Clinical question: Is 6 months of dual antiplatelet therapy (DAPT) therapy noninferior to 12 months, following ST-elevation myocardial infarction (STEMI) with placement of second-generation drug-eluting stents?
Background: DAPT has been the standard of care to prevent abrupt thrombotic closure of vessels following percutaneous coronary intervention (PCI) and placement of stents. The recommended duration of DAPT was lengthened from at least 30 days in bare metal stents to at least 12 months in earlier-generation drug-eluting stents after observation of high rates of in-stent thrombosis of drug-eluting stents.
Dr. Joshua Lennon
Trials have shown that there is no difference in outcomes comparing 6 month vs. 12 months in DAPT for PCI in the cases of non-ST-elevation MI and unstable angina. However, there are no randomized controlled studies comparing 6 vs. 12 months of DAPT with newer drug-eluting stents following STEMI. Newer drug-eluting stents are made of biocompatible polymers with thinner struts and are thought to be fully absorbed by 3 months. International guidelines still recommend 12 months of DAPT following drug-eluting stent placement following STEMI.
Study design: Prospective, unblinded, randomized, multicenter noninferiority trial.
Setting: The study was performed at 17 sites in the Netherlands, Norway, Poland, and Switzerland.
Synopsis: This study enrolled 1100 patients with STEMI started on DAPT during December 2011-June 2015. Overall, 870 patients were randomized to continue DAPT or to change to single antiplatelet therapy (SAPT) at 6 months. Exclusions included embolic events, cardiogenic shock, revascularization, bleeding, or being on anticoagulation. Patients were followed for 24 months.
The primary endpoint was a composite of all-cause mortality, any MI, any revascularization, stroke, or thrombolysis. Incidence of the composite endpoint was 4.8% of SAPT cases, and 6.6% of DAPT cases. Noninferiority was met (P = .004) because the upper 95% confidence interval of 1.27 was smaller than the prespecified noninferiority margin of 1.66. The secondary endpoint of safety and bleeding at 18 months was 3.2% for SAPT, and 4.3% for DAPT with HR of 0.75.
Medtronic’s new stent was used in 92% of the cases of this industry-sponsored study. Despite usage of a composite endpoint, there was no difference in the individual elements of the composite in subgroup analyses. There was a low event rate in both arms likely because of the exclusions that led to a lower-risk population. The individual operators were able to choose the P2Y12 inhibitor.
Bottom line: This industry-sponsored randomized, control trial showed noninferiority of 6 months of DAPT to 12 months of therapy following STEMI to prevent in-stent thrombosis with newer second- generation drug-eluting stents. However, the study’s results may be limited to lower-risk patients, without need for revascularization, oral anticoagulation, or with stroke or cardiogenic shock.
Citation: Kedhi E et al. Six months versus 12 months of dual antiplatelet therapy after drug-eluting stent implantation in ST-elevation myocardial infarction (DAPT-STEMI): Randomised, multicenter, noninferiority trial. BMJ. 2018;363:k3793.
Dr. Lennon is an instructor of medicine at Northwestern University Feinberg School of Medicine and a hospitalist at Northwestern Memorial Hospital, both in Chicago.
