INTRODUCTION — The development of bare metal stents (BMS) was a major advance relative to balloon angioplasty in the management of symptomatic coronary artery disease. BMS prevented restenosis by attenuating early arterial recoil and contraction. However, the rate of clinically indicated target lesion repeat revascularization due to restenosis at one year remained relatively high at 10 to 20 percent of patients and is often due to excessive growth of neointima [1-3]. (See "Intracoronary stent restenosis", section on 'Incidence of restenosis'.)
Drug-eluting stents (DES) were developed to reduce the high rate of restenosis and subsequent need for repeat revascularization with BMS. Clinical trials have confirmed a reduction of as much as 50 to 70 percent in target lesion revascularization by DES compared with BMS. These findings have led to the preferential use of DES in most stent cases.
This topic will attempt to clarify the role of BMS in contemporary coronary artery disease interventional practice. The discussions of the various types of DES and coronary artery stent types in development are found elsewhere. (See "Drug-eluting intracoronary stents: Stent types" and "Bioresorbable scaffold coronary artery stents".)
STENT CHARACTERISTICS — All coronary artery stents consist of a metallic backbone (table 1). Drug-eluting stents (DES) have an antiproliferative drug, and a polymer that serves as the vehicle for the drug and also controls the drug release rate. The drug inhibits excessive growth of neointima, a major cause of restenosis. Since each DES is unique, differences may be observed with respect to deliverability (ease of placement), efficacy (prevention of restenosis), and safety (rates of stent thrombosis). (See "Drug-eluting intracoronary stents: Stent types".)
WHEN TO CHOOSE A BMS — Based on the evidence provided above, we use second-generation drug-eluting stents (DES) rather than bare-metal stents (BMS) in most cases based on a significantly lower need for target vessel revascularization and a similar or better safety profile as long as dual antiplatelet therapy (DAPT) can be maintained for the recommended period of time. Our recommendations for the duration of DAPT are found elsewhere. (See "Long-term antiplatelet therapy after coronary artery stenting in stable patients", section on 'Summary and recommendations'.).
In patients who need to stop DAPT before the recommended duration of therapy, the likelihood of stent thrombosis significantly increases (see "Coronary artery stent thrombosis: Incidence and risk factors", section on 'Early and late stent thrombosis'). However, there is uncertainty regarding the relative rates of stent thrombosis with BMS and DES in patients who stop DAPT prematurely for any reason. Some experts have suggested the earlier endothelialization seen with BMS compared with DES might lead to a relatively decreased risk of stent thrombosis in patients treated with BMS who prematurely discontinue DAPT. There is no high-quality evidence that demonstrates the use of BMS is superior to second-generation DES in this setting.
Prior to 2015, patients at high risk of bleeding were often considered for BMS; however, there are now several randomized trials in this cohort comparing BMS with DES with a short DAPT duration.
●In the ZEUS trial, 1606 patients (with stable or unstable symptoms) for whom it was not clear whether DES or BMS was a superior choice (eg, high bleeding risk, low restenosis risk, or high stent thrombosis risk) were randomly assigned to Endeavor-zotarolimus-eluting stent (E-ZES) or BMS and treated with DAPT for at least 30 days, after which they received either aspirin or P2Y12 monotherapy [4]. The total duration of DAPT was prespecified based on the reason for inclusion, and the mean duration was 32 days. The primary endpoint of 12-month major adverse cardiovascular events (including death, myocardial infarction [MI], or target vessel revascularization) occurred less often with E-ZES (17.5 versus 22.1 percent; hazard ratio [HR] 0.76, 95% CI 0.61-0.95). This was driven by lower rates of MI and target vessel revascularization. The rates of definite or probable stent thrombosis were significantly reduced in E-ZES patients (2 versus 4.1 percent).
A prespecified analysis evaluated outcomes in 828 patients at high bleeding risk who had at least one of the following: age older than 80 years, clinical indication for treatment with oral anticoagulant agents, recent bleeding episodes that required medical attention or hospitalization, systemic conditions associated with increased bleeding risk, known anemia, and the need for long-term treatment with steroids or nonsteroidal antiinflammatory drugs [5]. The primary endpoint occurred less often with E-ZES (22.6 versus 29 percent; HR 0.75, 95% CI 0.57-0.98).
●In the LEADERS FREE trial, 2466 patients who were candidates for a BMS rather than a DES were randomly assigned to a polymer- and carrier-free drug-coated stent that transfers umirolimus (biolimus A9) into the vessel wall over one month or a similar BMS [6]. All patients received DAPT for one month followed by aspirin alone. The primary safety endpoint, a composite of cardiac death, MI, or stent thrombosis, occurred less often in the drug-coated group at 390 days (9.4 versus 12.9 percent; p = 0.005 for superiority), owing to a difference in spontaneous and type 4C (restenosis-related) MI during follow-up. The primary efficacy endpoint of target lesion revascularization occurred less often in the drug-coated stent group (5.1 versus 9.8 percent; p<0.001).
●The Onyx-One trial demonstrated noninferiority for the durable polymer Resolute-Onyx zotarolimus-eluting stent compared with the biolimus-eluting stent used in LEADERS-FREE (discussed directly above) [7]. (See "Drug-eluting intracoronary stents: Stent types".)
The ZEUS and LEADERS FREE trials suggest that even in patients who receive DAPT for as short as 30 days, outcomes are better with second-generation DES compared with BMS. Thus, we believe it may be reasonable to consider a second-generation DES or a BMS for patients who can receive 30 days of uninterrupted DAPT, but not the recommended longer duration of DAPT. However, the DES used in the LEADERS FREE trial is not available for clinical use in the United States, and the E-ZES used in ZEUS is no longer available.
We believe the evidence supports the use of a second-generation DES, rather than a BMS, in patients who are likely to receive short-duration DAPT.
There are decreasing circumstances in which implantation of a BMS may be reasonable, but the following is considered by some of our experts:
●Patients who require noncardiac surgery within four to six weeks of PCI.
●Patients with active bleeding at the time of PCI or those at very high risk of bleeding while taking DAPT.
●Patients unlikely to comply with antiplatelet therapy for at least one month.
BMS COMPARED WITH DES — We prefer drug-eluting stents (DES) to bare metal stents (BMS) in most clinical situations. Current-generation DES have lower rates of clinically indicated repeat revascularization compared with BMS and are not limited by late safety concerns as were the first-generation DES.
Restenosis and the need for target lesion revascularization usually occur within the first year after stent placement; it is within the first year that DES are superior to BMS. Late restenosis (after one year) has been documented with all types of intracoronary stents. The rate is approximately 1 to 2 percent per year and is similar between first- or second-generation DES and BMS [8-11]. In addition, for patients who are able to comply with recommendations for long-term dual antiplatelet therapy (DAPT), there is no significant difference in the rate of late (30 days to one year) and very late stent (after one year) thrombosis. Other parameters of safety, such as cardiac mortality, are the same or better with newer-generation DES [12].
Older drug-eluting stents — In most studies that have evaluated the efficacy or safety of BMS compared with DES, patients received older sirolimus- or paclitaxel-eluting stents (SES or PES); these have been called first-generation DES. In most studies, SES and PES outperform BMS with regard to the need for repeat revascularization, and there is no difference in long-term mortality.
There are few studies that directly compare current-generation everolimus-eluting (EES), zotarolimus-eluting (ZES), biolimus-eluting, or ridaforolimus-eluting stents with BMS (table 1). High-quality evidence of efficacy benefit (a lower rate of target vessel revascularization) from first-generation DES comes from multiple randomized trials and large percutaneous coronary intervention (PCI) registry data bases [13-22]. In nearly all settings, DES lower the rate of target lesion revascularization by 50 to 70 percent compared with BMS.
The first studies evaluated patients who had less complex and "on-label" lesions. A 2007 meta-analysis included 38 randomized trials involving over 18,000 patients [23]. On-label indications typically included de novo (not restenotic or bypass graft) lesions with a diameter of 2.5 to 3.75 mm and a lesion length of less than 28 mm and excluded complex anatomy such as left main disease, occluded vessels, or bifurcation lesions. The three largest studies in the meta-analysis were SIRIUS, TAXUS IV, and TAXUS V, and the duration of follow-up was one to four years. The first-generation SES or PES were used in these trials. The principal finding was that there was a significant reduction in target lesion revascularization with both SES and PES compared with BMS (an absolute difference of approximately 12 percent at four years). Multiple analyses of randomized trials demonstrated no difference between DES and BMS for safety end points (total mortality, cardiac mortality, or myocardial infarction [MI]) at up to four years when used for on-label indications [24-29].
Similar findings were noted in another meta-analysis and in several large registries [30-33]. The Ontario, Canada coronary intervention database evaluated 3751 propensity-matched pairs of patients who received either DES or BMS from 2003 to 2005 [31]. The following findings were noted in this registry of patients who likely had more complex lesions than those enrolled in clinical trials:
●At two years, the rate of target vessel revascularization was lower in patients who received DES (7.4 versus 10.7 percent; p <0.001). The benefit was limited to those patients with two or three risk factors for restenosis (diabetes, vessels <3 mm in diameter, and lesions ≥20 mm in length).
Other studies have confirmed benefit of DES compared with BMS in patients with larger vessels or shorter lesions, although the absolute difference in benefit is smaller. (See "Percutaneous coronary intervention of specific coronary lesions", section on 'Large coronary arteries' and "Percutaneous coronary intervention of specific coronary lesions", section on 'Long lesions or diffuse disease'.)
The lower absolute difference in benefit may enter into decision-making when choosing between BMS and DES. (See 'When to choose a BMS' above.)
●The three-year mortality was significantly lower in the DES group (5.5 versus 7.8 percent), while the rates of MI were not significantly different.
As experience with first-generation DES increased, these stents were used for (off-label) indications that were not initially approved by regulatory agencies, such as multilesion PCI, small vessels, large vessels, lesions longer than 30 mm, ostial lesions, restenotic lesions, lesions of the left main, total occlusions, bifurcation lesions, and saphenous vein graft stenosis, and in those with acute MI. Large observational studies demonstrated a lower rate of target vessel revascularization with first-generation DES compared with BMS when placed in off-label situations [11].
Five large observational studies of unrestricted (off- and on-label) stent use comparing BMS and DES (PES or SES) have addressed this issue: Three found lower rates of death or MI with DES [34-36] and two found equivalent rates [33,37]. Each of these observational reports is subject to unmeasured confounding, as there are several reasons for selection of BMS that may be associated with increased risk for mortality, including underlying malignancy, general frailty, etc. We believe that the best interpretation of these studies is that there is no clinically significant difference in the rates of death or MI between DES and BMS when selected for use in patients who are eligible for and likely to comply with appropriate duration of DAPT.
Contemporary drug-eluting stents — EES, ZES, biolimus-eluting stents, ridaforolimus-eluting stents, and others are referred to as second (current)-generation DES (see "Drug-eluting intracoronary stents: Stent types", section on 'Durable polymer drug-eluting stents'). The evidence presented below demonstrates similar or better outcomes for death from any cause, stent thrombosis, and nonfatal MI compared with BMS. In all studies, the risk of repeat revascularization is significantly lower with contemporary DES.
Meta-analyses performed before the NORSTENT trial raised the possibility of a lower rate of cardiac death or stent thrombosis with contemporary DES [38,39]. NORSTENT, which randomly assigned 9012 patients with stable or unstable coronary artery disease (2008 to 2011) to PCI with contemporary DES (EES or ZES) or contemporary, thin-strut BMS [40]. All patients were treated with DAPT for six months. At six years, there was no difference in the rates of the primary outcome (a composite of death from any cause and nonfatal MI) between the two groups (16.6 versus 17.1 percent, respectively; hazard ratio [HR] 0.98, 95% CI 0.88-1.09). The rate of repeat revascularization was lower with DES (15.5 and 19.8 percent, respectively; HR 0.76, 95% CI 0.69-0.85). The rates of definite stent thrombosis were low at 0.8 and 1.2 percent, respectively (p = 0.0498).
A 2019 individual patient data meta-analysis of 20 randomized trials (n = 26,616) comparing a variety of current-generation DES with BMS found the following at a mean follow-up of 3.2 years [12]:
●The risk of the composite outcome of cardiac death or MI was lower with current-generation DES (HR 0.84, 95% CI 0.78-0.90), mostly due to a reduction in MI (HR 0.79, 95% CI 0.71-0.88).
●The risk of definite stent thrombosis was lower with DES (HR 0.63, 95% CI 0.50-0.80), as was target-vessel revascularization (HR 0.55, 95% CI 0.50-0.60).
RECOMMENDATIONS OF OTHERS — Our recommendations for the choice of the type of intracoronary stent are generally consistent with those made in the 2014 European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines on myocardial revascularization [41].
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)
●Beyond the Basics topics (see "Patient education: Angina treatment — medical versus interventional therapy (Beyond the Basics)" and "Patient education: Stenting for the heart (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Bare metal stents (BMS) have a significantly higher rate of restenosis and the need for target vessel revascularization compared with all drug-eluting stents (DES). (See 'BMS compared with DES' above.)
●The safety profile of current-generation DES is similar to or better than BMS.
●For most patients undergoing percutaneous coronary intervention with stenting, we recommend current-generation DES rather than BMS (Grade 1A). (See 'BMS compared with DES' above.)
●Circumstances in which implantation of a BMS may be reasonable include (see 'When to choose a BMS' above):
•Patients in whom a DES cannot be implanted due to large vessel size (>5 mm).
•Patients who cannot take 30 days of dual antiplatelet therapy, such as those requiring urgent surgery or have active bleeding. However, the evidence for safety of BMS or benefit over DES in these settings is lacking.
