Most of the previous data regarding the efficacy of the EES was derived from studies comparing EES with BMS or EES with PES. Although sirolimus eluting stents (SES) have been shown to be the most efficacious drug eluting stent regarding inhibition of neointima and late loss, there have been no previous head to head comparisons between EES and ZES. Both everolimus and sirolimus are macrocyclic lactones that target the mTOR (mammalian target of rapamycin) to reduce vascular smooth muscle proliferation after vessel injury and therefore in principle may show similar results after stenting in humans. Data pooled from the EES arm that received follow up angiography in the SPIRIT III trial and the SES arm in the SIRIUS trial show similar rates of binary restenosis and late loss. However, the stent and polymer platform is not the same between the EES and ZES and it is reported that the EES system has the thinnest stent + polymer thickness (88.6um) of all of the previously KFDA-approved DES. In addition, there are no data available on the efficacy of the EES and ZES in "real world" lesions other than the selected lesions studied in the previous trials, such as acute myocardial infarction.