Ischaemic Heart Disease Flashcards
What are the causes of atherosclerotic coronary disease?
- chronic coronary insufficiency (angina)
- unstable coronary disease (MI/sudden ischaemic coronary death)
- heart failure
- arrythmia (acute ischaemia/scar related)
What is the subendocardial region?
the water-shed area of perfusion and the first region to become ischaemic
What cusp of the aortic valve becomes the right coronary artery?
right
What cusp of the aortic valve becomes the left coronary artery?
posterior
What are the risk factors for atherosclerotic coronary artery disease?
- age
- hypertension
- hypercholesterolaemia
- smoking
- diabetes
- obesity
- physical inactivity
Describe the different pathologies of atherosclerotic coronary artery disease
- fatty streak
- fibro-fatty plaque
- plaque disruption (rupture/erosion)
Describe the formation of the fatty streak
- endothelial cells that line coronary arteries upregulate
- attaches to monocytes by VCAM-1 adhesion molecules
- transmigrates and becomes macrophage
- ingests lipid in subendothelial space to become foam cell and form fatty streak
Describe the formation of fibro-fatty plaque
- macrophage through interaction with T cells secretes cytokines
- attracts smooth muscle cells from the tunica media to the subendothelial intimal space
- they then secrete fibrin and collagen to make an ECM that is very tough
How is angina represented on an ECG?
depressed ST
What is supply angina?
the mismatch of supply and demand of coronary blood flow
What is demand angina?
the mismatch of supply and demand of myocardial oxygen consumption
What are the 2 regulatory systems that control coronary circulation?
- autoregulation (myogenic control)
- metabolic regulation
Describe autoregulation of coronary blood flow in relation to exercise
- coronary blood flow can increase to accommodate an increase in O2 consumption during exercise
- a rise in HR accounts for 1/3 of increase in blood flow
What are the determinants of myocardial oxygen consumption?
- variable per unit mass of tissue:
- tension development (LV pressure/volume)
- contractility
- HR
- basal activity per unit mass (fixed)
- mass of tissue
Why is angina sometimes unpredictable in determining when it can come on?
variability in coronary blood flow due to factors (time of day/induced by the cold etc)
How can you anatomically assess for the identification of coronary heart disease?
- CT coronary angiography
- invasive angiography
What tests can you carry out to identify inducible ischaemia?
- exercise stress test
- dobutamine stress echo
- myocardial perfusion imagine with exercise/pharmacological stress
- cardiac MRI
How can angina be treated?
- therapeutically to reduce myocardial oxygen consumption
- improve coronary flow reserve through percutaneous coronary intervention/CABG/vasodilator drugs
What vessels are used for CABG?
- saphenous vein
- left internal mammary artery
What are the main causes of MI?
- plaque rupture
- plaque erosion
Explain how complete occlusion of a vessel can occur
- rupture/erosion of plaque
- tissue blood doesn’t normal see is exposed and results in blood clotting
- arteries adhere platelets which then contract and change shape
- exposed to prothrombinase complex leading to more clotting
- thrombus occludes vessel and propagates downstream which seals vessel
- complete epicardial coronary occlusion
Describe the pathology of an unstable plaque
- macrophage changes
- instead of directing healing factors to make a strong cap secretes MMPs that digest the matrix
- weak and vulnerable
- platelets adhere
What are the factors that can modify the presentation of an acute MI?
- time of the day
- inflammatory activity
- infection
- elevation in BP
- catecholamines
What are the different ways of classifying MI?
- by site of infarction (transmural/subendocardial)
- by ECG (STEMI/NSTEMI)
- by cause (type 1-5)
