Why do patients with Drug-Eluting Stents (DES) have to continue dual antiplatelet therapy for longer than those with Bare Metal Stents (BMS)? The simple answer is that even though DES do a better job at preventing restenosis, it increased the risk of thrombosis (especially after the DAPT was stopped). As such, when patients are on them, they have to keep DAPT on for at least 1 year (vs a few months for BMS). The DAPT reduces the risk of thrombosis that is high in DES.
Explanation
Bare-metal stents (BMS) were developed first (before the drug-eluting stents –DES) and were 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.” Uptodate.com
“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.”
Stent Characteristics
“All coronary artery stents consist of a metallic backbone. 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).” Uptodate
“Percutaneous coronary intervention (PCI) involves both nonstent and stent procedures. While bare-metal stents (BMS) are still utilized, drug-eluting stents (DES) now offer clinicians the ability to prevent restenosis via a different mechanism. BMS prevent restenosis by attenuating arterial recoil and contraction, which was observed with balloon angioplasty. DES supply an antiproliferative drug to the target lesion that inhibits excessive growth of neointima. DES consist of a standard metallic stent, a polymer coating, and an antirestenotic drug that is mixed within the polymer and released over time. First-generation DES include sirolimus-eluting stents (SES; 2003) and paclitaxel-eluting stents (PES; 2004) (TABLE 1). Second-generation DES, including zotarolimus- and everolimus-eluting stents (ZES, EES), were approved for use in the United States in 2008 (TABLE 1). Although the underlying principle of DES remains constant, each type may offer variations with respect to deliverability (ease of placement), efficacy (preventing restenosis), and safety (thrombosis rates). The use of dual antiplatelet therapy (DAPT) with stents has significantly improved outcomes in patients undergoing PCI.” US Pharm. 2012;37(2):HS-4-HS-7. https://www.uspharmacist.com/article/drug-eluting-stents
Choosing a stent
“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.”
Antiplatelet Therapy With Stents
“Coronary rethrombosis and coronary restenosis are sequelae of stent placement. Coronary rethrombosis is defined as reocclusion of coronary vessels by thrombin formation, and coronary restenosis is reocclusion of coronary vessels and smooth-muscle endothelial overgrowth.44 These sequelae can lead to devastating events such as MI and death. DES are associated with a reduced risk of restenosis but an increased risk of rethrombosis, specifically with early discontinuation of DAPT.45-48
Predictors of later DES thrombosis have been identified, including patient and angiographic characteristics. Patient characteristics consist of older age, diabetes mellitus, low cardiac ejection fraction, renal failure, and ACS. In addition, early discontinuation of antiplatelet medications has been identified as a risk factor for stent thrombosis. Angiographic characteristics such as long or overlapping stents, stent placement in small vessels, bifurcation lesions, and suboptimal stent results also increase the risk of DES thrombosis.” US Pharm. 2012;37(2):HS-4-HS-7. https://www.uspharmacist.com/article/drug-eluting-stents
Reference
https://www.uptodate.com/contents/clinical-use-of-intracoronary-bare-metal-stents