Thank you for your inquiry regarding CMS996v6, Appropriate Treatment for ST-Segment Elevation Myocardial Infarction (STEMI) Patients in the Emergency Department (ED). The measure defines ED arrival time using the following function found in the measure’s HTML file posted on the eCQI Resource Center [ https://ecqi.healthit.gov/sites/default/files/ecqm/measures/CMS996-v6.3.000-QDM.html ]. Global.EmergencyDepartmentArrivalTime(Encounter "Encounter, Performed")                start of First(("HospitalizationLocations"(Encounter))HospitalLocation                                where HospitalLocation.code in "Emergency Department Visit"                                sort by start of locationPeriod                ).locationPeriod This function defines ED arrival time as the time of the patient’s physical arrival to their first location during the ED visit. The function uses the locationPeriod attribute which defines the startTime as the time the patient arrived at the location and the time the encounter began (admission time). Therefore, the ED encounter time begins at the earliest time of arrival to the ED. We recommend working with your EHR vendor to align ED arrival time with the time of the patient’s physical arrival to the first location during the ED encounter. In a normal ED workflow, the patient’s arrival time is not always close to the time they are first roomed.