Coronary Bare-Metal Stent 

Bare-metal coronary artery stents are used in percutaneous coronary intervention (PCI) for a variety of indications, including stable and unstable angina, acute myocardial infarction (MI), and multiple-vessel disease.

Category

Bare-metal stents, coronary

Device details

Currently available bare-metal coronary stents include the following:

• Abbott Vascular - Multi-Link Vision Coronary Stent System, Multi-Link Mini Vision Coronary Stent System, Multi-Link Ultra Vision Coronary Stent System, Multi-Link Zeta Vision Coronary Stent System
• B. Braun - Coroflex Coronary Stent System, Coroflex Blue Coronary Stent System, Coroflex Blue Ultra Coronary Stent System
• Boston Scientific - Express² Coronary Stent System, VeriFLEX Bare-Metal Coronary Stent System
• Medtronic - Integrity BMS Coronary Stent System, Driver BMS Coronary Stent System

Many different bare-metal stents are currently available. These devices differ from each other with respect to composition (eg, stainless steel, cobalt chromium alloy, or nickel chromium alloy), architectural design, and delivery system (ie, the balloon catheter that delivers the stent).

Coronary artery stents are used in percutaneous coronary intervention (PCI) for various indications, including stable and unstable angina, acute myocardial infarction (MI), and multiple-vessel disease. Intracoronary stent placement is based on the notion that permanent implantation of a scaffold to hold open the coronary artery at the site of an intervention would improve outcomes. Stents, particularly stents coated with materials to reduce inflammatory and cell-growth responses, have resulted in greatly improved outcomes.

Since 1994, when the first intracoronary stent was approved by the US Food and Drug Administration (FDA), the implementation of intracoronary stents has risen dramatically. With the advent of drug-eluting stents, stents are now used in more than 80% of PCI cases in the United States. Various stents are currently available, differing from each other with respect to composition (eg, stainless steel, cobalt chromium, or nickel chromium), architectural design, and delivery system (ie, the balloon catheter that delivers the stent).

Although the problems of restenosis are seen less frequently with drug-eluting stents than with bare-metal stents, implanting a bare-metal stent during PCI may be preferable in some clinical situations, such as in patients undergoing urgent noncardiac surgery in whom antiplatelet therapy may have to be discontinued and in patients with known or potential medicine compliance issues (see Follow-up/Monitoring and Complications).

Despite differences in restenosis rates between bare-metal and drug-eluting stents, long-term rates of death and MI are comparable for the 2 device types.

Clinical

Clinical indications for PCI are as follows:

• Acute ST-elevation myocardial infarction (STEMI)
• Non-ST-elevation acute coronary syndrome
• Stable angina
• Angina equivalent (eg, dyspnea, arrhythmia, dizziness/syncope)
• Asymptomatic or mildly symptomatic patients with objective evidence of a moderate-to-large area of viable myocardium or moderate-to-severe ischemia on noninvasive testing

Clinical contraindications include significant comorbidities (a relative contraindication).

Angiographic

Angiographic indications for PCI include hemodynamically significant lesions in vessels serving viable myocardium (vessel diameter > 1.5 mm).

Angiographic relative contraindications include the following:

• Left main stenosis in a patient who is a surgical candidate (coronary artery bypass grafting [CABG] remains the preferred treatment for left main stenosis; however, safe and feasible PCI options are evolving rapidly)
• Diffusely diseased small-caliber artery or vein graft
• Other coronary anatomy not amenable to PCI

The major limitations of balloon angioplasty have been acute vessel closure and restenosis. Early studies with intracoronary stents showed that these devices were highly effective for treating or preventing acute or threatened vessel closure and thereby avoiding emergency bypass surgery.

Two randomized trials, the Benestent study^[1] and the Stent Restenosis Study (STRESS),^[2] demonstrated that coronary stenting of de novo lesions in native vessels reduced angiographic restenosis by approximately 30% as compared with conventional balloon angioplasty. Stenting produces a larger lumen diameter than conventional balloon angioplasty both immediately after the procedure (acute gain) and at follow-up (net gain), resulting in less restenosis.

The use of stenting, instead of balloon angioplasty, was compared with coronary artery bypass grafting (CABG) for the treatment of multivessel coronary artery disease in the Arterial Revascularization Therapies Study (ARTS).^[3] At 1-year follow-up, no differences were noted in the rates of death, stroke, or myocardial infarction (MI). Event-free survival was better in the surgery group than in the stent group (87.8% vs 73.8%), and fewer patients in the surgery group required a second revascularization procedure (3.5% vs 16.8%).

In the Argentine Randomized Trial of Percutaneous Transluminal Coronary Angioplasty Versus Coronary Artery Bypass Surgery in Multivessel Disease (ERACI)^[4] and the Bypass Angioplasty Revascularization Investigation (BARI) trial,^[5] 37% and 54% of patients, respectively, needed a second revascularization when treated with balloon angioplasty.

Overall, patients with diabetes and those who received incomplete surgical revascularization did worse.^{[4, 5]} The cost of the initial revascularization procedure was $4212 less for those treated with stent placement, but because of the need for more repeat revascularization procedures in the stent group, the cost advantage for stenting was reduced to $2973 after 1 year.

The Stent or Surgery (SoS) trial compared bare-metal stents with CABG in similar patients and reported a 21% 2-year target vessel revascularization rate in stent patients, compared with 6% in CABG patients.^[6] Death and MI rates were similar in the 2 groups; however, the SoS trial had a higher noncardiac death rate in the PCI arm, thought to be attributable to a type II error that may have affected the study results.

Few stent patients in the SoS trial received glycoprotein (GP) IIb/IIIa receptor inhibitors.^[6] Still, this trial and the ARTS study point to the safety of PCI treatment in multivessel disease. Mortality risk is low (if the noncardiac deaths are discounted), and the rates for repeat target vessel revascularization have been halved.

According to the New York Cardiac Registry, as in the preceding trials, patients who received PCI as the initial therapy had a higher incidence of target vessel revascularization (35.1%) than those who underwent CABG (4.9%).^[7] A total of 59,314 patients with multivessel disease who underwent either CABG (37,212) or PCI with bare-metal stents (22,102) were identified, and the reported endpoints were repeat revascularization and survival rates within 3 years.

The registry demonstrated, by unadjusted survival curves, that in patients who had 2-vessel disease without left anterior descending (LAD) involvement, PCI offered a small survival benefit. In patients who had 2-vessel disease with proximal LAD disease, the 2 procedures had similar mortalities (91.4% for CABG vs 91.2% for PCI). The registry reported a statistically significant survival benefit of CABG over PCI in patients who had 3-vessel disease with proximal LAD disease.^[7]

Stone et al, examining the safety and efficacy of drug-eluting and bare-metal stents in 3006 patients with STEMI undergoing primary PCI, found that the drug-eluting stents, as compared with bare-metal stents, significantly reduced angiographic evidence of restenosis and recurrent ischemia necessitating repeat revascularization at 12-month follow-up.^[8] However, rates of death and stent thrombosis were similar for the 2 groups. Patients were assigned to receive paclitaxel-eluting stents or otherwise identical bare-metal stents in a 3:1 ratio.

Coronary stents are implemented during percutaneous coronary intervention (PCI), typically after balloon angioplasty. The delivery system consists of a balloon-tipped catheter, over which the collapsed, appropriately sized stent is threaded. Once the stent is advanced to the site of interest, the balloon is inflated to expand the stent, thereby locking it into place. The stent subsequently becomes endothelialized.

Although stents are conventionally placed after balloon predilation, a meta-analysis by Piscione et al suggested that in selected coronary lesions, direct stenting may lead to better outcomes.^[9] In this analysis, myocardial infarction (MI) rates were lower with direct stenting than with conventional stenting (3.16% vs 4.04%), whereas rates of target vessel revascularization were similar.

Because stent thrombosis occurs most commonly in the subacute period within 1 month after percutaneous coronary intervention (PCI), the advisory issued by the American College of Cardiology (ACC), the American Heart Association (AHA), and the Society for Cardiovascular Angiography and Interventions (SCAI) for the prevention of stent thrombosis after coronary stent implantation recommends that at a minimum, patients should be treated with clopidogrel 75 mg and aspirin 325 mg for 1 month after bare-metal stent implantation.^[10]

The 2011 update to the American College of Cardiology Foundation (ACCF)/AHA guideline for unstable angina and non-ST-elevation myocardial infarction (NSTEMI) recommends that patients treated with PCI should receive clopidogrel or prasugrel 10 mg/day for at least 12 months.^[11]

According to a large multicenter cohort study, select low-risk patients undergoing elective PCI may be considered for same-day discharge.^[12] Although only 1.25% of patients were discharged the same day, there were no significant differences found in the death or rehospitalization rates at 2 days or at 30 days.

Percutaneous coronary intervention (PCI) is now associated with a mortality and an emergency bypass rate of less than 1%. The rate of nonfatal myocardial infarction (MI) after percutaneous transluminal coronary angioplasty (PTCA) with stent placement is 2-5% (compared with 5-15% for PTCA without stent placement).

Although drug-eluting stents have reduced restenosis events significantly, the rate of thrombosis with a drug-eluting stent is virtually identical to that with a bare-metal stent at 1 year (0.5-0.7%). However, late stent thrombosis (> 1 year) is exceedingly rare for bare-metal stents, though it continues to occur with drug-eluting stents. The factor contributing most significantly to stent thrombosis is interruption of antiplatelet therapy.