Role of platelet function and genetic testing in patients undergoing percutaneous coronary intervention

Interindividual variability in platelet reactivity among individuals with or without antiplatelet therapy: results from a large tertiary care hospital

Antiplatelet therapy is crucial for reducing thrombotic events in patients with atherosclerotic disease, but the response vary widely among individuals. The identification of patients at high (HPR), optimal (OPR) or low platelet reactivity (LPR) is dependent on high interlaboratory variability. We report results of a large dataset of patients to assess the gold standard light transmission aggregometry (LTA). A total of 11,913 patients who sequentially underwent LTA assessment using several stimuli (ADP-2µM, collagen-2 µg/ml, arachidonic acid 0.5 mM, epinephrine 10µM) with a standardized methodology between 2004 and 2022 were screened. After application of inclusion-exclusion criteria, 5,901 patients were included and divided into five groups: healthy-volunteers (HV; N = 534); controls (CTR; N = 1073); aspirin-treated patients (ASA; 75-150 mg/die; N = 3280); clopidogrel-treated patients (CLOP; 75 mg/die; N = 495) and patients treated with dual antiplatelet therapy, ASA plus CLOP (DAPT; N = 519). The mean PA% in response to ADP 2 μm was 72.4 ± 33.3 in the CTR population, 40.6 ± 29.9 in the ASA group, 25.1 ± 35.1 in the CLOP group and 10.2 ± 18.5 in the DAPT group. The mean PA% in response to collagen 2 ug/ml was 90.7 ± 10.5 in the CTR population, 40.8 ± 26.3 in the ASA group, 79.4 ± 21.8 in the CLOP group and 17.9 ± 19.9 in the DAPT group. The percentage of patients at OPR following ADP stimuli was 66%, 25%, and 26%, in the ASA, CLOP, and DAPT group, respectively. The percentage of patients at OPR following collagen stimuli was 56%, 22%, and 41%, in the ASA, CLOP, and DAPT group, respectively. LTA was significantly increased in response to ADP (72.4 ± 33.3vs62.7 ± 37.1; p < 0.001) and AA (90.7 ± 15.6vs87.6 ± 20.5; p < 0.001) in CTR compared to HV. Our findings support the concept that a significant proportion of individuals present a hyper- or hypo-reactive platelet phenotype potentially affecting the safety and efficacy of antiplatelet therapy. The variability in response to antiplatelet therapy was particularly evident in patients undergoing single as opposed to dual antiplatelet therapy regimens. These data support ongoing strategies of guided selection of antiplatelet therapy in patients with cardiovascular disease.

International Consensus Statement on Platelet Function and Genetic Testing in Percutaneous Coronary Intervention: 2024 Update

Current evidence indicates that dual antiplatelet therapy with aspirin plus a P2Y12 inhibitor is essential for the prevention of thrombotic events after percutaneous coronary interventions. However, dual antiplatelet therapy is associated with increased bleeding which may outweigh the benefits. This has set the foundations for customizing antiplatelet treatments to the individual patient. However, bleeding and ischemic risks are often present in the same patient, making it difficult to achieve this balance. The fact that oral P2Y12 inhibitors (clopidogrel, prasugrel, and ticagrelor) have diverse pharmacodynamic profiles that affect clinical outcomes supports the rationale for using platelet function and genetic testing to individualize antiplatelet treatment regimens. Indeed, up to one-third of patients treated with clopidogrel, but a minority of those treated with prasugrel or ticagrelor, exhibit high residual platelet reactivity resulting in an increased thrombotic risk. On the other hand, prasugrel and ticagrelor are frequently associated with low platelet reactivity and increased bleeding risk compared with clopidogrel without providing any additional reduction in ischemic events compared with patients who adequately respond to clopidogrel. The use of platelet function and genetic testing may allow for a guided selection of oral P2Y12 inhibitors. However, the nonuniform results of randomized controlled trials have led guidelines to provide limited recommendations on the implementation of these tests in patients undergoing percutaneous coronary intervention. In light of recent advancements in the field, this consensus document by a panel of international experts fills in the guideline gap by providing updates on the latest evidence in the field as well as recommendations for clinical practice.

Aspirin Hypersensitivity in Patients With Atherosclerotic Cardiovascular Disease

Low-dose aspirin remains the most commonly used antiplatelet agent among patients with atherosclerotic cardiovascular disease. Aspirin hypersensitivity occurs in 1% to 5% of patients and is among the most frequent causes for prohibiting the use of aspirin, posing a significant dilemma on how to manage these patients in clinical practice. Aspirin hypersensitivity is often misinterpreted and confused with aspirin intolerance, with treatment approaches being often unclear and lacking specific recommendations. Aspirin desensitization and low-dose aspirin challenge have emerged as pragmatic, effective, and safe approaches in patients with suspected or confirmed aspirin hypersensitivity who require aspirin therapy, but they are underused systematically in clinical practice. Furthermore, there is confusion over alternative antiplatelet agents to be used in these patients. The pathophysiological mechanisms and classification of aspirin hypersensitivity, as well as alternative strategies and practical algorithms to overcome the need for aspirin use in patients with atherosclerotic cardiovascular disease with suspected aspirin hypersensitivity, are discussed.

Antithrombotic Therapy in High Bleeding Risk, Part II: Noncardiac Percutaneous Interventions

Over the past decades, there have been great advancements in the antithrombotic management of patients undergoing percutaneous interventions, but most of the available evidence derives from studies conducted in the setting of cardiac interventions. Antithrombotic treatment regimens used in patients undergoing percutaneous cardiac interventions, in particular coronary, are frequently extrapolated to patients undergoing noncardiac interventions. However, the differences in risk profile of the population treated and the types of interventions performed may translate into differences is the safety and efficacy associated with antithrombotic therapy. Noncardiac percutaneous interventions are commonly performed in patients at high bleeding risk, which may indeed impact outcomes, hence underscoring the importance of risk stratification to guide clinical decision-making processes. In this review, we appraise the available evidence on antithrombotic therapy in high-bleeding-risk patients undergoing noncardiac percutaneous interventions.

Antithrombotic Therapy in High Bleeding Risk, Part I: Percutaneous Cardiac Interventions

Antithrombotic therapy after cardiac percutaneous interventions is key for the prevention of thrombotic events but is inevitably associated with increased bleeding, proportional to the number, duration, and potency of the antithrombotic agents used. Bleeding complications have important clinical implications, which in some cases may outweigh the expected benefit of reducing thrombotic events. Because the response to antithrombotic agents varies widely among patients, there has been a relentless effort toward the identification of patients at high bleeding risk (HBR), in whom modulation of antithrombotic therapy may be needed to optimize the balance between safety and efficacy. Among patients undergoing cardiac percutaneous interventions, recent advances in technology have allowed for strategies of de-escalation to reduce bleeding without compromising efficacy, and HBR patients are expected to benefit the most from such approaches. Guidelines do not extensively expand upon the topic of de-escalation strategies of antithrombotic therapy in HBR patients. In this review, we discuss the evidence and provide practical recommendations on optimal antithrombotic therapy in HBR patients undergoing various cardiac percutaneous interventions.

Comparative effects of different antiplatelet strategies in carriers of CYP2C19 loss-of-function alleles: a network meta-analysis

BACKGROUND

Carriers of cytochrome 2C19 (CYP2C19) loss-of-function (LoF) alleles treated with clopidogrel have impaired drug metabolism, resulting in reduced active metabolite levels, high platelet reactivity (HPR), and an increased risk of thrombotic events. Several alternative antiplatelet therapies have been proposed to overcome HPR in these patients, but their comparative effects remain poorly explored.

METHODS

Randomized controlled trials (RCTs) comparing different oral antiplatelet therapies in carriers of CYP2C19 LoF alleles undergoing percutaneous coronary interventions (PCI) were included. A frequentist network meta-analysis was conducted to estimate mean difference (MD) or odds ratios and 95% confidence intervals (CI). The primary outcome was platelet reactivity assessed by VerifyNow and reported as P2Y12 reaction unit (PRU). The secondary outcome was the rate of HPR. Standard dose of clopidogrel (75 mg daily) was used as a reference treatment.

RESULTS

A total of 12 RCTs testing 6 alternative strategies (i.e. clopidogrel 150 mg, prasugrel 3.75 mg, 5 mg, and 10 mg, ticagrelor 90 mg bid, and adjunctive cilostazol 100 mg bid) were included in the network. Compared with standard-dose clopidogrel, the greatest reduction in PRU was observed with prasugrel 10 mg (MD -127.91; 95% CI -141.04; -114.78) and ticagrelor 90 mg bid (MD -124.91; 95% CI -161.78; -88.04), followed by prasugrel 5 mg (MD -76.33; 95% CI -98.01; -54.65) and prasugrel 3.75 mg (MD -73.00; 95% CI -100.28; -45.72). Among other strategies, adjunctive cilostazol (MD -42.64; 95% CI -64.72; -20.57) and high-dose clopidogrel (MD -32.11; 95% CI -51.33; -12.90) were associated with a modest reduction in PRU compared with standard-dose clopidogrel.

CONCLUSION

Among carriers of CYP2C19 LoF alleles undergoing PCI, standard-dose prasugrel or ticagrelor are most effective in reducing platelet reactivity, while double-dose clopidogrel and additional cilostazol showed modest effects. Reduced-dose of prasugrel may represent a balanced strategy to overcome HPR without a significant increase in bleeding. The clinical implications of these pharmacodynamic findings warrant further investigation.

Outcomes of Ticagrelor Versus High-dose Clopidogrel in CYP2C19 Intermediate Metabolizer Undergoing Percutaneous Coronary Intervention for Acute Coronary Syndromes

ABSTRACT

Guidelines on antiplatelet recommendation for CYP2C19 intermediate metabolizer (IM) have not come to an agreement. This study aimed to evaluate the clinical benefit of ticagrelor when compared with high-dose clopidogrel in CYP2C19 IM after percutaneous coronary intervention for acute coronary syndromes. Patients were enrolled according to CYP2C19 genotype and individual antiplatelet therapy. Patient characteristics and clinical outcomes were collected through electronic medical record system. The primary outcome was major adverse cardiac and cerebrovascular event (MACCE), namely a composite of death from cardiovascular causes, myocardial infarction, stroke, and stent thrombosis within 12 months. The secondary outcome was Bleeding Academic Research Consortium scale bleeding events within 12 months. The Cox proportional hazards regression model was performed, with inverse probability treatment weighting (IPTW) adjusting for potential confounders. A total of 532 CYP2C19 IM were enrolled in this retrospective single-center study. No statistically significant difference in incidence rate of MACCE was found between patients receiving ticagrelor versus clopidogrel (7.01 vs. 9.52 per 100 patient-years; IPTW-adjusted hazard ratio 0.71; 95% confidence interval: 0.32-1.58; adjusted log-rank P = 0.396), but the incidence rate of Bleeding Academic Research Consortium type 2, 3, or 5 bleeding events was statistically higher in the loss of function-ticagrelor group than in the loss of function-clopidogrel group (13.53 vs. 6.16 per 100 patient-years; IPTW-adjusted hazard ratio: 2.29; 95% confidence interval: 1.10-4.78; adjusted log-rank P = 0.027). Ticagrelor treatment in CYP2C19 IM resulted in a statistically higher risk of bleeding compared with high-dose clopidogrel, whereas a clear association between treatments and MACCE warrants further investigations.

De-escalation of antithrombotic treatment after acute coronary syndrome, a new paradigm

After an acute coronary syndrome (ACS) it is imperative to balance the bleeding vs. the ischemic risk given the similar prognostic impact of the two events. Since the post-discharge bleeding risk is substantially stable over time whereas the ischemic risk accumulates in the first weeks to months, a strategy of de-escalation of antithrombotic treatment, consisting in the reduction of either the duration (i.e., early interruption of one antiplatelet agent) or the intensity (i.e., switching from the more potent P2Y12-inhibitors prasugrel or ticagrelor to clopidogrel) of dual antiplatelet therapy (DAPT), has been proposed. Reducing the intensity of DAPT can be carried out as a default strategy (unguided approach) or based on the results of either platelet function tests or genetic tests (guided approach). Overall, all de-escalation strategies have shown to consistently decrease bleeding events with no apparent increase in ischemic events as compared to 12-month standard-of-care DAPT. Owing however to several limitations and weaknesses of the available evidence, de-escalation strategies are currently not recommended as a routine, but should rather be considered for selected ACS patients, such as those at increased risk of bleeding.

CYP2C19 Genetic Testing for Oral P2Y12 Inhibitor Therapy: A Scientific Statement From the American Heart Association

There is significant variability in the efficacy and safety of oral P2Y12 inhibitors, which are used to prevent ischemic outcomes in common diseases such as coronary and peripheral arterial disease and stroke. Clopidogrel, a prodrug, is the most used oral P2Y12 inhibitor and is activated primarily after being metabolized by a highly polymorphic hepatic cytochrome CYP2C219 enzyme. Loss-of-function genetic variants in CYP2C219 are common, can result in decreased active metabolite levels and increased on-treatment platelet aggregation, and are associated with increased ischemic events on clopidogrel therapy. Such patients can be identified by CYP2C19 genetic testing and can be treated with alternative therapy. Conversely, universal use of potent oral P2Y12 inhibitors such as ticagrelor or prasugrel, which are not dependent on CYP2C19 for activation, has been recommended but can result in increased bleeding. Recent clinical trials and meta-analyses have demonstrated that a precision medicine approach in which loss-of-function carriers are prescribed ticagrelor or prasugrel and noncarriers are prescribed clopidogrel results in reducing ischemic events without increasing bleeding risk. The evidence to date supports CYP2C19 genetic testing before oral P2Y12 inhibitors are prescribed in patients with acute coronary syndromes or percutaneous coronary intervention. Clinical implementation of such genetic testing will depend on among multiple factors: rapid availability of results or adoption of the concept of performing preemptive genetic testing, provision of easy-to-understand results with therapeutic recommendations, and seamless integration in the electronic health record.

The pharmacology of antiplatelet agents for primary, secondary, and tertiary prevention of ischemic stroke

INTRODUCTION

Ischemic etiology accounts for two thirds of all strokes in which platelet activation and aggregation play a major role. A variety of antiplatelet therapies have been tested for primary, secondary, and tertiary prevention, with certain patient subtypes benefiting more than others from a specific regimen.

AREAS COVERED

This review aims at synthetizing current evidence on pharmacology of antiplatelet agents approved for primary, secondary, and tertiary stroke prevention and their application among possible patient subtypes that may benefit more from their administration.

EXPERT OPINION

Management of ischemic stroke has largely evolved over the past decades. A better understanding of stroke pathophysiology has allowed to identify patients who can benefit most from antiplatelet therapies, with varying degrees of benefit depending on whether these agents are being used for primary, secondary, or tertiary prevention. Importantly, the antiplatelet treatment regimens currently available have expanded and no longer limited to aspirin but include other drugs such as P2Y12 and phosphodiesterase inhibitors, also used in combination, as well as precision medicine approaches using genetic testing aiming at optimizing the safety and efficacy in this population.

Impact of ethnicity on antiplatelet treatment regimens for bleeding reduction in acute coronary syndromes: a systematic review and pre-specified subgroup meta-analysis

AIMS

Randomized controlled trials (RCTs) testing bleeding reduction strategies using antiplatelet treatment regimens (BRATs) in acute coronary syndromes (ACS) have shown promising results, but the generalizability of these findings may be significantly influenced by the ethnicity of the patients enrolled, given that East Asian (EA) patients show different ischaemic-bleeding risk profile compared to non-EA patients.

METHODS AND RESULTS

RCTs comparing a BRAT vs. standard 12-month dual antiplatelet therapy (DAPT) in patients with ACS undergoing percutaneous coronary intervention (PCI) were selected. The primary efficacy endpoint was major adverse cardiovascular events (MACE) as defined in each trial and the primary safety endpoint was minor or major bleeding. Twenty-six RCTs testing seven different BRATs were included. The only strategy associated with a trade-off in MACE was 'upfront unguided de-escalation' in the subgroup of non-EAs (risk ratio 1.16, 95% confidence interval 1.09-1.24). All but aspirin monotherapy-based strategies (i.e. 'short and very short DAPT followed by aspirin') were associated with reduced bleeding compared with standard DAPT in both EA and non-EA patients. There were no significant differences between subgroups, but the lack of RCTs in some of the included strategies and the difference in the certainty of evidence between EA and non-EA patients revealed that the evidence in support of different BRATs in ACS undergoing PCI is influenced by ethnicity. Moreover, absolute risk reduction estimation revealed that some BRATs might be more effective than others in reducing bleeding according to ethnicity.

CONCLUSION

The majority of BRATs are associated with reduced bleeding without any trade-off in hard ischaemic endpoints regardless of ethnicity. However, the supporting evidence and relative safety profiles of different BRATs might be significantly affected by ethnicity, which should be taken into account in clinical practice.

STUDY REGISTRATION

This study is registered in PROSPERO (CRD42023416710).

Antithrombotic Treatment for Chronic Coronary Syndrome: Evidence and Future Perspectives

BACKGROUND

The clinical presentation of coronary artery disease can range from asymptomatic, through stable disease in the form of chronic coronary syndrome, to acute coronary syndrome. Chronic coronary syndrome is a frequent condition, and secondary prevention of ischaemic events is essential.

SUMMARY

Antithrombotic therapy is a key component of secondary prevention strategies, and it may vary in type and intensity depending on patient characteristics, comorbidities, and revascularisation modalities. Dual antiplatelet therapy is the default strategy in patients with chronic coronary syndrome and recent coronary stent implantation, while antiplatelet monotherapy is commonly prescribed for long-term prevention of cardiovascular events. Oral anticoagulation, in combination with antiplatelet therapy or alone, is used in patients with, e.g., concomitant atrial fibrillation or venous thromboembolism.

KEY MESSAGES

This review provides an overview of antithrombotic treatment strategies in patients with chronic coronary syndrome. Key messages from current guidelines are conveyed, and we provide future perspectives on long-term antithrombotic strategies.

Personalised antiplatelet therapies for coronary artery disease: what the future holds

Coronary artery disease (CAD) is one of the leading causes of death globally, and antiplatelet therapy is crucial for both its prevention and treatment. Antiplatelet drugs such as aspirin and P2Y12 inhibitors are commonly used to reduce the risk of thrombotic events, including myocardial infarction, stroke, and stent thrombosis. However, the benefits associated with the use of antiplatelet drugs also come with a risk of bleeding complications. The ever-growing understanding of the poor prognostic implications associated with bleeding has set the foundations for defining strategies that can mitigate such safety concern without any trade-off in antithrombotic protection. To this extent, personalised antiplatelet therapy has emerged as a paradigm that optimizes the balance between safety and efficacy by customizing treatment to the individual patient's needs and risk profile. Accurate risk stratification for both bleeding and thrombosis can aid in selecting the optimal antiplatelet therapy and prevent serious and life-threatening outcomes. Risk stratification has traditionally included clinical and demographic characteristics and has expanded to incorporate angiographic features and laboratory findings. The availability of bedside platelet function testing as well as rapid genotyping assays has also allowed for a more individualized selection of antiplatelet therapy. This review provides a comprehensive overview of the current state of the art and future trends in personalised antiplatelet therapy for patients with CAD, with emphasis on those presenting with an acute coronary syndrome and undergoing percutaneous coronary revascularization. The aim is to provide clinicians with a comprehensive understanding of personalised antiplatelet therapy and facilitate informed clinical decision-making.

Management of Coronary Artery Disease in Older Adults: Recent Advances and Gaps in Evidence

Coronary artery disease (CAD) is highly prevalent in older adults, yet its management remains challenging. Treatment choices are made complex by the frailty burden of older patients, a high prevalence of comorbidities and body composition abnormalities (e.g., sarcopenia), the complexity of coronary anatomy, and the frequent presence of multivessel disease, as well as the coexistence of major ischemic and bleeding risk factors. Recent randomized clinical trials and epidemiological studies have provided new data on optimal management of complex patients with CAD. However, frail older adults are still underrepresented in the literature. This narrative review aims to highlight the importance of assessing frailty as an aid to guide therapeutic decision-making and tailor CAD management to the specific needs of older adults, taking into account age-related pharmacokinetic and pharmacodynamic changes, polypharmacy, and potential drug interactions. We also discuss gaps in the evidence and offer perspectives on how best in the future to optimize the global strategy of CAD management in older adults.

De-escalation of antiplatelet therapy in patients with coronary artery disease: Time to change our strategy?

Dual antiplatelet therapy (DAPT) is the gold standard after acute coronary syndromes (ACS) or chronic coronary syndromes (CCS) undergoing percutaneous coronary intervention (PCI). Because local and systemic ischemic complications can occur particularly in the early phase (i.e. 1-3 months) after ACS or PCI, the synergistic platelet inhibition of aspirin and a P2Y₁₂ inhibitor is of the utmost importance in this early phase. Moreover, the use of the more potent P2Y₁₂ inhibitors prasugrel and ticagrelor have shown to further reduce the incidence of ischemic events compared to clopidogrel after an ACS. On the other hand, prolonged and potent antiplatelet therapy are inevitably associated with increased bleeding, which unlike thrombotic risk, tends to be stable over time and may outweigh the benefit of reducing ischemic events in these patients. The duration and composition of antiplatelet therapy remains a topic of debate in cardiology due to competing ischemic and bleeding risks, with guidelines and recommendations considerably evolving in the past years. An emerging strategy, called "de-escalation", consisting in the administration of a less intense antithrombotic therapy after a short course of standard DAPT, has shown to reduce bleeding without any trade-off in ischemic events. De-escalation may be achieved with different antithrombotic strategies and can be either unguided or guided by platelet function or genetic testing. The aim of this review is to summarize the evidence and provide practical recommendations on the use of different de-escalation strategies in patients with ACS and CCS.

Pharmacogenetics of Antiplatelet Therapy

Antiplatelet therapy is used in the treatment of patients with acute coronary syndromes, stroke, and those undergoing percutaneous coronary intervention. Clopidogrel is the most widely used antiplatelet P2Y12 inhibitor in clinical practice. Genetic variation in CYP2C19 may influence its enzymatic activity, resulting in individuals who are carriers of loss-of-function CYP2C19 alleles and thus have reduced active clopidogrel metabolites, high on-treatment platelet reactivity, and increased ischemic risk. Prospective studies have examined the utility of CYP2C19 genetic testing to guide antiplatelet therapy, and more recently published meta-analyses suggest that pharmacogenetics represents a key treatment strategy to individualize antiplatelet therapy. Rapid genetic tests, including bedside genotyping platforms that are validated and have high reproducibility, are available to guide selection of P2Y12 inhibitors in clinical practice. The aim of this review is to provide an overview of the background and rationale for the role of a guided antiplatelet approach to enhance patient care.

Antithrombotic Treatment in Coronary Artery Disease

Coronary artery disease exhibits growing mortality and morbidity worldwide despite the advances in pharmacotherapy and coronary intervention. Coronary artery disease is classified in the acute coronary syndromes and chronic coronary syndromes according to the most recent guidelines of the European Society of Cardiology. Antithrombotic treatment is the cornerstone of therapy in coronary artery disease due to the involvement of atherothrombosis in the pathophysiology of the disease. Administration of antiplatelet agents, anticoagulants and fibrinolytics reduce ischemic risk, which is amplified early post-acute coronary syndromes or post percutaneous coronary intervention; though, antithrombotic treatment increases the risk for bleeding. The balance between ischemic and bleeding risk is difficult to achieve and is affected by patient characteristics, procedural parameters, concomitant medications and pharmacologic characteristics of the antithrombotic agents. Several pharmacological strategies have been evaluated in patients with coronary artery disease, such as the effectiveness and safety of antithrombotic agents, optimal dual antiplatelet treatment schemes and duration, aspirin de-escalation strategies of dual antiplatelet regimens, dual inhibition pathway strategies as well as triple antithrombotic therapy. Future studies are needed in order to investigate the gaps in our knowledge, including special populations.

Gender-differences in antithrombotic therapy across the spectrum of ischemic heart disease: Time to tackle the Yentl syndrome?

The incidence and clinical presentation of ischemic heart disease (IHD), as well as thrombotic and bleeding risks, appear to differ between genders. Compared with men, women feature an increased thrombotic risk, probably related to an increased platelet reactivity, higher level of coagulation factors, and sex-associated unique cardiovascular risk factors, such as pregnancy-related (i.e., pre-eclampsia and gestational diabetes), gynecological disorders (i.e., polycystic ovary syndrome, early menopause) and autoimmune or systemic inflammatory diseases. At the same time, women are also at increased risk of bleeding, due to inappropriate dosing of antithrombotic agents, smaller blood vessels, lower body weight and comorbidities, such as diabetes and chronic kidney disease. Pharmacological strategies focused on the personalization of antithrombotic treatment may, therefore, be particularly appealing in women in light of their higher bleeding and ischemic risks. Paradoxically, although women represent a large proportion of cardiovascular patients in our practice, adequate high-quality clinical trial data on women remain scarce and inadequate to guide decision-making processes. As a result, IHD in women tends to be understudied, underdiagnosed and undertreated, a phenomenon known as a "Yentl syndrome." It is, therefore, compelling for the scientific community to embark on dedicated clinical trials to address underrepresentation of women and to acquire evidence-based knowledge in the personalization of antithrombotic therapy in women.

Escalation and De-Escalation of Antiplatelet Therapy after Acute Coronary Syndrome or PCI: Available Evidence and Implications for Practice

Dual antiplatelet therapy (DAPT) is the gold standard for the antithrombotic management of patients with an acute coronary syndrome (ACS) or undergoing percutaneous coronary intervention (PCI). Implementation of intensified or prolonged DAPT regimens has proven to lower the risk of ischemic events but at the expense of increased bleeding. Importantly, bleeding is a predictor of poor prognosis. Risk stratification and selection of tailored antiplatelet strategies to maximize the net clinical benefit in individual patients with ACS or undergoing PCI is therefore potentially beneficial. Recently, novel approaches including DAPT de-escalation or escalation have been proposed as possible alternatives to standard DAPT. These strategies, which are generally based on patient's risk profile, genetics, and/or platelet function have been proposed to offer more tailored treatments in patients with ACS or PCI, with the ultimate goal of providing adequate ischemic protection while mitigating the risk of bleeding. This review summarizes the available evidence on DAPT de-escalation or escalation (both guided and unguided) and discusses the practical implications of these strategies in the contemporary management of patients with ACS and/or undergoing PCI.

Clinical pharmacology of antiplatelet drugs

INTRODUCTION

Platelets play a key role in arterial thrombosis and antiplatelet therapy is pivotal in the treatment of cardiovascular disease. Current antiplatelet drugs target different pathways of platelet activation and show specific pharmacodynamic and pharmacokinetic characteristics, implicating clinically relevant drug-drug interactions.

AREAS COVERED

This article reviews the role of platelets in hemostasis and cardiovascular thrombosis, and discusses the key pharmacodynamics, drug-drug interactions and reversal strategies of clinically used antiplatelet drugs.

EXPERT OPINION

Antiplatelet therapies target distinct pathways of platelet activation: thromboxane A₂ synthesis, adenosine diphosphate-mediated signaling, integrin α_IIbβ₃ (GPIIb/IIIa), thrombin-mediated platelet activation via the PAR1 receptor and phosphodiesterases. Key clinical drug-drug interactions of antiplatelet agents involve acetylsalicylic acid - ibuprofen, clopidogrel - omeprazole, and morphine - oral P2Y₁₂ inhibitors, all of which lead to an attenuated antiplatelet effect. Platelet function and genetic testing and the use of scores (ARC-HBR, PRECISE-DAPT, ESC ischemic risk definition) may contribute to a more tailored antiplatelet therapy. High on-treatment platelet reactivity presents a key problem in the acute management of ST-elevation myocardial infarction (STEMI). A treatment strategy involving early initiation of an intravenous antiplatelet agent may be able to bridge the gap of insufficient platelet inhibition in high ischemic risk patients with STEMI.

De-escalation of antiplatelet therapy in acute coronary syndromes: Why, how and when?

The synergistic blockade of the key platelet signaling pathways of cyclooxygenase-1 blockade and P2Y12 signaling by combining aspirin plus a potent P2Y12 inhibitor (prasugrel or ticagrelor), the so called dual antiplatelet treatment (DAPT), has represented the antithrombotic regimen of choice in patients with acute coronary syndrome (ACS) for nearly a decade. Nevertheless, the use of such antiplatelet treatment regimen, while reduced the risk of thrombotic complications, it is inevitably associated with increased bleeding and this risk may outweigh the benefit of a reduction of ischemic events in specific subgroup of patients. In light of the adverse prognostic implications of a bleeding complication, there has been a great interest in the development of antiplatelet regimens aimed at reducing bleeding without any trade-off in ischemic events. The fact that the ischemic risk is highest in the early phase after an ACS while the risk of bleeding remains relatively stable over time has represented the rationale for the implementation of a more intense antithrombotic regimen early after an ACS, followed by a less intense antithrombotic regimen thereafter. This practice, known as a "de-escalation" strategy, represents one of the more promising approaches for personalization of antithrombotic therapy in ACS. In this review we discuss the rationale, appraise the evidence and provide practical recommendations on the use of a de-escalation strategy of antiplatelet therapy in patients with an ACS.

Evaluation of race and ethnicity disparities in outcome studies of CYP2C19 genotype-guided antiplatelet therapy

Dual antiplatelet therapy with a P2Y12 inhibitor (clopidogrel, prasugrel, or ticagrelor) and aspirin remains the standard of care for all patients undergoing percutaneous coronary intervention (PCI). It is well-established that patients carrying CYP2C19 no function alleles have impaired capacity to convert clopidogrel into its active metabolite and thus, are at higher risk of major adverse cardiovascular events (MACE). The metabolism and clinical effectiveness of prasugrel and ticagrelor are not affected by CYP2C19 genotype, and accumulating evidence from multiple randomized and observational studies demonstrates that CYP2C19 genotype-guided antiplatelet therapy following PCI improves clinical outcomes. However, most antiplatelet pharmacogenomic outcome studies to date have lacked racial and ethnic diversity. In this review, we will (1) summarize current guideline recommendations and clinical outcome evidence related to CYP2C19 genotype-guided antiplatelet therapy, (2) evaluate the presence of potential racial and ethnic disparities in the major outcome studies supporting current genotype-guided antiplatelet therapy recommendations, and (3) identify remaining knowledge gaps and future research directions necessary to advance implementation of this precision medicine strategy for dual antiplatelet therapy in diverse, real-world clinical settings.

Precision medicine in interventional cardiology: implications for antiplatelet therapy in patients undergoing percutaneous coronary intervention

Precision medicine is a medical model that proposes the customization of medical treatments to the individual patient, as opposed to a one-drug-fits-all model. Such a "personalized medicine" approach has been widely adopted in several medical fields, such as cancer medicine, but the implementation of precision medicine in cardiovascular medicine has not been similarly straightforward. Because pharmacogenomics plays an important role in the safety and efficacy of cardiovascular drug therapy, there has been a great interest in the use of tools aiming at personalizing antiplatelet therapy. Moreover, antiplatelet therapy is essential for the treatment of cardiovascular patients to reduce the risk of thrombotic complications, particularly those undergoing percutaneous coronary intervention, but it is inevitably associated with increased bleeding risk. In this review, the authors discuss the rationale, summarize the evidence and discuss the current and future directions for the personalization of antiplatelet treatment regimens in patients undergoing percutaneous coronary intervention.