This arose from recog- nition that risk adjustment is less robust at the extremes of risk, as well as from acknowledgment of some of the un- intended negative consequences that could result from focus on this outcome, at the individual-operator level, in terms of avoidance of dif cult cases altogether or an undesirable displacement of them to nearby regions and operators subject to lesser scrutiny. 2) It was recognized that mortality rate has been a component of numerous prior efforts, and there was a desire to avoid duplicative efforts. For these reasons, the writing committee opted not to include a measure related to 30-day mortality rate. The occurrence of a negative outcome after PCI, such as restenosis or stent thrombosis, was also considered as an outcome measure. The writing committee generally agreed that restenosis and stent thrombosis are negative outcomes but was not in agreement that all of the factors that contribute to these outcomes are understood, or at least there was some lack of consensus about the extent to which these outcomes are related to factors within the operator s direct control. More importantly, restenosis and stent thrombosis are both now relatively low-frequency events for any individual operator. In addition, presentation with either restenosis or thrombosis is not always to the same medical center where the index procedure was performed, which creates a challenge to accurately ascertaining the incidence of these outcomes at the individual-operator or center level. For these reasons, the writing committee did not include any outcome measures related to restenosis or thrombosis. 6.3. Structural Measures Two additional structural measures related to use of standardized protocols were carefully considered by the writing committee. However, these structural measures were determined to be inappropriate for inclusion in the measure set at the present time. 