D.7 Drug-eluting stents

Question 1

Breifly describe what chronory heart disease is

Answer 1

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

Question 2

What is CABG and what does it involve?

Answer 2

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

Question 3

What is PTCA?

Answer 3

Percutaneous transluminal coronary angioplasty aka angioplasty:

Ballon procedure to open and obstruction or narrowing of a blood vessel

Less invasive and prefered

Question 4

What is the main problem with POBA?

Answer 4

plain old ballon angioplasty:

Restenosis (renarrowing of the artery)

Question 5

What are the 2 main mechanisms of restenosis?

Answer 5

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.

Question 6

What is a stent ?

Answer 6

A small mesh tube that is used to treat narrow or weak arteries

Stents eliminate tge concern of POBAs elastic recoil

Question 7

What do bare metal stents (BMS) differ in ?

Answer 7

Composition
Architectual disign
Delivery system

Question 8

What is the advantage and disadvantage of BMS?

Answer 8

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

Question 9

What is the the aim of drug-eluting stents?

Answer 9

Minimise neointimal and smooth muscle hyperplasia (growth)

Question 10

Where would the drug within the stent reside and what are the different layers within the drug-eluting stent

Answer 10

Stent platform (bare metal) inner most layer

Outer most layer called the polymer matrix where the drug would reside

Question 11

How does the release of drugs occure in drug-eluting stents?

Answer 11

Drug release occurs by slow diffusion of drug from, ther polymer matrix, this provides local delivery of drug and minimised side effects

Question 12

What is the goal of the drug in drug-eluting stents DES?

Answer 12

Slows dpwn and controls intimal healing

This means that less sm groth will occure meaning to less chance of blood vessels narrowing again.

Question 13

What procedure (ballon angioplasty, bare metal stent, drug-eluting stent) has the highest chance of restenosis and highest mortality rate ?

Answer 13

Ballon angioplasty
Bare metal stent
Drug-eluting stent

Question 14

What are the advantages of DES vs BMS?

Answer 14

DES over BMS significantly reduce the risk of restenosis

Question 15

What is the disadvantage of DES vs BMS?

Answer 15

More costly

Prolonged dual antiplatlet therapy after DES implantation

Question 16

What is stent thrombosis?

Answer 16

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

Question 17

What are the time based classification of stent thrombossis

Answer 17

Acute stent thrombosis
Subacute stent thrombosis
late stent thrombiosis
very late stent thrombosus

Question 18

Why may stent thrombosis happen?

Answer 18

When stent is inserterd into the artery dam,age may occure in the blood lining

Clots may form during ther healing process

Question 19

What has a stent has a quicker healing process and why?

Answer 19

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

Question 20

What can be used to prevent clots from forming after the incertion of a stent?

Answer 20

Dual antiplatlet therapy

Aspirin + either clopidogrel ir prasugrel

Question 21

How long should antiplatlet therapy be used in BMD and DES

Answer 21

BMS at least one moth after procedure

DES at least a year after procedure

Question 22

What are the benefits of second gen DES?

Answer 22

Decrease neoitimal response and more rapid re-endothelialisation

• Thinner strut stent backbone (less chances of restenosis)
• less inflammatory
• more biocompatible
• lower drug dosing

Question 23

What are the major issues with fully biodegradable stents?

Answer 23

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

Question 24

When should BMS be considered?

Answer 24

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