Coronary Stent - Dr Rudd Cardiology
Coronary stenting is starts similar to coronary angiogram (the diagnostic portion) and a therapeutic procedure is added. In coronary stenting, the catheters are exchanged for slightly larger diameter catheters that will enable tiny guidewires to slide inside the catheters through a tight narrowing, and an uninflated balloon catheter is advanced to this site and inflated. It is then deflated and removed. Now, a coronary stent, which is a metallic cylinder, is advanced to the site and inflated. The stent acts to scaffold a narrowed segment, enlarging it and letting more blood flow through.
Coronary Stenting Procedure
Bare metal stents
These stents do not have any drug-coating on the surface, and hence scar tissue covering the stent occurs much faster, typically within 4 weeks. During this time, dual antiplatelet therapy (usually aspirin + clopidogrel, much also aspirin + prasugrel) are prescribed to prevent clots from forming on the surface of the metallic stents. The duration of dual antiplatelet therapy (DAPT) is typically a minimum of 4 weeks for these kind of stents.
These newer stents are similar to bare metal stents, but have a thin coating of drug on the surface. The drug prevents excesssive scar tissue buildup within the stent, hence reducing the likelihood of further renarrowing of the stented area. Bare metal stents have a 10-20% likelihood of recurrent symptomatic narrowing within 3 – 6 months after insertion, whereas drug-coated stents (also called drug-eluting stents) have a restenosis (renarrowing) rate of only about 1%. As scar tissue covering the stent occurs at a slower rate, DAPT is usually given for a minimum of 12 months. This may prevent the individual from undergoing elective surgery within 12 months.
Newer developments include bio-absorbable stents, metallic stents with reservoirs to store different drugs, and drug-coated balloons.
Below is a video explaining the concept of a bio-absorbable stent:
Below is an example of a drug-eluting balloon:
Coronary angioplasty refers to balloon dilatation of a coronary narrowing, often before insertion of a stent. A dilated segment facilitates easier insertion of the metallic stent. Sometimes, balloon angioplasty is sufficient, especially if the artery is very large in diameter, and the result from this procedure is good enough.