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Heart Online First, published on July 18, 2014 as 10.1136/heartjnl-2013-305399
Review
Antiplatelet therapy for secondary prevention of coronary artery disease Thomas Pilgrim, Stephan Windecker ▸ Additional material is published online only. To view please visit the journal online (http://dx.doi.org/10.1136/ heartjnl-2013-305399). Department of Cardiology, Bern University Hospital, Bern, Switzerland Correspondence to Dr Stephan Windecker, Department of Cardiology, Bern University Hospital, Bern 3010, Switzerland; stephan.
[email protected] Received 18 April 2014 Revised 30 May 2014 Accepted 23 June 2014
ABSTRACT The choice and duration of antiplatelet therapy for secondary prevention of coronary artery disease (CAD) is determined by the clinical context and treatment strategy. Oral antiplatelet agents for secondary prevention include the cyclo-oxygenase-1 inhibitor aspirin, and the ADP dependent P2Y12 inhibitors clopidogrel, prasugrel and ticagrelor. Aspirin constitutes the cornerstone in secondary prevention of CAD and is complemented by clopidogrel in patients with stable CAD undergoing percutaneous coronary intervention. Among patients with acute coronary syndrome, prasugrel and ticagrelor improve net clinical outcome by reducing ischaemic adverse events at the expense of an increased risk of bleeding as compared with clopidogrel. Prasugrel appears particularly effective among patients with ST elevation myocardial infarction to reduce the risk of stent thrombosis compared with clopidogrel, and offered a greater net clinical benefit among patients with diabetes compared with patients without diabetes. Ticagrelor is associated with reduced mortality without increasing the rate of coronary artery bypass graft (CABG)-related bleeding as compared with clopidogrel. Dual antiplatelet therapy should be continued for a minimum of 1 year among patients with acute coronary syndrome irrespective of stent type; among patients with stable CAD treated with new generation drug-eluting stents, available data suggest no benefit to prolong antiplatelet treatment beyond 6 months.
INTRODUCTION Antiplatelet therapy represents an important pillar for secondary prevention of coronary artery disease (CAD) along with lifestyle modification and control of cardiovascular risk factors. Antiplatelet treatment strategies for the prevention of recurrent events are customised to clinical setting (acute coronary syndrome (ACS) versus stable CAD), patient comorbidities, and conservative versus invasive strategy, respectively. In this article we summarise the currently available evidence on choice, combination and duration of antiplatelet agents in various clinical settings.
MECHANISMS OF ACTION OF ANTIPLATELET AGENTS
To cite: Pilgrim T, Windecker S. Heart Published Online First: [please include Day Month Year] doi:10.1136/heartjnl2013-305399
Platelet activation and aggregation are part of the pathophysiological response to plaque rupture/ erosion. Uncontrolled amplification loops may result in partial or complete thrombotic occlusion of coronary arteries resulting in ischaemia or infarction.1 Antiplatelet agents currently used in the secondary prevention of CAD target different receptors and interfere with various stages of platelet aggregation, providing a rationale for
combination therapy.1 Mechanism of action, indications and potential interactions of antiplatelet agents used in secondary prevention of CAD are summarised in table 1. An overview on aspirin, thienopyridines and thienopyrimidines is provided in the online supplement.
SECONDARY PREVENTION IN VARIOUS CLINICAL SETTINGS Aspirin and clopidogrel have been investigated across the entire clinical spectrum of CAD. Randomised trials investigating the efficacy of antiplatelet agents for secondary prevention primarily focused on patients at high risk of cardiovascular events, namely patients with ACS, in which the beneficial effect is expected to be greatest. The novel ADP P2Y12 receptor antagonists prasugrel and ticagrelor have not been investigated in populations with stable CAD to date.
Stable CAD Aspirin Aspirin represents the cornerstone in secondary prevention of patients with stable CAD or ACS. In a randomised controlled trial aspirin was shown to reduce the rate of myocardial infarction early after percutaneous transluminal coronary angioplasty as compared with placebo (1.6% vs 6.9%, p=0.0113).2 Adherence to prolonged aspirin treatment was demonstrated to be effective for the prevention of myocardial infarction as compared with placebo in the Multi-Hospital Eastern Atlantic Restenosois Trial (M-HEART) with follow-up though 6 months.3 In a meta-analysis of the Antithrombotic Trialists’ Collaboration, treatment with aspirin at a dose of 75–150 mg daily reduced the incidence of serious vascular events by 33% in patients with stable CAD, and by 53% in patients undergoing percutaneous coronary intervention (PCI). Among patients with a history of myocardial infarction, aspirin therapy reduced the incidence of non-fatal reinfarction by 18 per 1000 patients, vascular death by 14 per 1000 patients, and non-fatal stroke by 5 per 1000 patients after a mean duration of follow-up of 27 months, with an excess of approximately 1 major extracranial bleed per 1000 patients per year. Secondary prevention with aspirin has been shown to reduce the yearly absolute risk of mortality from CAD by 34% and the risk of non-fatal myocardial infarction by 66%.4
Clopidogrel Clopidogrel has been widely investigated for secondary prevention in patients with stable CAD undergoing conservative management5 6 or PCI.7–11
Pilgrim T, et al. Heart 2014;0:1–7. 1 Copyright Article author doi:10.1136/heartjnl-2013-305399 (or their employer) 2014. Produced by BMJ Publishing Group Ltd (& BCS) under licence.
2
Review
Table 1
Summary of antiplatelet agents for secondary prevention Mechanism
Action
Onset of platelet inhibition
Biotransformation
Indications
Contraindications
Warnings
Aspirin
Inhibition of cyclo-oxygenase-1
Irreversible
30–40 min
Hydrolysis by esterase
Stable coronary artery disease Acute coronary syndromes
Active pathological bleeding Hypersensitivity to aspirin Severe hepatic impairment
Clopidogrel
Inhibition of P2Y12 unit of ADP-receptor
Irreversible
5–8% inhibition of platelet aggregation after 30 minutes*†
Cytochrom-P450-dependent oxidation (affected by genetic variability)
Stable coronary artery disease Acute coronary syndromes
Active pathological bleeding Severe hepatic impairment
Prasugrel
Inhibition of P2Y12 unit of ADP-receptor
Irreversible
31% inhibition of platelet aggregation after 30 minutes*
Hydrolysis by carboxylesterase and cytochrom-P450-dependent oxidation (unaffected by genetic variability)
Acute coronary syndromes with PCI
Active pathological bleeding History of stroke or TIA Severe hepatic impairment (Child-Pugh class C)
Ticagrelor
Inhibition of P2Y12 unit of ADP-receptor
Reversible
41% inhibition of platelet aggregation after 30 minutes†
None
Acute coronary syndromes
Active pathological bleeding History of intracranial haemorrhage Moderate to severe hepatic impairment Co-administration with strong CYP3A4 inhibitors
Severe hepatic impairment Severe renal insufficiency Severely decompensated heart failure Interaction with NSAIDs Combination with methotrexate Thrombotic thrombocytopenic purpura Recent (
