A comparison of the VASP index between patients with hemodynamically complicated and uncomplicated acute myocardial infarction

Cangrelor versus crushed ticagrelor in patients with acute myocardial infarction and cardiogenic shock: rationale and design of the randomised, double-blind DAPT-SHOCK-AMI trial

Cardiogenic shock (CS) is a devastating and fatal complication of acute myocardial infarction (AMI). CS can affect the pharmacokinetics and pharmacodynamics of medications. The unique properties of cangrelor make it the optimal P2Y12 inhibitor for CS-AMI, in terms of both efficacy and safety. The DAPT-SHOCK-AMI trial (ClinicalTrials.gov: NCT03551964; EudraCT: 2018-002161-19) will assess the benefits of cangrelor in patients with an initial CS-AMI undergoing primary angioplasty. This randomised, multicentre, placebo-controlled trial of approximately 550 patients (with an allowed 10% increase) in 5 countries using a double-blind design will compare initial P2Y12 inhibitor treatment strategies in patients with CS-AMI of (A) intravenous cangrelor and (B) ticagrelor administered as crushed tablets at a loading dose of 180 mg. The primary clinical endpoint is a composite of all-cause death, myocardial infarction (MI), or stroke within 30 days. The main secondary endpoints are (1) the net clinical endpoint, defined as death, MI, urgent revascularisation of the infarct-related artery, stroke, or major bleeding as defined by the Bleeding Academic Research Consortium criteria; (2) cardiovascular-related death, MI, urgent revascularisation, or heart failure; (3) heart failure; and (4) cardiovascular-related death, all (1-4) within 1 year after study enrolment. A platelet reactivity study that tests the laboratory antiplatelet benefits of cangrelor, when given in addition to standard antiplatelet therapy, will be conducted using vasodilator-stimulated phosphoprotein phosphorylation. The primary laboratory endpoints are the periprocedural rate of onset and the proportion of patients who achieve effective P2Y12 inhibition. The DAPT-SHOCK-AMI study is the first randomised trial to evaluate the benefits of cangrelor in patients with CS-AMI.

Intracoronary imaging guided percutaneous coronary intervention outcomes among individuals with cardiogenic shock

BACKGROUND

Limited data exist around the utility of intracoronary imaging (ICI) during percutaneous coronary intervention (PCI) in patients with acute coronary syndrome (ACS) and cardiogenic shock (CS), who are inherently at a high risk of stent thrombosis (ST).

METHODS

All PCI procedures for ACS patients with CS in England and Wales between 2014 and 2020 were retrospectively analysed, stratified into two groups: ICI and angiography-guided groups. Multivariable logistic regression analyses were performed to examine odds ratios (OR) of in-hospital outcomes, including major adverse cardiovascular and cerebrovascular events (MACCE; composite of all-cause mortality, acute stroke/transient ischaemic attack (TIA), and reinfarction) and major bleeding, in the ICI-guided group compared with angiography-guided PCI.

RESULTS

Of 15,738 PCI procedures, 1240(7.9%) were ICI-guided. The rate of ICI use amongst those with CS more than doubled from 2014 (5.7%) to 2020 (13.3%). The ICI-guided group were predominantly younger, males, with a higher proportion of non-ST-elevation ACS and ST. MACCE was significantly lower in the ICI-guided group compared with the angiography-guided group (crude: 29.8% vs. 38.2%, adjusted odds ratio (OR) 0.65 95% confidence interval [CI] 0.56-0.76), driven by lower all-cause mortality (28.6% vs. 37.0%, OR 0.65 95% CI 0.55-0.75). There were no differences in other secondary outcomes between groups.

CONCLUSION

ICI use among CS patients has more than doubled over 6 years but remains significantly under-utilized, with less than 1-in-6 patients in receipt of ICI-guided PCI by 2020. ICI-guided PCI is associated with prognostic benefits in CS patients and should be more frequently utilized to increase their long-term survival.

Newer P2Y12 Inhibitors vs Clopidogrel in Acute Myocardial Infarction With Cardiac Arrest or Cardiogenic Shock: A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the outcomes, safety, and efficacy of dual antiplatelet therapy (DAPT) with newer P2Y₁₂ inhibitors compared with clopidogrel in patients with acute myocardial infarction (AMI) complicated by cardiac arrest (CA) or cardiogenic shock (CS).

PATIENTS AND METHODS

MEDLINE, EMBASE, and the Cochrane Library were queried systematically from inception to January 2021 for comparative studies of adults (≥18 years) with AMI-CA/CS receiving DAPT with newer P2Y₁₂ inhibitors as opposed to clopidogrel. We compared outcomes (30-day or in-hospital and 1-year all-cause mortality, major bleeding, and definite stent thrombosis) of newer P2Y₁₂ inhibitors and clopidogrel in patients with AMI-CA/CS.

RESULTS

Eight studies (1 randomized trial and 7 cohort studies) comprising 1100 patients (695 [63.2%] receiving clopidogrel and 405 [36.8%] receiving ticagrelor or prasugrel) were included. The population was mostly male (68.5%-86.7%). Risk of bias was low for these studies, with between-study heterogeneity and subgroup differences not statistically significant. Compared with the clopidogrel cohort, the newer P2Y₁₂ cohort had lower rates of early mortality (odds ratio [OR], 0.60; 95% CI, 0.45 to 0.81; P=.001) (7 studies) and 1-year mortality (OR, 0.51; 95% CI, 0.36 to 0.71; P<.001) (3 studies). We did not find a significant difference in major bleeding (OR, 1.21; 95% CI, 0.71 to 2.06; P=.48) (6 studies) or definite stent thrombosis (OR, 2.01; 95% CI, 0.63 to 6.45; P=.24) (7 studies).

CONCLUSION

In patients with AMI-CA/CS receiving DAPT, compared with clopidogrel, newer P2Y₁₂ inhibitors were associated with lower rates of early and 1-year mortality. Data on major bleeding and stent thrombosis were inconclusive.

ADP-induced platelet reactivity and bleeding events in patients with acute myocardial infarction complicated by cardiogenic shock

While previous reports showed ADP-induced platelet reactivity to be an independent predictor of bleeding after PCI in stable patients, this has never been investigated in patients with cardiogenic shock. The association of bleeding events with respect to ADP-induced platelet aggregation was investigated in patients undergoing primary PCI for acute myocardial infarction complicated by cardiogenic shock and with available on-treatment ADP-induced platelet aggregation measurements. Out of 233 patients, 74 suffered from a severe BARC3 or higher bleed. ADP-induced platelet aggregation was significantly lower in patients with BARC≥3 bleedings (p < .001). Multivariate analysis identified on-treatment ADP-induced platelet aggregation as an independent risk factor for bleeding (HR = 0.968 per AU). An optimal cutoff value of <12 AU for ADP-induced platelet aggregation to predict BARC≥3 bleedings was identified via ROC analysis. Moreover, the use of VA-ECMO (HR 1.972) or coaxial left ventricular pump (HR 2.593), first lactate (HR 1.093 per mmol/l) and thrombocyte count (HR 0.994 per G/l) were independent predictors of BARC≥3 bleedings. In conclusion, lower on-treatment ADP-induced platelet aggregation was independently associated with severe bleeding events in patients with AMI-CS. The value of platelet function testing for bleeding risk prediction and guidance of anti-thrombotic treatment in cardiogenic shock warrants further investigation.

New insights into cardiogenic shock and coronary revascularization after acute myocardial infarction

Cardiogenic shock complicating acute myocardial infarction is challenging, and continues to be associated with high rates of in-hospital and long-term mortality. Coronary revascularization is critical for improving prognosis in CS. Thus, a systematic protocol-driven approach to cardiogenic shock, the development of specialized cardiac care centres, technical advances in interventional cardiology enabling treatment of more complex and severe lesions, the availability of recent antithrombotic therapies and the evolution of new haemodynamic support devices are important considerations in current management of cardiogenic shock complicating acute ischaemic heart disease. Despite these potentially meaningful developments, several substantial gaps in knowledge still exist regarding optimal coronary revascularization of patients with cardiogenic shock. This review will describe current principles in the revascularization of these patients, with a focus on: the time to transfer and revascularize; the choice of vascular access site; the need for complete revascularization or only a culprit lesion strategy; the optimal antithrombotic therapy; the type, place and timing of haemodynamic support; and the medical care system network.

Impaired aspirin-mediated platelet function inhibition in resuscitated patients with acute myocardial infarction treated with therapeutic hypothermia: a prospective, observational, non-randomized single-centre study

The majority of resuscitated patients present with underlying cardiac disease, and out of these myocardial infarction is most common. Immediate interventional treatment is recommended and routinely requires dual antiplatelet therapy including aspirin and a P2Y12-inhibitor. Therapeutic hypothermia or target temperature management is also recommended in these patients. Cardiogenic shock as well as reduced body temperature impacts platelet reactivity and its medical inhibition. The study aims to quantify aspirin- and P2Y12-mediated platelet inhibition in patients presenting with myocardial infarction and cardiopulmonary resuscitation. Twenty-five resuscitated patients were enrolled in this prospective, observational, non-randomized single-centre study. These patients were compared to 77 matched controls from the ATLANTIS-ACS database of non-resuscitated patients with myocardial infarction. Platelet function testing was performed by light transmittance aggregometry. Aspirin reactivity was monitored by inducing platelet aggregation with collagen and arachidonic acid, respectively. P2Y12 inhibition was recorded by stimulation of platelet aggregation with adenosine diphosphate. To quantify the overall platelet response, thrombin receptor-activated peptide was used. Aspirin-mediated platelet reactivity decreased significantly in resuscitated patients during the first days and was significantly weaker on day 3 (collagen AUC 253.8 (122.7–352.2) vs. 109.0 (73.0–182.0); p = 0.022). P2Y12-mediated platelet inhibition was also impaired in resuscitated patients on day 3 (mean ADP AUC (IQR): CPR 172.1 (46.7−346.5) vs. control 43.9 (18.9–115.2); p < 0.05). Aspirin- and P2Y12-mediated platelet inhibition is impaired in resuscitated patients treated with therapeutic hypothermia. On day 3, we recorded lowest inhibitory effects of both drug types and patients might be at particular risk at that time. Potentially, intravenous aspirin and P2Y12 inhibitors might still supply a more predictable and stable platelet inhibition.

Potent P2Y12 receptor inhibitors in patients with acute coronary syndrome

Blood platelets are highly activated in the setting of an acute coronary syndrome (ACS). This fact mandates the need for potent platelet inhibition in ACS patients and especially in patients undergoing a percutaneous coronary intervention (PCI). The 2nd generation thienopyridine clopidogrel has been the standard of treatment in the past. Due to its pharmacological properties including a delayed onset of action, a large response variability and an insufficient antiplatelet action in some patients (low responsiveness or high on-treatment platelet reactivity), there was a need to develop, to study and to introduce more potent agents with a fast, reliable and potent antiplatelet action. With the 3rd generation thienopyridine prasugrel and with ticagrelor two potent agents for antiplatelet treatment of ACS patients are available now. Both drugs have demonstrated their superiority compared to clopidogrel in terms of thrombotic risk reduction in large-scale randomized trials. However, for these agents and in line with the expectations towards a more potent anti platelet treatment regimen, a higher risk for bleeding was observed for prasugrel and ticagrelor. Further on, the new anti platelet agents have their own and characteristic contraindications and numerous issues to be considered in clinical practice.

This review aims to provide an overview on the state of the art P2Y12 receptor directed inhibition in ACS patients with a focus on patients undergoing a coronary stenting procedure.

Early clinical outcomes as a function of use of newer oral P2Y12 inhibitors versus clopidogrel in the EUROMAX trial

Objective

To ascertain whether different oral P2Y₁₂ inhibitors might affect rates of acute stent thrombosis and 30-day outcomes after primary percutaneous coronary intervention (pPCI).

Methods

The European Ambulance Acute Coronary Syndrome Angiography (EUROMAX) randomised trial compared prehospital bivalirudin with heparin with optional glycoprotein IIb/IIIa inhibitor treatment in patients with ST-segment elevation myocardial infarction triaged to pPCI. Choice of P2Y₁₂ inhibitor was at the investigator’s discretion. In a prespecified analysis, we compared event rates with clopidogrel and newer oral P2Y₁₂ inhibitors (prasugrel, ticagrelor). Rates of the primary outcome (acute stent thrombosis) were examined as a function of the P2Y₁₂ inhibitor used for loading and 30-day outcomes (including major adverse cardiac events) as a function of the P2Y₁₂ inhibitor used for maintenance therapy. Logistic regression was used to adjust for differences in baseline characteristics.

Results

Prasugrel or ticagrelor was given as the loading P2Y₁₂ inhibitor in 49% of 2198 patients and as a maintenance therapy in 59%. No differences were observed in rates of acute stent thrombosis for clopidogrel versus newer P2Y₁₂ inhibitors (adjusted OR 0.50, 95% CI 0.13 to 1.85). After adjustment, no difference was observed in 30-day outcomes according to maintenance therapy except for protocol major (p=0.029) or minor (p=0.025) bleeding and Thrombolysis In Myocardial Infarction minor bleeding (p=0.002), which were less frequent in patients on clopidogrel. Consistent results were observed in the bivalirudin and heparin arms.

Conclusions

The choice of prasugrel or ticagrelor over clopidogrel was not associated with differences in acute stent thrombosis or 30-day ischaemic outcomes after pPCI.

Trial registration number

NCT01087723.

High platelet reactivity and clinical outcome – Fact and fiction

In patients suffering from acute coronary syndromes or undergoing percutaneous coronary intervention, oral antiplatelet treatment is routinely administered with the primary aim of inhibiting platelet-mediated thrombus formation and subsequent abrupt vessel occlusion. Simultaneous inhibition of blood platelet cyclooxygenase-1 by aspirin and of the P2Y12 receptor by clopidogrel or prasugrel is currently recommended in this setting. Inter-individual response variability to aspirin and especially to clopidogrel is the subject of much debate as evidence has grown over the years linking an attenuated response to treatment with the occurrence of ischaemic events. Consequently, the clinical entity of high (on-treatment) platelet reactivity (HPR) was born and subsequently characterised in numerous studies over the last decade. Until recently, alternative treatment options were limited in patients exhibiting HPR. At present the antiplatelet therapy landscape is changing with the advent of prasugrel and ticagrelor as alternative and more potent treatment options. Different tests for monitoring platelet function are available and are being increasingly employed in research projects and clinical routine. These tests may prove useful for achieving optimal platelet inhibition for the individual patient, and several centres now incorporate such testing in day-to-day practice. Widespread adoption of this practice and incorporation into clinical guidelines awaits the results of ongoing trials in which treatment is changed based on platelet function monitoring. This review aims to summarise available facts and fiction in relation to platelet function testing and reactivity with a particular focus on P2Y12 receptor inhibition in patients undergoing coronary stent placement.

Early determination of clopidogrel responsiveness by platelet reactivity index identifies patients at risk for cardiovascular events after myocardial infarction

While acute myocardial infarction (MI) is associated with impaired clopidogrel responsiveness, systematic evaluation is lacking due to the inability of functional aggregation-based assays to analyse clopidogrel responsiveness in the presence of glycoprotein IIb/IIIa inhibitors. Using the P2Y12-specific, non-aggregation-based platelet-reactivity-index (PRI) we assessed clopidogrel responsiveness in patients with acute MI. Clopidogrel responsiveness was determined 24 hours (h) after loading with 600 mg clopidogrel in 54 patients with acute MI admitted for coronary intervention. A PRI > 50% was considered as suboptimal inhibition. Overall response in MI patients was suboptimal with a median PRI of 58%. Diabetes, low high-density lipoprotein and pre-hospital clopidogrel loading were associated with impaired clopidogrel responsiveness. Patients loaded at first medical contact had a significantly weaker platelet inhibition by clopidogrel after 24 h (PRI 63%) compared to those loaded peri-interventionally (PRI 54%, p=0.014). Clinical outcome was assessed as a combination of cardiac death, non-fatal MI, stent thrombosis, ischaemic stroke, and urgent target vessel revascularisation after 12 months. The pre-selected cut-off of PRI ≤ 50% yielded a sensitivity of 87% at a specificity of 26%, whereas a PRI ≤ 57% determined by receiver-operating characteristics (ROC)-analysis yielded a sensitivity of 80% at a specificity of 56% (event rate: PRI ≤ 57%: 12.0%; PRI > 57%: 41.4%, p=0.0136). In conclusion, PRI detects clopidogrel responsiveness in acute MI patients requiring glycoprotein IIb/IIIa antagonism; and impaired clopidogrel responsiveness predisposes to clinical events. Pre-hospital clopidogrel loading was associated with impaired response and more adverse events challenging the concept of earliest oral clopidogrel loading in MI patients.

Prasugrel vs clopidogrel in cardiogenic shock patients undergoing primary PCI for acute myocardial infarction

There is limited clinical data comparing different P2Y12-receptor inhibitors in patients with acute myocardial infarction (AMI) complicated by cardiogenic shock. The aim of the ISAR-SHOCK registry was to compare the clinical outcome of patients treated with clopidogrel vs prasugrel in this setting. Patients (n=145) with AMI complicated by cardiogenic shock and undergoing primary PCI in two centres (Deutsches Herzzentrum München and Klinikum rechts der Isar, Technical University Munich) between January 2009 and May 2012 were included in this registry. The use of prasugrel for patients within this registry reflected co-morbidities and platelet function testing results during the acute AMI phase. Early outcome at 30-days was reported with regard to all-cause mortality, myocardial infarction (MI), stent thrombosis (ST) and bleeding events. With regard to antiplatelet treatment in the 145 cardiogenic shock patients, 50 patients were initially treated or immediately switched to prasugrel while 95 patients were treated with clopidogrel. All-cause mortality was lower in prasugrelvs clopidogrel-treated patients (30 % vs 50.5%, HR: 0.51, 95% CI [0.29–0.92], p=0.025). No significant differences in prasugrel- vs clopidogrel-treated patients were observed for the occurrence of MI (p=0.233), ST (p=0.306) or TIMI major bleedings (p=0.571). Results of the ISAR-SHOCK registry suggest that the use of prasugrel in AMI patients complicated by cardiogenic shock might be associated with a lower mortality risk as compared to clopidogrel therapy without increasing the risk of bleeding. These findings, however, need confirmation from specifically designed randomised studies in this high-risk cohort of patients.

Clopidogrel in Critically Ill Patients

Only limited data are available regarding the treatment of critically ill patients with clopidogrel. This trial investigated the effects and the drug concentrations of the cytochrome P450 (CYP450) activated prodrug clopidogrel (n = 43) and the half‐life of the similarly metabolized pantoprazole (n = 16) in critically ill patients. ADP‐induced aggregometry in whole blood classified 74% (95% confidence intervals 59–87%) of critically ill patients as poor responders (n = 43), and 65% (49–79%) responded poorly according to the vasodilator‐stimulated phosphoprotein phosphorylation (VASP‐P) assay. Although the plasma levels of clopidogrel active metabolite normally exceed the inactive prodrug ∼30‐fold, the parent drug levels even exceeded those of the metabolite 2‐fold in critically ill patients. The half‐life of pantoprazole was several‐fold longer in these patients compared with reference populations. The inverse ratio of prodrug/active metabolite indicates insufficient metabolization of clopidogrel, which is independently confirmed by the ∼5‐fold increase in half‐life of pantoprazole. Thus, high‐risk patients may benefit from treatment with alternative platelet inhibitors.

Antithrombotic therapy before, during and after emergency angioplasty for ST elevation myocardial infarction

The first three hours after symptom onset hold the maximum potential for myocardial reperfusion and salvage in ST-elevation myocardial infarction (STEMI) patients. During this period timely primary percutaneous coronary intervention (PPCI) or, when PPCI is not promptly feasible, pre-hospital administration of fibrinolyis or a glycoprotein IIb/IIIa-inhibitor (GPI) have been shown to restore coronary patency and reperfusion and even result in myocardial infarction (MI) abortion. On the other hand, oral antiplatelet therapy may not yet guarantee sufficient platelet inhibition. Patients presenting after this golden time have less, if any, benefit from an aggressive antithrombotic treatment prior to PPCI. Antithrombotic treatment during primary angioplasty should be tailored on the basis of the coronary thrombotic burden, vascular approach and the patient's risk of bleeding complications. A GPI-based approach may be favourable in patients presenting early with large MI and high thrombus burden, whereas a bivalirudin-based approach without GPI may be preferred in patients with higher bleeding risk. There are no data to support the use of GPI in bailout conditions. The powerful oral P2Y₁₂ inhibitors, prasugrel and ticagrelor, have been clearly shown to prevent stent thrombosis and recurrent ischaemic events after emergency percutaneous coronary intervention in STEMI patients. Open issues remaining are the treatment of patients with high bleeding risk, such as the elderly and those requiring anticoagulation, as well as the duration of dual antiplatelet therapy after STEMI.

Pharmacokinetics and pharmacodynamics of oral P2Y12 inhibitors during the acute phase of a myocardial infarction: A systematic review

BACKGROUND

The immediate administration of oral antiplatelet therapy in the form of aspirin plus a P2Y12 inhibitor is the universally recognised standard of care for patients who present with acute myocardial infarction. Despite strong recommendations for their use, there are a paucity of data describing their onset of action and clinical efficacy during the short time frames from confirmation of diagnosis to reperfusion with primary percutaneous coronary intervention.

OBJECTIVES

To complete a systematic review evaluating the currently available evidence regarding the pharmacokinetic and pharmacodynamic activity of orally administered clopidogrel, prasugrel and ticagrelor during the acute phase of a myocardial infarction in relation to mechanical reperfusion with primary percutaneous coronary angioplasty.

METHODS

We searched PubMed and EMBASE databases up to January 2016 using the terms outlined in our search strategy.

RESULTS

Twelve papers were included in our final analysis; seven relating to pharmacodynamic studies, one to a pharmacokinetic study and four to pharmacokinetic/pharmacodynamic studies.

CONCLUSION

Our results indicate that despite the administration of oral P2Y12 inhibitors including newer more potent agents that should allow for greater and more consistent levels of platelet inhibition, the physiological state of ST segment elevation MI (STEMI) and the co-administration of opioid based analgesia are associated with a reduction in the degree of platelet inhibition achieved following their administration.

Platelet inhibition with prasugrel in patients with acute myocardial infarction undergoing therapeutic hypothermia after cardiopulmonary resuscitation

Acute myocardial infarction (AMI) is the leading cause for out-of-hospital cardiac arrest. Therapeutic hypothermia improves neurological outcome in combination with early revascularisation, but seems to affect clopidogrel responsiveness. The more potent thienopyridine prasugrel has not yet been sufficiently evaluated during therapeutic hypothermia. We investigated 23 consecutive AMI patients (61 ± 11 years) following out-of-hospital resuscitation undergoing revascularisation and therapeutic hypothermia. Prasugrel efficacy was assessed by the platelet-reactivity-index (PRI) before and 2, 4, 6, 12, 24, 48, and 72 hours (h) following a loading dose of 60 mg via a gastric tube. Mean PRI (± SD) was 70 ± 12 % prior to loading and 60 ± 16 % (2 h, ns), 52 ± 21 % (4 h, p< 0.01), 42 ± 26 % (6 h, p< 0.01), 37 ± 21 % (12 h, p< 0.01), 27 ± 23 % (24 h, p< 0.01), 18 ± 14 % (48 h, p< 0.01), and 13 ± 10 % (72 h, p< 0.01) after loading. Sufficient platelet inhibition occurred later compared to stable AMI patients (6 h vs 2 h); however, high on-treatment platelet reactivity significantly decreased over time and was non-existent after 72 h (PRI> 50 %: 2 h: 72 %, 4 h: 52 %, 6 h: 43 %, 12 h: 29 %, 24 h: 17 %, 48 h: 5 %, 72 h: 0 %). There was no relation between 30-day mortality rate (26 %) and PRI values. Prasugrel significantly reduced platelet reactivity even during vasopressor use, analgosedation and therapeutic hypothermia. Despite a significant delay compared to stable AMI patients, sufficient platelet inhibition was reached in 83 % of patients within 24 h. Therefore, prasugrel administration via gastric tube might be a useful therapeutic strategy in these patients at high risk, providing potent and effective P2Y12 inhibition.

The impact of therapeutic hypothermia on on-treatment platelet reactivity and clinical outcome in cardiogenic shock patients undergoing primary PCI for acute myocardial infarction: Results from the ISAR-SHOCK registry

INTRODUCTION

Mild therapeutic hypothermia (TH) is standard of care after cardiac arrest of any cause. However, its impact on on-treatment platelet reactivity and clinical outcome in patients with acute myocardial infarction (AMI) complicated by cardiogenic shock and undergoing PCI with P2Y12 receptor inhibitor treatment is less clear.

METHODS AND RESULTS

For the ISAR-SHOCK registry, 145 patients with AMI, cardiogenic shock and primary PCI in two centers (Deutsches Herzzentrum München and Klinikum rechts der Isar, Technical University Munich) between January 2009-May 2012 were analysed. Of these, 64 (44%) patients received TH treatment. The median [IQR] ADP-induced platelet aggregation following thienopyridine loading dose administration (clopidogrel in 95 and prasugrel in 50 patients) did not differ between the two groups (419 [283-684] for TH vs. 355 [207-710] AU x min for non-TH patients, P=0.22). After 30days follow-up, no significant differences were observed between both groups for mortality (42 vs. 44 %, HR: 0.93, 95% CI [0.56-1.53], p=0.77), MI (6 vs. 6%, HR: 0.99 95% CI [0.27-3.7], p=0.99) and TIMI minor bleedings (17 vs. 17%, HR 0.99 95% CI [0.45-2.18], p=0.98). TIMI major bleedings were numerically higher in the TH vs. non-TH cohort (25 % vs. 12 %, HR: 2.1 95% CI [0.95-4.63], p=0.07). Three definite stent thrombosis (ST) were observed in this registry and all STs occurred in the TH group of patients (p=0.09).

CONCLUSION

Results of this registry suggest that TH does not negatively impact on platelet reactivity in shock patients receiving either clopidogrel or prasugrel. The numerically higher rate of major bleedings and the clustering of STs in the TH cohort warrant further investigation.

Antiplatelet Therapy Considerations in Ischemic Cardiogenic Shock

Dual antiplatelet therapy with aspirin and a P2Y12 receptor antagonist remains a mainstay in the prevention of ischemic events following coronary stent placement. Significant controversy exists regarding the optimal management of high platelet reactivity despite antiplatelet therapy; however this finding has been consistently associated with poor clinical outcomes including greater risk of stent thrombosis and myocardial infarction. Variability in antiplatelet effects of clopidogrel and prasugrel has been linked to genetic polymorphisms and potential drug–drug interactions. Both of these factors have significant influence on the cytochrome P-450 enzyme system activity of the liver responsible for their biotransformation to the active form of both drugs. Very little has been publicized regarding differences in antiplatelet effects which may be associated with conditions in which the functional capacity of the liver may be temporarily compromised. Patients who present with cardiogenic shock due to acute coronary syndromes have evidence of multiorgan dysfunction including liver dysfunction that may affect the activity of these drugs. This review aims to explore existing evidence and propose additional considerations to the selection of antiplatelet therapy in patients with cardiogenic shock who receive catheter-based revascularization and stent placement.

A pharmacodynamic comparison of 5 anti-platelet protocols in patients with ST-elevation myocardial infarction undergoing primary PCI

Background

Despite advances in anti-platelet treatments, there still exists an early increase in both ischemic as well as bleeding events following primary PCI in patients with ST-elevation myocardial infarction (STEMI). Platelet inhibition data of different anti-platelet treatments in the acute phase of a myocardial infarction might offer some insight into these problems. The aim of this study was to evaluate the pharmacodynamic profile of 5 different anti-platelet treatments in the acute phase of STEMI in patients undergoing primary PCI.

Methods

A total of 223 STEMI patients undergoing primary PCI were prospectively included. Patients received either pre-hospital clopidogrel only, pre-hospital clopidogrel followed by prasugrel switch in the cath lab, prasugrel treatment only, pre-hospital clopidogrel followed by ticagrelor switch in the cath lab or pre-hospital ticagrelor only. Platelet reactivity was measured serially using vasodilator-stimulated phosphoprotein (VASP).

Results

Patients receiving pre-hospital clopidogrel followed by prasugrel switch showed similar platelet inhibition data as patients receiving prasugrel only, with more than 90% being good responders the day after PCI. Average time from prasugrel administration to a VASP value of <50% was 1.5 hours. In patients receiving pre-hospital ticagrelor, 50% were good responders at completion of PCI and average time to a VASP-value of <50% was 2.3 hours. Only 32% of patients receiving clopidogrel only were responders the day after PCI.

Conclusions

Switching from an upstream bolus dose of clopidogrel to prasugrel at the time of PCI, appeared as a safe and feasible option with no tendency for overshoot or attenuation of platelet inhibition. Pre-hospital administration of ticagrelor was associated with a 50% good responder rate at completion of PCI.

RUC-4: a novel αIIbβ3 antagonist for prehospital therapy of myocardial infarction

OBJECTIVE

Treatment of myocardial infarction within the first 1 to 2 hours with a thrombolytic agent, percutaneous coronary intervention, or an αIIbβ3 antagonist decreases mortality and the later development of heart failure. We previously reported on a novel small molecule αIIbβ3 antagonist, RUC-2, that has a unique mechanism of action. We have now developed a more potent and more soluble congener of RUC-2, RUC-4, designed to be easily administered intramuscularly by autoinjector to facilitate its use in the prehospital setting. Here, we report the properties of RUC-4 and the antiplatelet and antithrombotic effects of RUC-2 and RUC-4 in animal models.

APPROACH AND RESULTS

RUC-4 was ≈ 20% more potent than RUC-2 in inhibiting human ADP-induced platelet aggregation and much more soluble in aqueous solutions (60-80 mg/mL). It shared RUC-2's specificity for αIIbβ3 versus αVβ3, did not prime the receptor to bind fibrinogen, or induce changes in β3 identified by a conformation-specific monoclonal antibody. Both RUC-2 and RUC-4 prevented FeCl3-induced thrombotic occlusion of the carotid artery in mice and decreased microvascular thrombi in response to laser injury produced by human platelets infused into transgenic mice containing a mutated von Willebrand factor that reacts with human but not mouse platelets. Intramuscular injection of RUC-4 in nonhuman primates at 1.9 and 3.85 mg/kg led to complete inhibition of platelet aggregation within 15 minutes, with dose-dependent return of platelet aggregation after 4.5 to 24 hours.

CONCLUSIONS

RUC-4 has favorable biochemical, pharmacokinetic, pharmacodynamic, antithrombotic, and solubility properties as a prehospital therapy of myocardial infarction, but the possibility of increased bleeding with therapeutic doses remains to be evaluated.

Cangrelor: a review on pharmacology and clinical trial development

Dual antiplatelet therapy with aspirin and an oral ADP P2Y12 receptor antagonist is the standard-of-care for the prevention of ischemic events in patients with acute coronary syndrome or undergoing percutaneous coronary intervention (PCI). However, currently available ADP P2Y12 receptor antagonists have several limitations, such as interindividual response variability, drug-drug interactions, slow onset/offset and only oral availability. Cangrelor is a reversible, potent, intravenous, competitive inhibitor of the ADP P2Y12 receptor that rapidly achieves near complete and predictable platelet inhibition. Along with reversible binding to the receptor cangrelor also has a very short half-life (3-5 min), which in turn results in a rapid offset of action. These properties make cangrelor a promising drug for clinical use in patients undergoing PCI or patients waiting for major surgery but still require antiplatelet protection. This manuscript provides an update of the current status of knowledge on cangrelor, focusing on its pharmacologic properties and clinical trial development, including the BRIDGE and CHAMPION-PHOENIX trials.

Effects of P2Y12 receptor inhibition in patients with ST-segment elevation myocardial infarction

In ST-segment elevation myocardial infarction (STEMI), an effective antiplatelet treatment adjunctive to primary percutaneous coronary intervention is of utmost importance. High dose of clopidogrel, prasugrel, or ticagrelor provides a faster, more potent, and more consistent platelet inhibition than standard clopidogrel. Oral P2Y12 inhibitors have been studied in large clinical trials and are in use in clinical practice. Intravenously administered P2Y12 inhibitors such as cangrelor have also been tested. However, statistically significant anti-ischemic superiority of stronger platelet inhibition regimens versus standard clopidogrel has not been proved exclusively in patients receiving primary percutaneous coronary intervention. Whether orally administered antiplatelet agents suffice in patients with STEMI has been recently disputed, mainly because of their delayed onset of action. Platelet reactivity variability before P2Y12 blockade and its evolution over time, genetic predisposition, antiplatelet agent used, timing, and method of platelet function testing significantly affect the rates of high on-treatment platelet reactivity. Although ominous signs of greater bleeding potential of stronger antiplatelet regimens have not appeared in STEMI, this should be carefully tested.

Comparison of outcomes after percutaneous coronary intervention among different coronary subsets (stable and unstable angina pectoris and ST-segment and non-ST-segment myocardial infarction)

Percutaneous coronary intervention in the setting of acute myocardial infarction is known to predict stent thrombosis (ST). This study aims to compare the ST rates across different coronary subsets. This was an observational cohort study from a large, single-center registry. Included were 12,198 consecutive patients who underwent percutaneous coronary intervention with stenting. Patients were categorized according to their clinical presentation: stable angina pectoris (SAP, n = 3,700), unstable angina pectoris (UAP, n = 2,845), non-ST-segment elevation myocardial infarction (NSTEMI, n = 4,083), and ST-segment elevation myocardial infarction (STEMI, n = 1,570). The study end points were ST rates at 1 year. Patients with STEMI were younger with a lower prevalence of cardiovascular risk factors, except for smoking. More type C lesions were treated in STEMI, whereas drug-eluting stents were used less frequently in patients with STEMI compared with the other groups. Definite ST at 1 year was highest in patients with STEMI (1.4%; vs SAP, 0.4%; UAP, 0.5%; NSTEMI, 0.5%; p <0.001). One-year definite/probable ST rates were SAP, 0.8%; UAP, 1.1%; NSTEMI, 1.4%; and STEMI, 3.2% (p <0.001). On multivariable analysis, STEMI independently predicts definite ST (hazards ratio [HR] 3.07, 95% confidence interval [CI] 1.32 to 7.10), whereas both STEMI (HR 3.36, 95% CI 1.84 to 6.12) and NSTEMI (HR 2.04, 95% CI 1.20 to 3.07) were independent predictors of definite/probable ST. Clopidogrel cessation was the strongest predictor of ST (definite ST, HR 17.00, 95% CI 7.54 to 38.31; definite/probable ST, HR 4.69, 95% CI 2.39 to 9.20). In conclusion, in patients who underwent percutaneous coronary intervention, the acuity of clinical presentation corresponds to an increase in ST incidence. Adherence to clopidogrel is critical to prevent ST in patients who underwent percutaneous coronary intervention, especially in STEMI.

High on-treatment platelet reactivity in peripheral endovascular procedures

The use of aspirin is considered the "gold standard" for the decrease of major adverse cardiovascular events in patients with atherosclerosis, including peripheral arterial disease (PAD), whereas a dual-antiplatelet regimen with aspirin and clopidogrel is usually indicated for such patients after angioplasty and stent deployment. However, a substantial number of subsequent adverse events still occur, even in patients who receive double-antiplatelet therapy. The "high on-treatment platelet reactivity" (HTPR) phenomenon has been lately recognized and plays a major role in the management of patients with PAD. Greater and more rapid inhibition of platelet aggregation has become the goal for new antiplatelet agents with the expectation of further improving outcomes for percutaneous intervention for PAD. The purpose of this review article is to highlight current evidence regarding the prevalence, aetiology, and clinical implications of HTPR in PAD as well as to discuss the possibilities of novel alternative antiplatelet regiments.

High rates of prasugrel and ticagrelor non-responder in patients treated with therapeutic hypothermia after cardiac arrest

INTRODUCTION

After cardiac arrest due to acute coronary syndromes (ACS) therapeutic hypothermia (HT) is the standard care to reduce neurologic damage. Additionally, the concomitant medical treatment with aspirin and a P2Y12 receptor inhibitor like clopidogrel (Cl), prasugrel (Pr) or ticagrelor (Ti) is mandatory. The platelet inhibitory effect of these drugs under hypothermia remains unclear.

METHODS

164 patients with ACS were prospectively enrolled in this study. 84 patients were treated with HT, 80 patients were under normothermia (NT). All patients were treated with aspirin and one of the P2Y12 receptor inhibitors Cl, Pr or Ti. 24h after the initial loading dose the platelet reactivity index (PRI/VASP-index) was determined to achieve the platelet inhibitory effect.

RESULTS

In the HT-group the PRI/VASP-index was significantly higher compared to the NT-group (54.86%±25.1 vs. 28.98%±22.8; p<0.001). In patients under HT receiving Cl, the platelet inhibition was most markedly reduced (HT vs. NT: 66.39%±19.1 vs. 33.36%±22.1; p<0.001) compared to Pr (HT vs. NT: 37.6%±25.0 vs. 27.04%±25.5; p=0.143) and Ti (HT vs. NT: 41.5%±21.0 vs. 17.83%±14.5; p=0.009). The rate of non-responder defined as PRI/VASP-index>50% was increased in HT compared to NT (60.7% vs. 22.5%; p<0.001) with the highest rates in the group receiving Cl (CL: 82% vs. 26%, p<0.001; Pr: 32% vs. 23%; n.s.; Ti: 30% vs. 8%, n.s.).

CONCLUSION

The platelet inhibitory effect in patients treated with HT after cardiac arrest is significantly reduced. This effect was most marked with the use of Cl. The new P2Y12-inhibitors Pr and Ti improved platelet inhibition in HT, but could not completely prevent non-responsiveness.

Fractalkine promotes platelet activation and vascular dysfunction in congestive heart failure

Endothelial dysfunction and enhanced platelet reactivity in congestive heart failure (CHF) contribute to poor prognosis. CHF patients display an impaired responsiveness to clopidogrel. Fractalkine activates platelets and elevated plasma levels of this chemokine are a feature of CHF. We here addressed the interrelation of fractalkine, platelet reactivity and clopidogrel efficacy in humans and rats with CHF. Fractalkine serum levels determined by ELISA were increased in CHF patients (CHF: 1548 ± 650 pg/ml;

CONTROL

968 ± 575 pg/ml, p<0.01) and following CHF induction in rats (CHF: 1509 ± 753 pg/ml; Sham: 1181 ± 275 pg/ml, p<0.05). Expression of fractalkine and its receptor CX3CR1 was enhanced in aortas of CHF rats as determined by immunofluorescence microscopy and molecular analysis. Fractalkine significantly aggravated endothelial dysfunction and augmented P-selectin expression on platelets from CHF rats. Platelet surface expression of CX3CR1 was increased in CHF rats, who displayed an impaired response to clopidogrel (platelet reactivity to ADP: CHF 30 ± 22%; Sham: 8 ± 5%, p<0.05). Similarly in humans with CHF, elevated fractalkine levels were accompanied by reduced clopidogrel responsiveness. Patients with high on-clopidogrel treatment platelet P2Y12 reactivity displayed higher fractalkine levels (1525 ± 487 pg/ml) than those with sufficient clopidogrel response (684 ± 315 pg/ml, p<0.01). In conclusion, in CHF fractalkine was increased on the endothelium and in blood serum, and platelet surface-expression of CX3CR1 was enhanced. Fractalkine diminished endothelial function beyond the impairment already observed in CHF and was associated with a reduced responsiveness to the platelet inhibitor clopidogrel. These findings may indicate a novel pathophysiological mechanism contributing to impaired clopidogrel responsiveness in CHF.

Effects of prasugrel on platelet inhibition during systemic endotoxaemia: a randomized controlled trial

P2Y12 receptor antagonists have become a mainstay for the treatment of CVD (cardiovascular diseases). However, they have rarely been evaluated under pathophysiological conditions apart from arterial diseases. We hypothesized interactions between prasugrel and enhanced vWF (von Willebrand Factor) release in a model of systemic inflammation, and compared the pharmacodynamic effects of prasugrel against placebo on agonist-induced platelet aggregation and shear-induced platelet plug formation. A total of 20 healthy male volunteers were enrolled in a double-blind placebo-controlled two-way crossover trial. Each volunteer received either placebo or a 60 mg loading dose of prasugrel 2 h before endotoxin or placebo infusion. Platelet inhibition was measured with MEA (multiple electrode aggregometry), the PFA-100 system and the VASP (vasodilator-stimulated phosphoprotein) phosphorylation assay. Prasugrel blunted various platelet aggregation pathways, including those induced by ADP (−81%), AA (arachidonic acid) (−60%), ristocetin (−75%; P<0.001 for all) and, to a lesser degree, collagen or TRAP (thrombin-receptor-activating peptide). Prasugrel decreased shear-induced platelet plug formation, but vWF release during endotoxaemia partly antagonized the inhibitory effect of prasugrel as measured with the PFA-100 system. Endotoxaemia acutely decreased ristocetin and TRAP-induced platelet aggregation, and enhanced ristocetin-induced aggregation after 24 h. Strong in vivo blockade of P2Y12 inhibits a broad spectrum of platelet aggregation pathways. However, vWF release may reduce prasugrel's effects under high-shear conditions.

Biological efficacy of a 600 mg loading dose of clopidogrel in ST-elevation myocardial infarction

Optimal platelet reactivity (PR) inhibition is critical to prevent thrombotic events in primary percutaneous coronary intervention (PCI). We aimed to determine the relationship between high on-treatment platelet reactivity (HTPR) and ST-elevation myocardial infarction (STEMI) following a 600 mg loading dose (LD) of clopidogrel. We performed a prospective monocentre study enrolling patients on clopidogrel undergoing PCI. The VASP index was used to assess PR inhibition after clopidogrel LD. HTPR was defined according to the consensus as a VASP index ≥50%. The present study included 833 patients undergoing PCI. Most patients had PCI for an acute coronary syndrome (58.7%). The mean VASP index was 50 ± 23% with a large inter-individual variability (range: 1-94%). Patients with a VASP index ≥50% were significantly older (p= 0.03), with a higher body mass index (BMI) (p<0.001), more often diabetic (p=0.03), taking omeprazole (p=0.03), admitted for an acute coronary syndrome (ACS) and with a high fibrinogen level compared to good responders (VASP <50%). In multivariate analysis BMI, omeprazole use, ACS and high fibrinogen level (p<0.001) remained significantly associated with HTPR. Of importance, in this analysis STEMI was independently associated with HTPR when compared with the other forms of ACS (NSTEMI and unstable angina) with an odd ratio of 2.14 (95% CI: 1.3 -3.5; p=0.003). In conclusion, STEMI is associated with high on-treatment platelet reactivity following 600 mg of clopidogrel. The present results suggest that 600 mg of clopidogrel may not be able to achieve an optimal PR inhibition in STEMI patients undergoing PCI and more potent drugs may be preferred.

Thienopyridines and other ADP-receptor antagonists

Platelet P2Y12 receptor inhibition plays a pivotal role in preventing thrombotic vascular events in patients with ACS and in patients undergoing percutaneous coronary intervention (PCI). Among the P2Y12 receptor inhibitors, the group of thienopyridines include ticlopidine, clopidogrel and prasugrel, all of which are orally administered prodrugs leading to irreversible P2Y12 receptor inhibition. Non-thienopyridine derivatives including ticagrelor, cangrelor and elinogrel do not require metabolic activation and lead to a reversible P2Y12 receptor inhibition in contrast to thienopyridines. The extend of platelet inhibition is subject to the administered antiplatelet agent and influenced by individual genetic and clinical factors. Insufficient platelet inhibition, termed high platelet reactivity (HPR) is associated with an increased risk for ischemic events after PCI whereas exceeding platelet inhibition results in an increased bleeding risk. Pharmacologic properties and clinical outcome data differ substantially between the existing P2Y12 receptor inhibitors. Whether individualized antiplatelet treatment incorporating different P2Y12 receptor inhibitors improves patients' clinical outcomes warrants further investigation.

Early glycoprotein IIb-IIIa inhibitors in primary angioplasty-abciximab long-term results (EGYPT-ALT) cooperation: individual patient's data meta-analysis

BACKGROUND

Even although time to treatment has been shown to be a determinant of mortality in primary angioplasty, the potential benefits are still unclear from early pharmacological reperfusion by glycoprotein (Gp) IIb-IIIa inhibitors. Therefore, the aim of this meta-analysis was to combine individual data from all randomized trials conducted on upstream as compared with late peri-procedural abciximab administration in primary angioplasty.

METHODS

The literature was scanned using formal searches of electronic databases (MEDLINE and EMBASE) from January 1990 to December 2010. All randomized trials on upstream abciximab administration in primary angioplasty were examined. No language restrictions were enforced.

RESULTS

We included a total of seven randomized trials enrolling 722 patients, who were randomized to early (n = 357, 49.4%) or late (n = 365, 50.6%) peri-procedural abciximab administration. No difference in baseline characteristics was observed between the two groups. Follow-up data were collected at a median (25th-75th percentiles) of 1095 days (720-1967). Early abciximab was associated with a significant reduction in mortality (primary endpoint) [20% vs. 24.6%; hazard ratio (HR) 95% confidence interval (CI) = 0.65 (0.42-0.98) P = 0.02, P(het) = 0.6]. Furthermore, early abciximab administration was associated with a significant improvement in pre-procedural thrombolysis in myocardial infarction (TIMI) 3 flow (21.6% vs. 10.1%, P < 0.0001), post-procedural TIMI 3 flow (90% vs. 84.8%, P = 0.04), an improvement in myocardial perfusion as evaluated by post-procedural myocardial blush grade (MBG) 3 (52.0% vs. 43.2%, P = 0.03) and ST-segment resolution (58.4% vs. 43.5%, P < 0.0001) and significantly less distal embolization (10.1% vs. 16.2%, P = 0.02). No difference was observed in terms of major bleeding complications between early and late abciximab administration (3.3% vs. 2.3%, P = 0.4).

CONCLUSIONS

This meta-analysis shows that early upstream administration of abciximab in patients undergoing primary angioplasty for ST-segment elevation myocardial infarction (STEMI) is associated with significant benefits in terms of pre-procedural epicardial re-canalization and ST-segment resolution, which translates in to significant mortality benefits at long-term follow-up.

Management of patients with recently implanted coronary stents on dual antiplatelet therapy who need to undergo major surgery

About 5% of patients undergoing coronary stenting need to undergo surgery within the next year. The risk of perioperative cardiac ischemic events, particularly stent thrombosis (ST), is high in these patients, because surgery has a prothrombotic effect and antiplatelet therapy is often withdrawn in order to avoid bleeding. The clinical and angiographic predictors of ST are well known, and the proximity to an acute coronary syndrome adds to the risk. The current guidelines recommend delaying non-urgent surgery for at least 6 weeks after the placement of a bare metal stent and for 6-12 months after the placement of a drug-eluting stent, when the risk of ST is reduced. However, in the absence of formal evidence, these recommendations provide little support with regard to managing urgent operations. When surgery cannot be postponed, stratifying the risk of surgical bleeding and cardiac ischemic events is crucial in order to manage perioperative antiplatelet therapy in individual cases. Dual antiplatelet therapy should not be withdrawn for minor surgery or most gastrointestinal endoscopic procedures. Aspirin can be safely continued perioperatively in the case of most major surgery, and provides coronary protection. In the case of interventions at high risk for both bleeding and ischemic events, when clopidogrel withdrawal is required in order to reduce perioperative bleeding, perioperative treatment with the short-acting intravenous glycoprotein IIb-IIIa inhibitor tirofiban is safe in terms of bleeding, and provides strong antithrombotic protection. Such surgical interventions should be performed at hospitals capable of performing an immediate percutaneous coronary intervention at any time in the case of acute myocardial ischemia.

The future of platelet function testing to guide therapy in clopidogrel low and enhanced responders

Dual oral antiplatelet therapy with aspirin and clopidogrel is the therapy of choice in patients with acute coronary syndromes and in patients undergoing coronary stent placement to lower the risk of thrombotic events. Responsiveness to aspirin and especially to clopidogrel is not uniform and is subject to considerable interindividual variability. Furthermore, there is a broad consensus that clopidogrel low response or so-called high on-treatment platelet reactivity is linked to the occurrence of ischemic events. On the other hand, evidence is accumulating that enhanced clopidogrel responders are at increased risk of bleeding. Newer antiplatelet drugs, such as prasugrel and ticagrelor, are more potent and produce more consistent inhibition of platelet aggregation via the P2Y(12) ADP platelet receptor. A variety of methods of platelet function testing are available for evaluating platelet inhibition in percutaneous coronary intervention-treated patients in order to help determine the individual risk for ischemic and bleeding complications. Although not yet routinely undertaken, platelet function testing offers the potential to tailor antiplatelet therapy for individual patients. Whether alteration of therapy based on platelet function testing improves patients' outcomes remains unclear and is currently under investigation. This article reviews the impact of antiplatelet drug responsiveness on clinical outcomes with a focus on P2Y(12) receptor inhibition as well as on current and future concepts for personalized antiplatelet strategies.