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NSTEMI

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Acute coronary syndrome (ACS)\: sudden reduction in blood
damage. Includes STEMI, NSTEMI, and unstable angina.
NSTEMI\: myocardial infarction detected by rise in cardiac biomarkers without ECG changes indicative of STEMI. Accounts
for 64% of myocardial infarctions in the UK.
Aetiology\: mismatch between myocardial oxygen demand and delivery, often due to partial coronary artery obstruction,
vasospasm, or arteritis. In type 2 myocardial infarctions, conditions like severe anaemia or hypotension cause mismatch.
Risk factors\: Non-modi
(smoking, hypertension, hyperlipidaemia).
Symptoms\: sudden onset central crushing chest pain radiating to left arm/jaw lasting >20 minutes, diaphoresis, nausea,
shortness of breath. History should assess cardiovascular risk factors and di
Clinical
regurgitation, pulmonary oedema.
Di
sepsis, cardiotoxic agents.
Investigations\: 12-lead ECG (ST-segment depression, T wave inversion), serial troponin tests, baseline blood tests (U&Es,
glucose, FBC), coronary angiography, echocardiogram, chest X-ray.
Management\: immediate ABCDE approach, antiplatelet therapy (aspirin 300mg), analgesia (GTN or IV opioids),
antithrombin therapy (fondaparinux or unfractionated heparin), supplemental oxygen if SpO 2
\<94%, coronary angiography
for unstable patients within 24 hours.
Risk strati
angiography within 72 hours, low-risk patients consider conservative management.
Long term management\: ACE inhibitors/ARBs, dual antiplatelet therapy for up to 12 months, beta-blockers, statins,
lifestyle changes (diet, exercise, alcohol moderation, smoking cessation, weight management).
Complications\: mechanical (rare) and non-mechanical (arrhythmias, thromboembolic complications, heart failure,
pericarditis, depression). NSTEMI patients have worse long-term prognosis post-discharge than STEMI patients.
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A comprehensive topic overview

Introduction

Acute coronary syndrome (ACS) is a term used to describe a sudden reduction in blood
in irreversible damage to the myocardium.
ACS can be divided into three unique clinical entities\: ST-segment elevation myocardial infarction (STEMI), non-ST segment
elevation myocardial infarction (NSTEMI) and unstable angina.
NSTEMIs are de
changes indicative of a STEMI.
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In 2018/2019 there were 87,091 cases of myocardial infarction reported in the UK with 64% of these being NSTEMIs.
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DiSTEMI, NSTEMI and unstable angina has important implications for management.

Aetiology

Broadly speaking, ACS is caused by a mismatch between myocardial oxygen demand and myocardial oxygen delivery.
In a STEMI, the mismatch between myocardial oxygen demand and delivery is almost always caused by total occlusion of
a coronary artery from atherosclerotic plaque rupture and subsequent thrombus formation. The severity is dependent on
the size, location, and duration of the occlusion.
In NSTEMIs however, there are more varied causes of mismatch including partial coronary artery obstruction from a
ruptured plaque (most common), partial occlusion from a stable plaque, coronary artery vasospasm (Prinzmetal's angina) or
coronary arteritis.
In some cases, myocardial supply and demand mismatch may be caused by conditions that only indirectly a
coronary arteries (e.g. severe anaemia, hypotension, tachycardia, aortic stenosis, and pulmonary embolism).
In these situations, revascularisation strategies are unnecessary and the underlying cause should be addressed. These
are known as ‘type 2’ myocardial infarctions and often do not present with chest pain, their classi
controversial.

Risk factors

Risk factors for ACS include any factors which increase the risk of coronary artery atherosclerosis.
Non-modi
Male sex
Older age
Previous history of ACS/ischaemic heart disease
Family history of ACS/ischaemia heart disease
Renal insu
Diabetes
Modi
Tobacco smoking
Longstanding hypertension
Hyperlipidaemia

Clinical features

History

Initial assessment of anyone with acute chest pain involves a thorough history. See the Geeky Medics OSCE guide to a
comprehensive chest pain history.
The history should assess the acute presentation and features of ACS and include an assessment of cardiovascular risk
factors.
Typical symptoms of ACS/NSTEMI include\:
Sudden onset central crushing chest pain radiating to the left arm and/or jaw lasting longer than 20 minutes (if pain-free,
identify when their last episode of pain occurred)
Diaphoresis
Nausea
Shortness of breath
Other important areas to cover in the history include\:
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Assessment of cardiovascular risk factors\: hypertension, hyperlipidaemia, diabetes, smoking and family history
Assessment of di
respiratory and gastrointestinal symptoms.

Clinical examination

All patients with suspected ACS require a comprehensive cardiovascular examination. However, examination
be non-speci
A combination of thorough chest pain history, 12-lead ECG and high sensitivity troponin is the gold standard for diagnosis.
Although a physical examination is necessary to look for complications of ACS and to assess clinical stability, it should not
delay initial investigations and management.
Typical clinical
Signs of respiratory distress, pallor, diaphoresis, or
Tachycardia
High or low blood pressure
S4 heart sound\: due to reduced ATP production impairing left ventricular relaxation
Signs of papillary muscle dysfunction (e.g. mitral regurgitation)
Pulmonary oedema\: due to acute left-sided heart failure

Di

Chest pain has a wide range of dichest pain history for more
information on the typical clinical features of each di
Despite the high sensitivity of ST-segment deviation and raised troponins for acute thrombotic cardiac events, these
markers are not always speci
Troponin is a good indicator for myocardial damage but is not always due to myocardial ischaemia.
Several other pathologies may cause myocardial damage in the absence of coronary artery pathology and thus present
with raised serum troponin and ECG changes. These include\:
Myocarditis
Pericarditis
Pulmonary embolism
Aortic dissection
Acute heart failure
Arrhythmias
Sepsis
Cardiotoxic agents
It is important that these conditions are identi

Investigations

12-lead ECG

Serial 12-lead ECGs are important for assessing and monitoring patients with suspected ACS. A record of the patient’s
baseline ECG may be helpful in determining the presence of acute changes.
The presence of raised serum troponins in the absence of the following features indicates a diagnosis of an NSTEMI\:
Persistent ST-segment elevation
Evidence of a posterior MI
New left bundle branch block
Typical ECG
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Regional ST-segment depression
T wave inversion or
Any dynamic or new Q or T wave changes
See the Geeky Medics guides to ECG interpretation for more information.
Figure 1. Comparison of typical ECG
(blue). Pathological Q waves (shown in the STEMI image) may be found in both
conditions.
4

Troponin

High sensitivity troponin I or T are the recommended tests for suspected ACS.
Troponin is a structural protein which is found solely in cardiac myocytes. The presence of troponin within the blood
indicates myocardial necrosis.
When necrosis occurs, cardiomyocyte's membranes rupture, releasing intracellular enzymes including troponin into the
bloodstream.
5
To be indicative of myocardial damage, troponin levels need to be about three standard deviations from the normal range.
Typically, serial troponin tests are required in order to see the trend of troponin over time.
In an NSTEMI, the troponin is expected to rise two to three hours after the onset of chest pain, peaking 12-48 hours post
the incident and declining for the next 4-10 days.
5
It is, therefore, possible for someone to present to hospital with symptoms of ACS and have a normal troponin and ECG
initially, but still be having an NSTEMI.
A second troponin 30 minutes to three hours after initial presentation is typically required to exclude an NSTEMI in patients
at high risk of ACS.

Laboratory investigations

Other relevant laboratory investigations include\:
U&Es\: renal function may a
coronary artery related myocardial damage. In addition, CKD is a risk factor for coronary artery disease.
Glucose\: hyperglycaemia should be tested for and managed during ACS as hyperglycaemia has been associated with
poorer outcomes.
6
FBC\: underlying anaemia may exacerbate ACS or be indicative of an occult bleed.

Other investigations

Coronary angiography is important in high to moderate risk groups to identify the presence and location of coronary artery
vasculature blockage.
An echocardiogram is useful to assess left ventricular function in patients with both suspected and con
Chest X-ray may be useful to rule out other potential causes of chest pain (e.g. pneumothorax, pneumonia).
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Diagnosis

The diagnosis of NSTEMI is made from the combination of clinical history, abnormal troponins, and the absence of ST-
elevation on ECG.

Management

The following sections are in accordance with the 2020 NICE guidelines for the management of acute coronary
syndromes.
7

Immediate management

ACS is an emergency situation and an initial ABCDE approach should be taken. See the Geeky Medics guide to the acute
management of ACS for more information.
Immediate management of ACS includes\:
Antiplatelet therapy\: aspirin 300mg
Analgesia\: either GTN or intravenous opioids
Initial anti-thrombin therapy\: fondaparinux if low bleeding risk and the patient is not undergoing immediate angiography.
Unfractionated heparin can be used for patients with renal impairment.
Supplemental oxygen should be o2
of less than 94%.

Coronary angiography

Coronary angiography is an invasive procedure which utilises intravenous contrast and X-ray imaging to assess coronary
artery patency.
Percutaneous coronary intervention (PCI) involves a thin guide wire being placed in the a
in
A stent is placed around the balloon prior to insertion and will remain in the a
artery patent.
Coronary angiography is required for all clinically unstable adult patients diagnosed with NSTEMI as soon as possible and
at least within 24 hours of becoming clinically unstable.
Clinically unstable patients are de
Ongoing or recurring pain despite treatment
Haemodynamic instability (low blood pressure, shock)
Dynamic ECG changes
Left ventricular failure

Risk strati

After the diagnosis of NSTEMI has been con
using an established scoring system is recommended.
Categorisation based on 6-month mortality of patients diagnosed with unstable angina or NSTEMI aids in providing
appropriate short-term interventions and treatment.
The Global Registry of Acute Cardiac Events (GRACE) scale predicts 6-month mortality for patients admitted with ACS.
Low risk (predicted 6-month mortality \<3%)
For patients who are assessed as low risk, consider conservative management without coronary angiography. However,
younger patients may bene
O
Ticagrelor if bleeding risk not high
Clopidogrel or aspirin only if high bleeding risk
In low-risk patients, consider ischaemia testing before discharge. If ischaemia is present on testing, consider coronary
angiography and possible PCI.
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Left ventricular function should be assessed prior to discharge.
High or moderate risk (predicted 6-month mortality >3%)
If no contraindications, high or moderate risk patients should be o
subsequent PCI if required.
Patients undergoing coronary angiography should be o
Clopidogrel can be used if a patient is receiving ongoing anticoagulation for another indication.
If undergoing PCI, patients should be o
Left ventricular function should be assessed prior to discharge.

Long term management

Long term management of ACS is essentially the same for STEMI and NSTEMIs.
All patients with a diagnosis of NSTEMI, regardless of their risk strati
strategies.
Drug therapy
The following drug regime is recommended for all patients post NSTEMI and STEMI to reduce the risk of future ACS
(secondary prevention) and improve myocardial function\:
ACE inhibitor or ARB\: continued inde
Dual antiplatelet therapy (aspirin plus a second agent)\: for up to 12 months
Beta-blocker for at least 12 months\: continued inde
Statin\: continued inde
Lifestyle
include\:
Lifestyle changes and education are important in reducing the risk of a subsequent cardiovascular event. Advice should
Eating a Mediterranean diet and increasing fruit and vegetable intake
Regular physical activity\: 20-30 minutes a day
Low-risk drinking\: no more than 14 units a week
Smoking cessation
Maintaining a healthy body weight

Cardiac rehabilitation

Cardiac rehabilitation should be o
These programs involve\:
Advice on lifestyle, driving,
Tailored physical activity
Stress management
Health and lifestyle education

Complications

Mechanical complications such as papillary muscle rupture, ventricular aneurysm and free wall rupture are rare post-
NSTEMI.
8
Non-mechanical complications include arrhythmias, thromboembolic complications, heart failure, pericarditis, and
depression.
Though all-cause mortality is higher for STEMI patients vs NSTEMI patients during the initial hospital presentation, there is
evidence that of those surviving hospital discharge, NSTEMIs patients have a worse long-term prognosis.
In 2013, the 180-day all-cause mortality was 7.6%. for cases hospitalised with NSTEMI in the UK.
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References

Basit H, Malik A, Huecker MR. N o n S T S e g m e n t E l e v a t i o n M y o c a r d i a l I n f a r c t i o n . Published January 2020, Available from\:
[LINK]
NICOR, M y o c a r d i a l I s c h e m i a N a t i o n a l A u d i t P r o j e c t , published 10 th
December 2020, available from\: [LINK]
th
Life in the fast lane, M y o c a r d i a l I s c h e m i a , published 16 December 2020, available from\: [LINK]
Chowdhury MEH, Alzoubi K, Khandakar A, Khallifa R, Abouhasera R, Koubaa S, Ahmed R, Hasan A. C o m p a r i s o n o f E C G
c h a n g e s i n S T E M I a n d N S T E M I s . License\: [CC-BY]. Available from\: [LINK]
Stark M, Kerndt CC, Sharma S. Published July 10 th
2020, Available from\: [LINK]
Ishihara M. A c u t e h y p e r g l y c e m i a i n p a t i e n t s w i t h a c u t e m y o c a r d i a l i n f a r c t i o n . Circ J. 2012;76(3)\:563-571. doi\:10.1253/circj.cj-
11-1376
th
NICE, A c u t e c o r o n a r y s y n d r o m e s , published\: 18 November 2020, available from\: [LINK]
Elbadawi A, Elgendy IY, Mahmoud K, et al. T e m p o r a l T r e n d s a n d O u t c o m e s o f M e c h a n i c a l C o m p l i c a t i o n s i n P a t i e n t s W i t h
A c u t e M y o c a r d i a l I n f a r c t i o n . Published September 23 rd
2019, available from\: [LINK]
Gale C. A c u t e c o r o n a r y s y n d r o m e i n a d u l t s \: s c o p e o f t h e p r o b l e m i n t h e U K , Br J Cardiol 2017;24(suppl 1)\:S3–S9, published\:
September 2017, available from\: [LINK]

Reviewer

Dr Nicholas Taylor
Emergency Medicine physician with an interest in acute cardiology
Associate Dean Phase 2 at the ANU Medical School
Dr Simon O’Connor
Cardiologist
Clinical Senior Lecturer at the ANU Medical School

Related notes

Acute Coronary Syndrome (ACS)
Acute Heart Failure
Atrial Fibrillation (AF)
Atrioventricular Block
Brugada Syndrome

Test yourself

Contents

Introduction
Aetiology
Risk factors
Clinical features
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Di
Investigations
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