Drug-eluting stents (DES) are a standard metallic coronary stent with a polymer coating and an antiproliferative drug, which allows drug elution into the coronary wall for weeks to months after stent implantation.
Drug-eluting stents (DES), coronary
Durable polymer drug-eluting stents
TAXUS, ION (coated with paclitaxel)
PROMUS: ELEMENT, PREMIER (coated with everolimus)
Cordis - CYPHER (coated with sirolimus)
Abbott - XIENCE: XPEDITION, V, PRIME (coated with everolimus);
Medtronic - ENDEAVOR, RESOLUTE (coated with zotarolimus)
Bioabsorbable polymer drug-eluting stent
Boston Scientific - SYNERGY (coated with Everolimus)
Abbot - ABSORB (coated with Everolimus)
Drug-eluting stents (DES) are balloon-mounted, expandable, slotted tubular or multilink scaffolds constructed of a stainless steel or cobalt chromium matrix. Attached to the stent is a polymer that is embedded with an antiproliferative drug, which allows drug elution into the coronary wall for weeks to months after stent implantation to reduce the local proliferative healing response.
Coronary stents are generally indicated to increase coronary vessel diameter in the setting of ischemia due to coronary blockage, either by a combination of acute recoil, arterial contraction of a previously treated segment, and/or local neointimal hyperplasia.
Drug-eluting stents (DES) were developed in the early 2000's to reduce restenosis (ie, recurrent narrowing) rates in stented coronary lesions. These stents are FDA approved for single de novo coronary lesions of limited length within specific diameter size ranges. However, off-label use of drug-eluting stents is extremely common.
Clinical Trial Evidence
Initially, drug-eluting stents (DES) were compared to bare-metal stents (BMS) for efficacy. The first double-blind randomized study was the RAVEL trial,  which compared the sirolimus-eluting CYPHER stent with its noncoated counterpart, the BX velocity stent, in 238 patients with de novo lesions less than 18 mm in length in native coronary arteries 2.5-3.5 mm in diameter. At 6 months, the degree of neointimal proliferation, manifested as late luminal loss, was significantly lower in the sirolimus-stent group than in the bare-metal stent (control) group (-0.01 ± 0.33 mm vs 0.80 ± 0.53 mm; P <0.001). Although no patients in the sirolimus-eluting stent treatment group developed restenosis, nearly 27% of patients in the control group did (P <0.001).  In addition, at 1 year, the overall rate of major adverse cardiac events was significantly lower in the sirolimus-stent group than in the control group (5.8% vs 28.8%; P <0.001), primarily owing to a higher rate of target vessel revascularization in the control group.
The SIRIUS trial, which included 1058 patients with workhorse lesions who were randomly assigned to either sirolimus-eluting stents or BMS, demonstrated the long-term efficacy and safety of sirolimus-eluting stents. [2, 3] There was significant improvement in angiographic results (in stent late lumen loss: 0.17 mm vs 1.00 mm) as well as clinical outcomes (binary in-lesion restenosis: 8.9% vs 36.3%) in the sirlolimus stent treatment group relative to the BMS group. At 1-year follow-up, the rate of target revascularization was significantly reduced in the sirolimus-eluting stent group (4.1%) compared to the BMS group (16.6%) (P < 0.001). This difference in target vessel revascularization remained at 5 years follow up. 
In a 5-year study of outcomes from the j-CYPHER registry which compared sirolimus-eluting stent treatment in 397 patients with ostial right coronary artery (RCA) lesions with 3716 patients with nonostial RCA lesions, researchers concluded that sirolimus-eluting stent implantation for ostial RCA was associated with a higher risk of target legion revascularization than when used in patients with nonostial RCA lesions.  Restenosis remains an issue in coronary drug-eluting stent implantation for ostial RCA lesions. 
The paclitaxel-eluting stent was initially compared to bare-metal stents in sequentially numbered TAXUS trials. [5, 6] In each of these trials, the TAXUS stent resulted in lower target vessel revascularization rates when compared to bare-metal stents, but there was greater lumen loss than had been seen with the sirolimus-eluting stent in the RAVEL trial. [7, 8]
The everolimus-eluting stent is sold by two companies under separate names: XIENCE V and PROMUS. In the SPIRIT trial, the XIENCE V stent was shown to be superior to its bare-metal counterpart in terms of in-stent late loss and restenosis.  The SPIRIT II, III, and IV trials compared everolimus-eluting stent to other drug-eluting stents. [10, 11] These trials demonstrated a significant advantage in terms of target lesion revascularization, combined cardiac endpoints, and early and late stent thrombosis for the everolimus-eluting stent over the paclitaxel-eluting stent. As a result of findings from the SPIRIT trials, there was a major shift toward use of the everolimus-eluting stent and away from the paclitaxel-eluting stent. In the RESET trial, target lesion revascularization was similar for patients treated with everolimus- and sirolimus-eluting stents 1 year postprocedure. 
A comparison of intrastent conditions 12 months after implantation of second-generation everolimus-eluting stent in patients with ST-segment elevation myocardial infarction (STEMI) and stable angina found that the stent promoted favorable healing in both cases. 
The zotarolimus-eluting stent is marketed as the Endeavor stent. When studied against its bare-metal counterpart in the ENDEAVOR I  and II  trials, there was a reduction in target lesion and vessel revascularization for the Endeavor stent compared to the bare-metal stent. The Endeavor III trial compared the zotarolimus-eluting Endeavor stent to the sirolimus-eluting CYPHER stent. Despite initially higher angiographic late lumen loss, rates of clinical restenosis beyond the protocol-specified angiographic follow-up period remained stable with the zotarolimus-eluting stents compared with the rates for sirolimus-eluting stents, resulting in similar late-term efficacy. Over 5 years, significant differences in death, myocardial infarction, and composite endpoints favored treatment with the zotarolimus-eluting stents. 
The ENDEAVOR IV trial compared the Endeavor stent to the paclitaxel-eluting TAXUS stent in 1548 patients with single de novo coronary lesions and found that there were statistically significantly fewer myocardial infarctions during the 36-month follow-up period in the zotarolimus-eluting stent group, but no other differences between the stents emerged.  No comparative randomized data yet exist for directly comparing the two “second-generation” stents, the everolimus-eluting XIENCE stent and the zotarolimus-eluting Endeavor stent.
In the RESOLUTE All-Comers (Randomized Comparison of a Zotarolimus-Eluting Stent With an Everolimus-Eluting Stent for Percutaneous Coronary Intervention) trial, investigators found that the zotarolimus-eluting stent (ZES) was noninferior to the everolimus-eluting stent (EES) at 12 months for the primary end point of target lesion failure.  At the final 5-year follow-up, the ZES and EES had similar efficacy and safety in a population of patients who had minimal exclusion criteria.
In a meta-analysis of 42 trials with 22,844 patient-years of follow-up, everolimus eluting stents were the most efficacious and safe stents in patients with diabetes when compared to BMS and paclitaxel- or sirolimus-eluting stents.  Drug-eluting stents consistently demonstrated superiority in reducing ischemic coronary events in diabetic patients when compared to BMS. Although everolimus-eluting stents appeared to demonstrate the greatest relative efficacy advantage among drug-eluting stents, patient and lesion types were not always comparable across studies.
In a comprehensive network meta-analysis of 51 randomized controlled trials that included a total of 52,158 patients, Palmerini et al found that after a median follow-up of 3.8 years, all drug-eluting stents demonstrated superior efficacy compared with bare-metal stents.  Compared to first-generation drug-eluting stents, second-generation drug-eluting stents had substantially improved long-term safety and efficacy outcomes.
The most recent trend in this field are bioabsorbable stents. In October 2015, the SYNERGY stent became the first bioabsorbable polymer drug-eluting stent approved by the FDA. [21, 22] The EVOLVE trial compared two dose formulations of the SYNERGY stent, an EES with a bioabsorbable polymer, in 291 patients with the durable polymer platinum chromium EES.  At 30 days, target lesion failure occurred in 0%, 1.1%, and 3.1% of patients in the durable polymer EES, SYNERGY, and SYNERGY half-dose groups, respectively. At 6 months, there was no difference in in-stent late loss among the three groups, and there was no stent thromboses reported through 6-month follow-up. 
The EVOLVE II trial randomized 1684 patients with stable angina or non-ST segment elevation acute coronary syndrome to the SYNERGY stent or durable polymer platinum chromium EES. The investigators noted 12-month target lesion failure in 6.7% of patients in the SYNERGY group and 6.5% in the durable polymer EES-treated subjects (P = 0.83 for difference; P = 0.0005 for noninferiority) (primary endpoint). Clinically indicated target lesion revascularization (2.6% vs 1.7%, P = 0.21) or stent thrombosis (0.4% vs 0.6%) were similar between SYNERGY and polymer EES stent treatment groups. 
The FDA approved the ABSORB stent, the first fully absorbable stent to treat coronary artery disease, in July 2016.  The ABSORB III trial included 2008 patients with stable or unstable angina to receive an everolimus-eluting bioabsorbable vascular scaffold or an everolimus-eluting cobalt-chromium stent and found no significant difference in rate of target-lesion failure for cardiac death, target-vessel myocardial infarction, or ischemia–driven target-lesion revascularization at 1 year (7.8% vs 6.1%, respectively).  Results for the individual components of the primary end point were similar. Device thrombosis at 1 year occurred in 1.5% and 0.7% (P = 0.13 for superiority), respectively. 
Drug-eluting stent (DES) uptake was rapid and extensive following the release of the CYPHER sirolimus-eluting stent in 2003 and the TAXUS paclitaxel-eluting stent in 2004. In 2005, studies raised concerns regarding late stent thrombosis in association with drug-eluting stents.  This topic was extensively reviewed by the FDA in 2007, and a document was subsequently released stating that dual antiplatelet therapy (ie, clopidogrel plus aspirin) should be administered for a minimum of 1 year following drug-eluting stent implantation.
In head-to-head trials, relatively newer P2Y12 antagonists, prasugrel and ticagrelor, were both shown to be superior to clopidogrel in reducing major cardiac adverse events in patients receiving stents and, in the case of ticagrelor, also reduction in total mortality. [27, 28] A 2012 study by Valgimigli et al compared the effectiveness of 6-month versus 24-month dual antiplatelet therapy and found the longer therapy to be no more effective than the shorter regimen in reducing mortality. 
The FDA document concluded that drug-eluting stent placement is safe when used on-label. However, at least 60% of drug-eluting stent use occurs in off-label situations such as in the presence of overlapping stents, bifurcation lesions, or multiple stents placed in the same patient. 
Clinical trials of bioabsorbable stents are in progress in an attempt to improve the disadvantages of drug-eluting stents. The vascular scaffolding of these stents is in place only long enough to protect against subacute obstruction, restenosis, and wall recoil. The goal is to improve clinical outcomes in patients who need percutaneous coronary intervention or coronary artery bypass surgery.
In contemporary coronary stenting, women have a slightly higher procedural risk than men. 
Stent thrombosis may occur early (≤30 days), late (>60 days but <12 months), or very late (>12 months) after drug-eluting stent (DES) placement, with reports of this complication occurring as late as 4 years postprocedure or perhaps later. The incidence of early stent thrombosis is 1%-2%; thereafter, the rate of thrombosis is approximately 0.4% per year. The rates of early stent thrombosis are higher in individuals who are not compliant with dual antiplatelet therapy. Three genes (CYP2C19, ABCB1, and ITGB3) and two clopidogrel-related factors (loading dose and proton pump inhibitors) have been associated with early stent thrombosis. [32, 33]
When stent thrombosis occurs, it is associated with a 40%-60% mortality due to acute myocardial infarction.
Hypersensitivity reaction has been reported with first-generation drug-eluting stents (sirolimus, paclitaxel stents), and it is thought to contribute to the pathophysiology of stent thrombosis.  Acute interstitial pneumonitis has also been reported in a few cases, leading to death within 20 days after implantation of a paclitaxel-eluting stent. 
Coronary artery aneurysm may also occur after implantation of drug-eluting stents in 1.25% of cases. Risk factors include placement during acute myocardial infarction, multiple or longer such stents, and residual dissection. 
Statin therapy at hospital discharge may prevent late target lesion revascularization after stent implantation.