D.7 Drug-eluting stents Flashcards
Breifly describe what chronory heart disease is
Hearts blood supply is blocked or interupted by a build-up of plaque (fatty deposits (cholesterol), white blood cells ad other substances in the coronary arteries
What is CABG and what does it involve?
Coronary artery bypass graft:
Surgical procedure that diverts blood around narrowed or clogged parts of the major arteries, to improove blood flow and oxygen supply ot the heart
What is PTCA?
Percutaneous transluminal coronary angioplasty aka angioplasty:
Ballon procedure to open and obstruction or narrowing of a blood vessel
Less invasive and prefered
What is the main problem with POBA?
plain old ballon angioplasty:
Restenosis (renarrowing of the artery)
What are the 2 main mechanisms of restenosis?
Elastic recoil:
- Depends on the presence of elastin in the arterial wall.
- Passive process that occurs in seconds to minutes as a result of elastic laminae applying opposing force to overstrech cause of ballone inflation.
- Reduced lumen by up to 40%
Neointimal and smooth mucle hyper:
- reaction of immune system to the intrusion of angioplasty following damage incurred on the epithelial barrier at the site of ballon inflation
- remodelling of the arterial wall and neoitimal growth associated with smooth muscle cell proliferatyion produce a smaller overall vessel size.
What is a stent ?
A small mesh tube that is used to treat narrow or weak arteries
Stents eliminate tge concern of POBAs elastic recoil
What do bare metal stents (BMS) differ in ?
Composition
Architectual disign
Delivery system
What is the advantage and disadvantage of BMS?
No elastic recoil
The incidence of restenosis dropped to around 25% of patients, in-stent restenosis, surfaced within 3-6 months after surgery due to excessive neointima stent coverage
What is the the aim of drug-eluting stents?
Minimise neointimal and smooth muscle hyperplasia (growth)
Where would the drug within the stent reside and what are the different layers within the drug-eluting stent
Stent platform (bare metal) inner most layer
Outer most layer called the polymer matrix where the drug would reside
How does the release of drugs occure in drug-eluting stents?
Drug release occurs by slow diffusion of drug from, ther polymer matrix, this provides local delivery of drug and minimised side effects
What is the goal of the drug in drug-eluting stents DES?
Slows dpwn and controls intimal healing
This means that less sm groth will occure meaning to less chance of blood vessels narrowing again.
What procedure (ballon angioplasty, bare metal stent, drug-eluting stent) has the highest chance of restenosis and highest mortality rate ?
Ballon angioplasty
Bare metal stent
Drug-eluting stent
What are the advantages of DES vs BMS?
DES over BMS significantly reduce the risk of restenosis
What is the disadvantage of DES vs BMS?
More costly
Prolonged dual antiplatlet therapy after DES implantation
What is stent thrombosis?
Rare conditon that occurs when a blod clot forms on the surface of a stent, raising the risk of blood flow in artery to become reducedd or cut off
What are the time based classification of stent thrombossis
Acute stent thrombosis
Subacute stent thrombosis
late stent thrombiosis
very late stent thrombosus
Why may stent thrombosis happen?
When stent is inserterd into the artery dam,age may occure in the blood lining
Clots may form during ther healing process
What has a stent has a quicker healing process and why?
BMS has a quicker healting proices than DES.
DES release drug that slows down and controls the healing of the stent to prevent restenosis. This means that the healing of the artery walls will reduce to prevent ther risk of renarrowing
What can be used to prevent clots from forming after the incertion of a stent?
Dual antiplatlet therapy
Aspirin + either clopidogrel ir prasugrel
How long should antiplatlet therapy be used in BMD and DES
BMS at least one moth after procedure
DES at least a year after procedure
What are the benefits of second gen DES?
Decrease neoitimal response and more rapid re-endothelialisation
- Thinner strut stent backbone (less chances of restenosis)
- less inflammatory
- more biocompatible
- lower drug dosing
What are the major issues with fully biodegradable stents?
Lack of radio-opacity, which necessitates re=adio-opaque stent markers
reduces rafical force as compared with tainless necessitating thinnerr stent strunts
Reduces abilioty of stents to be deformed
When should BMS be considered?
Patients with low risk of restenosis
patients with a bleeding condition
patients who require coronary revascularization before undergoing a surgical procedure
patients at risk of late drug ecluting stent thrombosis
