Pushing drug-eluting stents into uncharted territory: simpler than you think--more complex than you imagine.

Mechanical failure is a characteristic of a material or device and not necessarily an indication of inadequacy. All devices will fail under some specific stress. It is only failure at the lowest levels of stress that may represent inadequacy. Stress on a material, for example, rises with strain until a critical load is exceeded, at which point the material fatigues and loses mechanical integrity. Failure analysis, the science by which these conditions are rigorously defined, is an important component of device design, development, and use. Once the transition point to failure is identified, material use can be restricted to the zone of safety or modified so as to have this zone expanded. Just as the characterization of a material is incomplete unless pushed to the limits of load bearing, characterization of an implantable device is incomplete unless preclinical and clinical environments test the limits of device functionality. It was in this light in 1999 that we noted the impossibility of defining the functional limits of novel bare metal stents in head-to-head trials, which, by necessity, could only include lesions into which the predicate device (the Palmaz-Schatz stent, Cordis, Warren, NJ) could be placed.2 Glimpses of superiority of 1 bare metal stent over another were only possible via registry data, “real world” reports, or small studies comparing advanced stent designs3 where more diverse patients and lesions could be considered and more granular determination of lesionor patient-specific predictors of failure determined.