Category of Stents

Information of Coronary Stents

In general, if coronary stenosis is not severe (<50%), medication treatment might be advised to control the disease. However, with arterial blockage in excess of 60% to 70%, Percutaneous Coronary Intervention (PCI) would probably be recommended and the procedure often involves the implantation of coronary stent(s) to provide scaffolding to keep the coronary artery open permanently.

In general, stent selection depends primarily on patients’ baseline characteristics, whilst lesion type, contra-indications and patients’ financial situation may also be factors for consideration.

There are currently 5 types of stents available in the market:

  1. Dual Therapy Stent
  2. Bioresorbable Vascular Scaffold
  3. Bio-engineered Stent
  4. Drug-Eluting Stent
  5. Bare Metal Stent

Dual Therapy Stent

Dual Therapy Stent (DTS) is the latest type of coronary stent in the world. It is a first-of-its-kind stent therapy combining the anti-proliferative effect of a Drug Eluting Stent (to minimize restenosis) and the pro-healing safety profile of a Bio-engineered Stent (to accelerate stent coverage).

DTS is coated with a biodegradable polymer (disappears in time) on the abluminal stent surface (facing vessel wall) embedded with an anti-proliferative drug that is fully released to control neointimal hyperplasia and minimize restenosis without the worry of chronic inflammatory responses. The stent’s luminal surface (side facing blood flow) is coated with antibodies to promote rapid capturing of endothelial progenitor cells (EPC) to promote healing and restoration of arterial function.

This combined therapy not only helps reduce chances of vessel re-narrowing but also lowers incidence of early and late stent thrombosis.

Bioresorbable Vascular Scaffold

Bio-Vascular Scaffold (BVS) is a new type of stent platform which could naturally be absorbed and metabolized by the body in time, leaving no permanent implant in blood vessels.

Similar to currently-available Drug Eluting Stents (DES) in metallic scaffolds, BVS is coated with an anti-proliferative drug released from a biodegradable polymer to minimize restenosis (re-narrowing); the scaffold will be fully dissolved after two years.

Currently there are some clinical limitations due to the scaffold material: may not be suitable in patients with calcified, tortuous and bifurcation lesions.

Bio-engineered Stent

Bio-engineered Stent (BES), also known as Antibody-coated stent, is the latest generation stent available in the market. This type of stent differs from DES in that it contains no polymer and uses no drug to inhibit healing. Instead, it rapidly promotes healing or re-endothelialization.

The antibody bound on the stent’s surface attracts circulating Endothelial Progenitor Cells (EPCs) derived from human bone marrow which help speed up the process of endothelialization (or formation of healthy endothelium). This course of action provides rapid coverage over the stent’s surface, hence, helps reduces incidence of early and late thrombosis.

Normally, the doctor will suggest a patient with the bio-engineered stent to take dual anti-platelet therapy for 30 days. BES is clinically proven to be a safe option for patients requiring coronary intervention.
Bio-engineered stent is ideal for the following types of patients:

  • In need of urgent or short-term surgeries (shortened DAPT)
  • Intolerant of or non-compliant to prolonged DAPT
  • Bleeding tendencies
  • At risk for thrombotic events.

Drug-Eluting Stent

Drug-Eluting stent (DES) is the 2nd-generation type of coronary stents and was first introduced in Hong Kong in 2002. It serves a similar function as BMS except its surface is coated with a polymer which holds a drug that elutes in a pre-set time frame to inhibit hyperplasia. This, in turn, reduces arterial re-narrowing or restenosis to about 10%.

Due to a relatively slower healing process, patients implanted with DES must strictly follow doctor's recommendation of DAPT to help reduce incidence of stent thrombosis which takes place when blood clots accumulate on a stent’s surface and potentially results in arterial blockage. Based on guidelines under ACC, AHA and SCAI, patients implanted with DES are advised to remain on DAPT for at least one year and in some cases life long, depending on severity of the disease and patients’ morbidity.

Bare Metal Stent

Bare metal stent (BMS) is the first generation of coronary stents made, and is typically made of stainless steel material or cobalt-chromium alloy. Compared with earlier methods of plain old balloon angioplasty (POBA) during which only balloon catheters are used to open up the lesion, the chance of arterial re-narrowing is greatly reduced.

Due to inner vessel wall injury caused by trauma during coronary intervention, however, development of scar tissue (from cell proliferation or hyperplasia) as part of vessel repairing process has a tendency to result in arterial re-narrowing. For this specific type of stent, restenosis or re-narrowing rate is comparatively high (30%) when compared with the other two alternatives.

For this type of coronary stent, the Dual Anti-platelet Therapy (medication-based regimen involving in take of blood- thinning agent such as Aspirin and anti-platelet agent such as Plavix) is 4 weeks.