Drug Eluting Stents: How They Work and Why They Are Used

Drug-eluting stents are small mesh tubes threaded into narrowed coronary arteries that slowly release medication directly into the vessel wall to prevent the artery from re-narrowing. They combine the mechanical scaffolding of a traditional metal stent with a pharmacological coating that suppresses the excessive tissue growth responsible for most repeat blockages. The technology has reshaped how cardiologists treat coronary artery disease since its introduction in the early 2000s, and understanding how these devices work reveals why they remain the default choice for the vast majority of stent procedures performed today.

How the Stent Delivers Its Drug

A drug-eluting stent starts as a thin metal scaffold, typically made from cobalt-chromium or platinum-chromium alloy. This scaffold is coated with a layer of polymer that acts as a reservoir and delivery vehicle for an antiproliferative drug. When a cardiologist inflates the balloon catheter during a percutaneous coronary intervention procedure, the stent expands against the artery wall, locking into place. Over the following weeks to months, the polymer slowly releases the drug into the surrounding tissue.

The drugs used fall into two main families. Sirolimus and its chemical relatives (everolimus, zotarolimus) inhibit a protein involved in cell growth, slowing down the smooth-muscle cell proliferation that causes arteries to narrow again after stenting. Paclitaxel, used in earlier devices, works by a different mechanism but achieves a similar result. The key insight behind the technology is local delivery: rather than flooding the entire body with an anti-growth drug, the stent puts a tiny dose precisely where the problem occurs. This keeps the drug concentration high at the vessel wall while keeping systemic exposure negligible.

Why They Replaced Bare-Metal Stents

Bare-metal stents solved one problem and created another. They held arteries open after balloon angioplasty, preventing the immediate elastic recoil that caused many early procedures to fail. But in a substantial fraction of patients, the body responded to the foreign metal by growing new tissue over and around the stent struts so aggressively that the artery re-narrowed within months. This process, called in-stent restenosis, sent many patients back to the catheterization lab for repeat procedures.

Drug-eluting stents dramatically cut those repeat procedures. A large analysis pooling data from 76 randomized trials covering nearly 118,000 patient-years of follow-up found that every type of drug-eluting stent reduced the need for repeat intervention on the treated vessel by roughly 39 to 61 percent compared with bare-metal stents, with everolimus-eluting stents showing the strongest performance.¹ A separate large trial following patients for six years confirmed that the rate of any repeat revascularization was about 16.5 percent with drug-eluting stents versus roughly 20 percent with bare-metal stents, and stent thrombosis rates were also lower.² For patients with left main coronary artery disease, one comparison found fewer cardiovascular deaths and fewer major adverse events with drug-eluting stents over a mean follow-up of two and a half years.³

How Stent Design Has Evolved

The first drug-eluting stents approved for clinical use were the sirolimus-eluting Cypher and the paclitaxel-eluting Taxus. These first-generation devices proved the concept worked but came with trade-offs: thicker struts, durable polymers that sometimes triggered chronic inflammation, and a concerning rate of late stent thrombosis that kept cardiologists watchful for years after implantation.

Second-generation stents addressed those weaknesses on multiple fronts. They used thinner metal platforms, different drugs (primarily everolimus and zotarolimus), and improved polymer coatings. A meta-analysis of over 31,000 patients from randomized trials found that second-generation devices reduced the odds of heart attack by about 22 percent compared with first-generation stents. Everolimus-eluting stents, in particular, cut the odds of definite or probable stent thrombosis by roughly two-thirds compared with paclitaxel-eluting stents.⁴ These improvements made the second-generation devices the standard of care, and first-generation stents have largely disappeared from clinical use.

Polymer Choices

The polymer coating is not just an inert wrapper. It controls how fast the drug releases and how the body reacts to the stent long after the drug is gone. Durable polymers remain on the stent permanently. Biodegradable polymers dissolve over time, ideally leaving behind a bare metal scaffold once the drug has finished its job. The appeal of biodegradable polymers is straightforward: once the polymer is gone, the chronic inflammatory stimulus it might cause disappears with it. This could be especially helpful in patients with diabetes, whose arteries tend to heal more slowly and develop new atherosclerosis within stents more readily.⁵

In practice, though, the clinical gap between the two polymer types has been modest. One trial of patients with acute coronary syndromes found that durable-polymer stents met non-inferiority criteria and actually showed a lower rate of device-related complications than biodegradable-polymer stents at 12 months, driven mainly by fewer repeat interventions on the treated lesion.⁶ So the theoretical advantage of biodegradable polymers has not consistently translated into better patient outcomes in head-to-head studies, at least not over the follow-up periods tested so far.

Why Strut Thickness and Shape Matter

Stent struts are the tiny metal bars that make up the mesh. Thinner, more streamlined struts cause less disruption to blood flow, which turns out to be important for healing. Laboratory work has shown that thinner struts with rounded profiles promote faster regrowth of the endothelial cell layer that normally lines the artery, while thick rectangular struts create zones of disturbed blood flow that impair this healing process.⁷ Faster endothelial coverage means the stent surface is sealed off from the bloodstream sooner, which reduces the risk of blood clots forming on exposed metal. This is one reason the shift to thinner cobalt-chromium and platinum-chromium platforms in second-generation stents coincided with lower thrombosis rates.

When Drug-Eluting Stents Are Especially Valuable

While drug-eluting stents are used broadly for coronary artery disease, certain patient populations and clinical scenarios benefit more than average.

Patients with Diabetes

Diabetes accelerates atherosclerosis and makes arteries more prone to re-narrowing after stenting. Drug-eluting stents have shown consistent benefits in this group. Data from the NHLBI Dynamic Registry found that drug-eluting stents reduced the risk of repeat revascularization by about 37 to 41 percent compared with bare-metal stents in both insulin-treated and non-insulin-treated diabetic patients.⁸ A broader mixed-treatment analysis of 42 trials covering nearly 23,000 patient-years in diabetic patients confirmed reductions of 37 to 69 percent in target vessel revascularization, depending on stent type, with everolimus-eluting and sirolimus-eluting stents again at the top.⁹

During a Heart Attack

There was early concern that placing a drug-coated device in a freshly ruptured coronary plaque during an acute heart attack might increase clotting risk. That concern has not borne out. A systematic review of trials and registries found that drug-eluting stents reduced the need for repeat interventions by roughly half compared with bare-metal stents in heart attack patients, with no increase in death, recurrent heart attack, or stent thrombosis over two years.¹⁰ A large observational study using matched pairs went further, reporting that two-year mortality was actually lower with drug-eluting stents in both ST-elevation and non-ST-elevation heart attacks.¹¹

Stents Versus Bypass Surgery for Complex Disease

When blockages involve multiple coronary vessels or the left main artery, the decision between stenting and coronary artery bypass grafting becomes more complicated. In patients with multivessel disease and severely reduced heart function, stenting with everolimus-eluting stents has shown similar long-term survival to bypass surgery, but with a higher rate of repeat revascularization and a lower rate of stroke.¹²

The complexity of the coronary anatomy plays a major role. In patients with high anatomical complexity scores, bypass surgery tends to produce fewer overall adverse events. A five-year comparison found that bypass was associated with about half the rate of heart attacks and a third the rate of repeat revascularizations compared with stenting in patients with high-complexity disease, while outcomes were comparable in patients with simpler anatomy.¹³ In patients with chronic kidney disease and multivessel disease, stenting and surgery have produced similar rates of death and heart attack, but stenting again carried a substantially higher rate of repeat procedures.¹⁴ The recurring theme across these comparisons: stenting tends to trade a lower procedural risk and a lower stroke risk for a higher likelihood of needing another procedure down the road.

Blood Thinners After Stenting

After any stent is placed, patients take dual antiplatelet therapy, typically aspirin plus a second blood-thinner, to prevent clots from forming on the stent before the artery’s inner lining has had time to heal over the metal struts. With early drug-eluting stents, this healing was slow because the drug intentionally suppressed cell growth. That delay in healing meant patients needed longer courses of dual antiplatelet therapy than they did with bare-metal stents, and stopping the medications too early risked potentially fatal stent thrombosis.¹⁵

The standard recommendation for years was 12 months of dual therapy after drug-eluting stent placement. But 12 months of two blood thinners also increases bleeding risk, and the trade-off between preventing clots and causing bleeds has driven an enormous amount of research into whether shorter courses might be safe with newer stent designs.

The evidence has increasingly supported shorter durations. A network meta-analysis published in BMJ found that longer courses of dual therapy led to higher rates of major bleeding (odds roughly 78 percent higher) and even higher non-cardiac death compared with short courses, without clear reductions in heart-related events.¹⁶ A 2024 systematic review in patients with acute coronary syndromes found that switching from dual therapy to a single antiplatelet agent after just one month cut major bleeding roughly in half compared with the standard 12-month course, with no detectable increase in major cardiac events.¹⁷ Data from trials using the latest everolimus-eluting stent platforms have confirmed that even one month of dual therapy followed by single antiplatelet therapy produced stent thrombosis rates well below one percent, in patients at high bleeding risk.¹⁸

This shift matters practically. Shorter dual therapy means fewer bleeding episodes, lower medication costs, and simpler management for patients who need non-cardiac surgery or have other reasons bleeding is especially dangerous. Your cardiologist will still tailor the duration based on your individual risk profile, weighing clotting risk against bleeding risk, but the overall trend is toward shorter courses than were standard a decade ago.

Stent Thrombosis and What Causes It

Stent thrombosis is the most feared complication of any coronary stent. A blood clot forming inside the stent can abruptly cut off blood flow, causing a heart attack that is often severe. With first-generation drug-eluting stents, the phenomenon of “late” and “very late” stent thrombosis (occurring months to years after implantation) raised alarm because it suggested the stent surface was never fully healing. The pathology pointed to uncovered stent struts as the primary substrate: where metal remained exposed to flowing blood, clots could form.¹⁹ Factors including stent struts penetrating into the fatty core of plaques, long or overlapping stents, and stenting at vessel branch points all contributed to delayed healing.

An imaging study using optical coherence tomography in patients who developed very late stent thrombosis identified a putative cause in 98 percent of cases. The most common findings were stent struts sitting away from the vessel wall (about 35 percent of cases), new atherosclerosis developing within the stent (about 28 percent), and uncovered struts (about 12 percent).²⁰ The associations between uncovered or malapposed struts and thrombosis held for both older and newer stent designs, though the absolute rates are considerably lower with current devices. The polymer and the drug’s suppression of healing both play a role: the drug does its job by slowing cell growth, but the same mechanism delays the endothelial coverage that would seal the stent off from the bloodstream.²¹

Polymer-Free Stents for Patients at High Bleeding Risk

Some patients cannot tolerate long courses of blood thinners, whether because of a recent surgery, a bleeding disorder, advanced age with frailty, or the need for blood-thinning anticoagulants for another condition like atrial fibrillation. For these patients, polymer-free drug-coated stents offer an intriguing option. Without a polymer, the drug is released very quickly from a textured or microporous metal surface, and the stent surface itself may provoke less chronic inflammation. The practical payoff is that dual antiplatelet therapy can be shortened to as little as one month.

The LEADERS FREE trial demonstrated this approach: a polymer-free umirolimus-coated stent paired with only one month of dual therapy was superior to a bare-metal stent on both safety and efficacy endpoints in high-bleeding-risk patients. The drug-coated stent cut target-lesion revascularization roughly in half and reduced the composite safety endpoint by about 29 percent over 13 months.²² When a polymer-free stent was compared head-to-head with a modern polymer-based zotarolimus-eluting stent in high-bleeding-risk patients (both with one month of dual therapy), the two performed similarly at one and two years, with no significant differences in safety or efficacy.²³ ²⁴ This means that for patients who truly cannot take prolonged blood thinners, modern stent technology can deliver anti-restenosis drug therapy without requiring prolonged antiplatelet therapy, closing what used to be a significant treatment gap.

Drug-Coated Balloons as an Alternative

Drug-coated balloons take the “leave nothing behind” philosophy to its extreme. Instead of implanting a permanent metal scaffold coated with drug, the cardiologist inflates a balloon coated with an antiproliferative agent (usually paclitaxel). The drug transfers to the vessel wall during balloon inflation, and then the balloon is removed. No stent remains in the artery.

This approach is particularly appealing in small coronary vessels, where metal stents can be prone to problems. A randomized trial in small vessels found that drug-coated balloons produced less late luminal loss (a measure of vessel re-narrowing) than drug-eluting stents, with similar rates of adverse cardiac events at one year and no cases of vessel thrombosis in the balloon group.²⁵ A meta-analysis of randomized trials comparing the two technologies in small vessels found similar rates of repeat revascularization and death, with a significantly lower risk of vessel thrombosis with balloons.²⁶ Drug-coated balloons are also used to treat in-stent restenosis when a previously placed stent re-narrows, avoiding the problem of layering a second stent inside the first. Their role in larger native coronary arteries remains less established compared with stents.

Imaging-Guided Stent Placement

How well a stent is deployed matters as much as which stent is chosen. A stent that is underexpanded, sitting away from the vessel wall, or too short to cover the diseased segment is at higher risk of thrombosis and restenosis regardless of its drug coating. Traditional stent placement relies on angiography, essentially a two-dimensional shadow image of the artery. Intravascular imaging, using either ultrasound or optical coherence tomography from inside the vessel, gives the cardiologist a cross-sectional view that reveals problems invisible on angiography.

Large randomized trials and meta-analyses have shown that imaging-guided procedures reduce major adverse cardiovascular events and improve long-term stent patency compared with angiography alone, especially in complex anatomy like left main lesions, bifurcations, and heavily calcified arteries.²⁷ Either imaging modality improves outcomes, and in most situations the two can be used interchangeably.²⁸ Despite this evidence, intravascular imaging is still not used in every procedure, often due to time, cost, or operator preference. If you are undergoing a complex stent procedure, it is reasonable to ask whether imaging guidance will be used.

Drug-Eluting Stents in Leg Arteries

The drug-eluting concept extends beyond the heart. Peripheral artery disease in the legs, particularly in the arteries below the knee, causes poor blood flow that can lead to pain, non-healing wounds, and amputation. The mechanical environment in leg arteries is harsher than in coronary arteries: the vessels flex, twist, and compress with every step, which makes keeping them open after treatment more challenging.

Early evidence in below-the-knee arteries showed that sirolimus-eluting stents substantially reduced restenosis and repeat interventions compared with bare-metal stents at six months, though the data came from small studies with short follow-up.²⁹ Multiple randomized trials have since confirmed improved short- and mid-term outcomes with drug-eluting stents over balloon angioplasty and bare-metal stents in the peripheral vasculature.³⁰ Drug-coated balloons and drug-eluting stents are now both used in the femoropopliteal and below-the-knee segments, with the choice depending on lesion characteristics and the need for scaffolding.³¹ The field is less mature than coronary stenting, and longer-term data are still emerging, but the principle of local drug delivery to suppress restenosis has proved as relevant in the legs as it is in the heart.

What Drug-Eluting Stents Cost

Drug-eluting stents cost more upfront than bare-metal stents, and for years this difference fueled debate about whether the technology was worth the extra expense. A large observational analysis found that the initial stenting cost was about $1,846 more per patient with a drug-eluting stent, but that by three years the savings from fewer repeat procedures completely offset that difference. However, when the cost of prolonged dual antiplatelet therapy was included, the net cost-effectiveness ratio per repeat procedure avoided ranged from roughly $4,700 to $6,400 over three years.³² The economic equation has shifted further in favor of drug-eluting stents as their prices have dropped, generic versions have entered the market, and the trend toward shorter antiplatelet therapy has reduced the medication cost that once weighed down their cost-effectiveness profile. A separate analysis in patients with stable coronary disease found that drug-eluting stents were probably not cost-effective in that lower-risk group, highlighting that the economic case is strongest where restenosis risk is highest.³³

Bioresorbable Scaffolds and Why They Stalled

The logical endpoint of the “leave nothing behind” philosophy was the bioresorbable vascular scaffold: a stent-like device made entirely of a material (usually polylactic acid) that dissolves over two to three years, leaving no permanent implant. The idea was that once the artery had healed, the scaffold would disappear, restoring the vessel’s ability to flex and respond normally. In theory, this could also eliminate very late stent thrombosis entirely.

Reality has been less encouraging. A network meta-analysis of 147 trials found that bioresorbable scaffolds had higher stent thrombosis risk than contemporary cobalt-chromium and platinum-chromium everolimus-eluting stents, and higher heart attack risk compared with some newer metal devices.³⁴ The thick struts required to give a dissolvable material enough structural strength contributed to worse blood-flow dynamics and slower healing, exactly the problems that second-generation metal stents had been engineered to minimize. The first commercially available bioresorbable scaffold was withdrawn from the market, and while research into thinner, next-generation designs continues, metallic drug-eluting stents remain the clinical standard by a wide margin.