Factors increasing the risk of stent thrombosis

Factors increasing the risk of stent thrombosis

The factors related to the stent which increase the chance of stent thrombosis are the following:

1. First generation drug eluting stents
2. Greater stent length
3. Stents deployed in bifurcations
4. Very small diameter stents
5. Stent size lesser than optimal for vessel diameter
6. Under deployment of the stent
7. Presence of in stent restenosis

Intravascular ultrasound and optical coherence tomography are two important tools which the interventionalist can use to optimize stent deployment. Under expanded regions which predispose to stent thrombosis can be identified and subjected to repeated balloon dilatations at higher pressures. Optimal stent size can be assessed better with intravascular ultrasound than by coronary angiography because angiographic measurements only give the luminal size. If there is diffuse narrowing of a vessel, actual vessel diameter may be underestimated by angiography, while intravascular ultrasound is able to detect this as an increase in the vessel wall thickness.

First generation stents have sometimes undergone thrombosis even several years later when antiplatelet agents are withheld prior to a surgical procedure or after a bleeding episode. Newer drug eluting stents are more immune to this risk.

Other factors which can enhance the risk of stent thrombosis are:

1. Diabetes mellitus
2. Left ventricular dysfunction
3. Cases presenting as acute coronary syndrome