Angioplasty’s

Fight

against Restenosis: Drug Eluting Stents & Bare Metal Stents

Balloon Angioplasty • minimally invasive treatment to open blocked arteries. • Within this procedure, a balloon catheter is employed to enlarge a narrowed vessel lumen stenosis. • have shown increased coronary arterial lumen diameter, increased coronary blood flow, and decreased chest pain.

Diagram of Angioplasty Procedure

What is Restenosis?

• the

re-narrowing

of a coronary artery after dilation Coronary Angioplasty has been performed.

• six months after the procedure restenosis typically affects between 25% to 45% of patients within results in a repeat procedure.

• Restenosis is also considered an exaggeration of “vascular healing” and “remodeling” that probably occurs to some degree in all cases

Restenosis of Balloon Angioplasty

Fighting Restenosis

• Prior to the mid 1990’s, balloon angioplasty was the primary treatment of arteriosclerosis • In the mid 1980's, radiologists and cardiologists worked on solutions to reduce restenosis rates; • rotational polishers, tiny shavers, and lasers, to be delivered via catheters.

Bare Metal Stents

• are small expandable metal tubular structures that support the vessel wall and maintain blood flow through the opened vessel (5). • In 2001, 84% of the 1,000,000 percutaneous coronary interventions were treated with stents. Of those million, 20% or 200,000 patients develop in-stent restenosis

History of the Bare Metal Stent

• The first stent was inserted into a human coronary artery by European researchers in 1986, in France, by Julio Palmaz and Richard Schatz. • Julio Palmaz and Richard Schatz, lead to the first stents to be approved in the United States in 1994 • The first company to produce a coronary artery stent was Cordis, a Johnson & Johnson company, in 1994.

Early Palmaz-Schatz stent

Stenting Diagram

Neointimal Hyperplasia

• is an abnormal increase in the number of cells causing a thickening of the intima of a blood vessel. • caused by platelets that are attracted by the damaged tissue caused by the placement of a stent. • tissue grows through the openings in the stent and eventually narrows the lumen of the vessel, therefore, reducing myocardial blood flow. • This restenosis leads to a repeat procedure.

Restenosis of Bare Metal Stents

• Prevalent in 10 to 30% of patients who receive bare metal stents . • usually eliminate abrupt closures, but typically result in a restenosis rate of 25% six months after being placed.

• The majority of restenosis occurring after a bare metal stent is placed usually occurs within 30 days.

Diagram of Reoccurring Restenosis

Drug Eluting Stents

The invention of the drug-eluting stent came into the angiographic procedures in 2002. The three major elements of drug-eluting stents are: • Stent • Drug • The mechanism for controlling drug release (usually a polymer to protect and control release)

Two Main Types of Drug Eluting Stents 1.Cordis CYPHER sirolimus-eluting stent (April of 2003) 2.Boston Scientific TAXUS paclitaxel-eluting stent system (March of 2004) • Both stents have shown benefits toward reducing restenosis rates up to 9%

Cordis CYPHER Sirolimus-eluting stent • Sirolimus is a drug used to help prevent the body from rejecting organ and bone marrow transplants. • it helps to limit normal tissue overgrowth (restenosis) following coronary stent implantation. • The polymer allows the drug to be released over 30 days which decreased restenosis effects. • Since the FDA approval it is estimated that almost 450,000 of these stents have been implanted in 300,000 U.S. patients

Cypher stent which uses Sirolimus

Boston Scientific TAXUS Paclitaxel-eluting stent • The drug Paclitaxel is an antineoplastic agent that inhibits cell migration and proliferation • coated with a polymer chemical compound called Transulte (also known as SIBS). • The Boston Corporation : Taxus I-VI studies. • These clinical trials have shown that paclitaxel eluting stents reduce restenosis and the need for revascularization with a neutral effect on mortality and myocardial infarction risk.

Taxus Stent which uses Paclitaxel

Controversy Arises with the use of Drug-Eluting Stents • Drug eluting vs. Bare metal stent. • Research shows that the revascularization rate for bare metal stents is only 12 to 14 percent. • It is said that the financial impact is not with the patient, but it is the hospital taking the biggest loss. (stage the procedure, ethical or not) • Drug eluting stents are about 2,000 dollars more than bare metal stents. (decrease $ for repeated procedures and decrease in surgery) • An Economical Analysis (Cincinnati network of hospitals) – 3 million dollars in costs to the provider or to the hospital for every 1000 treated patients.

The Future of Angioplasty and Restenosis • It is estimated that 800,000 to 900,000 individuals in the United States undergo some kind of percutaneous coronary intervention annually. Most of the procedures involve stenting. • Drug eluting stent research seems to be at the tip of the ice berg. • As studies progress, it will be clearer to health care providers of the details and benefits of the use drug eluting stents or bare metal stents.