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, but are not limited to, the following (see Table below):

• Abbott Vascular ^[1] : Multi-Link 8 SV Coronary Stent System, Multi-Link 8 Coronary Stent System, Multi-Link 8 LL Coronary Stent System, 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 Melsungen AG ^[2] : Coroflex Coronary Stent System, Coroflex Blue Coronary Stent System, Coroflex Blue Ultra Coronary Stent System, Coroflex Blue Neo Coronary Stent System

• Boston Scientific ^[3] : VeriFLEX Bare-Metal Coronary Stent System, REBEL

• Medtronic ^[4] : Integrity BMS Coronary Stent System, Driver BMS Coronary Stent System, MicroDriver BMS Coronary Stent System

Table. Currently Available Bare-Metal Coronary Stent Systems (Open Table in a new window)

 

FDA approval history

In June 1993, the US Food and Drug Administration (FDA) approved the very first coronary stent, Gianturco-Roubin stent. ^[5]  Cesar Gianturco, a radiologist, and Gary Roubin, an interventional cardiologist, designed this bare-metal coronary stent, which was manufactured and sold by Cook Inc. The Gianturco-Roubin stent was a balloon-expandable and coil-type stent manufactured using a flat 316 L stainless steel wire coil attached to a single longitudinal strut. The stent length ranged from 12 to 16 mm, and its diameter ranged from 2.5 to 5 mm.

In August 1994, the FDA approved the second coronary stent, the Palmaz-Schatz stent. ^[6] Julio C Palmaz, an interventional vascular radiologist, and Richard Schatz, an interventional cardiologist, designed this bare-metal coronary stent, which was manufactured and sold by Cordis. The Palmaz-Schatz stent was a balloon-expandable and slotted-tube type stent manufactured using 316 L stainless steel. Only one stent length (15 mm) was manufactured, but its diameter ranged from 3 to 5 mm.

Many different bare-metal stents are currently available. These devices can be divided into three different designs: coil, tubular mesh, and slotted tube. The coil design is characterized by metallic wire or strips formed into a circular coil shape. The tubular mesh design is characterized by wires wound together in a meshwork forming a tube. The slotted tube design is characterized by tubes of metals from which a design is laser cut.

These devices differ from each other with respect to composition (eg, stainless steel, cobalt chromium alloy, nickel chromium alloy), architectural design, and delivery system (ie, a balloon catheter that delivers the stent, self-expanding, or balloon expandable). These devices also have different strut patterns and widths, stent diameters, stent lengths, radial strength, radiopacity, thrombogenicity, and magnetic resonance imaging (MRI) compatibility. ^[7]

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. ^{[8, 9]} 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 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. As noted earlier, various stents are available, differing from each other with respect to composition, architectural design, and delivery system.

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. ^[8] (See the sections on Follow-up/Monitoring and Complications.)

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

Clinical indications

Clinical indications for PCI are as follows:

• Acute ST-elevation myocardial infarction (STEMI)

• Non-ST-elevation acute coronary syndrome (ACS)

• 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 indications

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

Contraindications to a coronary stent system are as follows:

• Patients in whom antiplatelet and/or anticoagulant therapy is contraindicated ^{[1, 2, 3, 4]}

• A coronary lesion that prevents complete inflation of an angioplasty balloon or proper placement of the stent ^{[1, 2, 3, 5]}

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.

The available evidence indicates that restenting with second-generation drug-eluting stents has the most likelihood to achieve the best angiographic and clinical outcomes. ^[10] Relatively recent developments in drug-coated balloons and bioresorbable vascular scaffolds have increased the potential options for in-stent restenosis. ^[10]

In the DARE trial, which compared the effectiveness of paclitaxel-eluting balloon versus everolimus-eluting stent for the treatment of any in-stent restenosis in 278 patients, investigators reported that with regard to the 6-month in-segment minimal lumen diameter, the drug-eluting balloon was noninferior to the drug-eluting stent and, thus, the use of a drug-eluting balloon may be a potential treatment option in this setting. ^[11] The target vessel revascularization at 12-month follow-up was also similar between the groups.

Two randomized trials, the Benestent study ^[12] and the Stent Restenosis Study (STRESS), ^[13] 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). ^[14] 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 (87.8%) than in the stent group (73.8%), and fewer patients in the surgery group required a second revascularization procedure (3.5% vs 16.8%, respectively).

In the Argentine Randomized Trial of Percutaneous Transluminal Coronary Angioplasty Versus Coronary Artery Bypass Surgery in Multivessel Disease (ERACI) ^[15] and the Bypass Angioplasty Revascularization Investigation (BARI) trial, ^[16] 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 than other patients. ^{[15, 16]} 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 to 6% in CABG patients. ^[17] Death and MI rates were similar in the two 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. ^[17] 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%). ^[18] 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 two-vessel disease without left anterior descending (LAD) artery involvement, PCI offered a small survival benefit. ^[18] In patients who had two-vessel disease with proximal LAD disease, both 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 three-vessel disease with proximal LAD disease. ^[18]

In a more recent study that compared mortality following surgical (CABG) versus percutaneous (PCI) revascularization in 6682 patients with multivessel disease (3358 CABG patients received single arterial or multiple arterial grafts; 2294 PCI patients received bare-metal stents, or first- or second-generation drug-eluting stents), investigators noted a higher 5-year mortality with PCI compared with CABG, regardless of the stent type used. ^[19]  When measured and unmeasured confounding were adjusted, 5-year mortality remained higher with PCI with bare-metal stents and first-generation drug-eluting stents; however, it was comparable to that of CABG for PCI with second-generation drug-eluting stents.

Drug-eluting stents, bare-metal stents, and self-expanding stents

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. ^[20] However, rates of death and stent thrombosis were similar for the two groups. Patients were assigned to receive paclitaxel-eluting stents or otherwise identical bare-metal stents in a 3:1 ratio.

Lee et al compared drug-eluting stents, bare coronary stents, and self-expanding stents in angioplasty for middle cerebral artery stenosis and concluded drug-eluting stents were more effective than bare-metal stents. ^[21]

A study by Hsieh and colleagues that compared the long-term outcomes of drug-eluting stents versus bare-metal stents in subgroups of different vessel sizes also concluded that the incidence of major adverse cardiac events was significantly reduced by the use of drug-eluting stents, but that benefits were lessened if the affected vessels were larger than 3.75 mm wide. ^[22]

Similarly, Kubo et al concluded after a 7-year study that with the exception of the two-stent procedure, the 7-year outcomes for left main coronary artery stenting showed the drug-eluting implantation outcomes were superior to those achieved with bare-metal stents. ^[23]

Using multicenter National Heart, Lung, and Blood Institute (NHLBI)-sponsored Dynamic Registry data of 3326 patients who underwent PCI with drug-eluting stent versus bare-metal stent to assess their 2-year safety (death, MI) and efficacy (repeat revascularization) outcomes across racial groups, Olafiranye and colleagues found that, compared with the use of a bare-metal stent, the use of a drug-eluting stent was associated with better 2-year safety outcomes in both black and white patients. ^[24] Relative to bare-metal stents, drug-eluting stents were associated with a significant 24% lower risk of repeat revascularization in white patients and with a nominal 34% lower risk of repeat revascularization in black patients. ^[24]

In a comprehensive network meta-analysis of 51 randomized controlled trials that included a total of 52,158 patients to evaluate the long-term safety and efficacy of drug-eluting and bare-metal stents, Palmerini and colleagues reported that, after a median follow-up of 3.8 years, all drug-eluting stents demonstrated superior efficacy compared with bare-metal stents. ^[25] Relative to first-generation drug-eluting stents, second-generation drug-eluting stents had substantially improved long-term safety and efficacy outcomes. ^[25]

In a retrospective study that compared the 4-year outcomes of bare-metal and everolimus-eluting stents using data from New York State (NYS) cardiac registries, NYS-wide hospital discharge data, the National Death Index, and the US Census file, Qian et al found that, compared to patients who received a bare metal stent, those receiving the second-generation drug-eluting stent had better outcomes, including a lower rate of 4-year mortality, acute MI, target-lesion PCI, and target-vessel CABG. ^[26]

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. ^[27] In this analysis, myocardial infarction (MI) rates were lower with direct stenting than with conventional stenting (3.16% vs 4.04%, respectively), whereas rates of target vessel revascularization were similar.

Stent thrombosis occurs most commonly in the subacute period within 1 month after percutaneous coronary intervention (PCI), thus, the American College of Cardiology (ACC), the American Heart Association (AHA), and the Society for Cardiovascular Angiography and Interventions (SCAI) advisory 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. ^[28]

The 2012 update to the 2007 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 75 mg/day, prasugrel 10 mg/day, or ticagrelor 90 mg twice daily for at least 12 months. ^[29]

According to a large multicenter cohort study, select low-risk patients undergoing elective PCI may be considered for same-day discharge. ^[30] 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. ^[30]

Percutaneous coronary intervention (PCI) is associated with an emergency bypass rate of less than 1%. ^[31] 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, although it continues to occur with drug-eluting stents. The factor contributing most significantly to stent thrombosis is interruption of antiplatelet therapy.

Bare-metal coronary stent implantation may cause many adverse events, including but not limited to, the following ^{[1, 2, 3, 4]} :

• Acute MI
• Allergic reaction to contrast medium/stent material/medications
• Arterial perforation/rupture
• Arteriovenous fistula
• Cardiac arrhythmia (including ventricular fibrillation and ventricular tachycardia)
• Cardiac tamponade
• Bleeding complications (requiring transfusion)
• Coronary artery spasm/perforation/dissection
• Death
• Drug reaction to antiplatelet agent
• Embolization (air, stent, tissue, or thrombotic)
• Emergency or nonemergent coronary artery bypass graft surgery
• Endocarditis
• Failure to deliver stent
• Hematoma
• Hypotension/hypertension
• Infection/sepsis
• Injury to the coronary artery
• Myocardia ischemia/infarction
• Pain and tenderness at the insertion site
• Peripheral ischemia/nerve injury
• Pseudoaneurysm (coronary/femoral/radial)
• Pyogenic reaction
• Restenosis of the dilated or stented segment
• Stent deformation, collapse, or fracture
• Stent embolization/thrombosis
• Stroke/cerebrovascular accident
• Total occlusion of the coronary artery
• Unstable angina pectoris
• Vascular thrombosis
• Vessel dissection/perforation/spasm

Candidates for a bare-metal stent rather than a drug-eluting stent

Patients who will likely not comply with a recommendation for 1 year of dual antiplatelet therapy (DAPT) or those who have a planned procedure that requires early cessation of antiplatelet agents may be candidates for a bare-metal stent rather than a drug-eluting stent.

Patients taking anticoagulants

Bare-metal stents or second-generation drug-eluting stents are recommended for patients receiving anticoagulation agents. DAPT for longer than 1 month places the patients at a high risk of bleeding. A bare-metal stent is preferred if the risk of restenosis is lower.