Managing the acute coronary syndrome patient: Evidence based recommendations for anti-platelet therapy

Highlights

• Acute coronary syndrome (ACS) is best managed by a team approach.

• Thrombus formation is involved with the majority of ACS presentations.

• Dual antiplatelet therapy (DAT) is recommended in initial- and post-ACS management.

• Providers are key to managing secondary prevention in post-ACS patients, e.g., DAT.

Abstract

Acute coronary syndrome (ACS) is best managed by a multidisciplinary team in which primary care physicians, physician assistants, nurse practitioners, and pharmacists play a key role. This article summarizes recent updates to American College of Cardiology Foundation/American Heart Association guidelines for the management of unstable angina (UA)/non ST-segment elevation ACS (NSTE-ACS) and ST-segment elevation myocardial infarction (STEMI), focusing on antiplatelet therapy. Dual antiplatelet therapy comprising aspirin plus a P2Y₁₂ inhibitor (clopidogrel, prasugrel, or ticagrelor) is recommended for patients with NSTE-ACS, and those with STEMI both during and after reperfusion. The guidelines provide recommendations regarding the utilization of P2Y₁₂ inhibitors in specific circumstances and are discussed in this review. Health care teams with a key role in post-ACS care need to be familiar with the latest guidelines and support patients with education on risk reduction and the benefits of long-term medication adherence.

Introduction

Acute coronary syndrome (ACS) is an umbrella term used to describe conditions of acute myocardial ischemia caused by occlusion of a coronary artery. This is usually due to the formation of a thrombus at the site of a high-risk atherosclerotic plaque, which partially or completely restricts blood flow through the affected coronary artery.¹ When the surface of a high-risk plaque ruptures or becomes eroded, the thrombogenic tissue fragments beneath the fibrous cap are exposed to the circulating blood, leading to platelet adhesion and activation, and clot formation.² Two different types of thrombi may form at the site of plaque rupture. Typically, in ACS, a platelet-rich thrombus (called a ‘white’ clot) forms first at the site of the ruptured plaque.² This may be followed by the formation of fibrin-rich thrombi (so called ‘red’ clots), which occur when the coagulation cascade has been activated in response to reduced blood flow, exacerbating occlusion at the site.²

Although all types of ACS are caused by coronary artery occlusion leading to myocardial ischemia, the clinical features vary according to the extent and severity of the ischemia (Fig. 1).³ Transient or partial occlusion that causes recurring and remitting chest pain, but does not result in myocardial tissue damage, is referred to as unstable angina (UA). Complete occlusion with no collateral perfusion results in a myocardial infarction (MI), and leads to the release of biomarkers of cell injury, such as troponins or creatine kinase myocardial fraction (CK-MB) enzymes. This insult will lead to irreversible damage to myocardial tissue if timely intervention is not applied. Electrocardiograph (ECG) readings provide additional important diagnostic information. The presence of ST segment elevation indicates ST-segment elevation MI (STEMI), in which the infarct-related artery is totally occluded, and patients often present with more severe and distressing signs and symptoms. Patients with normal ECG or non-specific changes that are non-diagnostic may have UA, or a non-ST segment elevation MI (NSTEMI). In fact, NSTEMI closely resembles UA in clinical presentation,¹ but patients with NSTEMI show elevated cardiac biomarkers, whereas those with UA do not.³ Collectively, UA and NSTEMI are known as NSTE-ACS. Patients with STEMI have complete occlusion of the infarct-related artery caused by a fibrin-rich clot, often accompanied by the secondary formation of a platelet-rich clot at the same site.² Therefore, there is an urgent need to recanalize the artery and restore blood flow in STEMI patients to limit the size of the infarction.³ Patients with NSTE-ACS may also need revascularization, but these patients only have platelet-rich clots and may not have completely occluded arteries.² In this group, the goal of revascularization is to increase blood flow and prevent reocclusion.² Treatment is also directed at preventing further thrombosis once the clot has been dissolved by endogenous fibrinolysis, particularly in NSTE-ACS where platelet-rich clots are the primary problem.²

The American Heart Association (AHA) estimates that someone in the USA has an MI every 44 s.⁴ Overall, more than 900,000 Americans had an ACS event in 2013, of which nearly 70% (620,000) were first events.⁴ Around one-third of ACS events were STEMI.⁴ The American College of Cardiology Foundation (ACCF) and AHA have recently updated their guidelines on the diagnosis and management of ACS.1, 5 Because platelet-rich thrombi are a common feature of all forms of ACS, antiplatelet therapies are indicated both in the acute phase of ACS and post-ACS to reduce the risk of reinfarction. The 2002 meta-analysis by the Antithrombotic Trialists' Collaboration showed that antiplatelet therapy for 2 years averted 38 serious vascular events (MI, stroke, or vascular death) for every 1000 ACS patients treated.⁶ Since then, dual antiplatelet therapy has become the standard of care, and new antiplatelet agents have become available. The updated guidelines include recommendations for the optimal use of antiplatelet therapy during and after hospitalization for ACS based on the most recent clinical data.

It is now recognized that ACS is best managed by a multidisciplinary team of health professionals, working together to optimize outcomes in the acute phase and to prevent recurrent events after hospital discharge.7, 8, 9 Physician Assistants (PAs), nurse practitioners (NPs), pharmacists, and primary care physicians (PCPs) play an important role in the prevention and management of ACS by identifying patients at risk, ensuring these patients minimize their risk factors as much as possible, and by educating them about the potential signs and symptoms of ACS so that they seek treatment early. Risk-factor management includes evidence-based screening, lipid control, optimal blood-pressure management, tobacco cessation, weight control, and an active, heart-healthy lifestyle.1, 5 These members of the health care team are also integral to the management of patients after ACS to ensure they are complying with recommended therapies to reduce their risk of recurrent events. This includes encouraging patients to attend cardiac rehabilitation, appropriate medication and dose selection, and monitoring and prevention of adverse drug effects.

This review summarizes recent updates to the ACCF/AHA guidelines for the management of NSTE-ACS and STEMI, with an emphasis on the revisions to recommendations for antiplatelet therapy, and what PAs, NPs, pharmacists, and PCPs need to know to optimally manage their patients before, during, and after an ACS event.