As a physician, what do you consider the most clinically significant measure or measures of efficacy in drug-eluting stent (DES) clinical trials, and why? In patients undergoing intervention, TLR (target lesion revascularization) is the most clinically relevant measure of efficacy in DES studies. TLR represents the entire analysis segment (the stented area along with the five millimeters proximal and distal to the stent) and is a report card on the success of treating the culprit lesion not just the stent itself (Figure 1). For example, a TLR rate of three percent means that during the follow-up period (typically nine months), three percent of patients required re-intervention. While there are many other measures of DES performance, such as in-stent and in-segment late lumen loss, they are really only data points and may not correlate well to the most significant efficacy measure of TLR. There has been some debate about how late lumen loss should be measured and how well it reflects DES performance. What are your thoughts on late loss as an efficacy measure? Late loss is the difference in millimeters between the lumen diameter immediately following stent implantation and the diameter at a later time, usually at eight or nine months in DES clinical studies. In-segment late loss, which includes the in-stent area and the five millimeters proximal and distal to the stent, is measured more like TLR and is the standard angiographic measurement of overall DES effectiveness in treating the specific lesion, since it represents the efficacy of both the device and the implant procedure. As discussed, TLR remains the most important measure of DES efficacy, and this measure includes this entire analysis segment. Based on data from DES clinical trials, what differences, if any, do you see in efficacy measures between the currently available DES systems? We do not have data from large, multicenter, randomized trials to make a scientific comparison between the two currently available DES systems. Based on the data published separately for these systems, the most clinically relevant measurements TLR and target vessel revascularization (TVR) are quite similar between systems and impressively low for both. Although some might try to correlate differences in angiographic measures such as late loss to differences in clinical restenosis, this type of analysis can be difficult because of the skewed distribution of late loss data and the intrinsic variability of the DES platforms (e.g., surface coverage in small vessels, etc.). A large, well-designed, head-to-head study of both platforms will be the only way to eliminate the confounding clinical and angiographic variables that can muddy indirect comparisons. What can cath lab staff take away from this information? How will it benefit their patients? An understanding of the important measures of efficacy and their clinical relevance in the current environment will make interpreting future data on these two platforms, along with others that are currently in clinical testing or development, less confusing and more relevant for our patients.An understanding of the important measures of efficacy and their clinical relevance in the current environment will make interpreting future data on these two platforms, along with others that are currently in clinical testing or development, less confusing and more relevant for our patients. Sponsored by Boston Scientific Corporation.