20. Coronary Heart Disease Flashcards
How does coronary artery disease present?
1) Sudden cardiac death
2) Acute coronary syndrome (acute MI, unstable angina)
3) Stable angina pectoris
4) Heart failure
5) Arrhythmia
Patients who present with sudden onset chest pain fall into what two categories?
Myocardial infarction
Progressive (unstable) angina
What can coronary artery disease lead to?
Heart failure
What does damage to the heart muscle lead to?
scar tissue formation within the myocardium
What does scar tissue in the myocardium a substrate of?
arrhythmia which in turn is the main substrate for sudden cardiac death
What is the number one cause of death world wide?
CVD
What type of angina has its incidence increasing?
Stable agina
How many cases of stable angina are there in the UK?
2 million
How many deaths per year are caused by CVD?
17 million
Define myocardial ischaemia
The mismatch between myocardial oxygen supply and demand. There is a primary reduction in blood flow where there is an inability to increase blood flow to match an increase in metabolic demand.
What are the main conductance vessels of the coronary circulation
Epicardial coronary arteries
What is the main function of the coronary circulation?
1) To make sure that over a wide range of perfusion pressures, flow remains constant -autoregulation
2) To make sure that coronary blood flow matches myocardial demand
How is coronary resistance divided in the large arteries?
50%
How is the coronary resistance divided in the smaller arteries and capillaries
50%
What is the resistance in the smaller arteries in the myocardium compared to the larger arteries outside?
Equal
What happens to the epicardial component when there is stenosis?
The resistance in the epicardial component increases
What happens to the intramyocardial resistance vessels when there is epicardial stenosis?
There is an increase in the diameter of the intramyocardial resistance vessels - thus decreasing the resistance in the intramyocardial component in maintain flow
What happens when the stenosis increases?
The resting blood flow remains unchanged up until a stenosis of greater than 70%.
What is the coronary flow reserve?
The ratio of
Resting blood flow:Blood flow achieved under maximal stress
Define coronary flow reserve
The ability to the coronary circulation to adapt to an increasing demand in the face of an increasing epicardial coronary stenosis
When does resting blood flow start to decrease?
At a stenosis of greater than 70% the coronary blood flow decreases rapidly
At what stage does the ability to maintain the requisite amount of flow needed under stressful conditions start to become impaired?
50% stenosis
Describe the symptoms of angina pectoris?
Tight feeling in the chest which can diffuse across the jaw, shoulders, back or arms
What can provoke angina pectoris?
Physical exertion, emotional stress or anxiety
How can you treat angina pectoris?
Use of an inorganic nitrate vasodilator which acts as a vasodilator. Reduces coronary resistance = increasing blood flow
It can also be relieved by rest
What is an example of a inorganic nitrate vasodilator?
glyceryl trinitrate
How would you perform a functional test for coronary artery disease?
Demonstrating that there is an imbalance between supply and demand
How would you perform a anatomical test for coronary artery disease?
Look at anatomical severity of the narrowing within the artery then make an inference about how it is compromising flow
Give examples for functional non-invasive tests for CHD?
Exercise ECG
Stress echo/cardiac MRI
Give examples for functional invasive tests for CHD?
CFR
Pressure wire
Both require ionising radiation