Acute coronary
syndrome
NOTES
Overview
Acute coronary syndrome (ACS) refers to three
states of myocardial ischaemia: unstable angina
(UA), non-ST elevation myocardial infarction
(NSTEMI) and ST elevation myocardial infarction
(STEMI).
ACS is a medical emergency requiring urgent admission. Around
100,000 people are admitted with ACS in the UK each year.
Atherosclerosis represents the most significant aetiological factor.
Classification
ACS is classified into one of three conditions according to clinical
features, ECG findings and cardiac enzymes:
1. STEMI: ST-segment elevation or new-onset left bundle branch
block and raised troponins.
2. NSTEMI: Non-specific signs of ischaemia or normal ECG,
raised troponins.
3. UA: Characteristic clinical features, non-specific signs of
ischaemia or normal ECG, normal troponins.
,Definition
A myocardial infarction (MI), which is more colloquially known as a
'heart attack', refers to death of cardiac tissue (i.e. myocardial
necrosis).
MI is defined as 'evidence of myocardial necrosis in a clinical
setting consistent with acute myocardial ischaemia'. For the
diagnosis, it requires the detection of a cardiac biomarker (e.g.
troponin) to show a rise and/or fall with at least one value above
the upper limit for normal (ULN).
In addition, there should be at least one of the following:
• Symptoms of myocardial ischaemia (e.g. chest pain)
• New or presumed new ECG changes: ST-T wave changes
or new LBBB
• Development of pathological Q waves
• Imaging evidence of infarction: loss of viable myocardium
or new motion abnormality
, • Angiography or autopsy evidence of thrombus
Aetiology
ACS is typically triggered by rupture of an
atheromatous plaque in the coronary arterial wall.
Atherosclerosis is the predominant cause of ACS. Atherosclerosis
leads to narrowing of the coronary vessels, which supply the heart.
Narrowing secondary to atherosclerosis is known is coronary artery
disease (CAD) or ischaemic heart disease (IHD).
CAD/IHD can lead to angina, which refers to typical chest pain
from myocardial ischaemia when there is an increase in the
oxygen supply/demand (e.g. on exertion). This quickly improves on
rest. If an atheromatous plaque ruptures, it leads to thrombus
formation and acute occlusion that causes ACS (i.e. leads to
myocardial necrosis, ECG changes and typical symptoms). See
pathophysiology.
Risk factors
There are a number of risk factors that increase the chance of
developing atherosclerosis, they may be divided into modifiable
and non-modifiable risk factors.
Modifiable risk factors:
• High cholesterol
• Hypertension
• Smoking
• Diabetes
syndrome
NOTES
Overview
Acute coronary syndrome (ACS) refers to three
states of myocardial ischaemia: unstable angina
(UA), non-ST elevation myocardial infarction
(NSTEMI) and ST elevation myocardial infarction
(STEMI).
ACS is a medical emergency requiring urgent admission. Around
100,000 people are admitted with ACS in the UK each year.
Atherosclerosis represents the most significant aetiological factor.
Classification
ACS is classified into one of three conditions according to clinical
features, ECG findings and cardiac enzymes:
1. STEMI: ST-segment elevation or new-onset left bundle branch
block and raised troponins.
2. NSTEMI: Non-specific signs of ischaemia or normal ECG,
raised troponins.
3. UA: Characteristic clinical features, non-specific signs of
ischaemia or normal ECG, normal troponins.
,Definition
A myocardial infarction (MI), which is more colloquially known as a
'heart attack', refers to death of cardiac tissue (i.e. myocardial
necrosis).
MI is defined as 'evidence of myocardial necrosis in a clinical
setting consistent with acute myocardial ischaemia'. For the
diagnosis, it requires the detection of a cardiac biomarker (e.g.
troponin) to show a rise and/or fall with at least one value above
the upper limit for normal (ULN).
In addition, there should be at least one of the following:
• Symptoms of myocardial ischaemia (e.g. chest pain)
• New or presumed new ECG changes: ST-T wave changes
or new LBBB
• Development of pathological Q waves
• Imaging evidence of infarction: loss of viable myocardium
or new motion abnormality
, • Angiography or autopsy evidence of thrombus
Aetiology
ACS is typically triggered by rupture of an
atheromatous plaque in the coronary arterial wall.
Atherosclerosis is the predominant cause of ACS. Atherosclerosis
leads to narrowing of the coronary vessels, which supply the heart.
Narrowing secondary to atherosclerosis is known is coronary artery
disease (CAD) or ischaemic heart disease (IHD).
CAD/IHD can lead to angina, which refers to typical chest pain
from myocardial ischaemia when there is an increase in the
oxygen supply/demand (e.g. on exertion). This quickly improves on
rest. If an atheromatous plaque ruptures, it leads to thrombus
formation and acute occlusion that causes ACS (i.e. leads to
myocardial necrosis, ECG changes and typical symptoms). See
pathophysiology.
Risk factors
There are a number of risk factors that increase the chance of
developing atherosclerosis, they may be divided into modifiable
and non-modifiable risk factors.
Modifiable risk factors:
• High cholesterol
• Hypertension
• Smoking
• Diabetes
