Cardiology: Acute Coronary Syndrome Flashcards
What usually causes acute coronary syndrome (ACS)?
The result of a thrombus from an atherosclerotic plaque blocking a coronary artery
What is a arterial thrombus mainly made of?
Platelets
Mainstay of treatment of arterial thrombi?
How does this differ from venous thrombi?
Arterial –> antiplatelets e.g. aspirin, clopidogrel and ticagrelor
Venous –> anticoagulants e.g. DOACs, heparin
What are the 3 types of ACS?
1) Unstable angina
2) ST-elevation myocardial infarction (STEMI)
3) Non-ST-elevation myocardial infarction (NSTEMI)
What does the right coronary artery supply?
1) Right atrium
2) Right ventricle
3) Inferior aspect of the left ventricle
4) Posterior septal area
What does the left coronary artery become?
Left circumflex artery and left anterior descending artery.
What does the left anterior descending (LAD) supply?
Travels down the middle of the heart and supplies:
1) Anterior aspect of the left ventricle
2) Anterior aspect of the septum
What does the circumflex artery supply?
Curves around the top, left and back of the heart and supplies the:
1) Left atrium
2) Posterior aspect of the left ventricle
ACS generally develops in patients who have ischaemic heart disease (IHD).
What is IHD?
IHD is a term synonymous with coronary heart disease and coronary artery disease.
It describes the gradually build up of fatty plaques within the walls of the coronary arteries.
There are 2 main problems:
1) Gradual narrowing –> less blood and therefore oxygen reaching the myocardium at times of increased demand (angina)
2) Risk of sudden plaque rupture –> may lead to sudden occlusion of the artery. This can result in no blood/oxygen reaching the area of myocardium.
Changes seen in IHD:
1) initial endothelial dysfunction is triggered by a number of factors such as smoking, hypertension and hyperglycaemia
2) this results in a number of changes to the endothelium including pro-inflammatory, pro-oxidant, proliferative and reduced nitric oxide bioavailability
3) fatty infiltration of the subendothelial space by low-density lipoprotein (LDL) particles
4) monocytes migrate from the blood and differentiate into macrophages.
These macrophages then phagocytose oxidized LDL, slowly turning into large ‘foam cells’. As these macrophages die the result can further propagate the inflammatory process.
5) smooth muscle proliferation and migration from the tunica media into the intima results in formation of a fibrous capsule covering the fatty plaque.
What is 1st step of atherosclerosis?
initial endothelial dysfunction is triggered by a number of factors such as smoking, hypertension and hyperglycaemia
What infiltrates the subendothelial space in atherosclerosis?
low-density lipoprotein (LDL) particles (fatty infiltration)
What are foam cells?
Foam cells are a type of cell that contain cholesterol:
1) monocytes migrate from the blood and differentiate into macrophages
2) These macrophages then phagocytose oxidized LDL, slowly turning into large ‘foam cells’.
3) As these macrophages die the result can further propagate the inflammatory process.
Symptoms of ACS?
Main feature is central, constricting chest pain.
This is often associated with:
1) Pain radiating to the jaw or arms
2) Nausea and vomiting
3) Sweating and clamminess
4) Feeling of impending doom
5) Shortness of breath
6) Palpitations
These symptoms should continue at rest for more than 15 minutes.
What is a silent MI?
when someone does not experience typical chest pain during acute coronary syndrome
Who is at risk of a silent MI?
Diabetics, elderly
What are the 2 most important investigations when assessing a patient with chest pain?
1) ECG
2) cardiac markers e.g. troponin
What are the 2 main ECG changes in a STEMI?
1) ST-segment elevation
2) New left bundle branch block
What are the 2 main ECG changes in an NSTEMI?
1) ST segment depression
2) T wave inversion
What do pathological Q waves indicate?
When do they appear?
Suggest a deep infarction involving the full thickness of the heart muscle (transmural)
Typically appear 6 or more hours after the onset of symptoms.
Which artery supplies the anterior aspect of heart?
Left anterior descending
Which artery supplies the anterolateral aspect of heart?
Left coronary artery
Which artery supplies the lateral aspect of heart?
Circumflex
Which artery supplies the inferior aspect of heart?
Right coronary artery
What leads can ECG changes be seen in and what artery is affected for the following aspects of the heart:
a) anterior
b) inferior
c) lateral
d) anterolateral
a) V1-V4, left anterior descending
b) II, III, aVF, right coronary
c) I, aVL, V5-V6, left cirumflex
d) I, aVL, V3-V6, left coronary artery
An MI affecting the left anterior descending would cause ECG changes in which leads?
V1-V4
An MI causing changes in leads II, III and aVF indicates damage to what aspect of the heart?
Inferior (right coronary artery)
An MI affecting the circumflex would cause ECG changes in which leads?
I, aVL, V5-V6
What is troponin?
Troponin is a protein in cardiac muscle (myocardium) and skeletal muscle.
What does a rise in troponin indicate?
myocardial ischaemia (released from the ischaemic muscle tissue)
Troponin results are used to diagnosse which type of ACS?
NSTEMI (they are not required to diagnose a STEMI, as this is diagnosed based on the clinical presentation and ECG findings)
A high troponin or a rising troponin on repeat tests, in the context of suspected ACS indicates what?
NSTEMI
Troponin is a non-specific marker, meaning that a raised troponin does not automatically imply acute coronary syndrome.
What are some other causes of a raised troponin?
1) CKD
2) Sepsis
3) Myocarditis
4) Aortic dissection
5) Pulmonary embolism
Investigations in ACS?
1) ECG
2) Cardiac markers e.g. troponin
3) Baseline bloods, including FBC, U&E, LFT, lipids and glucose
4) CXRto investigate for pulmonary oedema and other causes of chest pain
5) Echocardiogram once stable to assess the functional damage to the heart, specifically the left ventricular function
What investigation can be done once stable to assess the functional damage to the heart in ACS?
Echo (specifically the left ventricular function)
a STEMI can be diagnosed when the ECG shows either:
1) ST elevation
2) New left bundle branch block
How is an NSTEMI diagnosed?
When there is a raised troponin, with either:
1) A normal ECG
2) Other ECG changes (ST depression or T wave inversion)
When is unstable angina diagnosed?
When the symptoms suggest ACS, the troponin is normal, and either:
1) A normal ECG
2) Other ECG changes (ST depression or T wave inversion)