed. A weighted random effect meta-regression to determine the effect of thienopyridine pretreatment, enrollment year, control group mortality, and ischemic time on mortality benefit from GPI use was conducted.

RESULTS

Twenty studies (9 non-pretreated, 11 pretreated) with a total of 7,414 patients (3,811 GPI, 3,603 control) were included. GPI use reduces mortality (risk ratio, RR = 0.75 95% confidence interval (CI) 0.57-0.97, P = 0.03), target vessel revascularization (TVR) (RR = 0.63, 95% CI 0.50-0.80, P = 0.0002), but not reinfarction (RR = 0.66, 95% CI 0.44-1.0, P = 0.05) at 30 days. There was no effect of thienopyridine pretreatment on reduction in mortality (P = 0.39), reinfarction (P = 0.46), or TVR (P = 0.95) in subgroup analysis. Meta-regression analyses showed significant effect of control group mortality risk (B = -12.15, P = 0.034) but not of thienopyridine pretreatment, enrollment year or control group ischemic time on mortality reduction from GPI use.

CONCLUSION

The benefit from GPI use in primary PCI for STEMI appears to depend on mortality risk, and not on thienopyridine pretreatment.

Novel antiplatelet agent use for acute coronary syndrome in the emergency department: a review

Background. Acute Coronary Syndrome (ACS) is a clinical condition encompassing ST Segment Elevation Myocardial Infarction (STEMI), Non-ST Segment Elevation Myocardial Infarction (NSTEMI), and Unstable Angina (UA) and is characterized by ruptured coronary plaque, ischemic stress, and/or myocardial injury. Emergency department (ED) physicians are on the front lines of ACS management. The role of new antiplatelet agents ticagrelor and prasugrel in acute ED management of ACS has not yet been defined. Objective. To critically review clinical trials using ticagrelor and prasugrel in the treatment of ACS and inform practitioners of their potential utility in treating ACS in the ED. Results. Trials on the efficacy of ticagrelor and prasugrel achieve statistical significance in decreasing composite endpoints in select patient populations. Conclusion. The use of ticagrelor and prasugrel as first line ED treatment of ACS is not well established. Current evidence supports the use of several agents with the final decision based on treatment protocols conjointly developed between cardiology and emergency medicine (EM). Further clinical trials involving head-to-head trials or comparisons of drug-based strategies are required to show superiority in reducing cardiac endpoints with regard to ED initiation of treatment.

Pharmaco-mechanic antithrombotic strategies to reperfusion of the infarct-related artery in patients with ST-elevation acute myocardial infarctions

Primary percutaneous coronary intervention is the best treatment of patients with ST elevation myocardial infarction (STEMI). When managing a STEMI patient, our approach must be rapid and aggresive in order to interrupt the pathological process of thrombus formation and stabilization. The therapy must be initiated prior to angiography (pretreatment), continued during the procedure (periprocedural), recovery phase (in-hospital), and follow-up. The treatment strategies resulting in thrombus dissolution/extraction have focused on optimization of both pharmacological and interventional therapies. At present, there is no optimal evidence-based approach to all patients with STEMI, and the treatment of these patients needs to be modified with respect to the risk profile, availability of medical resources, and our experience. In this review, we summarize current pharmacological and interventional strategies used in the setting of STEMI and discuss potential benefits of novel dosing regimens and combinations of drugs and techniques.

Update on ischemic heart disease and critical care cardiology

This article summarizes the main developments reported during the year 2012 concerning ischemic heart disease, together with the most relevant innovations in the management of acute cardiac patients.

Novel antiplatelet agents: ALX-0081, a Nanobody directed towards von Willebrand factor

This manuscript reviews the studies performed with ALX-0081 (INN: caplacizumab), a Nanobody targeting von Willebrand factor, in the context of current antithrombotic therapy in coronary artery disease. ALX-0081 specifically inhibits platelet adhesion to the vessel wall, and may control platelet aggregation and subsequent clot formation without increasing bleeding risk. A substantial number of antithrombotics are aimed at this cascade; however, their generally indiscriminative mode of action can result in a narrow therapeutic window, defined by the risk for bleeding complications, and thrombotic events. Nonclinically, ALX-0081 compared favorably to several antithrombotics. In Phase I studies in healthy subjects and stable angina patients undergoing percutaneous coronary intervention (PCI), ALX-0081 was well tolerated, and effectively inhibited pharmacodynamic markers. Following these results, a phase II study was initiated in high-risk acute coronary syndrome patients undergoing PCI. Based on its mechanism of action, ALX-0081 is also being developed for acquired thrombotic thrombocytopenic purpura.

[Acute coronary syndrome -- 2012]

The acute coronary syndrome is the most severe form of coronary artery disease. It is an immediate threat of life and the mortality rate can be high without proper therapy and patient management. Based on the first ECG, two different forms can be distinguished: acute coronary syndrome with and without ST elevation. Besides adequate medication, management of these patients is an essential part of treatment. In case of ST elevation, coronarography and percutaneous coronary intervention is needed in general, within 24 hours from the onset of symptoms. When ST elevation is not detected on the ECG, individual ischemic risk factors and predictable mortality of the patient may define the necessity and the date of the invasive examination. The Hungarian hemodynamic laboratory network covers almost the whole country and, therefore, practically each patient may receive a state-of-the-art therapy. Although indicators of cardiovascular diseases are still prominent, the mortality rate of myocardial Infarction is decreasing in Hungary due to the well-organized invasive care.

Platelet P2Y₁₂ blockers confer direct postconditioning-like protection in reperfused rabbit hearts

BACKGROUND

Blockade of platelet activation during primary percutaneous intervention for acute myocardial infarction is standard care to minimize stent thrombosis. To determine whether antiplatelet agents offer any direct cardioprotective effect, we tested whether they could modify infarction in a rabbit model of ischemia/reperfusion caused by reversible ligation of a coronary artery.

METHODS AND RESULTS

The P2Y₁₂ (adenosine diphosphate) receptor blocker cangrelor administered shortly before reperfusion in rabbits undergoing 30-minute regional ischemia/3-hour reperfusion reduced infarction from 38% of ischemic zone in control hearts to only 19%. Protection was dose dependent and correlated with the degree of inhibition of platelet aggregation. Protection was comparable to that seen with ischemic postconditioning (IPOC). Cangrelor protection, but not its inhibition of platelet aggregation, was abolished by the same signaling inhibitors that block protection from IPOC suggesting protection resulted from protective signaling rather than anticoagulation. As with IPOC, protection was lost when cangrelor administration was delayed until 10 minutes after reperfusion and no added protection was seen when cangrelor and IPOC were combined. These findings suggest both IPOC and cangrelor may protect by the same mechanism. No protection was seen when cangrelor was used in crystalloid-perfused isolated hearts indicating some component in whole blood is required for protection. Clopidogrel had a very slow onset of action requiring 2 days of treatment before platelets were inhibited, and only then the hearts were protected. Signaling inhibitors given just prior to reperfusion blocked clopidogrel's protection. Neither aspirin nor heparin was protective.

CONCLUSIONS

Clopidogrel and cangrelor protected rabbit hearts against infarction. The mechanism appears to involve signal transduction during reperfusion rather than inhibition of intravascular coagulation. We hypothesize that both drugs protect by activating IPOC's protective signaling to prevent reperfusion injury. If true, patients receiving P2Y₁₂ inhibitors before percutaneous intervention may already be postconditioned thus explaining failure of recent clinical trials of postconditioning drugs.

ABCB1 C3435T polymorphism and response to clopidogrel treatment in coronary artery disease (CAD) patients: a meta-analysis

BACKGROUND

A number of investigators have evaluated the association between the ABCB1 polymorphism and clopidogrel responding, but the results have been inconclusive. To examine the risk of high platelet activity and poor clinical outcomes associated with the ABCB1 C3435T polymorphism in CAD patients on clopidogrel, all available studies were included in the present meta-analysis.

METHODS

We performed a systematic search of PubMed, Scopus and the Cochrane library database for eligible studies. Articles meeting the inclusion criteria were comprehensively reviewed, and the available data were accumulated by the meta-analysis.

RESULTS

It was demonstrated that the ABCB1 C3435T variation was associated with the risk of early major adverse cardiovascular events (MACE) (T vs. C OR, 1.34; 95% CI, 1.10 to 1.62; P=0.003; TT vs. CC: OR, 1.77; 95% CI, 1.19 to 2.63; P=0.005; CT + TT vs.CC: OR, 1.48; 95% CI, 1.06 to 2.06; P=0.02) and the polymorphism was also associated with the risk of the long-term MACE in patients on clopidogrel LD 300 mg (T vs. C: OR, 1.28; 95% CI, 1.10 to 1.48; P=0.001; TT vs. CC: OR, 1.59; 95% CI, 1.19 to 2.13; P=0.002; CT + TT vs.CC: OR, 1.39; 95% CI, 1.08 to 1.79; P=0.01). The comparison of TT vs. CC was associated with a reduction in the outcome of bleeding (TT vs. CC: OR, 0.51; 95% CI, 0.40 to 0.66; P<0.00001). However, the association between ABCB1 C3435T polymorphism and platelet activity and other risk of poor clinical outcomes was not significant.

CONCLUSIONS

The evidence from our meta-analysis indicated that the ABCB1 C3435T polymorphism might be a risk factor for the MACE in patients on clopidogrel LD 300 mg, and that TT homozygotes decreased the outcome of bleeding compared with CC homozygotes.

Microvascular effect of intracoronary eptifibatide in acute myocardial infarction

OBJECTIVES

In this prospective, randomized trial in patients with acute myocardial infarction (AMI) admitted for primary percutaneous coronary intervention (PPCI), loaded with 600 mg clopidogrel, we hypothesized that eptifibatide administered downstream of the coronary occlusion leads to a lower degree of microvascular obstruction compared with no additional eptifibatide.

METHODS

Fifty patients with AMI, loaded with 600 mg of clopidogrel at the first hospital contact, with occlusion of the left anterior descending artery (LAD), were randomized to an eptifibatide group (EG) or a control group (CG). In both groups, stenting was performed after thrombus aspiration. Microvascular reperfusion was assessed by angiography, electrocardiography, and transthoracic Doppler ultrasonography of the LAD.

RESULTS

TIMI myocardial perfusion grade 2-3 was not different between the EG (72%) and the CG (84%) (p = 0.31). ST segment resolution >70% was similarly detected in both groups (32 vs. 40%; p = 0.56). The mean diastolic deceleration time did not differ significantly between the CG (856.36 ± 397.88 ms) and the EG (935.72 ± 252.22 ms) (p = 0.41). Multivariate logistic regression revealed no significant influence of the treatment with eptifibatide on ST segment resolution (OR 0.47; 95% CI 0.11-2.10, p = 0.32), TIMI myocardial perfusion (OR 0.52; 95% CI 0.10-2.59, p = 0.42), and diastolic deceleration time (OR 0.21; 95% CI 0.03-1.51, p = 0.12).

CONCLUSIONS

In AMI patients loaded with 600 mg of clopidogrel undergoing PPCI, intracoronary administration of eptifibatide does not clearly improve microvascular obstruction.

Modern management of acute myocardial infarction

Disruption of intracoronary plaque with thrombus formation provides the pathophysiologic foundation for acute coronary syndromes, which comprise ST-segment myocardial infarction, non-ST-segment myocardial infarction, and unstable angina. Management differs depending on whether ST-segment elevation is present, but the general principles of timely restoration of coronary blood flow and initiation of secondary prevention strategies are applicable to all patients. The purpose of this review is to discuss first the epidemiology, pathophysiology, and diagnosis of acute myocardial infarction. Risk stratification and therapy for patients with ST-segment elevation myocardial infarction and non-ST-segment elevation acute coronary syndromes are then reviewed along with diagnosis and management of the complications of myocardial infarction.

Quantitative comparison of clopidogrel 600 mg, prasugrel and ticagrelor, against clopidogrel 300 mg on major adverse cardiovascular events and bleeding in coronary stenting: synthesis of CURRENT-OASIS-7, TRITON-TIMI-38 and PLATO

The convention of loading with clopidogrel 300 mg before coronary intervention may be due for change, but to what? Newer antiplatelet agents may offer better outcomes, at some financial cost. Disappointingly for decision-making clinicians, head-to-head comparisons for the newer alternatives are not available. We systematically review and compare the three alternative strategies: clopidogrel 600 mg, prasugrel and ticagrelor. A total of 14 studies have compared these strategies with the long-standing convention of 300 mg. Throughout this analysis, we consistently report incremental costs and consequences using clopidogrel 300 mg as the reference strategy. Risk ratios for major adverse cardiovascular events at 30 days were 0.74 (95% confidence interval 0.66-0.82, p=0.002) for clopidogrel 600 mg, 0.78 (0.69-0.89; p<0.001) for prasugrel and 0.88 (0.77-1.00; p=0.045) for ticagrelor. All-cause mortality risk ratios were 0.87 (0.74-1.03) with clopidogrel 600 mg, 0.95 (0.78-1.16) with prasugrel and 0.78 (0.69-0.89) with ticagrelor. TIMI major bleeding has risk ratio 0.92 (0.74-1.16; p=0.85) with clopidogrel 600 mg, 1.32 (1.03-1.16; p=0.03) with prasugrel and 1.25 (1.03-1.53; p=0.03) with ticagrelor. Incremental cost for the first year was £0.32 (US$0.50, €0.40) with clopidogrel 600 mg, £608 (US$977, €709) with prasugrel and £665 (US$1068, €775) with ticagrelor. All three strategies have shown a similar reduction in MACE at 30 days by comparison to clopidogrel 300 mg. All three strategies offer progressive benefit, most marked with Ticagrelor. Whether this is worth both the risk of non-compliance with twice-a-day dosing in real-life patients lacking the same motivation as their trial-volunteer counterparts, and the 2000-fold difference in incremental cost, is the remaining matter for debate.

Cardioprotection by clopidogrel in acute ST-elevated myocardial infarction patients: a retrospective analysis

Antiplatelet agents have been extensively used in acute coronary syndromes and improve clinical outcome in STEMI patients. Previous experimental studies of the impact of antiplatelet agents on infarct size have been equivoqual. We questioned whether clopidogrel might reduce infarct size in STEMI patients, independently of any antithrombotic effect, by activating a post-conditioning-like myocardial protection. We retrospectively analyzed three recent controlled, randomized, proof of concept clinical trials aimed at determining whether PCI post-conditioning might attenuated infarct size in STEMI. We addressed whether clopidogrel (300-600 mg before angioplasty) might have influenced infarct size using a multivariable linear regression analysis with infarct size as the continuous outcome variable and age, clopidogrel and GP IIb/IIIa inhibitors, post-conditioning, area at risk, ischemia time, coronary thrombectomy and final TIMI flow, as covariates. In this population of 88 STEMI patients, ischemic post-conditioning and clopidogrel administration were the only two therapeutic independent predictors of the final infarct size as determined by cardiac enzymes release (p = 0.005 and p < 0.0001, respectively) This retrospective analysis supports the proposal that clopidogrel attenuates lethal reperfusion injury.