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Acute coronary syndromes 

Acute coronary syndromes
Chapter:
Acute coronary syndromes
DOI:
10.1093/med/9780198832447.003.0007
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date: 12 May 2021

Introduction

Despite a significant ↓ in mortality rates from coronary heart disease (CHD) during the past four decades, statistics show that it continues to account for 66 000 deaths/yr in the UK, in contrast to 35 620 deaths/yr from lung cancer, 16 384 deaths/yr from colorectal cancer, and 11 563 deaths/yr from breast cancer.1 CHD costs the NHS approximately £2.2billion per year with in-patient care accounting for 57% of the total cost.2

The term acute coronary syndromes (ACS) refers to a clinical spectrum of the same disease process, and includes unstable angina to non-ST-segment elevation myocardial infarction (NSTEMI) and ST-segment elevation myocardial infarction (STEMI). The common underlying cause results in the formation of a platelet-rich thrombus and reduced coronary arterial blood flow, which either partially or completely occludes the artery. When complete occlusion of a coronary artery occurs (STEMI) limitation of the infarct size is vital and thus rapid initiation of treatment is essential to obtain the greatest benefit. The development of services such as pre-hospital thrombolysis, direct delivery of patients from the ambulance to the catheter laboratory, and ↑ numbers of 24h 1° percutaneous coronary intervention (PPCI) facilities available (Heart Attack Centres) have been important government initiatives that have been implemented to manage heart disease.

Central chest discomfort or pain remains the most common symptom that patients with an ACS report. Classically, the discomfort reported is retrosternal, radiating to the neck, jaw, and left shoulder or arm. In reality, symptoms are often ill-defined and the patient might describe a wide variety of symptoms that they do not initially associate with cardiac pain.

Treatment for this group of patients may be initiated and then continued across a variety of areas, which include the pre-hospital/community setting, emergency department, coronary care unit, cardiac catheter laboratory, general ward, and chest pain unit. Nurses will encounter patients with both ST-segment elevation ACS and non-ST-segment elevation ACS at various points in their journey, thus clear and effective communication between healthcare providers across these different areas is imperative. With this in mind this chapter aims to outline the pathophysiology, methods for rapid diagnosis, and appropriate clinical management of ACS so that it that may be applied within any area and at any point in the patient’s journey.

Pathophysiology

Rather than development and growth of an atherosclerotic plaque into a stenosis that limits blood flow, the symptoms and clinical conditions associated with ACS are, in general, related to the deterioration and rupture of an atherosclerotic plaque.

Certain factors ↓ the tensile strength of the plaque’s fibrous cap, making it unstable or vulnerable. Pressure from the pulsating blood flow through the coronary artery creates either fissures through the endothelium down into the plaque or areas of endothelial desquamation, ↑ the plaque’s vulnerability to sudden rupture/erosion and subsequent thrombus formation. The sudden rupture of an atherosclerotic plaque cap leads to the exposure of subendothelial collagen promoting platelet adhesion, activation, and aggregation, and a fibrin-rich thrombus develops. The presence of an occlusive or subocclusive thrombus overlying the plaque then results in ↓ coronary arterial blood supply. The pathological and clinical outcomes for patients who present with ACS depend on whether the thrombus partially or completely occludes the coronary artery, the degree of collateral blood supply to the myocardium, and the amount of myocardium affected.

  • Complete coronary artery occlusion is responsible for STEMI—myocardial ischaemia leads to myocyte necrosis within 15–20min and spreads from subendocardium to subepicardium.

  • Partial coronary artery occlusion is responsible for non-ST-segment elevation ACS and results in either unstable angina or NSTEMI.

In non-ST-segment elevation ACS, the formation of a thrombus is often associated with vasospasm, which causes intermittent obstruction to blood flow and fragments of the thrombus to break off and flow down the artery, where they lodge in smaller vessels. These distal emboli can therefore cause small areas of infarction without a complete occlusion of an epicardial vessel.

Identifying patients with acute coronary syndromes (ACS)

Because patients present with a wide variety of symptoms and with varying degrees of severity, the diagnosis of an ACS can be challenging. ACS should be suspected in those who describe any of the following symptoms:

  • Severe central, crushing chest pain

  • A heavy feeling, tightness, or a dull ache in the chest

  • Discomfort in the chest, described as indigestion but associated with other symptoms of ACS

  • A dull, numb, or tingling feeling in the chest or down the left arm.

Such pain/tightness/sensations might radiate to the any of the following parts of the body:

  • Neck/jaw

  • Down the left arm

  • Down the right arm

  • Across both shoulders

  • Down both arms and into the fingers.

The following signs and symptoms may also be present, again with varying degrees of severity:

  • Nausea

  • Vomiting

  • Sweating

  • Pallor

  • Cool and clammy peripheries

  • Fear and anxiety.

Chest pain associated with ACS can occur at rest, be precipitated by exercise, or be associated with ↑ frequency and severity over a short period of time. For some it may be the worst pain they have ever experienced and for others much milder symptoms are mistaken for a noncardiac cause to the extent that their presentation is significantly delayed. Other factors, e.g. stress, can be associated with an acute coronary event, and many patients, particularly ♀, also report recent fatigue and weakness before the event. A significant number of patients present with minimal symptoms or without any chest pain or discomfort at all. Such patients are more likely to be older, ♀, have hypertension, diabetes, and have a history of heart failure. Differential diagnosis of chest pain is discussed in Chapter 2 (Acute coronary syndromes Differential diagnosis of chest pain, p.[link]).

Principles for immediate nursing care of all patients with suspected ACS

If ACS is suspected after the initial assessment of the patient’s clinical signs and symptoms, the principles of nursing management are as follows:

  • Manage patient in an area with a defibrillator and personnel skilled in resuscitation.

  • 12-lead electrocardiogram (ECG)—record an initial 12-lead ECG and repeat at regular intervals (i.e. every 10–15min) while symptoms are experienced. Record another 12-lead ECG when the patient is symptom-free and at intervals such as 60min and 4h after symptoms have ceased.

  • Vital signs—blood pressure (BP), pulse, respiratory rate, SpO2, temperature—repeated, as the patient’s condition dictates.

  • Continuous cardiac monitoring.

  • O2 should only be administered if indicated by the SpO2 levels. Optimum SpO2 levels are >94% in patients without chronic obstructive pulmonary disease (COPD) and between 88 and 92% in those with COPD.3

  • Obtain venous access and take blood for determination of urea and electrolytes (U&E), full blood count (FBC), liver function test (LFT), cholesterol levels, clotting time, glucose level, and cardiac markers, e.g. troponin T or I (according to local policy).

  • Administer aspirin (300mg), as prescribed.

  • Administer thienopyridine, e.g. clopidogrel or ticagrelor, as prescribed.

  • Administer S/L nitrate, e.g. glyceryl trinitrate (GTN), as prescribed.

  • Administer diamorphine or morphine by slow intravenous (IV) injection, as prescribed, and titrate to the patient’s level of pain—aim for 1mg/min and observe the patient’s level of consciousness and respiratory rate, particularly in elderly and frail patients.

  • Ongoing assessment for symptoms—precipitating factors; location and duration of chest discomfort or pain; severity; description of symptoms (Acute coronary syndromes Chest pain, p.[link]).

  • Reassurance—anxiety can exacerbate symptoms and, ∴, information provision and reassurance are vital.

Implementing appropriate treatment regimens is initially guided by the patient’s symptoms and 12-lead ECG: treatment must not be delayed to await biochemical markers. The overall aim is common to all patients with ACS: relieve symptoms, resuscitate if needed, and prompt and effective restoration or preservation of coronary blood flow to relieve ischaemia and prevent further myocardial damage.

Patients with a suspected ACS must also be admitted to hospital for further assessment and potential treatment.

Specific principles for nursing patients with ST-segment elevation ACS: reperfusion

Patients with a good clinical history of ACS and the following criteria on their 12-lead ECG should be treated as a STEMI and must be rapidly assessed for reperfusion therapy (see Fig. 7.1). Individual hospital protocols vary slightly and ∴ it is vital that you check your local protocol. It is likely to include the following:

  • ST-segment elevation >1mm in two contiguous limb leads.

  • ST-segment elevation >2mm in two contiguous chest leads.

  • Presumed new left bundle branch block (LBBB).

  • Isolated ST-segment depression V1–V4, indicating a potential posterior infarct. The use of posterior leads V7, V8, and V9 (Fig. 7.2) will show ST elevation in those with a posterior STEMI. These additional leads will help identify those who will benefit from rapid reperfusion therapy.

Fig. 7.1 STEMI reperfusion strategies and target times.

Fig. 7.1 STEMI reperfusion strategies and target times.

Reproduced with permission from Ibanez B, James S, Agewall S et al. (2018) 2017 ESC guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation. European Heart Journal 39, 119–77.

Fig. 7.2 (a) Lead position for a posterior ECG. (b) Lead position for a right-sided ECG.

Fig. 7.2 (a) Lead position for a posterior ECG. (b) Lead position for a right-sided ECG.

Refer to Fig. 7.3 for the changes seen in the evolution of a STEMI. Box 7.1 shows the anatomical relationship of the leads on a 12-lead ECG. Figs 7.4 and 7.5 show 12-lead ECG changes in inferior and anterior STEMI.

Fig. 7.3 Changes seen in the evolution of a ST-segment elevation MI.

Fig. 7.3 Changes seen in the evolution of a ST-segment elevation MI.

Fig. 7.4 Inferior lateral ST-segment elevation MI.

Fig. 7.4 Inferior lateral ST-segment elevation MI.

Fig. 7.5 Anterior ST-segment elevation MI.

Fig. 7.5 Anterior ST-segment elevation MI.

Every effort must be made to restore blood flow in an obstructed coronary artery as quickly as possible, to limit the size of the infarct and minimize complications such as arrhythmias and pump failure. Blood flow can be restored:

Regardless of the reperfusion strategy employed, the most important factor is to start treatment as early as possible. Extensive research has shown that the prognosis for patients following a myocardial infarction (MI) is closely related to the length of time the coronary artery remains blocked: the longer the duration of the blockage, the higher the mortality and morbidity results.

Evidence suggests that PPCI is superior to thrombolytic therapy4; it is associated with early patency rates exceeding 90% and low rates of serious bleeding, recurrent ischaemia, and death. In contrast patency rates following thrombolytic therapy can be as low as 50%. Current guidelines recommend that the delivery of PPCI should occur within 12h of the onset of symptoms, and it should be delivered within 120min of the time when fibrinolysis could have been given. Fibrinolysis should be offered to patient who present within 12h of the onset of symptoms if PPCI cannot be delivered within 120min of the time when fibrinolysis could have been given (Fig. 7.1).5

Specific principles for nursing patients with ST-segment elevation ACS

The role of the registered nurse in reperfusion therapy is effectively preparing the patient for PPCI or to safely administer the prescribed thrombolytics and adjunctive anticoagulants (assuming there are no contraindications to therapy (Box 7.2), and they have not been administered in another setting). Observation for the following potential post-STEMI complications is also an important role:

  • Bleeding—usually limited to localized areas such as puncture sites (e.g. IV cannulas); avoid IM injections. However, intracerebral bleeding or bleeding from other sites, although much more rare, can occur and must be reported to the medical team (it is good practice to monitor the patient’s Glasgow Coma Score).

  • Failure to reperfuse from thrombolysis. After administration of a thrombolytic agent, it is crucial that that the patient is monitored for signs of successful reperfusion, both by the assessment of any ongoing symptoms and by performing a 12-lead ECG 90min after the administration of thrombolysis. Successful reperfusion is characterized by a >50% ↓ in the ST-segment 90min after the thrombolytic agent is administered. If the patient fails to reperfuse, they should be considered for rescue PCI.

  • Acute left ventricular failure (LVF).

  • Tachyarrhythmias (ventricular tachycardia and ventricular fibrillation).

  • Reperfusion arrhythmias.

  • Transient or prolonged bradyarrhythmias—most commonly complete heart block (CHB) (third-degree atrioventricular (AV) block) and Wenckebach’s phenomenon (Möbitz type 1 second-degree AV block), which is usually associated with an inferior MI. These bradyarrhythmias can also occur in the presence of an anterior MI, although they are not usually transient and indicate an extensive infarct (Acute coronary syndromes Atrioventricular blocks: second-degree heart block, p.[link]; Atrioventricular blocks: third-degree (complete) heart block, p.[link]). Möbitz II is more sinister. Accelerated idioventricular rhythm can also indicate reperfusion.

  • Pericarditis (Acute coronary syndromes Pericardial disease, p.[link]).

  • Cardiogenic shock (Acute coronary syndromes Cardiogenic shock, p.[link]).

  • Right ventricular (RV) infarct associated with an inferior MI.

  • Mitral valve regurgitation caused by papillary muscle dysfunction (Acute coronary syndromes Mitral valve regurgitation, p.[link]).

  • Ventricular septal defect.

  • Procedural complications associated with PPCI (Table 8.2).

Specific principles for nursing patients with ST-segment elevation ACS: ECGs

See Figs 7.3, 7.4, 7.5.

Specific principles for nursing patients with non-ST-segment elevation ACS

In contrast to ST-segment elevation ACS, in which the risk of adverse events is highest in the first few hours, those with non-ST-segment elevation ACS are at the highest risk following the event. It is on the basis of a characteristic pattern of release of cardiac biomarkers (such as troponin, creatine kinase muscle and brain (CK-MB), and myoglobin) that a diagnosis of a NSTEMI is made as opposed to unstable angina.

In addition to the principles of management outlined in Acute coronary syndromes Principles for immediate nursing care of all patients with suspected ACS, p.[link], the role of the registered nurse in the ongoing management of this group of patients also includes:

  • Serial 12-lead ECG recordings, monitoring for abnormalities such as horizontal ST-segment depression or T-wave inversion

  • Measurement of cardiac biomarkers on admission and 6–12h after symptom onset or according to local policy

  • Continuous monitoring of ongoing symptoms of ACS

  • Safe administration of medications—e.g. antiplatelet agents (aspirin and thienopyridines), antithrombin agents (low-molecular-weight heparin (LMWH), fondaparinux), β‎-blockers, ACE inhibitors, statins, and GP IIb/IIIa inhibitors

  • Risk stratifying patients and identifying those who might be at high risk of further adverse cardiac events

  • Highlight high-risk patients to the appropriate medical team.

Patients with the following features are at high risk of an adverse cardiac event:

  • Horizontal ST-segment depression, which reverses when symptoms have resolved

  • Cardiac arrhythmias (bradyarrhythmias and tachyarrhythmias)

  • Symptoms that continue regardless of analgesia, antiplatelet, and anticoagulant therapies

  • Haemodynamic instability

  • ↑ troponin I or T levels

  • Prolonged chest pain at rest (>20min) and recurrent pain at rest

  • Diabetes mellitus

  • Evidence of LVF

  • Aged >75yrs

  • Early post-infarction unstable angina.

Risk stratification of patients (i.e. identifying those who are at high or low risk of adverse events) with non-ST-segment elevation ACS helps to appropriately target both the type and the intensity of medical therapies and interventions. Several validated risk scores are available for use in clinical practice; however, the National Institute for Health and Care Excellence (NICE) (2013) recommends the Global Registry of Acute Coronary Events (GRACE) risk score.6 The risk of 6mth mortality is calculated on the basis of clinical features at presentation including: age, heart rate, systolic BP, serum creatinine, Killip heart failure classification, cardiac arrest, ST-segment deviation, and biochemical markers. Without appropriate and rapid initiation of treatment patients with non-ST elevation ACS will remain at risk of further coronary events and sudden cardiac death. High-risk patients benefit from more aggressive treatment regimens, e.g. the administration of GP IIb/IIa inhibitor and angiography (with follow-on PCI if indicated) within 96h of first admission. Angiography will provide information on any underlying CHD so that the most suitable intervention (PCI, CABG, or medical management) can be identified and initiated. Those at low risk might be discharged early and safely from hospital.

Specific principles for nursing patients with ACS after initial acute presentation

This should include the following:

  • Continuous cardiac monitoring—discontinuation of cardiac monitoring must be based on the individual patient’s haemodynamic status. As a guide, patients should be free of pain and arrhythmias and haemodynamically stable for a minimum of 24h before discontinuation.

  • Tight control of blood glucose levels in those with diabetes or a blood glucose level >11mmol/L on presentation.

  • Monitor for signs of LVF (low SpO2, tachycardia, shortness of breath, ↑ respiratory rate)—particularly in patients with extensive anterior infarcts.

  • Mobilizing patients after the acute phase must also be based on the patient’s individual haemodynamic status after an acute cardiac event. Patients who recover without complications (i.e. those who are without cardiac arrhythmia or LVF and who are haemodynamically stable) can be mobilized from bed to chair within 12h of their acute event and gently mobilized using telemetry monitoring after 12–24h.

  • Clear and timely provision of information regarding their condition. Advice and information provision regarding the aims of the patient’s stay in hospital, an explanation of the condition, any investigations, and contact details for key organizations or individuals to contact on discharge should form the basis of the information provided.

  • Assessment of risk factors (Acute coronary syndromes Risk factors for cardiovascular disease, p.[link])

  • Assessment of cardiac rehabilitation needs—might also require the patient to be referred to other services, e.g. cardiac rehabilitation nurse, dietician, or diabetic nurse (Acute coronary syndromes Cardiac rehabilitation, p.[link]).

Information on discharge must be individualized and should not be prescriptive. It should include the following:

  • The causes of their condition.

  • Risk factors for ACS and their management.

  • Importance of physical activity (if able) and which activities are best—it is important to build up activity gradually on returning home, it is not safe to exercise when the patient has a viral infection.

  • Exercise advice—regular moderate physical activity is best (unless the doctor advises against this) such as walking, cycling, swimming, dancing. Important to ↑ physical activity gradually, rest if feeling tired or breathless. Avoid activities after a large meal, or when the weather is very hot or cold.

  • Appropriate and patient-specific dietary advice—including alcohol.

  • Importance of relaxation.

  • Driving restrictions (up-to-date guidelines can be obtained from the DVLA website7).

  • Return to work advice.

  • When and how to use S/L nitrates.

  • Information regarding all prescribed medications and their potential side effects—ensuring that the patient is clear when and how to take their medications.

  • Advice on sexual activity—it is suggested that if an individual can climb a flight of stairs they should be able to safely participate in sexual activity. Some medications can interfere with sexual performance. The patient should discuss any worries or concerns with their doctor or nurse (Acute coronary syndromes Sex, p.[link]).

  • What follow-up to expect—such as GP clinics, 2° prevention clinics, cardiac rehabilitation programmes, local and national support groups, and out-patient appointments.

  • Smoking cessation advice (if applicable) (Acute coronary syndromes Smoking cessation, p.[link]) and community links.

  • When to seek advice and help if symptoms recur (dial for an ambulance if chest pain >15min and not relieved by GTN).

Investigations

These are generally performed during hospital admission. The role of the nurse is to ensure that the patient understands the importance of the investigation, what it involves, and the potential consequences.

Potential investigations include:

Medical management

The aim of medical treatment is to control symptoms and reduce the risk of further acute coronary events or sudden cardiac death occurring. All patients will receive medications (see Chapter 19), which will generally include:

  • GTN tablets or spray—the patient must be advised to keep this with them at all times

  • Aspirin

  • β‎-blocker

  • Statin

  • ACE-inhibitor

  • Thienopyridine (e.g. clopidogrel).

Interventions

Interventions may include PCI.

Related guidance

Ibanez B, James S, Agewell S, Antunes M et al. (2017) ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation. The Task Force for the management of acute myocardial infarction in patients presenting with ST-segment elevation of the European Society of Cardiology (ESC). European Heart Journal 39, 119–77.Find this resource:

Neumann FJ, Sousa-Uva M, Ahlsson A, Alfonsa F et al. (2018) ESC/EACTS Guidelines on myocardial revascularization. European Heart Journal 40, 87–165.Find this resource:

National Institute for Health and Care Excellence (2011) Hyperglycaemia in Acute Coronary Syndromes. CG130. NICE, London.Find this resource:

National Institute for Health and Care Excellence (2013) Unstable Angina and NSTEMI Early Managment. CG 94. NICE, London.Find this resource:

National Institute for Health and Care Excellence (2013) Myocardial Infarction with ST-Segment Elevation: Acute Management. CG167. NICE, London.Find this resource:

Roffi M, Patrona C, Collet JP, Mueller C et al. (2016) 2015 ESC Guidelines for the management of acute coronary syndrome in patients presenting without persistent ST-segment elevation. The Task Force for the management acute coronary syndrome in patients presenting without persistent ST-segment elevation of the European Society of Cardiology (ESC). European Heart Journal 37, 267–317.Find this resource:

Scottish Intercollegiate Guidelines Network (2016) Acute Coronary Syndrome. SIGN148. Health Improvement Scotland, Edinburgh.Find this resource:

Thygsen K, Alpert J, Jaffe A, Chaitman B et al. (2018) Fourth universal definition of myocardial infarction. European Heart Journal 40, 237–269.Find this resource:

Notes:

1 British Heart Foundation (2019) UK Factsheet. BHF, London.

2 British Heart Foundation (2019) Heart and Circulatory Disease Statistics 2019. BHF, London.

3 O’Driscoll BR, Howard LS, Earis J, Mak V on behalf of the BTS Emergency Oxygen Guideline Group et al. (2017) BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax 72(Suppl. 1), i1–90.

4 DH (2008) National Infarct Angioplasty Project (NIAP) Interim Report . Department of Health & British Cardiovascular Society, London.

5 National Institute for Health and Care Excellence (2013a) Myocardial Infarction with ST-Segment Elevation: Acute Management. CG167. NICE, London.

6 National Institute for Health and Care Excellence (2013b) Unstable Angina and NSTEMI Early Managment. CG 94. NICE, London.