Survival advantage in Medicare patients receiving drug-eluting stents compared with bare metal stents: real or artefactual?

BACKGROUND: Concerns have been raised regarding late mortality, particularly from late stent thrombosis, from drug-eluting stents (DES). Randomized clinical trials have shown that DES decrease restenosis but do not decrease mortality compared with bare metal stents (BMS). These studies utilized well-defined clinical and angiographic subsets. In the "real world" drug-eluting stents are used in a much broader crosssection of patients. We evaluated mortality in the first year after implantation of DES, specifically the sirolimus-eluting stent (SES), Cypher vs. BMS in "real world" older patients using the Medicare claims database. METHODS AND
RESULTS: Data for the years 2002 (n = 6,890; pre-DES) and 2003 (n = 7,566; first year of DES use) (May through December of each year) were analyzed. BMS and DES groups had similar baseline characteristics except for small but significant differences with BMS patients being somewhat older, having more males and African Americans, and a higher percentage of peripheral artery disease and heart failure while DES patients had a higher percentage of diabetics and patients with prior revascularization procedures. A significant improvement in mortality using both unadjusted and adjusted analyses was observed for DES (6.0% vs. 11.4%, P < 0.0001; hazard ratio 1.98, 95% CI 1.68-2.34). Controlling for comorbidity, extent of disease, and other characteristics by multivariable analysis or by propensity analysis had little impact on these results. On the other hand, there was no change in overall mortality in all stented patients in 2003 compared with all stented patients in 2002.
CONCLUSION: An observed mortality benefit for DES compared with BMS in 2003 was observed, demonstrating the safety of DES, and suggesting the possibility of superiority in outcome in older patients with DES vs. BMS. However, the lack of improved survival from 2002 to 2003 in all stented patients suggests that the mortality advantage with DES finding may be due to unidentified selection biases. Our data suggest that DES in the Medicare population is as safe as, and possibly superior, to BMS for survival over the first year after implantation. Copyright 2008 Wiley-Liss, Inc.