Results from the LESSON I trial presented during a Hotline session at ESC Congress 2010 provide preliminary evidence for the therapeutic benefit of the newer generation everolimus-eluting stent over the previous gold standard, the early generation sirolimus-eluting stent. Moreover, LESSON I provides evidence that stent thrombosis - the principal shortcoming of early generation drug-eluting stents - may be diminished with the newer generation everolimus-eluting stent.

"The latter observation," said principal investigator Professor Stephan Windecker from Bern University Hospital, Switzerland, "may have important implications for ongoing studies on prolonged duration of dual antiplatelet therapy after DES implantation, but will require confirmation in randomized clinical trials."

Drug-eluting stents (DES) are designed to scaffold narrowed coronary arteries resulting from coronary artery disease. By means of the radial strength of the cylindrical mesh, DES keep the artery open, maintain blood flow, and gradually release an anti-proliferative drug into the surrounding tissue. The role of the drug is to prevent re-narrowing of the artery within the stented segment by scar tissue.

The first generation of DES effectively prevented re-narrowing of the artery but were associated with a small risk of stent thrombosis late after stent implantation. Newer generation DES have been developed using modified polymers and thinner metal struts, whose aim is to further improve upon the results of early generation DES.

The LESSON I (Long-term comparison of Everolimus-eluting and Sirolimus-eluting Stents for cOronary revascularizatioN) study compared 1601 patients undergoing treatment with everolimus-eluting stents with 1532 patients having treatment with sirolimus-eluting stents in a propensity-score matched analysis. The study involved all patients having percutaneous coronary intervention (PCI) with either everolimus-eluting or sirolimus-eluting stents at Bern University Hospital between 2004 and 2009.

The primary endpoint of the study was a composite of death, heart attacks and repeat interventions. Results showed that up to three years after the procedure the numbers of deaths, heart attacks and repeat interventions tended to be lower in patients treated with everolimus-eluting stents (14.9% of patients in the everolimus-eluting stent group and 18.0% of patients in the sirolimus-eluting stent group, a relative risk reduction 17%, P=0.056).

The differences in favor of the everolimus-eluting stent were found to be most pronounced in reducing myocardial infarction (3.3% of patients in the everolimus-eluting stent group versus 5.0% in the sirolimus-eluting group, a 38% relative risk reduction, P=0.02).

"The lower risk of heart attacks was related at least in part to a lower risk of stent thrombosis in patients undergoing everolimus-eluting stent implantation," said Professor Windecker.