Ischaemic Heart Disease Flashcards
What is the subendocardial region?
- Between the epicardium and endocardium
- Least well supplied area for oxygen
- First area to become ischaemic
What are the 3 main coronary artery imaging techniques?
- Selective coronary angiography
- CT
- MR imaging
Describe the basic pathology of coronary artery disease
- Fatty streak
- Fibro-fatty plaque
- Plaque disruption
Plaque disrupture
Plaque erosion
What do macrophages become in the sub-endothelial layer when they uptake oxidised LDL?
Foam cells
What is the hallmark cell of a fatty streak?
Foam cells
What do foam cells release?
Cytokines and growth factors that recruit smooth muscle cells which then produce collagen
What is the cause of angina?
Sub-endocardial ischaemia
What does angina appear like on an ECG?
ST depression
What is angina due to
When the coronary blood flow is not sufficient enough to meet the oxygen demands of myocardial tissue
What is the basis of angina pectoris?
Epicardial coronary artery stenoses. Atherosclerotic plaque limiting coronary blood flow.
What are the two broad regulatory features of the coronary system?
- Autoregulation (myogenic control)
- Metabolic regulation
How much does coronary blood flow increase to accomodate a 20 fold increase in total body O2 consumption?
Can rise five fold (400 ml/min/100g)
What molecule is an extremely powerful coronary vasodilator?
Adenosine
What is the coronary flow reserve?
The maximum increase in blood flow through the coronary arteries above normal resting volume
What is the effect of angina on the coronary flow reserve?
Reduced
What determines myocardial oxygen consumption?
- Tension development
- Contractility
- HR
- Basal activity (10-20%)
- Mass of tissue
What causes the variancy in stable angina (why on some days does it occur frequently and others not)?
The variable coronary flow reserve
What tests are performed to test inducible ischaemia?
- Exercise stress test
- Dobutamine stress echo
- Myocardial perfusion imaging with either exercise or pharmacological stress
- Cardiac magnetic resonance imaging (cMR) (flow)
When investigating chest pain what are you looking for?
- Anatomical assessment
- Test of inducible ischaemia
- Measuring coronary flow reserve
What artery is often used in a CABG oprocedure to bypass an occluded portion of the LAD artery?
The left internal mammary artery
What are the two primary domains for treating angina?
- Reduction in myocardial oxygen consumption
- Reduction in the variability of coronary flow reserve
What are the main causes of myocardial infarction?
- Plaque rupture (~75%)
- Plaque erosion (~30%)
- Coronary embolism
- Coronary artery spasm (cocaine)
- Coronary anomaly
- Spontaneous coronary dissection
What group of people are susceptible to spontaneous coronary dissection?
Pregnant women
Describe how a plaque causes an MI (pathology)?
- Cause coronary thrombosus
- Plaque becomes exposed to blood
- Platelets adhere to the plaque activating coagulation
- This creates platelet rich thrombi which blocks the artery
- Blocks artery creating a propogation thrombus down through the artery
What are light bands through platelet rich thrombi called?
Bands of Zahn
How is coagulation triggered inside arteries to create an MI at a molecular level?
Macrophages produce MMPs which digest the fibrous cap. Macrophages themselves produce tissue factor which triggers the activation of the extrinsic pathway of coagulation.
What factors affect presentation of an AMI?
- Time of day (morning)
- Inflammatory activity (rheumatoid artheritis)
- Infection (respiratory) (pneumonia)
- Elevation of bp
- Catacholamines
How can MIs be classified?
- Full thickness, transmural or sub enocardial (site)
- STEMI or NSTEMI
- Type 1 - 4 (Cause)
What is the difference in affect of STEMIs and NSTEMIs?
- STEMI inplies transmural MI
- NSTEMI will include subendocardial infarction but does not exclude transmural infarction in regions remote from ECG.
What is a type 1 MI?
- Spontaneous
- Related to ischaemia due to coronary event such as plaque erosion and/or rupture, tissuring or dissection
What is a type 2 MI?
- MI secondary to ischaemia due to either increased oxygen demand or decreased supply
What is a type 3 MI?
Sudden unexpected cardiac death often with symptoms suggestive of MI
What is a type 4 MI?
MI associated with percutaneous coronary intervention or stent thrombosis
What is a type 5 MI?
MI associated with cardiac surgery
Are STEMIs or NSTEMIs more common amongst older people?
NSTEMIs peak incidence rate is 10 years older than STEMIs
What are the serum markers of Myocardial damage?
- Troponin T or 1
- Creatine kinase MB isoform (CKMB)
- Creatine Phosphokinase (CPK)
- AST
- Myoglobin
What medications are usually administered with a STEMI?
- Aspirin + clopidogrel or other antiplatelet (P2Y12 inhibitor).
Thrombolysis (streptokinase)
What procedure is used to treat a STEMI?
Primary PCI for immediate vascularisation
What medications are given after anti-platelets agnests and revascularisation?
- Statin drugs
- Ace inhibitors
- Beta blockers
What are the immeadiate complications of a STEMI?
- Ventricular arrhythmia and death
- Acute left heart failure
What are the early complications of a STEMI (day 2-7)
- Myocardial rupture
- Mitral valve insufficiency
- VSD
- Mural thrombus and embolisation
What are the late (beyond day 7) complications of a STEMI?
- LV dilation and HF
- Arrhythmia
- Recurrent MI
What is an NSTEMI caused by?
- Threatned STEMI
- Small branch occlusion
Occlusion of well collateralised vessel - Lateral STEMI in territory not well seen by ECG
- Implies sub-endocardial ischaemia
How does the treatment differ between an NSTEMI and a STEMI?
Same except angiography and revascularisation can be delayed slightly in NSTEMI
When would an NSTEMI be treated early?
- If symptoms continue
- If roponin raised
- Risk score (e.g GRACE)
