week 2 Flashcards
define atheroma
the accumulation of intracellular and extracellular lipids in the intima of large and medium sized arteries
name the 3 macroscopic features of an atherosclerotic plaque
fatty streak
simple (fibrous) plaque
complicated plaque
what is a fatty streak and what causes it
a slightly elevated zone on the arterial wall caused by accumulation of (a small number of) lipid cells
what is a simple (fibrous) plaque
accumulation of lipids both free and in cells
smooth muscle cells migrate from the media
fibrosis develops around the lipid and forms a cap over the lesion
what is a complicated plaque and what can it lead to
ulcers and fissures of the fibrous can expose plaque contents
can result in thrombosis
what is atherosclerosis
thickening and hardening of arterial walls as a consequence of atheroma
results from accumulation of lipid, connective tissue, inflammatory cells and smooth muscle cells in the intima
which layer of the artery has the most mechanical strength
medial (middle) layer
how does plaque develop
not fully understood thought to be a response to injury- initiated by endothelial dysfunction
name the 3 main components of plaques
lipid containing macrophages
extracellular matrix
cells, proliferating smooth muscle
describe how LDL is removed from circulation
- removed by LDL receptors and scavenger cells (macrophages)
- 70% is removed via LDL receptor pathway
where are most LDL receptor located- why is this significant
hepatocytes
hence liver is very important in LDL metabolism
what do scavenger cells do to LDL
when do they do this?
oxidise it
this happens when the patients diet contains a high level of trans fats, they smoke or have poorly controlled diabetes
how is hyperlipidaemia related to plaque formation
- when LDL becomes oxidised it enters the endothelium and may alter endothelium permeability
- this promotes accumulation of lymphocytes, dendritic cells and macrophages
- platelets can stick to areas of inflammation and cause hardened areas- called plaques
- oxidised cholesterol loaded macrophages forms a ‘foam cell’ and the plaque gets thicker
- macrophages release growth factors which recruit smooth muscle- these may form a cap around the plaque
non drug prevention of plaque formation
- smoking cessation
- reduce fat intake
- high intake fruit+veg
- alcohol in moderation
- regular exercise and weight management
MOA of aspirin
thromboxane A2 - platelet agonist produced by platelets
- aspirin bocks production of thromboxane A2 by inhibiting the platelet enzyme responsible for its synthesis- COX1
- action of aspirin on COX1 is permanent- lasting the lifetime of platelet (7-10 days)
clopidogrel mode of action
clopidogrel is an irreversible inhibitor of ADP (a platelet agonist produced and released by platelets) receptor on platelets (P2Y12 receptors) and so prevents ADP from activating platelets
statin MOA
HMG-coA reductase inhibitors- HMG-coA is involved in the synthesis of cholesterol
so statins reduce cholesterol synthesis in the liver and increase LDL-cholesterol clearance from the blood
(- given at bedtime because cholesterol synthesis is cyclical with greatest production during fasting states)
antiplatelet antithrombotic functions (3)
adenosine diphosphatase (degrades ADP from platelets)
prostacyclin (produced by the enzyme cyclooxygenase)
nitric oxide
anticoagulant antithrombotic functions (3)
heparin-like molecules (activate antithrombin 3)
thrombomodulin (activates protein C)
protein S
fibrinolytic antithrombin functions
prevents blood clots from growing
t-PA
procoagulant functions (3)
- production of vWF
- production of tissue factor
- binding of factors IXa and Xa
platelet adhesion and activation
- adherent platelets release ADP and thromboxane A2
- ADP and thromboxane A2 are platelet agonists, activate more platelets and recruit them to site of vascular injury
how long can a prescriber take to give a physical Rx after an emergency supply done over the phone, email or fax
72h
what is the maximum quantity a prescriber can give via an emergency supply
any quantity
which CD schedules can be given via emergency supply- prescriber request
schedule 4 (ie zopiclone) and 5 (ie co-codamol)
what is the max quantity that can be given via a emergency supply- patient request
30 days treatment
POM register requirements
- entry to be made day of supply or next day
- prescription date
- medicine details
- prescriber details
- patient details inc why supply was needed (if patient request)
- must be kept for 2 years from last entry
- if CD - only needs to go in CD register
- don’t need to put oral contraceptives in it
CPUS - patient eligibility (4)
- registered with Scottish GP practice - even if temp
- item has previously been prescribed
- if second supply in a row- shouldn’t really do it
- can give up to 1 repeat cycle so if patient normally gets 2 months - we can give this
define ischaemia
insufficiency in blood supply- coronary arteries are the only source of blood for heart muscle- if these are blocked the blood supply to the heart will reduce- resulting in chest pain called angina
what is the cause of angina
angina is the result of ischema caused by an imbalance between myocardial blood supply and oxygen demand
when does stable angina occur
occurs when coronary perfusion is impaired by fixed or stable atheroma or coronary arteries
name the 6 different stable anginas
- exertional angina
- anginal equivalent syndrome
- syndrome x
- silent ischemia
- decubitus angina
- nocturnal angina
exertional angina
*Arises from an increase in myocardial oxygen demand during exertion or emotion. Relief occurs by rest and nitroglycerine.
*Coronary artery obstructions are not sufficient to result in resting myocardial ischemia.
anginal equivalent syndrome
- Caused by myocardial ischemia
- Symptoms= shortness of breath or pain at a site- other than the chest (eg arm/ jaw)
syndrome x
- Typical, exertional angina with positive exercise stress test
- Anatomically normal coronary arteries
- Reduced capacity of vasodilation in microvasculature
- Long term prognosis is very good
silent ischemia
- very common
- More episodes of silent than painful ischemia in the same patient
- Difficult to diagnose
- Holter monitor (records heart rate and rhythm over a 24-hour period )
- Exercise testing
decubitus angina
- chest pain only occurs while lying down
- Usually associated with impaired left ventricular function
- Patient usually has severe coronary artery disease
- Occurs because gravity redistributes fluid in the body- which makes the heart work harder
nocturnal angina
- Awakes patient from sleep
- May be provoked by vivid dreams
- It may occur due to coronary artery spasm
unstable angina
- Is characterised by rapidly worsening chest pain on minimal exertion or rest
- Is associated with an ulcerated atheroma and thrombus formation- this produces a greater reduction of coronary blood flow to produce angina at rest
Prinzmetals
- Coronary artery spasm- sudden involuntary contraction of smooth muscle tissue of coronary artery
- Spasm temporarily narrows the coronary artery
- Causes transient impairment of coronary blood supply
- Not due to atherosclerosis or platelet aggregation
- Usually occurs at rest
- Majority of patients have an atherosclerotic plaque but is it often minor when compared to extent of pain
- Long term prognosis is very good
what are the 3 common causes of angina
- atherosclerosis with blood clot
- atherosclerosis
- spasm
cause of prinzmetal’s angina
coronary spasm
cause of syndrome X- microvascular angina
abnormal contraction or deficient endothelial- dependent relaxation of resistant vessels associated with diffuse vascular disease
define class one angina
angina only during strenuous or prolonged physical activity
define class two angina
light limitation with angina only during vigorous physical activity
define class three angina
moderate limitation - symptoms with everyday living activities
define class four angina
severe limitation
inability to perform any activity without angina or angina at rest
define exercise testing of angina
goal- is to induce a controlled, temporary ischemia state during clinical ECG observation (ST segment depression occurs with ischemia and reverses after ischemia disappears
normally treadmill/ bicycle - incline+ speed increase every 3 min
unstable angina characteristics
- angina at rest, not responding to therapy
- recent onset, less than 1 month
- increased frequency and duration of episode
- may be a serious indicator of an impending heart attack
why do plaques rupture
interplay between plaque vulnerability and external stresses
depends on plaque composition rather than plaque size
plaques rich in soft extracellular lipids are vulnerable to rupture- presence of smooth cells may provide resistance to rupturing
SIGN guidlines- first line for angina
beta blocker - bisoprolol 5mg once daily
can also give GTN spray too - to be used for immediate relief or before activities known to trigger
SIGN guidelines- second line for angina
if B blocker maxed out or in-tolerated - add or swap to calcium channel blocker ie nicorandil- 5mg 2x daily