CVS Lecture 18 - Coronary heart disease (CHD), Angina, Myocardial infarction (MI) and Embolism Flashcards
How is coronary artery disease presented?
Sudden cardiac death, heart failure, arrhythmia, acute coronary syndrome (acute MI and unstable angina)
What happens to patients who present with sudden onset of chest pain?
They are classified into 2 groups: Unstable angina or MI
What are the risk factors for CAD?
Tobacco, physical inactivity, harmful use of alcohol, unhealthy diet
What is the problem with risk factors for CAD?
Although one risk factor can cause it, if many together, then risk is multiplicative
What happens if you have CAD?
Damage of the heart muscle, can lead to HF, scar tissue formation in myocardium > can lead to arrhythmia and then sudden cardiac death
Epidemiology of CVD:
No. 1 cause of death worldwide, leading cause of death in women, accounts for 17M deaths per year
How does CHD burden the UK?
Commonest cause of premature death, 88,000 deaths/year
MI statistics for UK
190,000 MI/year, 33,000 deaths/year - 6% of all deaths in UK, £3.6b/year
Epidemiology of stable angina
^ incidence and prevalence, 2M cases in UK, 67,000 PCIs/year, 45K admission to hospital and 65K bed days
What are PCIs?
Percutaneous coronary intervention which is the same as a coronary angioplasty which is a catheter moves up the coronary artery and a stent is placed to open that artery
What is myocardial ischemia?
Mismatch between oxygen demand and supply in the myocardium
What is MI caused by?
A primary reduction in blood flow (blockage) or inability to increase blood flow to match ^ metabolic demand
What are the main roles of epicardial coronary arteries?
Conductance vessels which are dependent on arterial blood pressure
How are nutrients and O2 delivered to the myocardium?
Big conduit arteries are divided into smaller arterioles, which divide into the myocardium
What happens when BP changes?
Arterioles dilate/constrict depending on BP - subject to vasoconstriction/dilation from autonomic nervous system
What causes the changes in capillary resistance?
Myocardial metabolic stimuli
What is the job of the coronary circulation?
Autoregulation - to make sure that flow remains constant over wide range of perfusion pressures To match coronary blood flow to myocardial demands
What is the usual resistance between arteries and the intramyocardial arterioles/capillaries?
Usually they are equal pressure
What happens when the artery is blocked by a atherosclerotic plaque - stenosis?
The pressure in the epicardial part is higher than that in the intramyocardial part
What effect can the pressure difference between the intramyocardial and epicardial have?
There is a compensation by increasing the diameter of the intramyocardial resistance vessels up to around 70% blockage. As stenosis ^, blood flow remains unchanged because the intramyocardial vessels can’t dilate further, so coronary blood flow decreases rapidly
What is the coronary flow reserve ratio?
Resting blood flow: blood flow achieved under maximal stress
What is coronary flow reserve?
The ability of the coronary circulation to adapt to increasing demand due to ^ epicardial coronary stenosis
Around what % stenosis is there an impairment of ability to maintain blood flow needed under stressful conditions?
50% stenosis
What is flow response equation?
Peak stress/normal resting blood flow
What is angina pectoris?
Clinical diagnosis based on symptoms: tight feeling in the chest, jaw, shoulder, arm or back provoked by stress/exertion
How can angina pectoris be relieved?
By rest or Inorganic nitrate vasodilator (reduces coronary resistance and ^ blood flow, reversing the supply/demand imbalance)
How do you confirm stable CHD diagnosis?
Determine myocardial ischemia
How do you assess future adverse cardiovascular events risk?
The burden of MI, autonomic severity of CAD, Left ventrical function
What are the functional tests for CAD?
Demonstrate imbalance between supply and demand
What are the anatomical tests for CAD?
Look at severity of narrowing of the artery and make inference about how flow is compromised
What are the functional tests for CHD? *anything after means exposure to ionising radiation
Non-invasive: Exercise ECG, Stress echo, Stress cardiac MRI, *CT, Stress nuclear MPS, FFRct Invasive: *CFR, FFR (pressure wire), iFR, IVUS, OCT