Anti Platelet drugs

Question 1

what causes artterial thrombosis

Answer 1

lipid deposits in endothelium
damage to endothelium of arteries recruits foamy macrophages rich in cholesterol
forms cholesterol rich plaque
high pressure system causes plaques to rupture
platelets recruited, adhere to expose endothelium and released VWf
platelets become activate - release granules that activate coagulation (more platelets come and form platelet plug)
causes acute thrombosis

Question 2

how do platelets aggregate

Answer 2

via membrane glycoproteins (GPIIbIIIa) and fibrinogen

Question 3

what type of thrombus in aterial disease

Answer 3

platelet rich

Question 4

what is the treatment for arterial thrombosis

Answer 4

aspirin (+ other anti platelet drugs)

modification of risk factors (HPTx, diabetes, smoking)

Question 5

what are atherosclerotic plaques rich in

Answer 5

cholesterol

Question 6

what are stable atherosclerotic plaques like

Answer 6

hyalinised and calcified

cause stable angina (in coronary artery), intermittent claudication (leg artery)

Question 7

what do unstable atherosclerotic plaques cause

Answer 7

when rupture cause: sudden onset of symptoms, unstable angina/ MI
stroke
=acute organ ischaemia and infarction

Question 8

what are the risk factors for arterial thrombosis

Answer 8

(factors that cause damage to the endoethelium, increase in foamy macrophages and platelet activation)

• hypertension (damage to endothelium, platelet activation)
• smoking (endothelium (raises BP), platelets)
• high cholesterol (accumulated in plaque)
• diabetes (endothelium damage, platelets, cholesterol)

Question 9

how do you prevent arterial thrombosis

Answer 9

stop smoking
treat hypertension and diabetes
lower cholesterol
anti platelet drugs

Question 10

how are vessels damaged in Venous thrombosis

Answer 10

valves damaged (not atheromas like in arterial)

Question 11

what do platelets do in arterial disease

Answer 11

adhere at site of injury to exposed collaged with help of VWf
activate and secrete chemicals (ADP, thromboxan A2) which causes aggregation at site of injury

Question 12

how do platelets bind to subendothelial collagen

Answer 12

glycoprotein 1b and VWf

Question 13

what happens in platelet activation

Answer 13

platelets shape alters to expose more phospholipid on the surface-provides a greater surface area for coagulation activation and fibrin production to stabilise the clot

also release of granules (thrombin, thromboxane A2, ADP) which further stimuates platelet activation and recruitment (via ADP receptors on platelet surface)

Question 14

how does aspirin work

Answer 14

inhibits cyclo-oxygenase which is needed to produce throboxane A2 (platelet agonist released from granules, attracts other to site of injury)

Question 15

what are the side effects of aspirin

Answer 15

bleeding
blocks production of prostaglandins:
-GI ulceration (prostaglandins provide protective surface in the stomach, blockage of this more likely to get ulcer, and as on antiplatelet more likely to bleed from this)
-bronchospasm (having asthma a CI to aspirin)

Question 16

what are the type of anti platelet drugs

Answer 16

aspirin (cyclo-oxygenase inhibitor)

clopidogrel and prasugrel (ADP receptor antagonists)

dipyridamole (phosphodiesterase inhibitor: reduces cAMP production which is a second messenger in platelet activation)

abciximab (GP IIb/IIIa inhibitors - inhibit aggregation)

Question 17

when is abciximab or other GP IIb/IIIa inhibitors used

Answer 17

as emergency medication e.g. if having MI surgery

Question 18

how long do anti platelet drugs have an effect for

Answer 18

the whole of affected platelets life span: 7-10 days

stop them 7 days prior to elective operations

Question 19

how can anti platelet drugs be reversed

Answer 19

platelet transfusions

Question 20

Causes organ ischaemia and is an inflammatory disorder instigated by damage to the endothelium
= arterial or venous?

Answer 20

arterial

Question 21

are platelets involved in venous thrombosis

Answer 21

no